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Old 03-12-2019, 10:42 PM   #1
Join Date: Sep 2016
Location: Illinois
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Winch wiring to house battery or van battery?

Hello All,
After a couple close calls I’ve decided to install a winch onto my van. My question relates to the wiring. I’ve searched the forum and have found some good threads but none of them got to the bottom of anything. The install will be a Warn V12 on a 2010 SMB 6.0 with an aluminess bumper. On a past thread one of the members here suggested wiring the winch directly to the house battery to avoid possible FICM damage if the van battery voltage were to drop below 10v. Unfortunately that thread stopped there, and by the time that comment was posted it was so far off the original topic I decided to just start a new thread.
To me FICM damage sounds as equally problematic as being stuck in the mud so the idea of wiring a winch direct to the house battery seems pretty logical. However in thinking about it the battery separator will disconnect from all charging systems when the voltage falls below 13v which will mean I will be running the winch off the house battery without a charge coming into it. I know the charge coming into a battery with the van running is minimal, but at least its something. Battery math equations have never been my thing so I was hoping to hear some thoughts you all might have about the what option is better.

One nice factor when wiring to the house battery is that it’s much easier to make the connection. If memory serves me right I have blade terminals that I can simply connect the regular lugs too. However, If connecting to the van battery I would love some suggestions on how to do this as well. I’m assuming that I want to connect to the front battery on the rail as it looks like this is the one that gets power direct from the alternator but Im assuming that this battery has post terminals with limited space due to the inline wiring for the second battery. This sounds a little tricky, any suggestions would be great.


Thanks in advance.

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Old 03-13-2019, 01:15 PM   #2
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'09 6L and my Warn V12 is connected through the van batteries. Haven't used it yet but you should have the engine running when you do to keep from running the voltage too low. Curious to see what the experts have to say.

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Old 03-13-2019, 01:23 PM   #3
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Wouldn't worry as much about starting vs. house battery, as the size of the cabling needed to support 350+ amps...4/0 or larger for that length...or dual cables.
A battery is a battery. As long as it is connected to a charging system that can quickly replenish, and you know the battery, and charging limitations, should be good to go.
There are a multitude of battery terminals, and cable configurations, that can do what you need.
Will the winch be installed on the front or rear bumper?
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Old 03-13-2019, 04:13 PM   #4
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I was advised to wire the winch to the start battery.
This has worked without any problems.

Of course we use the winch only with the engine running, which is logical as you would want to "aid" the winch anyway by pressing the accelerator a bit and having the wheels turn slowly while you winch.
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Old 03-13-2019, 04:42 PM   #5
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Location: Illinois
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Thanks for the responses so far.
unreng, I will be installing on the front bumper and plan on using 2/0 wire especially considering the 12' run to the van battery and 16-20 ft run to the house battery.
Also, I have a tripp-lite 2000w inverter/charger so there will be charge on the house battery with the van running until the voltage falls below 13ish and the separator disconnects.

The likely hood of ever running the winch for more than 5 min is pretty slim but Im leaning towards the house battery. The upfront cost of more cable is about $60 but eliminating a immediate or lingering FICM issue due to a quick voltage drop seems to be worth it.

I would love for someone to call me crazy on this or point out what Im missing if there is anything.

Thanks again.
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Old 03-13-2019, 04:56 PM   #6
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this is a good question and im looking forward to seeing what others have to say as well.

paging member Scalf77!! hes posted some uber helpful info regarding the various electrical systems in these vans/campers.

I have mine hooked up with 0/0 gauge running to a pole connector in the rear. I have my winch on a receiver and move it from front to back as needed. I have no house batteries yet, so they are connected to the start batteries. I use mine a lot for woodcutting, but have only recovered a couple of vehicles and I don't consider pulling lightweight racecars onto a trailer much work for a 12k winch. no issues thus far, but the pcm issue is a great point to bring up. especially considering mine is not the original one that came with the van. makes me wonder what happened to the oem one...

one thing I have that's nice is the rpm control. whenever the system sees a big juice pull it automatically kicks up the idle to compensate.
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Old 03-13-2019, 06:11 PM   #7
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1) engine running to maximize he amount of available current going directly to the winch, minimizing the amount drawn from any battery

2) connect the winch to starting batteries as they are, by design, intended to provide high amounts of current for sort periods of time. Deep cycle are designed to provide relatively steady current over long periods of time even to a low state of charge

3) IMO most winch pulls will generally be less than 60 seconds at a time since you may have to re-rig, adjust the rigging, or give the winch motor downtime to prevent it overheating

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Old 03-13-2019, 09:51 PM   #8
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I agree with Herb, wire to the starter closest to the alternator. If you have control over your ACR/separator, I would disconnect and make sure all available power can go to the winch. While I think continued low voltage could be a problem for the FICM I don't think the winch time should cause an issue.

