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I have understood that most EVs have 400 volt batteries, but some newer EVs that can support fast charging rates have 800 volt batteries.

EVs can be charged in two ways: either by AC charger with charger in the car which is typically either 3.6 kW, 7.2 kW, 11 kW or 22 kW for European voltage standards (1-phase 16A, 1-phase 32A, 3-phase 16A, 3-phase 32A), or by fast charging where the charger is not located inside the car but rather in the fast charging station. Fast charging is DC where the car communicates its desired electrical parameters to the charger, and the charger supplies DC to the battery.

I also have understood that the 800 volt EVs can still be charged on a 400 volt fast charging station, but not at the same fast rates that 800 volt fast charging stations could support.

But how is the charging of a 800 volt battery on a 400 volt charging station implemented?

One possibility would be to first charge one half of the battery, then the other half of the battery, but the battery would go out of balance.

Another possibility is to alternately charge one half, the other half, one half, the other half, in 1-second long pulses for example. Is this how 400 volt stations charge 800 volt cars?

A third possibility would be a huge DC-DC converter inside the car that can convert 150-200 kilowatts of 400 volts into 150-200 kilowatts of 800 volts, but I cannot even imagine the size, expense and weight of such a monster.

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