How to Figure EV Charging Times

Recently, my brother-in-law reached out for help choosing a charging station for a Prius Prime. He was under the impression that purchasing a high-amperage charger would significantly speed up the charging process and didn't know that the car might actually be the limiting factor. This inspired me to share some insights on estimating charge times effectively, especially for those new to the electric vehicle (EV) scene or considering making the switch. Let's dive in!

Charging an electric vehicle (EV) might seem straightforward, but there's more to it than meets the eye. The time it takes to charge your EV can vary significantly based on several factors, so it's important to understand how to estimate charge times effectively. Let's dive into the essentials to demystify the process and ensure you get the fastest charge possible.

Forget Hours, Think Miles:

Traditionally, we've grown accustomed to expressing charge times in hours from "empty" to "full.“ However, this method isn't always practical since most EV drivers don't run their batteries down to zero. Instead, it's more useful to consider the miles of range added per hour of charging.

Factors Affecting Charge Time:

Several factors come into play when determining how long it takes to charge your EV:

1. Battery Size: The energy stored in your vehicle's battery pack, usually measured in kilowatt-hours (kWh), directly impacting the EV's range.
2. Charging Station Output Power: The amperage (A) and voltage (V) of the charging station determine the maximum power (in kilowatts) it can supply to your EV.
3. Battery Acceptance Rate: The maximum power your EV can accept from a charging station is a limiting factor in the charging process.

You can find detailed information on your EV's specifications like battery size and acceptance rate in the owner's manual or on the manufacturer's website. Additionally, Enphase has a charging station selector tool on its website that gives this information. Navigate to https://enphase.com/ev-chargers/find-an-ev-charger and choose your vehicle's make and model. The tool will return results for a suggested charger based on the closest match of power to the acceptance rate, but it also gives information about the vehicle. The first image below shows where to click and expand to locate the information for your vehicle; the second shows an example of the information you will find on the tool.

Example: Chevy Bolt vs. Charging Stations:

Consider the 2020 Chevy Bolt with a 7.2kW acceptance rate. While a 32A IQ 40 charger adds around 24 miles of range per hour, upgrading to a 40A IQ 50 won't speed up charging due to the Bolt's acceptance rate limitation. Opting for the IQ 40 ensures the fastest possible charge.

Calculating Charge Times:

To estimate charge times:

1. Determine the charging station's output power by multiplying its voltage and amperage, then converting the result to kilowatts.
2. Divide your EV's battery pack size by the lower limiting factor—the vehicle's acceptance rate or the charging station's output power.
3. Calculate the miles of range added per hour by dividing the total range of the EV by the hours to a full charge.

For instance, using an IQ 60 charger with a Tesla Model 3 Long Range (acceptance rate of 11.5kW) and a 75kWh battery pack:

• Charging Station Output Power: 11.52kW
• Hours to Full Charge: 75kWh / 11.5kW = 6.52 hours
• Miles of Range Added Per Hour: 310 miles / 6.52 hours = 47.5 miles

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Future-Proofing Your Charging Solution:

While selecting the optimal charger for your current EV is essential, considering future needs is also wise. Purchasing a high-powered charger like the IQ 60 for your Chevy Bolt may not allow for faster charging. However, it opens doors for future possibilities. Imagine a scenario where a friend with a Tesla visits—they'll undoubtedly appreciate the speedier charge rate provided by your robust charger.

Moreover, as most EV owners gradually replace other internal combustion engine (ICE) vehicles in their families with EVs over time, the landscape of acceptance rates may evolve. With each new addition to your EV fleet, there's a chance of acquiring a vehicle with a higher acceptance rate. By investing in a powerful charger upfront, you're future-proofing your charging infrastructure, ensuring it can accommodate the evolving needs of your electric vehicle lineup.

As time progresses, the likelihood of EVs featuring higher acceptance rates increases. By anticipating this trend, you can make a strategic choice today that pays dividends in the future. So, while you're enjoying the convenience of fast charging for your current EV, remember that your charging station investment is also paving the way for tomorrow's electric mobility needs.

Conclusion:

Understanding the intricacies of EV charging can optimize your charging experience and ensure you get the most out of your electric vehicle. By considering factors like battery size, charging station output power, and acceptance rate, you can make informed decisions to achieve faster charging times. So, the next time you plug in your EV, remember to think in miles, not just hours.

Please contact me if you need clarification on your EV's specs or assistance choosing the right charger. I’m happy to help or put you in touch with someone who can.

Happy charging!

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