So I just finished installing my Kodiak dual battery system (Thanks to Kingpin for his install pics. Helped solve the debate between the battery module instructions which claimed the back post on the isolator went to the auxiliary battery and the main directions which claim it went to the main battery - fyi, it goes to the main).

I also have a Warn winch and I installed the positive cable to the positive terminal on the main battery. But where should I install the negative cable? I connected it to the negative post on the main battery but I am wondering if it should have gone to the negative post on the auxiliary battery. Or does it even matter?

The install took much longer than planned (there is no relatively 'easy' job that I am not capable of extending by multiple hours) so I haven't been able to test the winch yet.

(additional install note - if you are using a box wrench to tighten the connections on the negative terminal make sure that you don't accidentally touch the positive terminal with the other end of the wrench. Just saying.)

Doesn't matter. Grounds a ground. Regardless of whether it's on your main battery, aux battery, or on the chassis somewhere.

As for that install tip, it happens. All my battery's have side posts too, which makes sticking a wrench down there even MORE fun. Ha.

Thanks! That's what I had suspected but wasn't 100% sure and I've gotten in trouble with assumptions before though.

i would think it would work better being grounded on the same battery.

Why do you say that? His aux battery is likely connected directly to his main battery at the negative terminal which means it grounds to the exact same place. Only merit to your point I can see is for convenience if he has to swap something out everything is wired to the same battery.

IMHO this is smart concern. If possible I would keep the wiring as simple as you can.

for normal accessories that would work great. but you're talking about a winch, it could pull 400+ amps, its better if its not having to pull through all the cable first.

if it were me, id hook the winch to one battery, and everything else to the other.

I agree with you to an extent. As Philly mentioned, I like to keep everything on the aux battery just for less confusion, but in either instance the ground is at the same location whether he wires it to either battery. If he wires it to his aux then his aux is grounded via the main as well which means same distance to final ground. So, for performance it won't matter either way. It would bother me just for OCD purposes to have something wired on two different batteries, though.

Basically just keep the wiring for the winch as short as possible, and use the starter battery. Winches use a lot of power and the alternator will provide just as much power as the battery when the winch is running.

if the winch ground is on one battery, and the positive is on the other, the power has to go through the connecting cable, before getting to the winch.

unless hes using very heavy, expensive cables, there will be a loss. maybe not enough to notice, we have no way of knowing. but it will be there.

winches are no joke, they need to be connected directly to the battery, and NOT on sideposts either.

I agree with the first part but not the second. If he's running other accessories off the aux battery he should keep ALL accessories on the aux battery and leave the main battery for starting. If you want to leave the aux battery as a true backup/spare then wire everything to the main and only use the aux in emergencies. Putting accessories on both only increases your chance of failure at both.

That said, I run all accessories from the aux and leave the main for the factory intended purpose.

I don't think we're communicating effectively. The ground is at the same location no matter which battery. What you're talking is about drawing current from one of the batteries to power the winch. My point is that it doesn't really matter where he grounds the winch because the ground terminates in the same place whether it's on the main or aux. how he draws power from the battery is a completely separate issue.

Edit: Maybe I got mixed up at some point because I could have sworn he wired positive to aux. Sorry for the confusion. Your point stands as valid.

I would run the ground to the shortest route possible- most likely a chassis ground FWIW.

Like Jango said- ground is ground and the shorter the wiring the better.

he was asking where to wire the winch. all im saying is it needs to be connected to the same battery, both positive, and negative.


and to the above, i wouldnt ground the winch out at the frame.
it has a massive amp draw, you want as much power getting to the winch as possibe, and the best way to do that is connected directly to the source.

Why do you say this? Right now my winch is on the starter but when I rewire a few things I'm thinking of putting it on the AUX. My thinking is that I want my Main battery unmolested so that the truck always starts.