Battery Master Switch w/Key (1 Per Quantity) Waterproof single battery master switch is UL rated. Key is detachable therefore the switch also serves as an anti-theft device. Max load (10 sec.): 12 volts 1000 amps; 24 volts 500 amps. Max continuous rating: 12 volts 50 amps; 24 volts 25 amps.