Help with the right gauge wire for a winch..

[ccrunner]

I'm setting up a small Harbor Freight ATV winch on my trailer, and the power for it will come from the front of the tow vehicle's battery (2017 Ford Escape)..

The winch is fairly small (2500#), and will be used to pull my 900# Berkeley up onto the trailer. The challenge I'm having is knowing what gauge wire will be required to make the run from the front of the Escape (car's battery) to the rear bumper plug, and then again, from the Escape's bumper plug to the winch mounted on the trailer..

I'm guessing it will end up at about 18'-20' total run.. I don't have the winch yet to know what wiring it calls for, just trying to get ready (that, and my wiring need is unusual in that it must run the full legth of the vehicle)..

Any thoughts on what gauge wire I should use for this long (+12v) lead run?

Thanks guys-

--ccrunner

[rx7locost]

Current draw is directly related to the pull load and the layer of cable (i.e. leverage). FYI, all HF equipment has on-line manuals. From their website, I opened manual for the Badland ZXR2500 winch and found the attached table.

Figure the load based on expected weight of the car, angle of ramp, and how much cable will be on the spool. Once you have an estimate of the load current, you can size the wiring accordingly.

HF rates the winch based on the 5.8ft long 10ga leads connected directly to a battery. Running 10 ga to your battery is very unreasonable for your application IMO.

I would be tempted to run 6ga if you can get it. Lower number wire will net you a higher voltage at the motor. That will result in a slightly faster winch speed. Also keep in mind that any vehicle to trailer connecter should also be rated for a similar current. The HF winch mentioned is rated for up to 132 amps.

I'm not sure what the winch's internal current protection is rated for. If you find the winch draws too much current, you could lower the current draw by using a snatch block but that will also lower your load speed. Alternatively, you can remove any extra winch cable resulting in a better leverage and lower current draw too. FWIW, I drove my Locost up the ramps onto and off of my trailer. I installed permanent wheel chocks at the front telling be when to stop. I had a hand winch on the tongue if I ever needed to load a broken Locost.

[rx7locost]

If you choose to, you could add a small battery on your trailer. HF says 12VDC, Minimum 12 Ah. I think a lawn tractor battery should suffice nicely. Disconnect any wiring to the trailer before winching. That way the wiring size from the car's battery and through the trailer connector will not have to be very large. The wire from the car would recharge the trailer battery when running down the road, a much lower current draw. Don't forget to fuse the cable from the car's battery too.

[horchoha]

If you choose to, you could add a small battery on your trailer. HF says 12VDC, Minimum 12 Ah. I think a lawn tractor battery should suffice nicely. Disconnect any wiring to the trailer before winching. That way the wiring size from the car's battery and through the trailer connector will not have to be very large. The wire from the car would recharge the trailer battery when running down the road, a much lower current draw. Don't forget to fuse the cable from the car's battery too.

I agree with Chuck 100%. IMO that's a more practical way to go, most likely cheaper also. Heavy gauge wire is expensive.

[ngpmike]

Totally agree with Chuck & Perry on this. I'm planning on doing the same thing to my trailer, but with the HF 3500 winch for loading my Locost (assuming I ever get it built) onto the trailer. The secondary battery on the trailer was in my plans too. Good Luck!!!

[KB58]

This reminds me of a funny story:

I work in Field Support and one day, someone issued a disposition regarding towing equipment into a garage. After reading it, I went and found the author, asking him "Was she hot?" He asked, "huh?", and I said, "you wrote, 'tow the equipment into the garage using a wench', so I'm wondering, was she hot?" He still didn't get it until I explained the difference between "winch" and "wench."

[rx7locost]

I just had to check to see if I misspelled winch.

[horchoha]

I just had to check to see if I misspelled winch.

Yeah, I too went through the whole thread to see if someone typed wench instead of winch

[KB58]

Hah, no, it's used correctly here, it just reminded me of the alternative.

Another one is when lose, loose, and loss get mixed up.

