Wait what? How does the motor voltage affect charging rate? That's limited by the chemistry in the cells and perhaps heat dissipation, isn't it?
The confusion arises because a given DC charger can deliver twice as much power at 800 volts as it can at 400, assuming it's running at its max current. But that's a limitation of the charger, not the battery. This article has a brief discussion:
https://insideevs.com/news/512344/porsche-taycan-fast-chargi...
[ I used to work for a car company, programming battery charge controllers among other things ]
https://insideevs.com/news/519382/tesla-model3-82kwh-chargin...
Nope, the charging circuitry (most commonly) and/or BMS (less common) inside the car can handle this easily.
Sure, it's technically possible to do voltage conversion on the car side, but it either requires expensive and heavy hardware (A device that can convert 300 kilowatts from 400v to 800v isn't cheap!), or it requires funky use of the electric motor inverters and coils for voltage conversion instead - which in turn constrains the design and forces compromises.
In either case, you probably with have ~3% efficiency losses, which effectively increases the total energy bill for the customer over the lifetime for the car by 3%, which might be thousands of dollars.
Except the battery pack on the car is 300V to 400V depending on the model car, but the grid voltage is 120V (mobile charger) to 480V (Supercharger station). Some EVs are 800V even. So tell me again how the input voltage matches the battery voltage? ;)
The reality is that either the charger or maybe the BMS, either inside the car or elsewhere, is not only stepping up or stepping down the voltage to match the battery, but also rectifying the AC grid input into DC for the battery packs.
> In either case, you probably with have ~3% efficiency losses, which effectively increases the total energy bill for the customer over the lifetime for the car by 3%, which might be thousands of dollars.
There is more than 3% efficiency losses usually and some commercial charge providers handle that differently. Most directly expose the overhead by charging for “kwh used” whereas car shows “kwh stored in battery”, but Tesla does (or did until recently) just charge for what was “stored”.