The Hybrid inverter system has a DC-DC converter section that converts the hybrid battery 288 volts DC to 12 volts DC to charge the 12 volt Auxiliary battery. The DC-DC converter's job is to keep the 12 volt battery always charged when the ignition is on.

Thus, the 12 volt battery is charged directly by the inverter and the inverter uses the 288 VDC hybrid battery as one of its power sources. If the hybrid battery charge level becomes low while in ready mode in park (not neutral) the engine will automatically start and stop to use MG1 to maintain the hybrid battery charge level.

There is a 120 amp fuse between the battery and the inverter so this is an absolute max limit to the charging capacity of the Dc-Dc converter. I don't know the continuous rating of the DC-DC converter though 50 amps would appear to be conservative considering the load with all accessories, lights, seat heaters, blower fans, and rear window defogger all powered simultaneously.