OK, I've decided to add a second battery to my 1980 F-150. I'll be wiring it parallel (pos-pos, neg-neg) and adding a battery isolator for protection.I want to power some accessories with the extra battery, cd player, extra lights etc. Can anyone give me some tips on where and how to mount the extra battery? I'd like something reasonably safe for off-roading and such.
Also, if I want to wire up this extra stuff to be used by the second battery, would I need to make a basic fuse box for the items? I've did the direct wiring to the positive terminal in the past (w/inline fuse) but I know that drains a battery after a while.
Hints tips and advise is greatly appreciated

Dave S

 

You have only one choice of the two in the above sentence. You can either wire it pos to pos and neg to neg, or wire it with an isolator. Looking at the goals you listed in the rest of your post, you will be going the isolator method. So forget about the pos to pos and neg to neg hookup.

If you use the isolator, the only connection between the two batteries will be a small charge wire, and this small charge wire will have the isolator hooked between the batteries("isolating" the batteries from each other).

An aux fuse box would be a great idea. Also go buy some Bosch type 30 amp foglamp relays. Anything circuit you want to be hot with the key on only, will run out of the aux fuse box, to the relay contacts, and then to the component to be powered. The small relay coil wires will run to a key on hot anywhere you can find it. This way it will not run down the aux battery if the key is off.

 

Hey Dave,
any ideas for an aux fuse box, or could I just get a factory model from the boneyard and use that? Which would be better though in your opinion, wiring in parallel or just using the isolator?

Thanks,
Dave

 

Wiring in parallel bascially does nothing but create one huge battery. You may be able to use this "battery" longer before it runs down, but you still never know how long you can use it with the engine off, and still be able to reliably start the engine. And the amount of time you could use it would change with the weather conditions, etc.

With the isolator method, you have the original starting battery that is always fresh and able to start the engine, and you have a specialty aux battery that is marine/deep cycle, that is designed to be run way down and then recharged with no harm. A regular starting battery cannot be run down and recharge very many times before it goes bad. With the isolator, the aux battery can be run completely down, and the truck will still have the fresh starting battery to start the truck. Then the alternator can charge both batteries when the engine is turning.

I woudl not use an OEM fuse box from the junkyard. It's too hard to deal with. Just go to the auto parts store or JCWhitney, and get a small one with 2 or 3 spots on it. You do not have to go crazy with the fusing. You just want something to open the circuit to keep a fire from happening. You could even buy circuit breakers if you wanted.

 

for fuse panels, local radio shack, or electrical store.