Installing second battery

I have a deep cycle battery I want to install in the boot so my stereo / computer can run direct from it without draining the main battery. How do I wire it up to only charge when the car is running? It is only a 35Ah cell, and I will only be pulling about 15A with everything running. I was thinking of using a couple of 60A relays connected to the ignition and alternator warning light on the dash. So, when the ignition is on, but before I start the car, the alternator warning light is illuminated and there is no connection between batteries. It is not until the car starts and the alternator light goes out that it connects the main battery in series with the deep cycle for charging. Would the factory regulator handle this?

Noone has any suggestions at all????

And by the way, I meant 'in parallel' not 'in series' in the original post :)

The best thing to do when installing a second battery is to buy 2 of the same kind and replace you current car bat. as well. you can get kits on line all over the place with mounting brackets for the extra battery. all instructions included kits run around 100.00

not saying you have to do it but it is usally the best thing to do , get you kit and install it to the directions and you should be fine very easy to do

what would these kits be called..... can you give me an idea of where to look????

What you need is a battery isolator. It will monitor both batteries and give charge to the battery that needs it and balances the charge out between the two. The battery isolators wil run between $ 50 - $ 200 depending on where you purcahse and how high end you want it.Jeff

Velocity Custom Home Theater

Mobile Audio/Video Specialist

Morden, Manitoba CANADA

Ahhh, thank you very much :)