Let's assume worst case, 163 Volts down to 138 Volts at 400 Amps. (In reality, a resting voltage is artificially high and you really should use 2 different currents and two voltages, like 200 Amps and 400 Amps). Also, going down to only 138 Volts is pretty good.
(163 Volts - 138 Volts) / (400...