The 400V vs 800V is nominal voltage for both the output from the charger and the battery pack. There's some trickery I've heard about with switching half the pa

The 400V vs 800V is nominal voltage for both the output from the charger and the battery pack. There's some trickery I've heard about with switching half the pack from parallel with the other half to series while charging. But generally the voltage across the output from the pack will be equal to the voltage coming from the charger.