EV Charging basics - A Comprehensive guide

1. EVSE

1.1. What is EVSE systems?

ELECTRIC VEHICLE SERVICE EQUIPMENT or EVSE systems provide a safe transfer of energy between the electric utility power supply and the electric vehicle. PHEVs and BEVs require the EVSE in order to charge the vehicle's on-board battery.

With the penetration of EVs into the Indian automotive market, a corresponding penetration of this charging equipment will be required.

There are two basic options of charging infrastructure:

1. It can be connected to a central backend system via wireless internet, which is called "Networked" or "SMART" Systems.
2. Or it is not connected to any network, meaning that it is not connected to an IT system. This is commonly called "DUMB" System.

The "DUMB CHARGERS" or Un-Networked chargers are cheaper, but the "SMART CHARGERS" are functionally much better and absolutely safe to use for the electric vehicle battery (and a must for Lithium-Ion Battery)

The manufacturers of Dumb Chargers are switching to Smart Chargers (e.g., India). Fig below shows details of SMART Charger benefits.

1.2: BEV & PHEV TYPES OF ELECTRIC VEHICLES

We will focus on the engineering details of (1) BEV and (2) PHEV as these two configurations are relevant to understand the EV chargers.

1.2.1. Battery Electric Vehicle (BEV)

Some examples: Nissan Leaf, Hyundai Ioniq EV, Tesla Model S, Tesla Model X, Chevrolet Bolt, Volkswagen e-Golf, BMW i3.

How it works?

The BEV has no gasoline engine. There’s no fuel tank, no exhaust pipe, and no engine oil to change. These vehicles are at the extreme end of vehicle electrification and unlike all other configurations, they use a battery-powered electric motor drive system to drive the vehicle, 100 percent of the time.

BEVs are recharged via plugging into an electrical outlet or charging station, which restores the on-board battery. This is often built into the vehicle’s floor.

Recharging a BEV takes considerably longer than refueling a conventional vehicle. Depending on the type of charger used and the ambient temperature, a full battery charge can take several hours.

However, many newer BEV models offer a quick-charge function that enables a large, partial boost in battery charge in a short time - perhaps charging to 70 percent in just 30 minutes when plugged into a high-output quick-charge station.

In BEV, total driving range is considerably less than that of a conventional hybrid – though due to recent advancements in battery technology, higher range BEVs are being manufactured. As the driving range in a single charge is only a few hundred kilometers, BEV drivers need to be conscious of the availability of nearby charging infrastructure.

Most advanced BEVs and PHEVs recapture some of the energy used through regenerative braking that is using the electric motor as a generator during braking.

When regenerative brake is applied, BEVs can typically recover 5 to 15 percent of the energy used to drive the vehicle prior to braking.

Solar photovoltaic (PV) panels on vehicle roofs can also provide power to operate some small accessory loads (such as the radio) and help charge the battery.

A typical System Block of a standard BEV is shown in above Fig. Since the BEV has no other significant energy source, the battery must be selected properly to meet the BEV range and power requirements. These EV batteries are typically more than ten times as powerful as batteries used in conventional internal combustion engine (ICE) vehicles.

1.2.2: Plug-in Hybrid Electric Vehicle (PHEV):

The PHEV is a unique vehicle that fits somewhere between a hybrid and BEV.

Some examples:

Toyota Prius Prime, Chevrolet Volt, Hyundai Ioniq PHEV, Chrysler Pacifica PHEV, BMW i8, Ford C-Max Energi, Porsche 918 Spyder.

How it works?

PHEV functions like a regular hybrid, but with a major modification to its battery. Compared to a regular hybrid, the PHEV battery has a much higher capacity, so high, in fact, that a full battery charge cannot be achieved solely via the on-board charger and requires plugging into an electrical outlet or a charging station.

So, a PHEV is like a hybrid, but with additional battery capacity for extended all-electric driving. With a fully charged battery, a PHEV can typically drive up to somewhere between 25 to 50 kilometer solely on stored battery power, while the Chevrolet Volt can do more like 80 km. Once that range is used up, the vehicle works like a normal hybrid, until it is recharged again.

Plug-in Hybrid Electric Vehicle i.e. PHEV configuration operates on both battery and an ICE powered by gasoline, diesel, or other liquid or gaseous fuels. PHEVs have two main design configurations, a Series Hybrid, and a Parallel Hybrid.

2. EVSE Types

2.1: What are the basic Infrastructures of EVSE?

Just as there are different makes and models of combustion engine cars for different uses, there are various types of EV users who have different places they can charge at different times. EV infrastructure plan must consider these different users, as well as how to plan, zone, and legislate for the changing requirements of the future.

Each level of charging delivers different charging speeds. Different EVSE Charging configurations have a maximum charge power they can accept. Choosing the right EVSE Charger minimizes hassle and installation costs and maximizes electric car driving pleasure.

There are two type of Electric Vehicle Charger:

1. Internal or “On-Board” ChargerThe on-board charger is built-in inside the electric car. The On-Board Charger (OBC) controls internal power flow to safely charge EV battery.
2. External Charger or “EVSE”The charger with box-and cord device has a technical name “Electric vehicle supply equipment” or EVSE. The EVSE delivers power from the grid (or other source like solar panels) to EV’s on-board charger. Still, everyone tends to call the EVSE a “charger.”Fig below shows three types of basic charging infrastructure details. We will go into engineering details, design criterion, installation and commissioning infrastructure details of the different types of EVSE Chargers in coming Chapters.

There are three basic types of EV chargers. The electric vehicle service equipment (EVSE) refers to the AC charging source that supplies the charger in case of Level-1 & 2 and the DC Power developed by the Level 3 Fast Chargers which is delivered direct to the electric vehicle battery.

below is a tabulated data of EVSE type classification having details of power supply, charger power and charging time for a 24 KWh Lithium-Ion Battery Pack for Electric Vehicle use.