UNDERSTANDING DIFFERENT METHODS OF ELECTRIC VEHICLE CHARGING TECHNOLOGY
vijay tharad
Director Operations at Corporate Professional Academy for Technical Training & Career Development
Charging with a Power Supply
Batteries can be charged manually with a power supply featuring user-adjustable voltage and current limiting.
Lead Acid
Before connecting the battery, calculate the charge voltage according to the number of cells in series, and then set the desired voltage and current limit. To charge a 12-volt lead acid battery (six cells) to a voltage limit of 2.40V, set the voltage to 14.40V (6 x 2.40). Select the charge current according to battery size. For lead acid, this is between 10 and 30 percent of the rated capacity. A 10Ah battery at 30 percent charges at about 3A; the percentage can be lower. An 80Ah starter battery may charge at 8A. (A 10 percent charge rate is equal to 0.1C.)
Observe the battery temperature, voltage and current during charge. Charge only at ambient temperatures in a well-ventilated room. Once the battery is fully charged and the current has dropped to 3 percent of the rated Ah, the charge is completed. Disconnect the charge. Also disconnect the charge after 16–24 hours if the current has bottomed out and cannot go lower; high self-discharge (soft electrical short) can prevent the battery from reaching the low saturation level. If you need float charge for operational readiness, lower the charge voltage to about 2.25V/cell.
You can also use the power supply to equalize a lead acid battery by setting the charge voltage 10 percent higher than recommended. The time in overcharge is critical and must be carefully observed.
Stationary batteries are almost exclusively lead acid and some maintenance is required, one of which is equalizing charge. Applying a periodic equalizing charge brings all cells to similar levels by increasing the voltage to 2.50V/cell, or 10 percent higher than the recommended charge voltage.
An equalizing charge is nothing more than a deliberate overcharge to remove sulfate crystals that build up on the plates over time. Left unchecked, sulfation can reduce the overall capacity of the battery and render the battery unserviceable in extreme cases. An equalizing charge also reverses acid stratification, a condition where acid concentration is greater at the bottom of the battery than at the top.
Experts recommend equalizing services once a month to once or twice a year. A better method is to apply a fully saturated charge and then compare the specific gravity readings (SG) on the individual cells of a flooded lead acid battery with a hydrometer. Only apply equalization if the SG difference between the cells is 0.030.
During equalizing charge, check the changes in the SG reading every hour and disconnect the charge when the gravity no longer rises. This is the time when no further improvement is possible and a continued charge would have a negative effect on the battery.
The battery must be kept cool and under close observation for unusual heat rise and excessive venting. Some venting is normal and the hydrogen emitted is highly flammable. The battery room must have good ventilation as the hydrogen gas becomes explosive at a concentration of 4 percent.
Equalizing VRLA and other sealed batteries involves guesswork. Observing the differences in cell voltage does not give a conclusive solution and good judgment plays a pivotal role when estimating the frequency and duration of the service. Some manufacturers recommend monthly equalizations for 2–16 hours. Most VRLAs vent at 34kPa (5psi), and repeated venting leads to the depletion of the electrolyte, which can lead to a dry-out condition.
A power supply can also reverse sulfation. Set the charge voltage above the recommended level, adjust the current limiting to the lowest practical value and observe the battery voltage. A totally sulfated lead acid may draw very little current at first and as the sulfation layer dissolves, the current will gradually increase. Elevating the temperature and placing the battery on an ultrasound vibrator may also help in the process. If the battery does not accept a charge after 24 hours, restoration is unlikely.
Applying ways to minimize sulfation
Sulfation occurs when a lead acid battery is deprived of a full charge. This is common with starter batteries in cars driven in the city with load-hungry accessories. A motor in idle or at low speed cannot charge the battery sufficiently.
Electric wheelchairs have a similar problem in that the users might not charge the battery long enough. An 8-hour charge during the night when the chair is not being used is not enough. Lead acid must periodically be charged 14–16 hours to attain full saturation. This may be the reason why wheelchair batteries last only 2 years, whereas golf cars with the identical battery deliver twice the service life. Long leisure time allows golf car batteries to get a full charge overnight
Solar cells and wind turbines do not always provide sufficient charge for lead acid banks, which can lead to sulfation. This happens in remote parts of the world where villagers draw generous amounts of electricity with insufficient renewable resources to charge the batteries. The result is a short battery life. Only a periodic fully saturated charge can solve the problem. But without an electrical grid at their disposal, this is almost impossible.
An alternative solution is using lithium-ion, a battery that prefers a partial charge to a full charge. However, Li-ion is more than double the cost of lead acid. Although more expensive, the cycle count is said to be cheaper than that of lead acid because of the extended service life.
What is sulfation? During use, small sulfate crystals form, but these are normal and are not harmful. During prolonged charge deprivation, however, the amorphous lead sulfate converts to a stable crystalline and deposits on the negative plates. This leads to the development of large crystals that reduce the battery’s active material, which is responsible for the performance.
There are two types of sulfation: reversible (or soft sulfation), and permanent (or hard sulfation). If a battery is serviced early, reversible sulfation can often be corrected by applying an overcharge to an already fully charged battery in the form of a regulated current of about 200mA. The battery terminal voltage is allowed to rise to between 2.50 and 2.66V/cell (15 and 16V on a 12V mono block) for about 24 hours. Increasing the battery temperature to 50–60°C (122–140°F) during the corrective service further helps in dissolving the crystals.
Permanent sulfation sets in when the battery has been in a low state-of-charge for weeks or months. At this stage, no form of restoration seems possible; however, the recovery yield is not fully understood. To everyone’s amazement, new lead acid batteries can often be fully restored after dwelling in a low-voltage condition for many weeks. Other factors may play a role.
A subtle indication whether lead acid can be recovered or not is visible on the voltage discharge curve. If a fully charged battery retains a stable voltage profile on discharge, chances of reactivation are better than if the voltage drops rapidly with load.
Several companies offer anti-sulfation devices that apply pulses to the battery terminals to prevent and reverse sulfation. Such technologies will lower the sulfation on a healthy battery, but they cannot effectively reverse the condition once present. It’s a “one size fits all” approach and the method is unscientific.
Applying random pulses or blindly inducing an overcharge can harm the battery by promoting grid corrosion. There are no simple methods to measure sulfation, nor are commercial chargers available that apply a calculated overcharge to dissolve the crystals. As with medicine, the most effective remedy is to apply a corrective service for the time needed and not longer.
While anti-sulfation devices can reverse the condition, some battery manufacturers do not recommend the treatment as it tends to create soft shorts that may increase SELF DISCHARGE. Furthermore, the pulses contain ripple voltage that causes some heating of the battery. Battery manufacturers specify the allowable ripple when charging lead acid batteries.
Lithium-ion
Lithium-ion charges similarly to lead acid and you can also use the power supply but exercise extra caution. Check the full charge voltage, which is commonly 4.20V/cell, and set the threshold accordingly. Make certain that none of the cells connected in series exceeds this voltage. (The protection circuit in a commercial pack does this.) Full charge is reached when the cell(s) reach 4.20V/cell voltage and the current drops to 3 percent of the rated current, or has bottomed out and cannot go down further. Once fully charged, disconnect the battery. Never allow a cell to dwell at 4.20V for more than a few hours.
Please note that not all Li-ion batteries charge to the voltage threshold of 4.20V/cell. Lithium iron phosphate typically charges to the cut-off voltage of 3.65V/cell and lithium-titanate to 2.85V/cell. Some Energy Cells may accept 4.30V/cell and higher. It is important to observe these voltage limits.
NiCd and NiMH
Charging nickel-based batteries with a power supply is challenging because the full-charge detection is rooted in a voltage signature that varies with the applied charge current. If you must charge NiCd and NiMH with a regulated power supply, use the temperature rise on a 0.3–1C rapid charge as an indication of full charge. When charging at a low current, estimate the level of remaining charge and calculate the charge time. An empty 2Ah NiMH will charge in about 3 hours at 750–1,000mA. The trickle charge, also known as maintenance charge, must be reduced to 0.05C.
Charging Nickel-cadmium
Nickel-based batteries are more complex to charge than Li-ion and lead acid. Lithium- and lead-based systems are charged with a regulated current to bring the voltage to a set limit after which the battery saturates until fully charged. This method is called constant current constant voltage (CCCV). Nickel-based batteries also charge with constant current but the voltage is allowed to rise freely. Full charge detection occurs by observing a slight voltage drop after a steady rise. This may be connected with plateau timing and temperature rise over time (more below).
Battery manufacturers recommend that new batteries be slow-charged for 16–24 hours before use. A slow charge brings all cells in a battery pack to an equal charge level. This is important because each cell within the nickel-cadmium battery may have self-discharged at its own rate. Furthermore, during long storage the electrolyte tends to gravitate to the bottom of the cell and the initial slow charge helps in the redistribution to eliminate dry spots on the separator.
Battery manufacturers do not fully format nickel- and lead-based batteries before shipment. The cells reach optimal performance after priming that involves several charge/discharge cycles. This is part of normal use; it can also be done with a battery analyzer. Quality cells are known to perform to full specifications after only 5–7 cycles; others may take 50–100 cycles. Peak capacity occurs between 100–300 cycles, after which the performance starts to drop gradually.
Most rechargeable cells include a safety vent that releases excess pressure if incorrectly charged. The vent on a NiCd cell opens at 1,000–1,400kPa (150–200psi). Pressure released through a re-sealable vent causes no damage; however, with each venting event some electrolyte escapes and the seal may begin to leak. The formation of a white powder at the vent opening makes this visible. Multiple venting eventually results in a dry-out condition. A battery should never be stressed to the point of venting.
Full-charge Detection by Temperature
Full-charge detection of sealed nickel-based batteries is more complex than that of lead acid and lithium-ion. Low-cost chargers often use temperature sensing to end the fast charge, but this can be inaccurate. The core of a cell is several degrees warmer than the skin where the temperature is measured, and the delay that occurs causes over-charge. Charger manufacturers use 50°C (122°F) as temperature cut-off. Although any prolonged temperature above 45°C (113°F) is harmful to the battery, a brief overshoot is acceptable as long as the battery temperature drops quickly when the “ready” light appears.
Advanced chargers no longer rely on a fixed temperature threshold but sense the rate of temperature increase over time, also known as delta temperature over delta time, or dT/dt. Rather than waiting for an absolute temperature to occur, dT/dt uses the rapid temperature increase towards the end of charge to trigger the “ready” light. The delta temperature method keeps the battery cooler than a fixed temperature cut-off, but the cells need to charge reasonably fast to trigger the temperature rise. Charge termination occurs when the temperature rises 1°C (1.8°F) per minute. If the battery cannot achieve the needed temperature rise, an absolute temperature cut-off set to 60°C (140°F) terminates the charge.
Chargers relying on temperature inflict harmful overcharges when a fully charged battery is repeatedly removed and reinserted. This is the case with chargers in vehicles and desktop stations where a two-way radio is being detached with each use. Reconnection initiates a new charge cycle that requires reheating of the battery.
Li ion systems have an advantage in that voltage governs state-of-charge. Reinserting a fully charged Li-ion battery immediately pushes the voltage to the full-charge threshold, the current drops and the charger turns off shortly without needing to create a temperature signature.
Full-charge Detection by Voltage Signature
Advanced chargers terminate charge when a defined voltage signature occurs. This provides a more precise full-charge detection of nickel-based batteries than temperature-based methods. The charger looks for a voltage drop that occurs when the battery has reached full charge. This method is called negative delta V (NDV).
NDV is the recommended full-charge detection method for chargers applying a charge rate of 0.3C and higher. It offers a quick response time and works well with a partially or fully charged battery. When inserting a fully charged battery, the terminal voltage rises quickly and then drops sharply to trigger the ready state. The charge lasts only a few minutes and the cells remain cool. NiCd chargers with NDV detection typically respond to a voltage drop of 5mV per cell.
