EV Fast Charging Explained: AC, DC and kW in 5 Minutes
Why does your car not always charge at the speed shown on the station? The basics of AC, DC, kW and kWh.
Motorway chargers advertise impressive power figures, yet charging is not always as quick as expected. Here is why.
AC and DC charging
A battery stores direct current. With AC charging, the car’s onboard charger does the conversion, so the speed depends on the car. With DC charging, the station converts the power itself, which allows much higher speeds.
kW and kWh: stop mixing them up
kWh measures energy (the size of the “tank”). kW measures power (the flow of the “pump”). A 60 kWh battery charged at 60 kW would, in theory, take one hour to go from 0 to 100%.
Why power drops near the end
To protect the cells, the car reduces charging power as the battery fills. That is why charging from 10 to 80% is the fastest part: beyond that, every percent takes longer.
- Arrive at the charger with a low battery.
- Precondition the battery if your car allows it.
- Leave at 80% instead of waiting for 100%.
Read next: LFP vs NMC Batteries: What Is the Difference for Your EV?
