Dual Battery questions.

telam · Feb 18, 2006

What's the best way to run dual batteries? I'm gonnna run them in both my Grand and my Wrangler. My wrangler will need them for winching and accessories, and My ZJ will just need it for accessories and as a utility truck. It will also be my DD. I'm back in school and broke. I'm all for building things myself. I prefer it. I just need a "jump start" (hehehe) in the right direction. I'm about to start an electrical course at school but I'm still very ignorant. Help a guy out? Thanks

idrivejunk · Feb 18, 2006

I mounted the battery behind the rear seat and it has worked great for six months or so. I used a batt. isolator and ran 1/0 wire to it and used an optima

Phaze · Feb 19, 2006

You COULD get technical and mount both batteries in the rear. Open the extra room up in your engine bay while you're going to the work of hooking them up in the back IMO. that way you can also pick up a dual batt enclosure online and make it look really clean.

JayH · Feb 19, 2006

My understanding is that batteries work/charge better when they're warm vs. cold.

I mounted a yellow top in place of the stock air box, a red top in stock position (rotated 90 degrees to make room for a second alternator,) an isolator under the windshield cowling, and a four way switch just behind the yellow top. Everything is in the engine compartment.

I have since heard that an isolator doesn't allow the alternator to fully charge a battery, but haven't (heard) any expertise to back it up.

Works great for me so far.

bchcky · Feb 19, 2006

doesn't optima's site specifically recommend against mixing a red and yellow top somewhere? i don't run a dual batt set up, but one of my buddies with a zj is looking into doing it, we've also found that it is wise to run identical batteries, and not to mix old and new.

JayH · Feb 19, 2006

bchcky said:
doesn't optima's site specifically recommend against mixing a red and yellow top somewhere?

dunno. I like to switch to the yellow when running winch, converted powered tools with the jeep off, and then back to the red for starting. Haven't had any issues so far and it's been about a year

RSL · Feb 19, 2006

bchcky said:
doesn't optima's site specifically recommend against mixing a red and yellow top somewhere? i don't run a dual batt set up, but one of my buddies with a zj is looking into doing it, we've also found that it is wise to run identical batteries, and not to mix old and new.

One of the biggest problems when running dual batteries is when people get cheap and hook them together in parallel with no isolation between the 2 batteries. What happens is the internal resistance is different between the 2 batteries and they "fight " each other and and start to lose their charge.
The best way, IMHO, to hook 2 batteries together is to use a constant duty solenoid to isolate the 2nd battery. Use a relay hooked to an ignition on source to trigger the solenoid only when the vehicle is running. You can also run a switch to trigger the solenoid manually in case you ever need to boost yourself if the primary battery goes dead.

telam · Feb 20, 2006

Can I build my own isolator? or am I getting in way over my head? to much work for the money and such.
What is the difference between a solenoid and an isolator, specifically? I have heard pros and cons for both.
Has anyone seen pics of a completely enclosed box for the batteries? I haven't found one. I thought I would since an electrical fire is a VERY real hazard. Thanks for all your posts.

Dual Battery questions.

telam

idrivejunk

Phaze

JayH

bchcky

JayH

RSL

telam

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