To achieve a reliable voltage signature, the charge rate must be 0.5C and higher. Slower charging produces a less defined voltage drop, especially if the cells are mismatched in which case each cell reaches full charge at a different time point. To assure reliable full-charge detection, most NDV chargers also use a voltage plateau detector that terminates the charge when the voltage remains in a steady state for a given time. These chargers also include delta temperature, absolute temperature and a time-out timer.
Fast charging improves the charge efficiency. At 1C charge rate, the efficiency of a standard NiCd is 91 percent and the charge time is about an hour (66 minutes at 91 percent). On a slow charger, the efficiency drops to 71 percent, prolonging the charge time to about 14 hours at 0.1C.
During the first 70 percent of charge, the efficiency of a NiCd is close to 100 percent. The battery absorbs almost all energy and the pack remains cool. NiCd batteries designed for fast charging can be charged with currents that are several times the C-rating without extensive heat buildup. In fact, NiCd is the only battery that can be ultra-fast charged with minimal stress. Cells made for ultra-fast charging can be charged to 70 percent in minutes.
FIGURE CHARGE CHARACTERISTIC OF Ni Cd CELL
Figure 1 shows the relationship of cell voltage, pressure and temperature of a charging NiCd. Everything goes well up to about 70 percent charge, when charge efficiency drops. The cells begin to generate gases, the pressure rises and the temperature increases rapidly. To reduce battery stress, some chargers lower the charge rate past the 70 percent mark.
Charge efficiency is high up to 70% SoC* and then charge acceptances drops. NiMH is similar to NiCd. Charge efficiency measures the battery’s ability to accept charge and has similarities with coulombic efficiency.
* SoC refers to relative state-of-charge (RSoC) reflecting the actual energy a battery can store. Full charge will show 100% even if the capacity has faded.
Ultra-high-capacity NiCd batteries tend to heat up more than standard NiCds when charging at 1C and higher and this is partly due to increased internal resistance. Applying a high current at the initial charge and then tapering off to a lower rate as the charge acceptance decreases is a recommended fast charge method for these more fragile batteries. (See BU-208: Cycle Performance)
Interspersing discharge pulses between charge pulses is known to improve charge acceptance of nickel-based batteries. Commonly referred to as a “burp” or “reverse load” charge, this method assists in the recombination of gases generated during charge. The result is a cooler and more effective charge than with conventional DC chargers. The method is also said to reduce the “memory” effect as the battery is being exercised with pulses. While pulse charging may be valuable for NiCd and NiMH batteries, this method does not apply to lead- and lithium-based systems. These batteries work best with a pure DC voltage.
After full charge, the NiCd battery receives a trickle charge of 0.05–0.1C to compensate for self-discharge. To reduce possible overcharge, charger designers aim for the lowest possible trickle charge current. In spite of this, it is best not to leave nickel-based batteries in a charger for more than a few days. Remove them and recharge before use.
Charging Flooded Nickel-cadmium Batteries
Flooded NiCd is charged with a constant current to about 1.55V/cell. The current is then reduced to 0.1C and the charge continues until 1.55V/cell is reached again. At this point, a trickle charge is applied and the voltage is allowed to float freely. Higher charge voltages are possible but this generates excess gas and causes rapid water depletion. NDV is not applicable as the flooded NiCd does not absorb gases because it is not under pressure.
Charging Nickel-metal-hydride
The charge algorithm for NiMH is similar to NiCd with the exception that NiMH is more complex. Negative Delta V to detect full charge is faint, especially when charging at less than 0.5C. A mismatched or hot pack reduces the symptoms further.
NDV in a NiMH charger should respond to a voltage drop of 5mV per cell or less. This requires electronic filtering to compensate for noise and voltage fluctuations induced by the battery and the charger. Well-designed NiMH chargers include NDV, voltage plateau, delta temperature (dT/dt), temperature threshold and time-out timers into the full-charge detection algorithm. These “or-gates” utilize whatever comes first. Many chargers include a 30-minute topping charge of 0.1C to boost the capacity by a few percentage points.
Some advanced chargers apply an initial fast charge of 1C. When reaching a certain voltage threshold, a rest of a few minutes is added, allowing the battery to cool down. The charge continues at a lower current and then applies further current reductions as the charge progresses. This scheme continues until the battery is fully charged. Known as the “step-differential charge,” this method works well for all nickel-based batteries.
Chargers utilizing the step-differential or other aggressive charge methods achieve a capacity gain of about 6 percent over a more basic charger. Although a higher capacity is desirable, filling the battery to the brim adds stress and shortens the overall battery life. Rather than achieving the expected 350–400 service cycles, the aggressive charger might exhaust the pack after 300 cycles.
NiMH dislikes overcharge, and the trickle charge is set to around 0.05C. NiCd is better at absorbing overcharge and the original NiCd chargers had a trickle charge of 0.1C. The differences in trickle charge current and the need for more sensitive full-charge detection render the original NiCd charger unsuitable for NiMH batteries. A NiMH in a NiCd charger would overheat, but a NiCd in a NiMH charger functions well. Modern chargers accommodate both battery systems.
It is difficult, if not impossible, to slow charge a NiMH battery. At a C rate of 0.1C to 0.3C, the voltage and temperature profiles do not exhibit defined characteristics to trigger full-charge detection, and the charger must depend on a timer. Harmful overcharge can occur when charging partially or fully charged batteries, even if the battery remains cold.
The same scenario occurs if the battery has lost capacity and can only hold half the charge. In essence, this battery has shrunk to half the size while the fixed timer is programmed to apply a 100 percent charge without regard for battery condition.
Many battery users complain about shorter than expected service life and the fault might lie in the charger. Low-priced consumer chargers are prone to incorrect charging. If you want to improve battery performance with a low-cost charger, estimate the battery state-of-charge and set the charge time accordingly. Remove the batteries when presumed full.
If your charger charges at a high charge rate, do a temperature check. Lukewarm indicates that the batteries may be full. It is better to remove the batteries early and recharge before each use than to leave them in the charger for eventual use.
Simple Guidelines for Charging Nickel-based Batteries
How do Battery Chargers Work?
A good battery charger provides the base for batteries that are durable and perform well. In a price-sensitive market, chargers often receive low priority and get the “after-thought” status. Battery and charger must go together like a horse and carriage. Prudent planning gives the power source top priority by placing it at the beginning of the project rather than after the hardware is completed, as is a common practice. Engineers are often unaware of the complexity involving the power source, especially when charging under adverse conditions.
Chargers are commonly identified by their charging speed. Consumer products come with a low-cost personal charger that performs well when used as directed. The industrial charger is often made by a third party and includes special features, such as charging at adverse temperatures. Although batteries operate below freezing, not all chemistries can be charged when cold and most Li-ions fall into this category. Lead- and nickel-based batteries accept charge when cold but at a lower rate.
Some Li-ion chargers (Cadex) include a wake-up feature, or “boost,” to allow recharging if a Li-ion battery has fallen asleep due to over-discharge. A sleep condition can occur when storing the battery in a discharged state in which self discharge brings the voltage to the cut-off point. A regular charger treats such a battery as unserviceable and the pack is often discarded. Boost applies a small charge current to raise the voltage to between 2.2V/cell and 2.9V/cell to activate the protection circuit, at which point a normal charge commences. Caution is required if a Li-ion has dwelled below 1.5V/cell for a week or longer. Dendrites may have developed that could compromise safety. which Figures 5 examines the elevated self-discharge after a Li-ion cell had been exposed to deep discharge.
Lead- and lithium-based chargers operate on constant current constant voltage (CCCV). The charge current is constant and the voltage is capped when it reaches a set limit. Reaching the voltage limit, the battery saturates; the current drops until the battery can no longer accept further charge and the fast charge terminates. Each battery has its own low-current threshold.
Nickel-based batteries charge with constant current and the voltage is allowed to rise freely. This can be compared to lifting a weight with a rubber band where the hand advances higher than the load. Full charge detection occurs when observing a slight voltage drop after a steady rise. To safeguard against anomalies, such as shorted or mismatched cells, the charger should include a plateau timer to assure a safe charge termination if no voltage delta is detected. Temperature sensing should also be added that measures temperature rise over time. Such a method is known as delta temperature over delta time, or dT/dt, and works well with rapid and fast charge.
A temperature rise is normal with nickel-based batteries, especially when reaching the 70 percent charge level. A decrease in charge efficiency causes this, and the charge current should be lowered to limit stress. When “ready,” the charger switches to trickle charge and the battery must cool down. If the temperature stays above ambient, then the charger is not performing correctly and the battery should be removed because the trickle charge could be too high.
NiCd and NiMH should not be left in the charger unattended for weeks and months. Until required, store the batteries in a cool place and apply a charge before use.
Lithium-based batteries should always stay cool on charge. Discontinue the use of a battery or charger if the temperature rises more than 10oC (18oF) above ambient under a normal charge. Li ion cannot absorb over-charge and does not receive trickle charge when full. It is not necessary to remove Li-ion from the charger; however, if not used for a week or more, it is best to place the pack in a cool place and recharge before use.
Types of Chargers
The most basic charger was the overnight charger, also known as a slow charger. This goes back to the old nickel-cadmium days where a simple charger applied a fixed charge of about 0.1C (one-tenth of the rated capacity) as long as the battery was connected. Slow chargers have no full-charge detection; the charge stays engaged and a full charge of an empty battery takes 14–16 hours. When fully charged, the slow charger keeps NiCd lukewarm to the touch. Because of its reduced ability to absorb over-charge, NiMH should not be charged on a slow charger. Low-cost consumer chargers charging AAA, AA and C cells often deploy this charge method, so do some children’s toys. Remove the batteries when warm.
The rapid charger falls between the slow and fast charger and is used in consumer products. The charge time of an empty pack is 3–6 hours. When full, the charger switches to “ready.” Most rapid chargers include temperature sensing to safely charge a faulty battery.
The fast charger offers several advantages and the obvious one is shorter charge times. This demands tighter communication between the charger and battery. At a charge rate of 1C, which a fast charger typically uses, an empty NiCd and NiMH charges in a little more than an hour. As the battery approaches full charge, some nickel-based chargers reduce the current to adjust to the lower charge acceptance. The fully charged battery switches the charger to trickle charge, also known as maintenance charge. Most of today’s nickel-based chargers have a reduced trickle charge to also accommodate NiMH.
Li-on has minimal losses during charge and the coulombic efficiency is better than 99 percent. At 1C, the battery charges to 70 percent state-of-charge (SoC) in less than an hour; the extra time is devoted to the saturation charge. Li-ion does not require the saturation charge as lead acid does; in fact it is better not to fully charge Li-ion — the batteries will last longer but the runtime will be a little less. Of all chargers, Li-ion is the simplest. No trickery applies that promises to improve battery performance as is often claimed by makers of chargers for lead- and nickel-based batteries. Only the rudimentary CCCV method works.
LEAD ACID cannot be fast charged and the term “fast-charge” is a misnomer. Most lead acid chargers charge the battery in 14–16 hours; anything slower is a compromise. Lead acid can be charged to 70 percent in about 8 hours; the all-important saturation charge takes up the remaining time. A partial charge is fine provided the lead acid occasionally receives a fully saturated charge to prevent Sulfation.
The standby current on a charger should be low to save energy. Energy Star assigns five stars to mobile phone chargers and other small chargers drawing 30mW or less on standby. Four stars go to chargers with 30–150mW, three stars to 150–250mW and two stars to 250–350mW. The average consumption is 300mW and these units get one star. Energy Star aims to reduce current consumption of personal chargers that are mostly left plugged in when not in use. There are over one billion such chargers connected to the gird globally at any given time.
