Winch wiring suggestions with dual batts

tremors834

Adventurer
I have a dual battery set-up installed. All systems in the truck are off the main battery.
The main battery is under the hood. The Aux battery is in the rear. The batteries are isolated via a solenoid.
Typically the batteries are only connected/joined while the engine is running and able to charge the batteries.
I can overide the system and disconnect or connect the batts at anytime, for instance-should the main battery become depleted I can jump start the main battery from the aux battery if needed.
Now I want to wire in a winch. Should I wire it to the main battery?
If so, do I keep the aux battery isolated from the main battery while winching or have the winch drawing from both at the same time?
Thoughts?
 

Antichrist

Expedition Leader
If it were me I'd use the battery in the rear as the main battery, and the battery under the hood as the winch battery, and wire it so the winch only draws from the winch battery.

This allows keeping the cable from the rear mount battery smaller (starter doesn't draw as much as a winch) and you don't have to worry about being too aggressive with your winching and killing both batteries. Your starting battery will always be good.
 

cruiseroutfit

Supporting Sponsor: Cruiser Outfitters
I used to be under the beleif that I should 'split' the loads, ie putting long drain items fridge, etc) on my aux. deep cycle battery and others on the start. National Luna recommended otherwise and I've come to agree with their logic. So in my latest personal install (04' DC Tacoma) I have 100% of the leads on the main battery including the winch, fridge, etc with the aux truly serving as a backup. If/when you have a main battery failure, you have the aux. If you've got loads coming off of either the chance of two deads is a possibility. Now, the NL Intelligent Solenoid is the key to this operation, it keeps that aux. battery charged and provides you with an incab winch overide so you can manually pair up the battery for high demand needs.
 

ntsqd

Heretic Car Camper
My own logic is to put all of the loads used with the engine off on the aux battery (radios, fridge, stereo, camp lighting, etc.). Leave the main battery for running the vehicle. I fully acknowledge that this still leaves me possibly in the position where both could be flat. However, my whole reason for a second battery is to support those drains that are not original to the vehicle, not as a back-up starting battery. In essence I'm holding the original starting battery in reserve. If the main goes flat then I've over-looked some predictable failure mode.
 

keezer37

Explorer
Depends on your priority. If being able to crank the engine is your first priority, then I would isolate it and abuse one battery for everything. This is what I do.
Not shown is a dash mounted switch that has charge/combine/isolate positions. Also my 1AWG from the isolator goes direct to the starter.
I've had this setup for four years now. I've changed out the OE battery in Jan. '09. The aux did cranking duty for about a week during that time with the OE removed from the truck. It was fairly cold, low teens if I recall.
DualBattDrawing.jpg

Disclaimer: No winch.
 

dwh

Tail-End Charlie
I agree. Leave the engine battery for the engine, and put everything else on the aux battery. If you are going to run a battery dead, it's best to be able to start the engine so you can recharge.

With an isolation solenoid, when the engine is running the batteries are tied together anyway, which is the situation you would want when winching - i.e., both batteries tied and the engine running for maximum potential amps available.
 

Antichrist

Expedition Leader
I agree. Leave the engine battery for the engine, and put everything else on the aux battery. If you are going to run a battery dead, it's best to be able to start the engine so you can recharge.
Yes, the point of my (and others') post.

With an isolation solenoid, when the engine is running the batteries are tied together anyway, which is the situation you would want when winching - i.e., both batteries tied and the engine running for maximum potential amps available.
The problem with connecting them when winching is that it defeats the purpose of always keeping your starting battery "safe".
If you want to hook them up like that, I'd wire in a normally closed relay to control the solenoid that opens when you power on the winch.

I should also add that it could also depend on how you travel.
- If you always travel with others then it probably doesn't matter if you don't isolate your starting battery as you can get a jump.
- If you travel alone, I highly recommend keeping your starting battery safe.
 

tremors834

Adventurer
Thank you everyone, all great points. I'll ponder it over the next few days.
Since everything so far has been wired off the main batt, I think I'll just leave it that way. I am guessing you should shutdown any un-needed systems while winching anyway??
Currently lighting, transceivers, etc are wired to an Aux fuse block, I can easily swap the positive lead to the aux block from the main batt over to the aux batt should I decide to change it later.
The next major electrical addition after the winch will be a fridge. Without a doubt I will have it run off the AUX battery.
I'll start by winching off the main battery only at first. If needed I'll know I have the aux battery in reserve for additional winching amps or jump starting.
 

Skrewball

Observer
always put the winch on the main battery. the winch does not need to run off of two batteries. it is always a good idea in older vehicles or any thing with an upgraded alternator to run a heavy gauge cable from the output terminal of the alternator to the battery. the stock wiring is usually not rated for high amp output.

run a fridge off of the aux battery. most fridges are "smart", they can be set to shut off or "sleep" at a preset voltage. If the fridge is set properly the aux battery will still provide enough jump starting voltage even after the fridge has run it down.

this is my opinion and not fact. i have put dual battery setups in alot of different vehicles with different needs. i understand that not everyone has the same requirements, but these guidelines usually stand true in any setup.
 

Antichrist

Expedition Leader
Not if the engine is running.
My point was the scenario where you're winching a heavy load and run both batteries down (which you can do if they are connected while winching) and for whatever reason the engine dies. You stall it, space out and turn it off, whatever. Now you may not have enough juice in your starting battery to start the engine.

It's probably not an extremely likely scenario, but for me, since I travel alone 99% of the time, I don't want to run the risk.
 

dwh

Tail-End Charlie
My point was the scenario where you're winching a heavy load and run both batteries down (which you can do if they are connected while winching) and for whatever reason the engine dies. You stall it, space out and turn it off, whatever. Now you may not have enough juice in your starting battery to start the engine.

It's probably not an extremely likely scenario, but for me, since I travel alone 99% of the time, I don't want to run the risk.

Ahh, I get it. Yea, good point. I like to have every erg of juice for a winch, but if the one battery + alternator is capable of handling the load, then your way would be better (safer).
 

tremors834

Adventurer
Ahh, I get it. Yea, good point. I like to have every erg of juice for a winch, but if the one battery + alternator is capable of handling the load, then your way would be better (safer).

I would venture to guess that there are more expo/offroad winches in use drawing power from a single battery and alternator compared to 2 batteries and alternator.
 
The one thing I didn't see mentioned in this discussion is what TYPE of batteries you are using. Is your main battery a regular automotive SLI? A dual-purpose marine? What about the auxiliary battery? A true deep-cycle? A marine? A regular automotive? I would think that would be a major factor in deciding how to wire things.

How deeply is the fridge going to discharge whichever battery it is hooked up to before it is recharged?

Ideally, everything that drains a battery overnight should be drawing from a true deep-cycle battery, which should NOT be used for starting your engine, except under occasional emergency circumstances.

My $0.02, FWIW
Regards
John
 

dwh

Tail-End Charlie
The one thing I didn't see mentioned in this discussion is what TYPE of batteries you are using. Is your main battery a regular automotive SLI? A dual-purpose marine? What about the auxiliary battery? A true deep-cycle? A marine? A regular automotive? I would think that would be a major factor in deciding how to wire things.

Not really. The engine battery is going to be a starting battery, and regardless of what type they have for an aux it's still going to be pretty much wired the same way.

The only real wiring question is which battery to connect the winch to.


How deeply is the fridge going to discharge whichever battery it is hooked up to before it is recharged?

Ideally, everything that drains a battery overnight should be drawing from a true deep-cycle battery, which should NOT be used for starting your engine, except under occasional emergency circumstances.

My $0.02, FWIW
Regards
John

Tru dat.
 

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