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econjo 12-27-2011 01:01 PM

Dual Battery Wiring/Alternator Questions
So I just got a winch and some lights that I am going to put on my 1995 2.5 YJ. I have heard some talk about needing an extra battery to run the extra power for the lights and winch. I have 8 lights that will go on there. Eventually I plan on running onboard air and a sound system as well.

So my questions are:
1. Do I need a heavier alternator for two batteries? ( i.e. mean green or something along those lines)
2. How would I wire in the second battery?

Any help would be much appreciated. I'm usually pretty good with wiring but in this case I want to make sure everthing is right so I dont fry anything.

Thank you!!

Timberwolf 12-27-2011 01:12 PM

mean greesns are probably overkill
you can swap in a higher amp alt from a gr cherokee
you want to upgrade all the wiring for it as well ( battery cables, grnds etc)

you can wire them basically 2 ways:

2 standard batt in parallel which will give more amps all the time. these should be identical batts of the same age
or wire a second marine type separately thru a switch or isolator which you attach the lights and winch to. it can also a serve as a backup for starting if the primary goes dead

there are a lot of write ups floating around for the specifics and diagrams

sevenservices 12-27-2011 01:24 PM

if interested you can get an A/B switch from a marine (boat) shop to switch back and forth. some of the newer ones can be wired up for bat. 1, bat 2 or both.

econjo 12-27-2011 02:43 PM

Could I use something like this to keep both batteries charged properly?

BSR Dual Battery Isolator Setup | Dual Battery Wiring Installation Setup

sevenservices 12-27-2011 02:51 PM

seems like it would work... never used one though.

Timberwolf 12-27-2011 02:52 PM

looks like a good option

ballistx 12-27-2011 03:10 PM

dual batteries and dual alternators
I don't have A/C so I utilized that location to mount a 2nd alternator. Used a Motorcraft with external regulator so I could get 120VDC. I don't remember just what I used for a mount. Will try to get a picture of it this evening when I get home.

I got two smaller batteries and installed in the location of the normal battery. One for the standard system and one for the winch. If you want to run the other lights you can install a separate fuse block and use it to wire whatever you want. You can run a continuous duty solenoid to the new fuse block and power it from the switch power.

I installed a solenoid between the batteries and powered it from a momentary switch under the dash. Then, if the main battery was dead, or weak, I can just flip the momentary switch and that parallels the batteries.

I have temporarily abandoned the system as I was not close to the Jeep. Will now re-establish it over the next few months.

The 2nd battery can also be used for an emergency welder if need be.

I like the idea of 2 separate systems. I had the issue of having the winch solenoids weld during a vicious snowstorm (60mph winds and snowing) and left me stranded in the middle of the blizzard with no power. No one could get close enough to jumper as we were trying to rescue stranded people so we were pretty well inaccessible. Proved the point that when it can't happen, it will.

econjo 12-27-2011 04:11 PM


Originally Posted by ballistx (Post 1863443)
I don't have A/C so I utilized that location to mount a 2nd alternator.

Do you need a different size belt in order to run a second alternator there?

ballistx 12-27-2011 08:10 PM

Yes, you need a longer belt, same ribs. The pulley on the alternator is smaller than on the compressor so it isn't that belt. Don't remember exactly. May be able to get the number off the belt.

here are some pics of the installation. Not pretty as I was working with some very limited tools. When I rebuild it now I will dress it up. All it is is two lengths of angle iron with the holes drilled to accomodate it and relieved across the middle. Put a strap across the top to protect from hitting the fins.

Hope this helps a little.

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