Hello, I am thinking of connecting my small gadgets (Bttf speedometer, ThinkGeek flux capacitor, GPS, etc.) to a secondary battery, instead of using the main battery and the car`s cigar lighter adapter. I would mostly use it when I am on a veteran car meeting or a comic-con, so the car is just parking for several hours and the engine is switched off.
Can you recommend a battery that would fit in the glove box (or in the compartment behind the driver`s seat)? What would be the min/max technical requirements? I had some universal 6V batteries (4 Ah) at home, connected 2 of that and did some initial testing: it worked well, but after a few hours it killed the 1 Amp fuse of my Garmin GPS. I guess I`d need something more sophisticated here.