What separator do you have? Will your separator meet max load?

Since the max load of the Warn V12 is about 457 amps, even 105C #4/0 would be to small, 125C should just clear it. I don't suspect that a lot of winch owners run that, again because of the duration.

As far as the PCM blowing, I had three blow on my van in the 1st 6000 miles. It fortunately is part of the reasons I dug into RV electrical systems. While the root cause was identified (at least in my mind, i'd have to blow another PCM to prove) and fixed, I am just about to hit 100,000 this year. I would be more worried about the winch being on the house battery.

Originally Posted by Spr View Post
Also, I have a tripp-lite 2000w inverter/charger so there will be charge on the house battery with the van running until the voltage falls below 13ish and the separator disconnects.
For the record the tripp-lite 2000w inverter/charger will only charge the house battery off of shore power. The separator charges it via the alternator

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Old 03-14-2019, 09:53 AM   #9
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Scalf77, thanks for the reply.
The ACR is the PN 7620B. This is the one without the manual control. I do have the momentary switch to connect the banks on the drivers side headliner area but I’m not sure if this also isolates the batteries and/or for how long it isolates them. I’m afraid I don’t know what the max load of the separator is, and the 105 degree C at #4/0 is also way above my pay grade. Assuming that’s wire/load talk I was told by Warn that 2/0 wire up to a 40ft run is more than enough current and considering I would only be at 12ft for the starter battery or 18ft for the house battery 2/0 would be more than sufficient. However this is based on a normal winch to battery setup and the whole reason we are even discussing this is because we get to deal with separators, house batteries, chargers, PCM’s etc.

Thanks for the clarifications about the inverter/charger not doing the charging. That’s good to know.

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Old 03-23-2019, 09:59 AM   #10
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If you wire your winch to the starting battery on a stock setup 6.0 PSD, you are eventually going to a have a bad a day... It may not be a problem the first time you winch, but every time you winch, your chance of a problem goes up.

As you suspect, dropping supply voltage to the FICM is bad news. Most other vehicles are pretty much fail-safe from low starter battery voltage, because if the battery voltage is too low, the PCM will just turn itself off. The FICM will just cook itself instead.

That said.... there's more than one way to avoid this....

1) Install an aftermarket alternator that provides more power at idle.

2) Install a high-idle switch, and only winch using fast idle.

3) Install more or better batteries. Using house batteries is fine. But using the start batteries are fine too if you have a good separator and wiring that will keep it all in parallel while winching.

4) Do what you propose, and connect to house batteries with a cut-out... Downside is the length of wiring needed to reach most house batts. But the 6.0 starting batteries are remote as well. Either way make sure the wire gauge is sized for the extra distance.

5) Deep cycle batteries are good for starting too, provided they also output the CCA needed for your motor. When you winch, you may be deep cycling the battery, depending on the situation. With a regular starting battery, eventually it won't hold a charge anymore. Bad starting batteries are really the root cause FICM failures on rigs with high electric demands.

6) Install a more robust FICM

7) Test wet cell batteries periodically, using a carbon-pile tester (then recharge them with a charger!), and clean the terminals when you do that.

Any of the above will provide good insurance against FICM damage. Doing more than one is even better!

Also, winching methods will greatly change power demands from the winch. This higher the winch-line load, the higher the power demand. This is a good guide for winch-line forces:

The one thing not mentioned in that guide, is drum load forces. The more wraps around the drum, the harder it was to work. The manual that came with your winch describes that well.

Lastly, if you're only winch yourself, and you still have drive power, chances of exceeding the abilities of your charging system is low. But if you get stuck without drive power, or have to recover somebody else, or have to winch while pulling a trailer, or have to do multiple pulls... Your stock system probably won't keep up.

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