seafarinman

I was wondering what would be the best way to hook up a dual battery setup. I have a pair of Optima red tops with one in the bed of my truck in a marine battery box. I have seen the isolators, so would I just disconnect the alternator lead from the battery and connect it to the isolator input, and run separate leads to each battery? If I did this, what gauge would be required? Also where can I get those heavy duty grommets for running the cable through the floor of my bed? Has anyone done this?

Salue

When I had the dual battery setup on my '87, I followed Joe Chacon's write-up. It seems that his site is no longer available, at least I can't get to it. But, the way he did it and the way I followed did not have an isolator. So it was just two batteries wired in parallel with a main switch between the Positive wires so that when I didn't want to drain from the main battery, I just turned the switch so that it wouldn't drain from it and only drain from the accessory battery. Then when I wanted to recharge the acc. battery, I'd turn the switch so that it would get current when driving and would recharge both batteries. I don't think this is the best way to do it but it was the easiest. I know that if you do it this way, the less charged battery would take some charge from the higher charged battery until they were about even. I think you going the isolator route is better. I would like to do this to my '94, so keep us posted. Have you considered putting the extra battery in the engine? I'm considering doing this by doing the intake mod in the tech section but altering it a little so that I would have a spot to put the second battery where the air filter currentl lies.

Whatever you do, please take pics.

Salue

Cebby

For an isolator, do what you said, run the alternator wire to the isolator. Then run wire to each battery. 4 Ga. should be more than adequate. If you still have your stock alt that is. If you have a hi-amp model, the alt to iso wire might want to be 2Ga or 1/0. Be sure to fuse the wires with the appropriate value fuses.

Here's a link for
snap in bushings.

These are what I use when passing through metal. They make a ton of different sizes. The snap right in, then I hit the wire with a little silly cone to make it watertight.

MNBOY

I'm not sure it is the best way, but I'll explain how I have mine set up. I have a cap on my truck with interior lights and a 12v plug for running a small TV or laptop. (I live in my truck for days at a time while in Moab or similar places) The lights and such are run off a second battery mounted in the bed, which is connected to my main truck battery with 2 ga. battery cable and a high voltage on/off switch. This way I can turn the switch to on if I want some extra power while running the winch, but it stays separate from the starting battery. The secret to keeping the second battery charged is a little device called a battery combiner. I work in the marine industry, and these are pretty common on larger boats that run multiple batteries. The combiner installs between the two batteries, and only charges the second battery after the first is back up to a certain voltage, meaning your starting battery always has enough charge to start the truck. It's kind of like an isolator, but the isolators have a large voltage drop that prevents the alternator from ever fully charging either battery. I think the only place to get the battery combiners is at a marine store called West Marine, but they have a reasonably priced model that works great with stock alternators.

partszar

I'm not sure if this is what your thinking about but I saved the picture for reference material incase I wanted to put a aux. battery in my bed. I have a cap on my truck.

jruz

One other suggestion...for the extra battery, use a deep cycle battery such as the Optima Yellow top. That way, when you run it 'til its empty (watching TV or whatever you do), it will come back alive without a problem. Frequently draining a Red top over time will kill it a lot faster.

Jim

Cebby

Isn't that diagram the one that was blowing fuses? I remember that thread, let me see if I can find it...

Cebby

Here's the thread.

914runner

I am thinking of adding a second battery for some acc. I will be adding later on. Would someone please tell me what parts I would need other than a second battery and wire(not sure what guage though)?
Thanks

seafarinman

Thanks for all of the info. I am planning on cleaning up the wire "forest" on the + terminal of my battery, with only the winch, stereo, and the original circuits running from the main battery. I want to run all of the accessories from the "rear" battery- Off-road lights, 800W/1100W inverter, bed mounted outdoor 115V receptacle, 200W tripod worklight, canopy lighting, and other accessories, etc. I think that I will look into installing the inverter. Does it need to be close to the alternator/main battery? I was looking under the hood and space is awful scarce there! Thanks again everyone.

codlord

Regarding the "diagram that was blowing fuses" that was mine and it certainly was blowing fuses, however I have since sorted the problem (sorry forgot to update the thread). I have updated details on my site:
http://www.showmesome.info/hilux/workshop/battery.htm

Basically I used 35 amp wire and a 35amp fused relay and all is fine now (although I would have my doubts wether the system would cope with the draw from a winch or something like that but thats not an issue for me).

I read that you should NOT use very heavy guage wire between the two batteries (in this sort of relay-based system) becuase this can allow a large flow of electricity between a discharged battery and a charged battery - better to use smaller wire so that you get a trickle charge.

Cebby

If Rome goes the isolator route, it will be a non issue. Thanks for the update.