Simple Guidelines when Buying a Charger
The primary cause of environmental pollution, which worsens air quality and contributes to global warming by releasing harmful air pollutants (such as sulfur dioxide, nitrogen oxides, carbon monoxide, etc.), is the growing number of fossil fuel-powered vehicles, such as motorcycles, cars, trucks, buses, etc. Hazardous gases?harm practically every organ system in the human body and threaten the environment . Because of these serious problems, there is a critical need for vehicles that are safer, cleaner, and more efficient, like battery electric vehicles.?(BEVs).
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Wired and Wireless Charging?
Wired and wireless charging are the two charging methods for battery?electric vehicles. Due to their promising characteristics, like low pollution, no greenhouse gas emissions, and high efficiency, EVs have increasingly gained attention over the past few decades. Recent studies have shown significant and positive improvements in the use of EVs. Lower fuel costs and improved energy efficiency have increased EV market penetration.
BEVs satisfy the basic requirements for environmentally friendly transportation sources, with improved fuel economy and decreased emissions. For instance, the market share of BEVs has increased significantly since 2014. The effectiveness and cost of these specific BEVs are influenced considerably by the batteries and related charging technologies. To continue their growth rates, businesses are investing more heavily in their research into BEV charging systems.
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Electric Vehicle Charging Technology
Due to their potential achievements, BEVs are currently gaining more and more attention every day. Further developing their charging systems has proven difficult due to numerous considerations, including an optimal structural design with fewer components, safety precautions, high efficiency, fast charging, etc. Two different charging technologies can be distinguished from one another: wired charging (contact charging) and wireless charging (contactless charging).
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Wired Charging Technologies
First, wired charging methods, which may be further broken down into AC and DC charging technologies, require a direct cable connection between the EV and the charging equipment to achieve charging. Figure 1 shows the overall charging technologies available for BEVs.
Figure 1. Overall charging system for BEVs using wired/wireless. Image used courtesy of IEEE Access
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AC Charging
By using AC charging technologies, EV batteries are not charged directly; rather, the battery is charged by the ONBOARD CHARGER?(OBC) that supplies the battery. These technologies add weight to the entire system because the conversion unit, which converts AC into DC, is housed inside the vehicle. They are frequently charged using either single-phase (1? ) onboard slow charging or three-phase (3? ) onboard fast charging systems.
Most of the time, the AC charging method sends power to the OBC, which turns the AC into regulated DC. Not only do OBCs take over the conversion from AC to DC, but they also improve the quality of the regulated current (fewer ripples, less switching loss, and less electromagnetic interference, or EMI). AC charging technologies are also mostly used in BEVs, with power levels and charging times of less than 20 kW and 2–6 h, respectively.
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DC Charging
In contrast to AC charging methods, DC charging technologies can directly charge the battery, providing fast charging capability. Off-board fast charging and off-board rapid charging systems are two more subgroups of DC charging technologies. Because the conversion unit is distinct from the vehicle, such technologies can result in a reduction in the overall size and weight of the driving system in the car.
DC charging methods have been developed that can charge a high-capacity battery in less than an hour. Figure 2 shows how the system for charging BEVs with wired and wireless charging works. As shown in this diagram, the OBC is mostly built into the BEV. It comprises a full-bridge rectifier, a power factor correction circuit, and a chopper like a dual-active bridge, which indirectly charges the battery. Unlike the onboard charger, the off-board charger is installed outside of the BEV at a charging station and feeds the battery directly.
Installing the battery management system?(BMS) is more expensive, and they do not provide the flexibility to charge the battery in multiple locations. Wired charging solutions have made some impressive and encouraging advancements, but one of their main limitations is that they are rigid, which restricts where they may charge. The BMS?should also be considered regarding the demands for safety and dependability, both of which are challenging.
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Figure 2. Overall charging system for BEVs using wired/wireless charging technologies. Image used courtesy of IEEE Access
Emerging Charging Technologies
Emerging charging technologies are revolutionizing the way electric vehicles are powered. Innovations such as wireless charging and ultra-fast charging stations promise to enhance convenience and reduce charging times, making electric vehicles more appealing and practical for a broader range of users.
Inductive (Wireless) Charging: Static and Dynamic Methods
Inductive (wireless) charging for electric vehicles offers a seamless charging experience through static and dynamic methods. The static approach involves parking the vehicle directly over a charging pad, which can transfer power up to 22 kW, allowing for convenient charging at home or public stations without the need for plugging in.?
On the other hand, dynamic wireless charging is designed for on-the-move energy transfer. This innovative method embeds charging equipment under road surfaces to charge EVs as they drive, potentially revolutionizing travel by reducing the need for frequent stops to recharge and maintaining continuous vehicle operation.?
Both methods exemplify the push towards more adaptable and user-friendly EV infrastructure.
As the EV market grows, innovative charging methods like wireless charging will become more common. Pulse Energy is at the forefront, providing platforms that support the latest in EV technology, ensuring businesses can adapt and thrive in an ever-evolving landscape.
Wireless Charging Technologies
On the other hand, the problems with wired charging technologies, such as the need for charging cables, maintenance, and safety concerns, have led to research into wireless charging technologies. In these kinds of technologies, the BEV has to park above the charging system to get the high-frequency charging current. Wireless charging technologies can be divided into three categories: near-field, medium, and far-field.?
Near-field Charging and Medium-field Charging
Near-field charging includes inductive charging, magnetic-resonant charging, and capacitive charging. Medium-field charging includes magnetic-gear charging. The first two charging methods, near-field and medium-field charging, also known as mechanical charging, are the most common and used today for BEVs. Each day, more people are requesting wireless charging technology.
EV batteries do not need to be directly connected to wireless charging methods, which are less expensive than cable charging technologies. Instead, by converting the grid-frequency AC (50/60 Hz) to a high-frequency AC (up to 600 kHz), which is then delivered via a transmitter pad and received by a receiver pad attached to the BEV being charged, it is possible to wirelessly charge the batteries.
Far-field Charging
Far-field charging technologies, like laser charging, microwave charging, and radio wave charging, are still the subject of a lot of research and are expected to be the future of wireless charging technologies. Far-field charging methods are considered the best option for EV charging in the future. Nevertheless, if the connection between the transmitter and the receiver is lost, one of the biggest problems of wireless charging technologies is that they can quickly become out of control.
Takeaways of Electric Vehicle Charging Technology
This article has discussed the charging technologies of battery electric vehicles. Some of the takeaways follow.
The complete guide to EV charging
Charging an EV can be as simple as plugging in a phone, but there are considerations to be kept in mind.
Living with all manner of electric vehicles, we’ve realised that before you even get to range anxiety, there’s sometimes plug-in worry. Not the nail-biting kind, but stuff like, will it charge fast enough, or why does your car have a different plug and can you charge it at any outlet? So here’s our guide to help you know more about charging an EV.?
What are the different ways to charge?
15Amp?
Let’s begin with the familiar 15A? AC (Alternating Current) plug point. Yes, the broad 3-pin socket that you plug in your heavy-duty appliances at home can also power up your EV, and as the 15A point is pretty ubiquitous, it’s convenient. But with an output of just 3.3kW, it’s also slow.?
Still, for a small battery, an overnight charge will easily top it up. For example, the Citroen eC3’s 29.2kWh battery pack can go from 10-100 percent in 10.5 hours on a wall socket. But larger batteries can take well over a day. So the 15A socket works best for small batteries like in electric two-wheelers and smaller cars, and since it’s easy to find, the 15A socket is also a good back-up in case you are stranded.?
AC Fast charger?
Next up is the AC wall charger. These are units that, like the 15A socket, also deliver AC power but at a higher wattage, typically somewhere between 7kW and 22kW. They are pretty compact, can be installed at homes and most companies offer such a charger with their products. For instance, the Tiago EV has an optional 7.2kW charger that can charge the 24kWh battery from 10-100 percent in 3 hours 35 minutes, whereas the standard 3.3kW charger takes 6 hours 20 minutes.?
DC fast charger?
In general, batteries function on direct current; even when you plug in your phone, the charger converts electricity from AC to DC to charge your phone’s battery. It’s the same with EVs too. However, you can bypass the AC to DC convertor of your EV and allow the batteries to soak in some direct current. You do this by plugging into a DC charger, which converts the grid’s alternating current to direct current and sends that straight to your battery. In this way, EVs so designed can handle a much higher charging rate. Taking the Tiago EV as an example again, Tata Motors says the 24kWh battery on a DC fast charger with a 50kW output will take 57 minutes to go from 10 to 80 percent.?
These chargers aren’t for home use though, they are large and need special installation, and thus, are only found at specific public charging outlets. The speed of DC chargers is also increasing and today, some chargers can go up to 350kW. In India, companies like Kia, for example, have installed 240kW DC chargers, but remember, while your vehicle may be able to handle a DC charger, the maximum speed at which it will take on the direct current will depend on what it’s designed to handle plus other limiting factors, details of which we will get into later in this article. On a DC charger, you also have the option to select either the time, energy or total cost that you want to charge with.
V2V Charging?
Much like siphoning fuel from one car to fill another, you can also use the battery charge of one vehicle to top up another, but this is generally very slow and best only if a car is stranded. For this to work, both vehicles – donor and recipient – need to be designed for V2V charging as beyond the ability to reverse the flow of electricity, both vehicles’ onboard power electronic systems need to be able to communicate with each other to allow the exchange to take place. This isn’t very common, but there are a few models capable of this; the Hyundai Ioniq 5 and Kia EV6, for instance. Besides this method, an EV low on charge can also be plugged into another EV that has a regular 3-pin AC outlet.?
Does an EV charge at the same speed all through?
That’s a common query; most people expect the battery to charge at its maximum rate continuously. However, that’s not always the case. On slow and medium AC chargers, the power flow is at pretty much the same rate, so an EV will charge at roughly the same speed all through with only a small period of slow charging at the start and finish. However, on a DC charger, the power flow delivery is shaped like a step curve, which rises quickly and then descends as the vehicle charges. This is to protect the battery from overheating and overcharging individual cells. When a battery is in use – discharging or charging – it heats up, and to keep heat build-up in check, the charging pace is slowed as the battery gets fuller. Additionally, since no two cells are identical, they charge at slightly different speeds, thus, towards the end of any charge cycle when some cells are full and others may not be, the charging pace is slowed down so that empty cells can continue charging, while the full ones are not damaged.?
The DC charging curve varies from model to model, typically the pace rises to a peak quickly, after which it gradually drops, and at 80 to 90 percent, it drops rapidly. This rapid slowdown post 80 percent is also why many EV owners feel that it’s good etiquette to not keep charging past that mark while on a public charger. The time taken is disproportionately long for the range gained, thus unplugging and allowing the next customer to charge is a nice thing to do. Charging to 80 percent is also a recommended way of preserving your battery life.?
Other limiting factors
Ambient Temperature
There are other factors that also play a part in charging speed and one of them is ambient temperature. Remember Goldilocks, who didn’t like her porridge too hot or too cold? Batteries, too, are just like that and do not like extreme temperatures. The ideal operating temperature is roughly between 15 to 25°C, so in both very low or very high temperatures, the charging pace drops.?
Load
Another factor is load. Most EVs allow you to use some systems while charging, for instance, you can sit inside your car with the HVAC system running while it charges. Naturally, this will take longer for your car to charge up, not just because the battery is also powering some systems, but also because the battery management system will slow things down to manage heat.?
What Is EV Smart Charging?
The idea behind electric vehicles (EVs) is to provide green transportation as a replacement for petrol or diesel-powered vehicles. However, electricity generation relies on various sources including natural gas, petrol, coal, nuclear fission, and solar energy.
