Sneaky Bastard

Problem: The car battery keeps dying because the refrigerator draws power overnight. A typical automotive battery is made to put out a lot of amps quickly at engine startup, and then be charged up again by the alternator. It can’t handle long periods of moderate use.

Solution: Put a deep cycle battery into the vehicle. This type of battery can handle the long drain, and it’s separated from the battery under the hood by an automatic isolation switch. When the engine is started up in the morning, it will recharge the deep cycle battery.

PowerStream has a 12 VDC 80 amp solid state isolation switch for this application: PST-SSB2180. A Trojan 27TMX deep cycle battery would provide 105 AH at a reasonable load. The isolation switch is $85; the battery is about $175 and weighs about 55 pounds. Battery Systems in Oxnard carries Trojan, so hopefully it won’t need to be shipped directly.