I run my 12V chargers in the house using one of the Car Jump Start packs with the jumper cables on it. Cost about $35 at the warehouse store. Also works at the field if you can't bring your car right up to the flight area.

I put a post out for kids who fly electrics on how to charge at the field when you can't bring your car. There are several different types of packs that can be carried on a bike or in a back pack.