I'm building a bit of any odd hybrid system that involves a small capacity 20S battery pack installed in a vehicle that is continuously trickle-charged by the cars existing 12V infrastructure. I've been able to isolate every other aspect of the "HV" system but don't know how I can charge while maintaining galvanic isolation. A traditional boost converter will link chassis ground and HV negative which is what I am specifically trying to avoid. I have a BMS to balance all the cells and prevent under/over voltage. I just need to figure out a way to step up ~12V to 80V with about 200W of power without sharing a common ground. Any suggestions would be welcome!