Just thinking about installing an alarm which its primary power source would be a small 12V battery (like the ones that come in a computer UPS). Would it be feasible to hook the power up to the fuse box of the car, in order to charge it? I don't want to hook it up directly. I want the battery to charge when the car is running. When the car is off, I want the connection to the main battery to be terminated. In this way, if the alarm goes "hay wire", it will only drain down the 2ndary battery, and not the main battery of the car. The only problem I can think of is overcharging the battery, because nothing is controlling its recharge rate. Thanks for any advice....

 

It's possible but probably not worth it.

You'd need a secondary 12v battery or higher voltage battery with a 12v regulator circuitry, that can sustain the alarm for however long you need. Then you'd need a custom charging circuit (not really that hard to find by searching around the internet).

hope that helps

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