As EVs continue to evolve, researchers and manufacturers are exploring ways to eco-friendly charging through Smart Charging. This technology optimizes charging efficiency while reducing energy consumption and ultimately provides cost savings to consumers.
Superior-Quality EV Charger Manufacturer
Understanding EV Smart Charging
Smart Charging is a safe and convenient way of charging EVs at certain times when there is less demand for electricity, for example at night, or during periods when there is more renewable energy on the grid.
It basically connects all factors including the charger, the utility company, and the power grid, and in most cases the EV onboard computer through a data connection.
Smart Charging allows the utility companies to place limits on energy consumption, so the grid is not overloaded by a demand for more energy than is being produced.
This will be very important as more and more people start using EVs, saving them time and money to better protect the planet's precious resources.
Features of EV Smart Charging
Smart charging is a technology that enables an EV to receive power in an efficient and cost-effective way, considering factors such as electricity cost, availability, and the driver's needs. It accomplishes this by creating a data connection between the EV, charger, cloud-based platform of the charge point operator, and the power grid, which allows for monitoring and adjustment of energy consumption.
The main features of the system are:
How Does EV Smart Charging Work?
There are two main factors that make a smart charger different from a regular, non-smart charger, and they are the hardware and the software.
While a smart charger still has the same basic design as a regular EV charger, a key feature is the ability to connect to the internet to send and receive data. This requires a modem to link to a network, and this is built into the smart charger.
Apart from the hardware to allow connectivity, a smart charger also needs software to collect and analyze the usage data, and this is done through a charging app which manages the charger. The EV user can control charging sessions remotely and get accurate energy-usage information to help optimize performance and reduce energy costs.
How to Smart Charge a Car?
It is estimated that there is plenty of capacity to meet the future electricity demand – but not if everyone charges at the same time. Smart charging optimizes the capacity so charging is done at off-peak times. This is most often at night, so Smart Charging is usually done at home.
You should have a display screen on your home Smart Charge point which allows you to enter your preferences, or you can use a Smart Charge app on your mobile device.
What Are the Benefits of EV Smart Charging?
Smart Charging has a number of benefits to the EV user and also to the power supply system in general.
For the Consumer
For the Power Supply System
In terms of the power system as a whole, as EVs become more popular there could be problems with many users wanting to charge their EVs at the same time, for example as soon as they come home from work, or simply all plug in overnight.
This could lead to overuse and high demand peaks, eventually requiring electricity networks to be expanded at significant cost. Smart Charging provides benefits to the electricity generating system as a whole by optimizing and stabilizing energy flow within the grid while ensuring a more reliable service.
The overall benefit of Smart Charging is that less power is consumed, which means less cost to the EV driver and to businesses, and less need for increased power generation which is a benefit to the environment.
How Much Does EV Smart Charging Cost?
A smart charger is an efficient investment that can significantly reduce your power expenses by managing the charging process during off-peak hours, when the demand for electricity is lower and the costs are the most economical.
However since this requires a more sophisticated system than the basic charger, there is an increased initial cost with the charger unit.
The cost of a basic home charger ranges from $300 to $500, and a smart charger with added data connection capability and extra software comes at a higher price, usually around $600 to $800 or even more. This depends on the features and power output that meets both your needs and budget.
In terms of installation, you should expect to pay from $300 to $500 dollars to have a wall-mounted unit installed, depending on local labor rates. This does not include the cost of a permit, which is needed for any EV charger installation in your home.
Depending where you live, there may be state or local incentives for installing an EV Charger. For example, Los Angeles Department of water and Power is offering a rebate of up to $500 for the purchase of a qualifying Level 2 charger.
Conclusion
Early model EVs could be charged at home using a Type 1 charger unit or at highway charging stations, but charging times were generally slow. The introduction of fast charging systems highlighted the need for more power in a shorter time, which could result in system overloading if not properly managed.
As a solution, Smart Charging was developed to balance electrical loads among EVs, homes, and businesses during off-peak demand times. As more EVs are adopted, efficient power management through Smart Charging will become crucial in minimizing running costs and optimizing environmental impact.
Electric vehicle (EV) charging standards and how they differ
As more and more consumers make the green decision to forego their combustion engines for electric vehicles, they may not be as in tune with charging standards. kW, voltage, and amps might sound like jargon compared to miles per gallon, but these are essential units to understand to get the most efficiency out of your shiny new EV.
Key charging terms to understand
Before we get into the charging standards for electric vehicles, you must be sure you understand some of the terminology you never came across with your ICE car. The transition to electric energy output rather than combustion brings a new slew of units and the dreaded use of math (we know). Here are some key terms you will come across daily, so be sure to study up.
Basics of Electric Vehicle Charging
Electric vehicle (EV) charging is a very important aspect of owning an electric car, offering several methods to suit different needs and lifestyles. Depending on the battery size, availability of services, and even usage.
Level 1 Charging, through a standard 120-volt outlet, adds about 4 to 5 miles of range per hour, ideal for overnight home charging.?
Level 2 Charging accelerates the process with a 240-volt source, providing about 12 to 80 miles of range per hour and is perfect for daily use and faster home charging. For those on the go!?
DC Fast Charging can boost a battery to 80% in just about 20 minutes, though it's best used sparingly to maintain battery health.
With various standards like CHAdeMO, CCS, and Tesla Superchargers available, choosing the right charging method can greatly enhance your EV experience.
The Importance of Understanding Different Charging Options
Understanding different EV charging options is an important process for optimizing your electric vehicle's usage and efficiency. By familiarizing yourself with the strengths and limitations of Level 1, Level 2, and DC Fast Charging, you can make informed decisions that enhance your driving experience and fit your daily routine.?
This not only ensures that your vehicle is always ready when you need it but also helps in maximizing battery longevity and minimizing downtime, ultimately leading to a more sustainable and cost-effective use of your electric vehicle.
Types of EV Charging
Electric vehicle (EV) charging can be categorized into several types, each with its own unique characteristics and uses. Understanding these types helps you choose the right charging method for your needs. Here's a closer look at the main types of EV charging: Trickle Charging, AC Charging, and DC Charging.
Trickle Charging (Level 1 Charging):?
Trickle Charging, also known as Level 1 Charging, is the most basic form of EV charging. Let’s take a look at the key points about Trickle Charging:
AC Charging (Level 2 Charging):?
AC Charging, also known as Level 2 Charging, is a faster alternative to Trickle Charging. Here are the key points about AC Charging:
DC Charging (DC Fast Charging or Level 3 Charging):
DC Charging, also known as DC Fast Charging or Level 3 Charging, is the quickest method for charging electric vehicles. Let’s see what are the key points to keep in mind about DC Charging:
Each type of charging serves different purposes and meets different needs. Trickle charging is low-cost and convenient for home use, AC charging balances speed with practicality for daily charging, and DC fast charging provides rapid power for long journeys.
Comparative overview of Trickle, AC, and DC charging methods
Now let’s take a look at the concise comparative overview of Trickle, AC, and DC charging methods, highlighting their key features to help you make an informed decision based on your needs.
CHARGING METHOD Trickle Charging (Level 1)
VOLTAGE LEVEL 120 VOLTS
APPROXIMATE MILES OF RANGE PER HOUR 4 TO 5 MILES
TYPICAL USE CASE Overnight home charging, emergency top-ups
EQUIPMENT REQUIRED Standard household outlet, no special equipment needed
2. CHARGING METHOD AC Charging (Level 2)
VOLTAGE LEVEL 240 VOLTS
APPROXIMATE MILES OF RANGE PER HOUR : 12 TO 80 MILES
TYPICAL USE CASE : Daily use, faster home and public charging
EQUIPMENT REQUIRED : Level 2 charging station or home charger
CHARGING METHOD : DC Charging (Fast Charging or Level 3)
VOLTAGE LEVEL : 480 volts
APPROXIMATE MILES OF RANGE : 60-100 miles in 20 minutes
TYPICAL USE CASE : Long-distance travel, quick recharges
EQUIPMENT REQUIRED : Dedicated DC fast charging station
Understanding Charging Levels
Understanding the different levels of EV charging is crucial for optimizing how you recharge your electric vehicle. Each level offers distinct advantages and is designed to meet specific charging needs, from everyday convenience to rapid energy replenishment during long trips.
AC vs. DC Charging
AC Charging: Converts alternating current (AC) from the power grid to direct current (DC) inside the vehicle to charge the battery.
DC Charging: Supplies direct current (DC) directly to the vehicle's battery, bypassing the vehicle's onboard converter for faster charging.
Fundamental Differences between AC and DC Charging Methods
Understanding the differences between AC and DC charging is crucial for electric vehicle owners as it affects how and where they can charge their vehicles efficiently.
Feature AC Charging
Current Type Alternating Current (AC)
Conversion Conversion from AC to DC happens inside the vehicle
Speed Slower than DC, suitable for home and public use
Infrastructure Commonly found in residential and commercial settings
Cost Generally less expensive to install and maintain
Impact on Battery Gentler on the battery, promotes longer life
Feature DC Charging
Current Type : Direct current (DC)
Conversion : Directly charges the battery without conversion
Speed : Faster, ideal for quick recharges during travel
Infrastructure : Typically located at highway rest stops and urban fast-charging stations
Cost : More expensive due to higher power outputs and technology
Impact on Battery : Frequent use can reduce battery lifespan due to heat and stress
What are the different types of charger plugs available?
As we had with mobile phones – and still do to a small extent – different EV manufacturers use different types of charging connectors and that’s based on the region they are from. And before you ask, it’s likely going to be a long while before there is a global standard.?
Let’s begin with AC connectors: North American and Japanese manufacturers use the Type 1 – J1772 connectors, and these only make use of single phase electricity and are thus slow. The IEC 62196 – Type 2, also called the Mennekes connector, is used by the Europeans and can use the three-phase electric connection. Interestingly, it uses the same Type 1 – J1772 signalling or communication protocol, and thus, carmakers use either type of plug depending on the market it is sold in without having to reconfigure the entire charging system. China uses the GB/T connector, which looks much like the Type 2 plug, however, the cables are reversed and thus GB/T connector is not compatible with the Type 2. Meanwhile, Tesla uses its own propriety connector that can handle AC and DC current, however, some of its models like the Model X, which is sold in Europe, also have the Type 2 plug. In India, it’s the Type 2 that is in use, though early models like the Mahindra e2O and the older Tigor EV used different connectors.
Moving on to DC chargers, there are various types as well. Let’s start with the CCS (Combined Charging System), which is an interesting set-up wherein two additional pins are added to the bottom of the Type 1 and Type 2 AC plug, and thus, form the CCS 1 and CCS 2 plug, respectively. The added pins handle the actual charging, while the AC pins only handle the communication and Earthing. In this way, cars save space as they do not need two separate AC and DC ports, which is the case with the third type of DC charger – the CHAdeMO plug used by Japanese manufacturers in addition to the Type 1 AC plug. For DC charging, China also uses an additional GB/T plug with a different pin arrangement from the AC GB/T plug. Given that the Type 2 AC plug is used in India, the CCS 2 is in use for DC charging here.
Now that we’ve covered the levels you can choose from when charging, we will focus on the equipment you may encounter. These charging connectors vary by electric vehicle and are separated into two categories – The standard Level 1 and Level 2 connector, and DC fast charging connectors. Here’s how they differ.
SAE J1772
This connector is the industry standard for all electric vehicles performing Level 1 or Level 2 charging. Whether it’s the cord provided with the purchase of your EV or the Level 2 charger outside of Whole Foods, the J1772 is going to connect.
CHAdeMO
This is the first of three types of connectors currently present on EVs and first introduced. Originally it was implemented to be the industry standard, developed through the collaboration of five different Japanese automakers.
As a result, the CHAdeMO connector remains affluent in Japan and on EVs from Japanese manufacturers. This includes automakers such as Toyota, Mitsubishi, Subaru, and Nissan.
