Ive been thinking about a dual battery setup for a while and I just now thought to make a thread about it. Anyone running a dual battery setup? The reason I want to is I have a pretty killer stereo system and I already have an Optima yellow top and 200 amp alternator. All charge/ground wires are upgraded to 0 gauge wiring and im still having bad voltage drops and dimming lights. So I was thinking another battery would help out. So I have my interstate battery sitting in my garage with nothing wrong with it. How exactly would I wire up 2 batteries? How would the alternator charge 2 batteries?

 

Wire your batteries Positive to positive and negative to negative. That is called parallel. The Alt will charge them just fine.

 

Wouldn't there be a problem with doing this since I have 2 different batteries? Would one try to drain the other battery?

 

The factory has been doing it that way for as long as I can remember. Assuming you are starting with 2 fully charged and good batteries, the 2 would act as one.

I run 2 SLA Batteries (That is what your Optima is) wired in parallel in my shack. No problems to date and I have a fairly heavy current draw (about 40A) with all of my radios and station accessories up and running.

 

So I wouldn't need a battery isolator?

http://www.ehow.com/how-does_5005295...ator-work.html

 

You could certainly use one if you wished but it is not necessary. A battery isolator would be helpful if you were to have 2 separate circuits. 1 to run the truck on, and another to run your accessories on.

For what you are wanting to do, it is not necessary. If it were, I assure you, Ford would have one on every dual battery truck they sold.

 

40 amps ain't nothing, my lights alone can pull more than that. I do agree with the batteries in parallel, every Ford diesel truck is wired like that, actually if you go to a junkyard you can grab the whole setup from one of those trucks, battery tray and cables and all.

 

ok thanks for your help man. Ill hook it up as soon as I can.

 

I'm happy for you. I am talking about my radios in my shack with a float charger on the batteries. I wouldn't know what to do with that much lighting. How long will your battery support those lights with a 2A charger? How long will they support those lights when your engine is off and you ALT is not charging them?

BTW, 40A is a huge load when you charge with a float charger and need the batteries to work sometimes for days when the power goes out.

My batteries are 50aH and if I am not mistaken, that Optima is 55aH. Slightly larger then mine.
I just built a float charger for one of those Optima batteries that my club will be using as a battery back-up for our repeater.

 

All I meant is that even a factory two-battery setup will work good for much higher loads too. And honestly, I don't know what to do with that much lighting either I just had the lights so I put them on - I have four rear flood lights for backing up (cause I have a big topper and I can't see squat with the factory lights), my factory low beams are used as DRLs, my factory high beams are used as low beams, and I have four driving lights that I use as high beams. Why I have them reassigned like that - cause factory lights suck big time, I wanted something that has output comparable to the headlights in the newer vehicles, and no one makes Euro lenses with H4 bulbs for the "bricknose" truck body style that I have. So at any given day I'm using from 110W to 350W of headlights, and also 220W of reverse floods. The 400W overhead array I hardly ever use. And to tell you the truth, my 130amp alternator cannot keep up with the current draw when all lights are on... But I do agree with you that 40 amp is a very big load for the length of time you're preparing your radios to work if needed, IIRC my batteries have 200-something amp/hr reserve so 40 amps would drain them in right about half a day!