ssnip

Just looking for a cheap and simple way to use the spare battery
without any major electrical surgery to the car or caravan.

Charge it when the car runs, not when it isn't. The latter gains you
nothing.

Yes, I am intending to charge it when the car is running; I don't want to
flatten the car battery.
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AMD FX-6300 in GA-990X-Gaming SLI-CF running Windows 7 Pro x64

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