CCS
Shortly after the CHAdeMO was introduced, a second connector called the Combined Charging System (CCS) was implemented as an additional charging standard.
Where CCS connectors differ from CHAdeMO, is that they allow for AC/DC charging on the same port. CHAdeMO-equipped EVs require an additional J1772 connector cord to achieve Level 1 or 2 charging.
This connector is the preferred mode of charging amongst European and American automaakers, including BMW, Ford, Jaguar, GM, Polestar, Volkswagen, and even Tesla. Additionally, CCS is will be present on the upcoming Rivian EVs.
Tesla Supercharger
From day one, Tesla has chosen to pave its own way in the EV industry, and that is no different with its Supercharger connector. This proprietary connector exists on all Tesla models in North America, although it does offer CHAdeMO and CCS adapter for certain markets.
For example, its Model 3 was built with a CCS connector for Europe. Furthermore, older European Teslas were retrofitted with adapters to support the existing connector plus the standard CCS type 2. This helped Tesla owners utilize the growing charger network overseas.
Even after testing the connector adapter in the Korean market last December, Tesla has yet to bring it to North American drivers. Last month, however, EVgo announced it would be bringing Tesla compatible connectors to over 600 of its US charging stations. Regardless of the other connectors and their compatibility, Tesla's Supercharger network already features over 20,000 charging stalls at over 2,100 stations around the world.
ISO 15118 / Plug and Charge
Regardless of whether you’re on an AC or DC charger offering any of the connectors above, it’s important to learn about ISO 15118 and the “Plug and Charge” capabilities currently being offered by more and more EV automakers.
ISO 15118 is a Vehicle to Grid (V2G) communication interface that allows for bi-directional charging/discharging of?electric vehicles. One of the main features that utilizes this standard interface is Plug and Charge.
Essentially, the Plug and Charge protocol communicates with any charging station you plug into and relays what kind of EV you’re plugging in, seamlessly billing the driver. In this sense, the only action required by drivers is to plug the charging cable into their EV.
As a result, Plug and Charge eliminates the need for various swipe cards, fobs, or phone apps required by different charging networks pone might face on a given route.
Tesla has been offering this Plug and Charge technology for about a decade now, but other EVs like the Mustang Mach-E, the Lucid Air, and the Porsche Taycan support technology as a standard feature.
Resources for finding a charger
So you know what level you’re planning to charge at, and you’ve identified your proper connector. Now you’re out all day running errands, and you need to find a spot to recharge. Where to begin?
Luckily there is a vast library of public charger maps for you to utilize, usually in app form. If you’re not driving this very second, the touchscreen in your EV can probably help direct you too.
If not, here are some other resources to check out:
Home vs. Public Charging Stations
When considering electric vehicle (EV) charging options, the choice between home and public charging stations involves weighing factors like convenience, cost, and charging speed to find the best fit for your needs and lifestyle.
Differences in Convenience, Speed, and Availability
Convenience, speed, and availability vary between home charging and public stations, impacting the overall electric vehicle (EV) charging experience.
Home Charging:
Public Stations:
Home charging offers convenience and availability but may be slower, while public stations provide faster charging but may require more effort and planning.
For businesses contemplating between setting up home-like convenience charging stations or more universal public stations, Pulse Energy offers comprehensive solutions that balance cost, convenience, and speed, promoting an enhanced EV charging infrastructure.
Benefits and Drawbacks of Home Charging vs. Public Stations
Both home charging and public stations offer unique benefits and drawbacks, influencing EV owners' charging choices.
Home Charging Benefits- Convenient, cost-effective, and always available
Home Charging Drawbacks- Slower charging speeds, limited for longer journeys
Public Charging Benefits - Faster Charging, Ideal for longer trips or emergencies
Public Charging Drawbacks - May require travel and could be less cost-effective
EV charging explained: Here's all the different charger types
Charging an electric vehicle sounds simple in theory, right? Park up, plug in and recharge your battery. Job done. The reality is a little bit different, as anyone who owns or has driven an EV will doubtless agree. It’s certainly not quite as straightforward as pulling into a gas station and filling up, which can all happen within the space of a few minutes.
This is because electric vehicle charging is still evolving. Our gas and diesel refuelling infrastructure has been around for years and much of the basic setup hasn’t changed all that much. Pumps are slightly more advanced than they used to be and paying for your gas is certainly more straightforward.?Then again it's possible to recharge an EV for free, despite some recent opposition to that concept.
But the basic principle remains unchanged. Charging an EV on the other hand can sometimes feel like a step backwards.
EV chargers are not all equal
Part of this is down to the different ways in which electric vehicles get charged. Depending on the model of car you’ve got, the port used to plug in and recharge varies. It’s a bit like the different plug sockets you get around the globe.
Thankfully, anyone heading off on vacation simply needs to pack a multi-headed travel plug, which allows them to plug in and charge their phone, shaver or hairdryer using a plug that suits the socket. Unfortunately, it’s not possible to do this with an electric vehicle.
Tesla has done a great job in developing its own proprietary system, which lets you quickly and easily access the arguably superior Supercharger network. These Superchargers can be found across the US, Europe and many other parts of the world, with over 30,000 individual chargers and counting.
The rapidly expanding network is also supplemented by Tesla’s Destination Chargers, found in hotel parking lots and other popular tourist locations. These are slow, but use the same plug and socket mechanism as the rapid-power Superchargers.
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You have to know when to level-up
Following behind is everyone else. EV ports and the chargers that connect to Non-Tesla vehicles come in several variants across the U.S. You also get different levels of charging: Level 1, Level 2 and Level 3. The higher the number, the more powerful (and faster) the charging should be.
Which one you can use depends on the type of EV you want to charge and its ability to accept the power supply. The good news on that front is the car will be able to figure this out for you, so you won’t inadvertently fry your battery when you plug in.
Level 1
Level 1, 120 Volt AC charging is the ‘entry-level’ option, and much slower as a result. The bonus is if you don’t mind adding a miserly 3 to 5 miles of range per hour is that it allows you to plug in and charge at home without having to install any specialist charging equipment. Overnight makes the most sense and lets you avoid the public charger scenario altogether.
Level 2
Level 2, which is 208 Volts to 240 Volts AC, is speedier and your options are greater, although there are still limitations. You might get up to 80 miles from an hour’s charge, though this could drop down to just over 10 in other cases. EV chargers that offer Level 2 charging are becoming more commonplace, however, and can often be the ones to look for at locations like fast food outlets, shopping mall complexes and hotels.
Level 3
Level 3 DC rapid charging is the most appealing in terms of speed and efficiency. The 400 Volts to 900 Volts DC rapid charge and Supercharging options can deliver up to 20 miles per minute thanks to that direct current supply and higher voltage rating.?Tesla owners get to enjoy this via the Supercharger network, while other makes and models don’t always get that luxury.?
If you don’t have a Tesla but want to be up there with the big boys, then Level 3 charging is the one to head for — provided it’s available where you are, or where you’re headed.?
Different chargers have different plugs
In terms of the plugging-in part of the charging process, in North America the connectors are standardized for both Level 1 and Level 2 charging using a so-called ‘J-Plug’. This plug is also known as Type 1, with the alternate Type 2 charger being used in Europe and other parts of the world.
Level 3 comes with a trio of standardized connection options. While Tesla has its own proprietary thing going on, the majority of other auto manufacturers currently use the Combined Charging System, or CCS, which is a combination style plug. The CCS charging standard shares the same J Plug as Level 1 and Level 2 chargers, but also includes two additional DC pins at the base to support higher electrical current.
Meanwhile certain automakers, particularly Japanese automakers like Nissan and Mitsubishi, have been using the CHAdeMO charging system. This utilizes a totally separate plug and socket combination than the slower AC charging, and has slowly been supplanted by CCS in North America and Europe.
The only recent car you’re likely to come across with a CHAdeMO charging is the Nissan Leaf. However since the Nissan Ariya is set to launch with a CCS charger, it looks like CHAdeMO's days are numbered.
Finding a charger is a cinch
The easiest part of the EV charging procedure is locating a compatible unit that can replenish your battery. Like everything else, there’s an app for that.?
In fact, there are numerous apps that can help you find a suitable charger, check its compatibility with your vehicle, tell you the availability and detail plus any costs involved. Each charging network has its own app that can guide you, while there are plenty of other options, like Plugshare or EVG0, that offer better support for multiple networks.?
Alternatively, Google Maps has tools to help you search for nearby chargers, while your EV should have built-in features — often as part of the infotainment system — that can point your vehicle in the right direction. In some cases, if you use the built-in navigation system, the EV will automatically route you to a charging station if you’re likely to run out of power mid-trip.
Of course, what you find when you arrive at the location of the charger doesn’t always match that of the description you’ve been getting during the journey. When it works, using tech to find a suitable charger is one of the easiest ways to charge an EV. When it doesn’t, well, you could find you’re greeted by an incompatible charger though more likely it won’t work as expected. It might be in use or, annoyingly, blocked by another non-electric vehicle.?
Worst of all though, it might not be working at all. That’s why EV ownership, or rental for that matter, involves a little more thought and, ideally, a plan of action. Short hops around town are no biggie as you should be able to find at least one location where you can top up as needed.
Longer journeys, or beefy road trips, require careful planning using an app and any available in-car tech so you do at least have a fallback charging option if the location of choice is out of commission.
Which chargers are best?
It’s not so much which charger is best, as much as what will be compatible with your EV. The best thing about charging connectors and their respective ports is that they only fit if they’re compatible with each other.?
If you’re new to charging, or just in a state of minor panic due to a battery that’s nearly empty, it can be easy to overlook this point. However, a deep breath and quick examination of the connector head and port is all that’s needed to check one will mate happily with the other.
Assuming you’ve got that figured out, the next thing is the speed factor. Chargers are, generally speaking, getting faster and more efficient. However, there are factors that can slow things down, such as the electricity infrastructure where you’re charging along, the number of other vehicles being charged in close proximity, your current battery level and the car itself.
In fact, all sorts of dull, contributory factors can slow a charge. And, as if that isn’t bad enough, cold conditions will help to slow down any charge being added to your battery. Tedious, huh?
EV charging has an exciting future
If you’re already a fan of wireless charging your smartphone you’ll be glad to hear that you might be able to rejuice your EV in the not-too-distant future using the same technology.?
This inductive charging process is still in its infancy though, with the likes of BMW and Genesis working on how best to make it a practical solution for EV owners. Not having any cables to plug in or charging ports to fathom sounds like a brilliant idea to us.
In the meantime, however, you’ll just need to familiarize yourself with your EV’s port and charging compatibility, plug in and put up with the time you’ll need to pass while the thing recharges.?
In many cases, electric vehicle chargers are getting higher powered and faster as a result, although this depends on many factors such as the location, the infrastructure of the area you’re in and, of course, the vehicle’s ability to accept the right amount of charge.
Things are getting better and EV chargers are becoming more commonplace, but we’re a long way off gas station convenience levels yet. At least some of the better EV charging locations are situated in places you want to be, such as the parking lot of your local shopping mall, so you can go and enjoy some retail therapy or grab a bite to eat while you wait for the battery to be rejuvenated.
Alternatively, investigate the home charging options available where you live. There are plenty of domestic EV charging solutions, but these are only as good as the power source you have available in your locality. You may well be able to install a Level 2 home charger without too much hassle, but you’ll want to consult an electrical expert to ensure that’s going to be possible.
Unlike filling up with good old gasoline, the situation is not quite as black and white as it could be. But charging at home does mean you won’t spend a small fortune over time on needless tat, unwanted purchases and fast food while you wait for a public charger to get the job done.
