how to run dual batteries?

94STXRanger · May 1, 2008

So i will be acquiring a cheap Optima from work, it has passed its sale date and is now 'reconditioned'. So i want to put it on my truck just to run thinks like lights, cb, other misc. electrical items, and maybe a jumper battery if mine dies. So i was discussing how to wire it up to the system with my electronics teacher and we figured on running a cable from my normal battery to a heavy duty relay, and to the optima with say 6g wire, and just ground to the engine or a good ground. And then wire the relay just to a switch in the cab. This would allow me to charge the battery off of the alternator whenever, and also to seperate it to only what the optima is running.

Would this be how you guys would wire it up, so that you can have it seperate from the system and charge off of the alternator as well? Any advice would be great.
Thank you

High Desert Ranger · May 2, 2008

They make a dual battery box that can charge two batterys. Simple enough to wire up.

Then you could use a stock Ranger starter solenoid to connect the two together in event of primary battery failure.

mjonesjr · May 2, 2008

I have just the thing for you.

http://www.therangerstation.com/forums/showthread.php?t=16595

The isolators run about $140 by themselves.

Look at the second post. It is a dual battery Isolator. It allows you to run 2 batteries. Battery #1 is isolated so that if you drain battery #2, battery #1 will still have a charge to start the vehicle. Both batteries charge at the same time when the truck is running.

You want to run no less than 2AWG wire to the isolator and then from the isolator to each battery. Make sure you fuse the wire with 150A fuse or circuit breaker that goes from the alternator to the battery isolator.

shadetree · May 2, 2008

Your circuit will work just fine. Get a Ford starter relay from salvage, use standard gauge battery cables to attach to the 2nd battery, #4 will be fine. This is in case you do want to use it to jumper your truck. Starters draw huge amounts of current. Fuse the load side of the battery. 30 amps should be fine as you don't appear to be using anything to draw heavy current. Doing it this way will cost virtually nothing.

If you do decide to use loads that draw heavy current, such as apmlifiers, etc., starter relays will not hold up as they are meant for momentary contact. You want heavy duty relays (constant current) such as used on winches, etc. They look identical to the starter relays, and are connected the same way, but the windings in the relay are designed to keep the contacts closed without burning up the relay.

Battery isolaters are for heavy current loads, and where you want the system to be self sustained. There are several different models, but most are costly. You can make your own. There are several diagrams on the net.

Good luck with your project. shady

94STXRanger · May 2, 2008

So the circuit i described would work fine for charging the extra battery, starting the vehicle with them connected, and to isolate it and everything? If there are any problems with any of it let me know.

Mjones, i might be interested in that isolator, but what would be the advantage of all that over the circuit i layed out? Just curious what the benifits are for that thing, as i have never done this.
Thanks guys

mjonesjr · May 2, 2008

That isolater will isolate the primary battery. If the secondary battery goes dead while the truck isn't running, it will "isolate" the primary battery so the truck will still start.

The way you have it layed out, it will drain both batteries.

94STXRanger · May 2, 2008

i see. Would you take 25 for it

mjonesjr · May 2, 2008

No I can't take $25 for it. I paid close to $175 for the box and the isolator; that is what I am selling for $50.

94STXRanger · May 2, 2008

o shit well alright. Are you in a rush to get rid of it or could you hold on to it for a couple weeks?

mjonesjr · May 2, 2008

it isn't going anywhere.

igiveup · May 2, 2008

Hello

Get an isolator so you don't kill your new battery. Mixing new with old will kill your new one over time. Deppending on what your running (high powered amps, high powered lights ect) you might need a bigger alternator to keep up.

igiveup

shadetree · May 2, 2008

mjones said:
The way you have it layed out, it will drain both batteries.

Not if the remote relay is turned off. He only wants to have it on when charging the battery. shady

how to run dual batteries?

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