Zombie apocalypse? No worry! We’ve got a super-simple way to keep your devices charged in an emergency. We take a car battery, add some 12v receptacles, and hook in a power inverter to light up our devices.The total cost of this project will very greatly w/ size/quality of battery. My local Costco stocks a deep cycle group 24 battery for $80, $20 for battery box, figure another $20-30 for terminals, wire, and cigar lighter sockets.