Then there’s the whole issue of how much charging will cost you, which is another thing altogether. Most likely your home energy plan will charge you less on a kWh by kWh basis than a charging station, but it pays to double check.
The quick and easy route to take on this front brings us back to the humble app. Pick the right one and prices should be updated dynamically. That should allow you a quick reference check on how your next charge is gonna look when it comes time to pay the bills.
Fast and Ultra-fast Chargers
Ultra-fast Chargers
Nowhere is ultra-fast charging in bigger demand than with the electric vehicle (EV). Recharging an EV in minutes replicates the convenience of filling 50 liters (13 gallons) of fuel into a tank that delivers 600kWh of energy. Such large energy storage in an electrochemical device is not practical as a battery with such a capacity would weigh 6 tons. Most Li-ion only produces about 150Wh per kg; the energy from fossil fuel is roughly 100 times higher.
Charging an EV will always take longer than filling a tank, and the battery will always deliver less energy per weight than fossil fuel. Breaking the rule of law and forcing ultra-fast charging adds stress, even if the battery is designed for such a purpose. We must keep in mind that a battery is sluggish in nature. Like an aging man, its physical condition becomes less ideal with use and age. So is the ability to fast-charge. One assumes that all charge energy goes into the battery, whether charged slowly, rapidly or by ultra-fast method. Batteries are nonlinear devices and most chemistry accepts a fast charge from empty up to about 50% state-of-charge (SoC) with little losses. NiCd does this best and suffers the least amount of strain. Stresses occur in the second half of the charge cycle towards full charge when acceptance becomes labored. An analogy is enjoying the dessert after the hunger is stilled.
Applying an ultra-fast charge when the battery is empty and then tapering off the current when reaching 50% SoC and higher is called step charging. The laptop industry has been applying step charging for many years, so does the EV. The charge currents must harmonize with the battery type as different battery systems have dissimilar requirements in charge acceptance. Battery manufacturers do not publish charge rates as a function of SoC. Much of this is proprietary information.
Research companies claim to achieve benefits with pulse-charging Li-ion instead of applying the regular CCCV charge . The scientific community is skeptical of alternative charging and takes the “wait-and-see” approach.
As our bodies work best at 37oC (98oF), so does the transport mechanism improve when a battery is warm. Modern EVs will enable the “pre-charge” feature to prepare the battery temperature for the pending fast-charge while driving.
Whether you own an EV, e-bike, a drone, a portable device or a hobby gadget, the following conditions must be respected when charging a battery the ultra-fast way:
An ultra-fast charger can be compared to a high-speed train (Figure 1) traveling at 300km per hour (188 mph). Increasing power is relatively simple. It’s the track that governs the permissible speed of a train and not the machinery. In the same manner, the condition of the battery dictates the charging speed.
A well-designed ultra-fast charger evaluates the condition of the “chemical battery” and makes adjustments according to the ability to receive a charge. The charger should also include temperature compensations and other safety features to lower the charge current when certain conditions exist and halt the charge if the battery is under undue stress.
A “smart” battery running on SMBus or other protocols is responsible for the charge current. The system observes the battery condition and lowers or discontinues the charge if an anomaly occurs. Common irregularities are cell imbalance or the need for calibration. Some “smart” batteries stop functioning if the error is not corrected.
The 10-minute Charge
The automotive industry is demanding ultra-fast charging. Research laboratories are responding by heating Li-ion batteries to a temperature that prevents lithium plating while limiting the growth of solid electrolyte interphase (SEI) that occurs at elevated temperatures. The chosen charging temperature is 60oC (140oF), heated by heating elements for the duration of the charge and then cooled to about 24oC (75oF) with the onboard cooling system of the EV to limit the time the battery dwells at high heat. This enables charging Li-ion at a C-rate of 6C to 80% SoC in 10 minutes.
Figure 2 Cycle performance of Li-ion with 1C ,2C , 3C charge and discharge
Charging at 60oC prevents lithium plating while deterring SEI growth because of the short duration at high temperatures.
A technology called Aligned Graphite? Technology claims to reduce a charge time of 25 minutes to only 15 minutes by organizing the graphite flake on the negative electrode into vertical order. Battrion, a spin-off of the Swiss Federal Institute of Technology (ETH Zurich), says that this orientation reduces the distance lithium travels, enabling very high charge and discharge currents without degradation.
Limitations to ultra-fast charging Li-ion
The maximum charge current a Li-ion can accept is governed by cell design, and not the cathode material, as is commonly assumed. The goal is to avoid lithium-plating on the anode and to keep the temperature under control. A thin anode with high porosity and small graphite particles enables ultra-fast charging because of the large surface area. Power cells can be charged and discharged at high currents, but the energy density is low. Energy Cells, in comparison, have a thicker anode and lower porosity and the charge rate should 1C or less. Some hybrid Cells in NCA (nickel-cobalt-aluminum) can be charged above 1C with only moderate stress.
Apply the ultra-fast charge only when necessary. A well-designed ultra-fast charger should have the charge-time selection to give the user the option to choose the least stressful charge for the time allotted. Figure 3 compares the cycle life of a typical lithium-ion battery when charged and discharged at 1C, 2C and 3C rates. The longevity can further be prolonged by charging and discharging below 1C; 0.8C is the recommended rate.
FIGURE 3 CYCLE PERFORMANCE OF LI-ION WITH 1C, 2C, 3C CHARGE AND DISCHARGE
Charging and discharging Li-ion above 1C reduces service life. Use a slower charge and discharge if possible. This rule applies to most batteries.
Lithium deposition
Lithium deposition forms if the charge rate exceeds the ability by which lithium can be intercalated into the negative graphite electrode of Li-ion. A film of metallic lithium forms on the negative electrode that spreads uniformly over the host material or gravitates to one region in planar, mossy or dendritic format. The dendritic form is of concern because it may increase self discharge that in extreme cases can create a short and lead to venting with flame.
Environmental conditions affect the deposition of lithium as follows:
Consumers demand fast charging at low temperatures and this is especially critical with the electric vehicle. Solutions include special electrolyte additives and solvents, optimal negative to positive electrode ratios, and special cell design.
The question is often asked; “Why do ultra-fast chargers charge a battery to only 70 and 80 percent?” This may be done on purpose to reduce stress, but is also caused naturally by a lag between voltage and state-of-charge that amplifies the faster the battery is being charged. This can be compared to a rubber band lifting a heavyweight. The larger the weight, the wider the lag becomes. The ultra-fast charge forces the voltage to the 4.20V/cell ceiling quickly while the battery is only partially charged. A full charge will occur at a slower pace as part of saturation.
Lithium Titanate may be the exception and allow ultra-fast charging without undue stress. This feature will likely be used in future EVs; however, Li-titanate has lower specific energy than cobalt-blended Li-ion and the battery is expensive.
Nickel-cadmium is another battery chemistry that can be charged in minutes to 70 percent state-of-charge. Like with most batteries, the charge acceptance drops towards full charge and the charge current must be reduced.
All ultra-fast methods need high power. An ultra-fast EV charge station draws the equivalent electrical power of five households. Charging a fleet of EVs could dim a city.
Summary
All batteries perform best at room temperature and with a moderate charge and discharge. Such a sheltered lifestyle does not always reflect real-world situations where a compact pack must be charged quickly and deliver high currents. Such typical applications are drones and remote control devices for hobbyists. Expect a short cycle life when a small pack must give all it has.
If fast charging and high load requirements are prerequisites, the rugged Power Cell is ideal; however, this increases battery size and weight. An analogy is choosing a heavy diesel engine to run a large truck instead of a souped-up engine designed for a sports car. The big diesel will outlive the light engine even if both have the identical horsepower. Going heavier will be more economical in the long run. Below Table summarizes the charge characteristics of lead, nickel and lithium-based batteries.
TYPE Slow Charger
CHEMISTRY Nicd, Lead Acid
C RATE 0.1 C
TIME 14 HOURS
TEMPERATURES 0oC to 45oC (32oF to 113oF)
CHARGE TERMINATION Continuous low charge or fixed timer. Subject to overcharge. Remove battery when charged.
TYPE RAPID CHARGER
CHEMISTRY NiCd, NiMH,Li-ion
C RATE 0.3-0.5C
TIME 3 TO 6 HOURS
TEMPERATURES 10oC to 45oC(50oF to 113oF)
CHARGE TERMINATION Senses battery by voltage, current, temperature and time-out timer.
TYPE FAST CHARGER
CHEMISTRY NiCd, NiMH, Li-ion
C RATE 1C
TIME 1 HOUR
TEMPERATURES 10oC to 45oC(50oF to 113oF)
CHARGE TERMINATION Same as a rapid charger with faster service.
TYPE ULTRA FAST CHARGER
CHEMISTRY Li-ion, NiCd, NiMH
C RATE 1 - 10 C
TIME 10 TO 60 MINUTES
TEMPERATURES 10oC to 45oC(50oF to 113oF)
CHARGE TERMINATION Applies ultra-fast charge to 70% SoC; limited to specialty batteries.
Simple Guidelines Regarding Chargers
Everything You Need to Know About Wireless EV Charging
Most people whose phones can charge wirelessly wonder how they got along without it. We cannot overstate the value of not needing to worry as much about running out of power or finding a place to plug in.
Now think of having that same convenience for your EV. It’s not a dream. Wireless EV charging is already here, at least in some parts of Europe and Asia, and promises to be in the USA soon.
The global wireless electric vehicle charging system market is projected to exceed $825 million by 2027.?
Let’s review how wireless EV charging works, its features and benefits, and where the U.S. is at with adopting this technology. Then we’ll review major EV wireless charging industry players as of the end of 2022.
How Wireless EV Charging Works
Like your phone, wireless EV charging uses resonant electromagnetic induction to transmit electrical current, a process that is also known as inductive charging. Your phone has a magnetic coil inside that receives electricity from the magnetic coil inside the charging pad.?
Wireless charging for EVs works the same way, with a magnetic coil in the charger that sends current to a magnetic coil on the car’s underside. When the two pads align, charging begins.
Wireless charging for EVs is considered as efficient and fast as charging with a plug. For example, most EV plugs have 80-95 percent efficiency rating . According to WiTricity, a leading provider, their wireless EV chargers achieve 90-93 percent efficiency.
Wireless charging for EVs can also deliver up to 20kW of charging power, essentially a Level 2 charging speed, and there’s no technological limitation preventing higher speeds. However, supercharger-level speeds are not expected in the marketplace anytime soon.
The technology isn’t new; Qualcomm, for example, debuted the Halo system in 2012. But interest has increased in recent years with the growth in EV sales.?
The U.S. Market
Although wireless EV has a foothold in U.S. market, it’s not yet on par with Europe and Asia. American businesses and entrepreneurs are waiting for a reasonable volume of EVs equipped for wireless charging to be sold here.?
Currently, only one EV sold in America has wireless charging as a factory option – the BMW 530e hybrid sedan. Wireless charging provider WiTricity, which received a $25 million investment from Siemens in 2022, is developing licensing agreements that have reportedly drawn the interest of General Motors.?
There’s no lack of interest in wireless charging among American EV owners. When WiTricity questioned 1,000 current and prospective EV owners in the U.S., they found that 81% are very to extremely interested in EVs equipped for wireless charging.
Wireless EV Charging Options?
Wireless EV charging comes in two types: static EV charging, which is the most similar to what EV owners do now, and dynamic EV charging, which takes place on the open road.
Static EV Charging (Home or Office Charging Station)
Static EV charging simply means the EV is not moving while charging. Rather than plugging in, the wireless-equipped EV is parked over the installed wireless charging coil in the designated space.
Dynamic EV Charging (Roads and Highways)
Eventually, induction charging is expected to be built into the roadways so that owners can charge their EVs continuously as they go.? It will work similarly to regular wireless charging and is expected to operate smoothly at speeds up to 65 mph, allowing EV owners to drive long distances without having to stop for a charge or risk running out of power.
