Cody Hatfield

Using Maximum Charging Power to Evaluate Electric Vehicles

A common metric that is used when comparing how fast electric vehicles charge is the maximum charging power. This is measured in kilowatts (kW) and is the maximum power a vehicle can receive while charging.

Let's explore how well this metric may or may not help people understand which electric vehicles are more or less convenient to charge.

Pro: Simple and easy to understand

A single number is used for each vehicle and the scale is linear. 200 kW is twice as fast as 100 kW. This is simple for the human mind to understand.

Pro: Battery size does not matter

Compared to some other metrics, the size of the vehicle's battery does not matter.

Charging at 100 kW for ten minutes will result in the same amount of energy being added, regardless of the battery's size and range.

Con: Not familiar

Unlike time and distance, power is not as familiar to many people. It can be difficult to put this metric in perspective with other concepts in our lives.

Even where power is familiar, it is hard to relate to it at this scale. An efficient light bulb may only use a few watts, but what the heck is 250 kilowatts?

Con: Efficiency is not taken into account

This metric does not, however, put a vehicle's efficiency into account.

Two vehicles that charge at the same power for the same amount of time will have the same amount of energy added. This energy will result in a different amount of range for each vehicle depending on its efficiency.

An alternative metric that does put efficiency into account is range replenishing speed.

Con: Max power is rarely achieved in practice

Most vehicles actually rarely achieve their maximum charging power. Even if they do achieve it, it is only for a brief amount of time.

The average charging power and time it takes to charge from 20 to 80 percent are alternative metrics that try to acknowledge this limitation.

Con: Difficult to compare to other fuels

Maximum charging power also means nothing when comparing to how quickly an internal combustion engine (ICE) vehicle refuels.

This metric is limited to only comparing electric vehicles and not with alternative fuel vehicles such as gasoline or fuel cell.

The time it takes to charge from 20 to 80 percent and range replenishing speed are easier to compare with alternative fuels.

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Copyright © 2021 Cody Hatfield