ChargeGuards are specifically designed for installation in vehicles that have power-hungry accessories that
will kill the battery if left on overnight with the engine off. This specific model is easily configured
to operate on either sensing the alternator running or via a line from the "accessory" circuit in the car.
They have a configurable timer, and if the engine stays off for some set amount of time (like 15 minutes),
it'll turn power to the accessories off. It also has an override button to turn power back on or trigger
an immediate shut-down. (and you can even mount an external switch in a more convenient location!)
I've found the ignition sense to be unreliable though, especially in cold weather. I suggest configuring it
to operate from the accessory line so it will work more reliably.
These are constantly showing up cheap on eBay as police cars, ambulances, and other state vehicles are being
taken out of service and stripped before selling. These service vehicles all have power-hungry radios and
other electronic systems that can easily kill a battery and disable a critical vehicle if not protected, so
they ALL have charge-guards installed. When the auction house is stripping the cars for sale to the public,
these end up listed on eBay. $20-35 (shipped) is a fair price.