Not surprisingly, that will be a costly undertaking. The automaker Sellantis is already working on a solution to build wireless charging for EVs into certain roadways. In September 2021, the state of Michigan announced a partnership with Electreon to create the first wireless EV charging road in the U.S., a one-mile stretch in Detroit that will be available to the public when completed.
Wireless EV Charging Benefits
Although charging cables have advantages, they also have limitations. Wireless EV charging offers several benefits, particularly for commercial vehicles.
No Wires
By definition, the number one benefit of wireless EV charging is that there are no wires. EV owners do not need to carry heavy charging cables or plug their cars in at every charging station, alleviating range anxiety.
Lower Accident Risk
EV charging cables can become damaged over time, particularly in extreme heat and cold areas, which can be hazardous to the vehicle and its owner. No wires mean less risk, and replacing cables is expensive, too.
More Convenience
Wireless charging is simply more convenient, even when only available as static charging – and imagine the convenience if and when dynamic charging becomes a reality.
Save Time
Although wireless charging is no faster than regular EV charging, you save a little time by not having to get out of the vehicle to plug in, etc. And again, once dynamic charging becomes a reality, the amount of time saved on charging could be substantial.
Wireless EV Charging Infrastructure Costs
Plugless Power Plugless Power is currently the leading supplier of wireless charging solutions. They offer a third-generation wireless charger for about $3,500, plus installation. This will change as the market expands, but there are no projections on how much.
Major Players in the EV Wireless Charging Industry
Continental AG
Continental AG offers safe, efficient, intelligent solutions for electric machines and vehicles worldwide. For the EV wireless charging systems market, the company provides the AllCharge charging system and automated wireless charging solution. Continental AG focuses on innovation such as automated driving, connectivity, technology for future mobility, electric mobility (including EV wireless charging), safety technologies, infotainment systems, and agriculture.?
The company has several subsidiaries and a strong distribution network, giving it a significant presence across North America, Europe, and Asia.
Daihen Corporation
With ten sales offices and eight production facilities worldwide, Daihen is an electronics manufacturing company based in Japan. They produce transformers, solar inverters, power distribution equipment, welding machines, cutting machines, industrial robots, and wireless power transmission systems, among other products and systems.
Daihen operates through four reportable segments – Semiconductor & FPD Related, Welding & Mechatronics, Power Products, and Others – and provides wireless power transfer systems through its Welding & Mechatronics business segment.
Delachaux Group
Delaxchaux Group, headquartered in France, was established in 1902 and boasts worldwide clientele, including 50 percent of the world’s railways, two-thirds of the world’s seaports, and half of the planes now flying. Between subsidiaries and a strong distribution network, the company has a presence across Europe, MEA, the Americas, and APAC.
Delachaux offers brands such as Frauscher (Austria) in rail signaling, Pandrol (France) in rail infrastructure, DCX Chrome (France) in chromium metal, and Conductix Wampfler (Germany) in energy and data management systems. They operate in the wireless EV charging market through Conductix Wampfler.
Electreon, Inc.
Electreon, Inc. is a publicly-traded company in Israel that develops and implements wireless Electric Road Systems (ERS). They have developed intelligent road technology using a dynamic wireless electric system for transportation to reduce the need for heavy batteries.?
Electreon focuses on smart road technology, wireless energy, public transit, electric vehicles, E-mobility, and autonomous vehicles. They are presently conducting pilot projects on dynamic wireless charging in Israel, Italy, and Germany, among other locations.
ELIX Wireless
ELIX Wireless is a privately held Canadian company founded in 2013 to develop wireless power transfer technologies. They use magneto dynamic coupling to deliver safe and sufficient power for applications such as autonomous vehicles, warehouse and material handling robots, and automated guided vehicles (AGV).
ELIX Wireless provides solutions to buses and trucks, passenger cars, mining equipment, anti-idling, material handling, and industrial, medical, and subsea applications.
HEVO, Inc.
HEVO develops EV wireless charging solutions with three components: App & Cloud Sync, Power Station, and Wireless Receiver. The HEVO app shows nearby charging stations, monitors and evaluates charging statistics and bill payment status, and indicates charging stations’ availability.?
Headquartered in Brooklyn, New York, HEVO also maintains Silicon Valley, California, and Amsterdam, Netherlands offices.
InductEV (formerly Momentum Wireless Power)
Founded in 2009 in Pennsylvania as Momentum Wireless Power, InductEV develops high-power wireless charging solutions for electric vehicles. Their magnetic induction systems allow all-weather charging for EV batteries with fully automatic operations.?
Their solution is designed to charge city buses, commercial vehicles, auto fleets, and industrial vehicles.?
Mojo Mobility, Inc.
Mojo Mobility of California was established in 2005 to develop wireless power transfer technology. They provide solutions for applications such as mobile charging, wearable technology, automotive infrastructure, electric vehicle charging, consumer, and other applications.?
The company works with different technologies, including position-free wireless charging technology, multi-device integration, wireless vs. cord charging, and safe charging technology.
WAVE, Inc.
Wireless Advanced Vehicle Electrification, or WAVE, Inc., develops and manufactures wireless charging systems for electric buses with a capacity of up to 250kW.?
WAVE’s Salt Lake City depot can charge multiple vehicles automatically without manual valet work and moving plug-in chargers. The company specializes in wireless power transfer, inductive power, and electric cars. They were acquired in 2021 by Ideanomics, Inc.
WiTricity Corporation
Founded in 2007 in Massachusetts as an MIT spinoff, WiTricity specializes in wireless electricity, power transfer, charging, magnetic resonance, and electric cars and provides automotive solutions, engineering services, licensing, and support.
In addition to the U.S., the company has a presence in Europe, China, Japan, and South Korea through a network of subsidiaries and distributors.
Is wireless EV charging efficient?
Transmitting power through thin air seems like it should be vastly inefficient when compared to wired charging. And, to be clear, there is a loss of efficiency when you're talking about wireless charging, but it's hard to pin a specific number onboard.?
General wireless charging efficiency figures for devices like smartphones tend to be around 70 to 80 percent, meaning a significant 20 to 30 percent loss. When it comes to charging EVs, the numbers aren't so simple.?
Amy Barzdukas is CMO at WiTricity, one of the leading providers of wireless charging solutions for electric vehicles. She says that the company's wireless chargers have an overall efficiency of 88 to 93 percent, with the wireless transmission itself being between 96 to 99 percent efficient. "Because we use magnetic resonance with specially designed low-loss resonators to transfer power, the loss is very small," Barzdukas said in an overview of overall charging efficiency.
However, Barzdukas points out that your average, wall-mounted, wired charger typically delivers an overall efficiency in the 80 to 90 percent range. There are many variables depending on everything from cable type to manufacturer, but the important point is that wired charging is not necessarily much more efficient.?
It's also not necessarily faster to charge your EV using a cable. WiTricity offers speeds of up to 11 kW from the company's Halo wireless charger, which is close to the 11.5 kW output you'll get from most Level 2 chargers that support 48A as maximum output.?
That might mean an eight-hour wired charge would take an extra 20 minutes wirelessly, which is hardly a deal breaker if your car is sitting there overnight anyway.
What are the advantages of wireless EV charging?
The biggest advantage of wireless charging is simplicity. You park your car and walk away. Eventually, this could become so automatic that you forget you're even charging your car in the first place.
Because of this, you're more likely to partially charge your car in small doses, keeping your battery within the 20 to 80 percent charging range where it's most happy. Fewer, larger charging cycles do more battery damage than more frequent, smaller ones.?
Finally, wireless charging could also simplify public charger installation. While embedding chargers into parking spaces and the like could be expensive, maintenance could be easier than keeping cables and their connectors functional and operational in all weather conditions.
Does wireless charging have disadvantages?
The biggest concern with wireless charging is availability, which we'll get into in just a minute. Beyond that, a significant problem is cost. Some of the most popular residential EV chargers are available for under $400. While pricing for the company's home EV charger isn't available yet, WiTricity's Barzdukas told us it will "come at a premium to existing L2 chargers today."?
Expect to pay thousands rather than hundreds, plus they'll require modification of your car to install.??
Another disadvantage is heat. Wireless charging has the potential to generate additional unwanted heat during charging compared to wired charging. However, this is mostly only a concern in consumer electronics like smartphones. Modern EVs have advanced battery cooling systems that should mitigate this issue.?
Which electric cars have wireless charging?
Today, the answer is basically none. Plugless Power promised a charging solution for the Tesla Model S in 2016, but it has yet to deliver. BMW offered a wireless charging option for its 530e plug-in hybrid in 2017, but that was just a limited pilot program. Meanwhile, WiTricity has demonstrated its Halo working in numerous mainstream electric vehicles, like the Genesis GV60 and the Ford Mustang Mach-E. Still, that system is unavailable for consumer purchase.?
The news should get a little cheerier soon. When Ram introduced its 1500 Revolution concept electric truck at CES in 2023, it showed off a novel wireless charging solution. Instead of installing a charging pad on the floor of your garage or driveway, Ram's pad was motorized. The idea is that you park your truck and the charging pad scurries across the floor to start the charge.
That was a bit of a flight of fancy, but it shows that a major manufacturer saw wireless charging as a priority for the future, at least. WiTricity's Barzdukas told us it's coming soon, but not necessarily with trucks: "We think that some of these more vocal early adopters will lead to rapid growth, likely beginning with luxury brands, which is where new automotive technologies tend to be introduced first."
In the nearer term, WiTricity's consumer-grade wireless chargers will start in the low-speed vehicle, or LSV market. LSVs are a class of small vehicles that are closer to a golf cart than G-Class. They're popular in larger, age-restricted communities like The Villages in Florida. LSV's are largely electric, and WiTricity's solution allows owners to charge them wirelessly at home. This solution is slated to hit the market in the summer of 2024.
Can you wirelessly charge a Tesla?
At this point, the answer is also no, but that may change soon. In early 2023, Tesla acquired Wiferion, a European company specializing in wireless charging technology. Since that company had licensed WiTricity's technology, there was speculation that future Teslas might include the same wireless charging technology standard.
The new Cybertruck is also said to have additional connectors that might be used for a wireless charging add-on, so there's hope a solution might be coming soon.
Are there public wireless charging stations?
Since there really aren't any mass-produced cars available with wireless charging installed, it makes sense that there's no public wireless charging, either. With no clients to support, there's simply no infrastructure.
But it's coming. "We're past hoping for it, we expect it," WiTricity's Barzdukas told us. "By being able to install chargers curbside where people actually go, drivers will be able to grab “power snacks,” which is what we call short charging events in convenient curbside parking spots."
With any luck, once a few manufacturers start offering wireless charging in their cars, the market will quickly follow. Maybe then we can finally stop dragging dirty cables around every time we park and can instead just go about our business.
?
Battery Type
Technology for EV batteries must advance significantly to meet this demand. A good EV battery should be lightweight, affordable, safe, and long-lasting. It should also have a high energy density and a high-power density. The ability of a battery to hold energy is referred to as energy density. A gadget can be maintained and charged longer with a massive energy-density battery since it can store more energy . Cycle durability is also an important phenomenon in batteries. This is the number of “full” charge/discharges cycles the battery can tolerate before its capacity drops to under 80% in terms of its life cycle. If a battery is only 60% discharged and fully charged, it has not gone through a charge/discharge cycle. Depending on the battery type, the percentage may vary. The conclusion is that an EV battery shouldn’t have a short life cycle.
Table 2. Battery Types .
The battery’s memory effect describes a situation in which it retains the rate of its most recent discharge and won’t produce any more than that (even throughout a fresh charge/discharge cycle). Alternatively, the battery “remembers” how much of its capacity was used up the prior time and won’t supply it anymore. The memory effect is no longer a concern because of advancements in battery technology.
