Quickcharging an EV, how much power do I need?

There are two points on which people criticise Electric Vehicles (EV):

  • Their range
  • The time it takes to charge them

The first can be solved by ‘simply’ adding a larger battery, this can be in physical size or having more Wh’s (What Hours) per Kilogram.

Filling the tank of a car with a ICE (Internal Combustion Engine) takes about 3 minutes, it is something we are used to. But charging a EV can take up to several hours.

A lot of people say that they will start driving an EV as soon as the range gets better or charging can be done fast, like they are used to right now.

Charging a EV really quick has a few problems which can not be solved that easily:

  • The batteries can’t be charged that fast (Yet)
  • It takes a lot, really A LOT of energy to charge that fast

Take a Tesla Roadster for example, this car has a 53kWh battery pack. 53kWh equals to 190800000 Joule (53 * 1000 * 3600). If we want to charge this battery in 5 minutes, we would need to put 636000 Joules per second into that battery. 636000 Joule equals to a current of 636kW (636000 / 1000).

A simple micro-wave in your kitchen uses about 1kW of energy, charging a EV that fast would use the energy of 636 micro-waves! That would put a lot of stress in the grid, too much stress.

If we charge the EV in 10 minutes we would ‘only’ require 318kW of energy, 20 minutes 159kW and 30 minutes would take 106kW of energy. Those are still high numbers, but they come closer to what is possible.

Take the Nissan Leaf for example, this car has a 24kWh battery which can be charged to 80% in 30 minutes, let’s calculate how much energy we would need.

80% of 24kWh is 19.2kWh, that equals to 69120000 Joule (See my calculations above). 30 minutes equals to 1800 seconds, so charging in 30 minutes requires 38400 Joule per second, or 38.4kW of energy.

Charging that quick will mostly be done at 480 Volt. 38400W / 480V = 80A, that is how much we need to charge a Leaf that fast.

3-phase 480 Volt is not that hard to find / get here in Europe, so charging a Leaf that fast is feasible on a lot of locations.

Not only will quickcharging put a lot of stress on the grid, it would also be unsafe for humans to connect such cables. If the current which flows through that cable would be exposed to a human, you would instantly be killed, no doubt.

Quickcharging a EV has a few drawbacks, let’s sum them up:

  • Bad for the battery

  • Puts a lot of stress on the grid
  • It would be very dangerous for humans to handle such cables

But why would we want to do that? A EV can be charged everywhere! Your car will be parked for most of the time during the day. Those are all possible charge possibilities, we should work towards utilizing those moments. Ofcourse, there will be some places where quickcharging will be possible, but I think they will be placed on strategic locations like road-side restaurants.

I think we need to let go of the concept of filling up our car within a few minutes. In the future battery technology will improve and we will start to see battery packs ranging from 75kWh to 150kWh, which will bring us where we want to go, charge there and get back again.

Published by

Wido den Hollander
