Quick winch wiring question.

Gonna wire up my warn m8000 to my disco got 90ah and 750 cca on the battery which is new. Don't plan to do any hefty winching. Maybe just the odd self recovery or helping others or pulling trees.

I understand I need some heavy wiring so I'm gonna get some that is 450-500amp cable. My query is that do I need a cut off switch? I understand if I have to wire this in and this will also run whatever current is coming out the winch, so I need a fairly hefty switch.

Is just running an earth and live straight to and from the Batt/winch a good idea? Don't want to be hindering the winch by breaking the circuit at less than half load.

Cheers

yes. always get a cutoff switch. stops the toadys cutting yo car in half .
fit the switch inside the engine bay or inside the cabin. when winching, open the bonnet.

theres 10000,s of freds on ere regarding winchs do a search and read some of them it will keep u occupied for a couple of days

wiltshire landyman said:

theres 10000,s of freds on ere regarding winchs do a search and read some of them it will keep u occupied for a couple of days

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I've looked but can never find much specific. Are those red key switches sufficient enough? Will they not melt under load?

RobRainford said:

I've looked but can never find much specific. Are those red key switches sufficient enough? Will they not melt under load?

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Yes
No

I burnt out 3 red key type cutoffs there rubbish

I've had no problem with mine.

Steve_R1979 said:

I've had no problem with mine.

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are u running an 8274 with uprated motor and do a lot of winch challenges?

Husky with a bowmotor, but no, no winch challenges, an from the sound the of the op he isn't doing challenges either!!!

Sometimes problems will occur with the cut-off switch, it largely depends on HOW it is used.

Off load switching. If it used to finally connect the circuit so that everything is connected before using the winch then you shouldn't get trouble.

On load switching. If you're using it to actually start and stop the winch then problems from arcing and eventually heating will break the cut-off switch.

On the subject of cabling, I would go for the more expensive method of running both pos and neg back to the battery; in fact that's the way I would do any high current wiring. For a smaller winch I would use 35 square millimetre cable and for the larger ones use 50 square mil.

correct me if I'm wrong, but isn't the huge cabling less to do with the power requirements of the winch, but more to do with voltage drop, which at 12V can be quite significant.

timtheenchanteruk said:

correct me if I'm wrong, but isn't the huge cabling less to do with the power requirements of the winch, but more to do with voltage drop, which at 12V can be quite significant.

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Both really but the ampage draw is what would worry me really. that cable will get really hot really quickly if your doing a long pull.

On my vw T4 there is a 1.5v drop from the battery to the headlights, but the length of cabling travelled to get there is over 5 metres!

from my defender to the winch i dont have a drop, that could be due to a bigger surface area in the cable or just because DC current dosent drop that much in a short run?

Someone who knows more than me might be able to confirm or deny.

timtheenchanteruk said:

correct me if I'm wrong, but isn't the huge cabling less to do with the power requirements of the winch, but more to do with voltage drop, which at 12V can be quite significant.

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Yes Tim and BGB, you're both correct, it is all about the voltage drop along the cables.
As you probably know, the thinner the cable, the higher the resistance, consequently when more current is drawn through it, according to Mr Ohm and his famous law the greater will be the voltage drop along it.

Now looking at the power consideration, the greater the voltage and current (P = V x I); or in this case 'Power dissipated by the cable equals the voltage drop along the cable multiplied by the current drawn through the cable' which could cause a failure due to overheating if the cable is too small for the job. Also bare in mind that if the cable is covered or protected by something like flexible conduit then the overheating problem can be exaserpated because of the lack of cooling air around the cable.

It is for this reason that I would recommend the sizes I've aleady quoted, and why when I used to install radio kit in police cars the power cables were at least 6 sq. mm and usually about 10 sq. mm.

It is for the same reason that I would recommend that both pos and neg are wired straight back to the battery because there is the possibility that the welding on some earthing points of a vehicle (new or used) might not be up to the job of carrying such high currents and voltage drops can also occur across them.