What is the best switch to connect a 2nd battery in parallell with battery on car for emergency jumps?

My car keeps draining batteries like crazy. Dealer can't fix it and it's not worth spending too much money on an old car. My solution is to connect a second battery (stationed in the trunk) via wires to the actual battery in the car and put a switch somewhere on my dashboard so that when I need to turn the car on i can switch the trunk battery on and basically jump the car without taking out the jumper cables. Does anyone know what specifications the wire and/or the switch need to work best with the 12V car battery? Or any switch with an On/Off position will do? What about the cable? Is any material better than others? Any help will be appreciated!|||what kind of car?


did you check the battery?


did you check the alternator?


did you check the regulator and diodes?


anyone check for a short or open circuit?|||Use a cable the same size as the battery cable or larger to connect the positive side and connect the negative side to a good ground like the frame with the same size cable. As far as the switch I would ad a heavy duty relay like a starter relay and just have a switch to turn it on.|||Here are some switches used for rv's.








http://www.rvadenver.com/electrical1.htm|||My 94 cavalier was doing this. It turned out that because the interior dome lights were burned out there was not enough draw on another part of the circuits to close a electronic switch after turning ignition off. Before I had a specialist look at it I had thought the draw was in the drivers door lock or drivers seat belt circuit. Taking it in let me stop disconnecting the battery each time I parked it and also let me re-connect seat belt wiring electrically and depend on the seat belt to function properly when the foot-break was applied..|||Get a rechargeable jumper, they are cheap and you don't need cables, or try to park next to someone, and you can take it with you when you sell your car, and cost less than all that other crap, batteries, 00 guage wire, relays, and switches don't come cheap and can cause more problems.