The discharge rate is the pace at which a battery expends or discharges energy. A high-discharge-rate battery is inappropriate for EVs since it cannot be utilized for extended durations while being charged. Numerous EV battery technologies exist; some are listed below:
When examined independently, Li-S has a rapid life cycle and a high discharge rate. Zn-Air is a “potential” future option for EV battery technology because its “theoretical/in-lab experiments” show a high energy density of 1700 W/kg, which is comparable to the conventional internal combustion engine . However, the major drawback of a Zn-Air battery is its low power density and short life cycle. However, it is still a prototype and not ready for purchase. Similar circumstances apply to Li-Air, which is still in the prototype stage and not yet on the market. For a detailed comparison of the various battery types, Lithium-ion battery operation’s temperature and voltage windows define the battery’s safe and dependable operating range. As electrolytes begin to self-destruct above 150 °C, going over these limits would quickly reduce battery efficiency and may even cause a safety consequence (e.g., trigger a fire or explosion) . The majority of EVs and PHEVs currently use this sort of battery.
Lead and zinc batteries perform worst in specific power (up to 100 W/kg), whereas Ni-MH and Li-ion batteries perform best (up to 1000 W/kg and 3000 W/kg, respectively). In terms of cell voltage, lithium-ion and sodium batteries (Na-S and Na-NiCl) need a higher voltage than batteries made of nickel and zinc. On the other hand, lead-acid and Ni-MH batteries provide the worst performance in terms of life cycles. Finally, whereas lithium batteries can sustain up to 3000 cycles, Na-S batteries perform better and can support up to 4500 cycles.
Since these battery types could increase the range of electric vehicles, further study is being done to enhance them. To guarantee the successful operation of electric vehicles, additional subsystems are included inside the battery system, such as a system to manage the batteries and an adequate thermal management system. When all the considerations are considered, current electric cars employ lithium-ion technology for their batteries since it performs the best across most of the analyzed qualities.
4.3.2. Battery Cost
Another EV difficulty that keeps it from succeeding on the market is the expensive price of batteries. Some key drawbacks of EV battery technology are a limited driving range, an expensive battery cost, prolonged battery charging time, unpredictable battery life, the excessive weight of EV batteries, and battery safety . As a result, a study should be done to create high-performance and affordable battery technology.
By 2025, battery costs are expected to drop by 70%, promoting EV adoption because of the high energy density. This is evident in the case of lithium-ion batteries (Li-Ion), whose price has drastically lowered because of their growing use in mobile devices and laptops.
4.3.3. Electric Vehicle Charging Devices
Most conventional electric vehicle charging devices are one-directional, making incorporating them into the system challenging. Nonetheless, this issue may be resolved using a bidirectional EV charger. Future “super-fast” direct current chargers are anticipated to be readily available in households, significantly reducing charging time . The smart grid may experience a decrease in load because of this advancement, and battery life may be extended. More study is required to advance this field, which also addresses EV battery technology, and overcome the EV charging problem.
4.4. Enhancing EV Charging Procedures—Battery Switching Stations
To lessen range anxiety, battery swapping stations might be utilized in place of battery charging stations. Standard, fully charged batteries are kept on hand at battery switching points for EV drivers to swap out and continue their trip quickly. In this way, EVs at a charge station along a highway can be changed immediately. The battery changing stations’ operational mechanism is depicted in . This technology of charging EVs instantly is already being used by Tesla and U.S. and European battery vendors .
Figure 7. The battery changing stations’ operational mechanism.
Most conventional vehicles can operate on any of the three fuels: petrol, diesel, and petrol, as shown by comparing traditional petrol stations and battery switching stations. Battery switching stations will need to handle a broad range of batteries, and they may run out of one type periodically. This might cause EV drivers to get anxious. Batteries come in various kinds: configurations, energy, and power densities.
EV drivers will be able to monitor the several battery types that are accessible thanks to smartphone applications developed by battery switching facilities. Even better, they may store extra batteries in advance to replace their exhaust ones. Giving the battery switching locations and the electric vehicle driver a communication platform can significantly reduce waiting times and eliminate range anxiety. This enables the driver to go beyond the usual velocity range of the vehicle.
However, this can present further issues for the battery switching stations, as they might need to keep many more batteries on hand to service clients, especially if some switch batteries numerous times daily. Multiple approaches can be used to solve this issue. The possibilities include limiting the number of swaps executed daily, adding a fee for each extra swap executed within a single day, penalizing customers for exceeding their daily limit, etc. As indicated, imposing fines may deter people from implementing EVs, so we need to consider which solutions are workable. Furthermore, the inconsistency of some battery types being available is another issue with battery switching stations. Due to the possibility that switching stations could not always have enough charged batteries it might be challenging to service all their clients/EV drivers .
An EV battery-swapping station operator must continually modify charging and swapping guidelines to account for changing energy prices and save operational costs. A novel queuing network model with a service quality guarantee was used by to research the optimal charging procedures for battery swapping stations. They also updated the model to incorporate battery swapping facilities and renewable energy in the power system to flatten the power generation curve by considering locations and billing orders. A charging regulation was devised by for EV battery swapping stations. They recommended a hybrid particle swarm optimization and evolutionary method to determine the optimum course of action. To investigate the optimal charging/discharging method for a vehicle-to-grid (V2G) technology-based EV battery swapping station that enables two-way energy transfer between EVs and the power grid, ref. created a Markov decision process model. It was demonstrated that the best course of action was monotone, making it possible to compute it quickly. According to the techniques for battery exchange suggested on a scientific level, ref. also developed an in-line routing system for electric cars that permits replacing the batteries in BEs using Markov’s random choice processes. This method would reduce the waiting time by about 35%. Ref. developed robust optimization models to help with the planning process for battery swaps.
In this regard, it is worth noticing that battery swapping technology has gained significant traction in China. One of the key players in this space is NIO, a Chinese EV manufacturer, which has implemented battery swapping stations across China. These stations are fully automated and use a robotic arm to remove the depleted battery from the EV and replace it with a fully charged one. NIO claims that the entire process takes less than five minutes, providing a convenient and efficient way for EV drivers to continue their journey. They have installed over 1323 battery swapping stations across China as of March 2023.
Another company, called CATL, has developed a standardized battery swapping solution that can be used across different EV models. This approach provides flexibility for EV manufacturers and enables them to implement battery swapping technology without having to develop their own proprietary solutions . Furthermore, a study by McKinsey & Company suggests that battery swapping technology could account for up to 30% of EV charging in China by 2030. The study also notes that battery swapping can provide benefits such as reducing the cost of EV ownership, improving the utilization of EV batteries, and reducing the need for large-scale charging infrastructure .
Given China’s success in deploying battery swapping technology, other countries could benefit from learning and adopting similar techniques. Battery swapping provides a convenient and efficient alternative to traditional charging methods, which could help accelerate the adoption of electric vehicles and reduce reliance on fossil fuels.
How to Charge and When to Charge?
Early batteries were reserved for commercial use only, such as telecommunications, signaling, portable lighting and war activities. Today, batteries have become a steady travel companion of the public at large to reach a friend, they allow working outside the confines of four walls, provide entertainment when time permits and enable personal transportation. Best of all, batteries help in missions when people are in need. Folks are eager to learn more about this wonderful portable energy device and one of the most common questions asked is, “What can I do to prolong the life of my battery?” Table 1 addresses how to care for your batteries to meet their needs. Because of similarities within the different battery families, the table addresses the needs and wants of only the most common systems by keeping in mind that these desires extend to almost all batteries in use.
Frequently asked questions
Lead acid (Sealed, flooded) Battery comes fully charged. Apply a topping* charge.
Nickel-based (NiCd and NiMH) Charge 14–16h. Priming may be needed to format
Lithium-ion (Li-ion, polymer) Apply a topping charge before use. No priming needed
2. Can I damage a battery with incorrect use?
Lead acid (Sealed, flooded) Always store battery fully charged.
Nickel-based (NiCd and NiMH) Battery is robust. New pack will improve with use.
Lithium-ion (Li-ion, polymer) Keep partially charged. Low charge can turn off protection
3. Do I need to apply a full charge?
Lead acid (Sealed, flooded) Fully charge every few weeks or months. Continuous low charge causes sulfation.
Nickel-based (NiCd and NiMH) Partial charge is fine
Lithium-ion (Li-ion, polymer) Partial charge better than a full charge
4. Can I disrupt the charge cycle?
Lead acid (Sealed, flooded) Partial charge causes no harm when applying periodic fully saturated charges.
Nickel-based (NiCd and NiMH) Repeat charges can cause heat buildup
Lithium-ion (Li-ion, polymer) Partial chargecauses no harm
5. Should I use up all battery energy before charging?
Lead acid (Sealed, flooded) No, deep discharge wears battery down. Charge more often
Nickel-based (NiCd and NiMH) Apply scheduled discharges only to prevent memory
Lithium-ion (Li-ion, polymer) Deep discharge wears the battery down
6. Do I have to worry about “memory”?
Lead acid (Sealed, flooded) No, there is no memory
Nickel-based (NiCd and NiMH) Discharge NiCd every 1–3 months
Lithium-ion (Li-ion, polymer) No, there is no memory
7. How do I calibrate a “smart” battery?
Lead acid (Sealed, flooded) Not applicable
Nickel-based (NiCd and NiMH) Apply discharge/charge when the fuel gauge gets inaccurate. Repeat every 1–3 months
Lithium-ion (Li-ion, polymer) Apply discharge/charge when the fuel gauge gets inaccurate. Repeat every 1–3 months
8. Can I charge with the device on?
Lead acid (Sealed, flooded) Avoid load if possible.
Nickel-based (NiCd and NiMH) Parasitic load can alter full-charge detection and overcharge battery or cause mini-cycles
Lithium-ion (Li-ion, polymer) Parasitic load can alter full-charge detection and overcharge battery or cause mini-cycles
9. Do I remove the battery when full?
Lead acid (Sealed, flooded) Charger switches to float charge
Nickel-based (NiCd and NiMH) Remove after a few days in charger
Lithium-ion (Li-ion, polymer) Not necessary; charger turns off
10. How do I store my battery?
Lead acid (Sealed, flooded) Keep cells above 2.10V; topping-charge* every 6 months.
Nickel-based (NiCd and NiMH) Store in cool place; can be stored fully discharged
Lithium-ion (Li-ion, polymer) Store in cool place partially charged
11. Does battery heat up on charge?
Lead acid (Sealed, flooded) Gets lukewarm towards end of charge
Nickel-based (NiCd and NiMH) Warm but must cool down when ready
Lithium-ion (Li-ion, polymer) Must stay cool or slightly warm
12. How do I charge when cold?
Lead acid (Sealed, flooded) Slow charge (0.1): 0–45°C (32–113°F)
Fast charge (0.5–1C): 5–45°C (41–113°F)
Nickel-based (NiCd and NiMH)
Lithium-ion (Li-ion, polymer) Do not chargebelow freezing
13. Can I charge at hot temperatures?
Lead acid (Sealed, flooded) Lower threshold by 3mV/°C above 25°C
Nickel-based (NiCd and NiMH) Battery will not fully charge when hot
Lithium-ion (Li-ion, polymer) Do not charge above 50°C (122°F)
14. What should I know about chargers?
Lead acid (Sealed, flooded) Charger should float at 2.25–2.30V/cell when ready
Nickel-based (NiCd and NiMH) Battery should not get too hot and should include temp sensor
Lithium-ion (Li-ion, polymer) Battery must stay cool and no trickle charge when ready
* Topping charge is applied on a battery that is in service or storage to maintain full charge and to prevent sulfation on lead acid batteries.