The EV 'charging conundrum'

This is where the input of electricity gets divided by the number of cars plugged in at a charging site wanting to charge.

ie. if you want a 350 kW fast charger, the site needs at least a 350 kW power feed. If it has say 500 kW feed, and two electricity-guzzling big EV's plug in, they get roughly 250 kW each. That extends the charging time for a mostly 'flat' EV by about 1/3 (so half hour out to about 40 minutes).

If four EV's plug in, each one will roughly get only 125 kW, so that blows out charging time to up to (or over) an hour.

And so on.

The BYD claim of a 5 minute charge doesn't explain where all the electricity will come from and how it will be delivered.

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ArishMell · 70-79, M

Interesting point.

Do multi-charger stations have some sort of automatic load-sharing that would give that effect? If not, their system would soon be overloaded - though I would expect they are protected against that.

zonavar68 · 56-60, M

@ArishMell tbh I don't know. But it's pretty obvious that if a public charging multi-car site has a 1 mW power feed coming in and 10 vehicles plug in at the same time, each vehicle can only get an average of about 100 kW.

You would not expect a single vehicle to take 500 kW and then only 'permit' the other 9 to get 50 ish kW each.

But at the end of the day, the *total* power than be delivered to all plugged in vehicles is limited to the max power that the site can draw from the grid, or it's solar/battery 'farm' if there is one.

ArishMell · 70-79, M

@zonavar68 Yes, I see that, but to achieve it would need some sort of regulation to balance the loads.

I don't know how they are in fact connected but I think it more likely the complete installation is designed so all the cars can be charged at full rates at the same time. The limit then is the number of chargers that can be installed, not set in operation by current-limiting on each charger.

While such load-sharing might be possible, it would be bad commercially by giving extra uncertainty. Already it's a gamble that you won't have to queue to recharge your car, but load-sharing would make the likely times uncertain.

I have been told of a large charging-station built in South-West England that cannot yet be used, because at busy times it would draw far more current from the supply than presently available. I don't know what the reality is there, but it would not surprise me. It's not National Grid's fault, but that of the charger owners not ensuring what is possible, first.

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