[ccrunner]

As a HS English teacher, my lizard brain latches on to spelling and word use everywhere- a switch I can't seem to turn off .. I, too, had to go back into this post and see if I was having trouble gauging my wench... often, it seems

Thanks guys for the insight on wiring this thing up... I'm planning to mod the trailer next month, so I'll see then what direction that little project takes

--ccrunner

[duratec7]

If you do use a battery on the trailer you can put a current limiter (like this https://www.ebay.com/itm/DC-DC-CC-CV-Buck-Converter-Step-down-Power-Module-5-40V-to-1-2-35V-20A-300W/323781838480?hash=item4b62e6c690:g:rZIAAOSwmHJexknd) in your tow vehicle on the power lead, then you do not need to worry about forgetting to unplug, or about popping the fuse in the vehicle if you happen to drag the battery down flat.

Set the current limit to whatever your feed circuit wire size allows and you are done (they make bigger versions if your 7pin uses heavier wiring).

Otherwise if the battery is sagged low, the in-rush current from the tow vehicle trying to charge it can easily get above the limit of the circuit in the tow vehicle.

Some vehicles use self-resetting breakers on the trailer power circuit, but this would keep it on and just cap the current.

Or you could build it into your battery box on the trailer so varying tow vehicles do not matter.

[ngpmike]

"If you do use a battery on the trailer you can put a current limiter... in your tow vehicle... " Thanks d7! This is precisely what I was about to start searching for to use in my towing rig!

[rx7locost]

That "buck" converter is not a current limiter. It is a voltage regulator. Being a Buck converter, the output voltage is always less than the input. From the specifications, it appears that the output would be close to 5V less than the input voltage. unless you are charging a 6V battery, it won't do the job.

You want a buck/boost converter. something like this one.

https://www.ebay.com/itm/152947310464

It can be set to current limit at 7Amps. That should be under the trailer connector's current rating. I would add a 10A circuit breaker in the line from the tow car for safety. Packaging design for water protection and heat dissipation would be left for you to figure out.

It won't be temperature compensated like a car's alternator voltage is. So long as you wet the voltage at 13.8V, you should be OK.

[duratec7]

Yes it is a buck converter, voltage drives current (can't flow current without voltage differential) so dropping voltage is the only way to limit current. It is a CC / CV unit, you set either limit. Agreed, it is not a constant current device, so it will not force the current by pushing the voltage up, but it will cap the maximum amount of current flowing through the circuit.

We have not seen the output having anywhere near a 5V drop. More like ~.2V
I do see the spec does limit input to 40 V, and output to 35 V, but I do not believe that is stating this version has a minimum of 5V drop to function.

I may not have linked the specific unit we have use as a CC limiter, but the one we have only drops .2V on 12V, the unit linked is 300W max, so will handle up to ~20 A at charging voltage (unless you set it to limit lower than that). But the unit linked does have CC output, so you can set the current limit as desired.

The concern on a buck/boost is that if the vehicle battery sags for any reason, the unit will still continue to charge the trailer. Not the end of the world, unless you forget and it draws down the vehicle. So would work also from what I've seen.

And since charging system temperature compensation is relatively newer, I agree, setting at a constant 13.8 V is a simple solution.

All that said, I have not yet used one of these in this specific application, so YMMY, previous performance is no guarantee of future results, etc...

[rx7locost]

I do agree that a 5V drop is rather large for a buck converter. However, a volt or two could be expected when operating at higher currents, close to a power supply's rating. Especially for low end converters where they are built to a price point rather than market leading performance. I have no experience with the buck converter you linked so all I have is the specs as written. Higher end converters can have a very low voltage drop at the current limit.

Yes, a buck/boost module will keep the output voltage at setpoint and can discharge the car's battery if left connected. The good news is, while driving down the road, a tow car's alternator would not present such a situation. Easily addressed with a relay that connects the trailer system only when the engine is running.

A couple of minor points. Temperature compensation is not a new concept for battery charging. My old MGA with a Lucas electromechanical regulator (vibrator style), built in the 1950's had temperature compensation. There are such things as current sources which drive a current without needing a voltage differential.

Cheers