Two car batteries and a power inverter for short trips. Or if camping for longer I take a small 2000 watt generator if in a place without power. It will run my whole camper too, quiet and very efficient.
I charge with an inverter clipped into the battery terminals on a truck. I have run the truck battery down more than once. So... I’ve found that I need to run the truck engine about half the ebike charge cycle— not ideal.