Winch Electrics

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Griffdowg

Griffdowg

New Member
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7,194
Location
Somewhere in Bristol
Eve. all,

a few questions for the auto electrical minded people out there.

im planning on fitting my winch soon and need to run a long pos and neg batt cable from the solonoid/winch to the batt. i have the 3 cables which run from the winch to the solonoid which are 25mm square ones. my question is, is it worth buying 40mm square main pos and neg leads? or will this be wasted cos i only have 25mm ones linked to the winch? would it be worth upgrading the lot? this is however very expensive! or will 25mm suffice? ive heard the heat build up can be alot with 25mm's

also, i found a good mail order place for cable but they wont fit the ends for me. can i do this with a ****ty solder iron and a basic tools?

cheers,

G
 
i used to make cables up fer pullin stuff and i used a specially adapted pair of bolt cropper to crimp the ends before i soldered them. yer problem is stopping the heat going back up and melting the insulation before the solder has flowed. you can get round this by stickin some mole grips on the exposed cable as a heat sink.
if part of yer cable run is 25mm² then having a bit of 40mm² int gonna help much
 
Every inch of cable run that is 40 sq mm is better than that same inch being 25 sq mm cable.

It has less resistance and carries more current while heating up less. In other words, heavier lower resistance cable is always better.

Go for it, and don't worry about the short run of 25 sq mm cable. What you are proposing is the next best thing to 40sq mm cable all the way.

CharlesY
 
CharlesY said:
Every inch of cable run that is 40 sq mm is better than that same inch being 25 sq mm cable.

It has less resistance and carries more current while heating up less. In other words, heavier lower resistance cable is always better.

Go for it, and don't worry about the short run of 25 sq mm cable. What you are proposing is the next best thing to 40sq mm cable all the way.

CharlesY
Click to expand...

cheers Charles,

the short run of 25mm isnt that short though as im mounting my albright solonoid up under the wing. so the lengths are between 1 and 1.5m. with the pos being around 3m from solonoid to batt and the neg being 2m from winch to batt.

im just not sure on the best route of action.

G
 
CharlesY said:
Every inch of cable run that is 40 sq mm is better than that same inch being 25 sq mm cable.

It has less resistance and carries more current while heating up less. In other words, heavier lower resistance cable is always better.

Go for it, and don't worry about the short run of 25 sq mm cable. What you are proposing is the next best thing to 40sq mm cable all the way.

CharlesY
Click to expand...


you sure about that? cos yer still trying to shove the current through 25mm² no matter how long it is
 
any electrical circuit is only as strong as its weakest part. so if the 25mm^2 is the weakest part than if a short occurs - it will act like a fuse!
 
so i will only burn out the 2nd hand used cheaper 25mm? ;) i might do the lot in 40mm... see how much $$$ the 2 longer lengths are 1st. Bristol auto electric look out!
 
Nope.

What I said was that every bit he changes from 25sqmm to 40 sqmm will help his system. That is a fact of electrical life.

Remember most circuits are protected by a fuse - a very short thin wire that will JUST carry the maximum design load.

If the whole cable run was made of cable as thin as the wire in the fuse it wouldn't last more than a few seconds before the whole wire went up in smoke and flames.

Sure, the circuit is only as strong as its weakest section, but believe me boys, a 25 sq mm cable will carry hundreds of amps, WAY more than a modest winch will normally use. What I am saying is that 40 sqmm cable will do it better.

In fact, there isn't any doubt about it. Since electricity was discovered, that's the way it has been. More area of wire means less resistance, means less heating-up, means better ability to carry current without losing it as heat on the way. The resistance of a cable increases if the wire heats up, so the wire then heats up more, faster. A vicious cycle starts up, possibly leading to cable failure.

But for convenience, they usually design things with wires that are just and no more going to carry the current required. Starter motors carry more current than any other device in most cars. They may have to carry 400 or 500 amps for a few seconds when doing a cold start. So it has the thickest cable. Next thickest is usually the cable(s) out of the alternator, which would be rated to handle 100 amps or so, and for much longer.

What's the rated current draw of the winch?

CharlesY
 
Hi CharlesY....Thanks for your explanatory note above...

What is the equavalent cable size in sq mm to 300 amp? If there is any conversion chart?

Also, in welding cable that is 300AWP, what amperage does it has? Can I assume its 300amp?
 
Welding cable would be great as long as it was COPPER wire.
Aluminium wire has more resistance than copper by quite a margin - copper is by far the best.

The beauty of welding cables is they are multi-stranded, and hence very flexible and long-lived. If they are copper, you can crimp ends on AND solder them too. The ENDS are a potential source of poor connections and thus dodgy current flow and heating up.

I have been hunting for a table of wire areas to carry currents but haven't found it yet. If you use STARTER motor sized cables, or electric welding cables, I reckon you'll get on fine.

When laying out (routing) cables to for high currents, always try to keep them exposed as much as possible. This helps to reduce heat build-up, and if it does heat up you see it (smell it!) sooner, and it's easier to replace.

CharlesY
 
CharlesY....will let you know if I comeby any of those tables......its something to do with conductivity of copper over area (per sq mm)

Am planning to use welding cable (300AWP) between winch battery to winch...
 
The current carrying capacity of cable varies according to the application and materials used for the conductor and insulator. It also varies, to a lesser extent) according to the voltage - due to edge effects at higher voltages.
As a rule of thumb for most domestic / auto applications -
1 mm sq = 5 Amps
1.5 mm sq = 10 Amps
2.5 mm sq = 15 Amps
6 mm sq = 30 Amps
10 mm sq = 45 Amps
25 mm sq = 80 Amps
40 mm sq = 100 Amps

However, with short cable runs (e.g. <5m), and for short durations, you can get away with a lot more than this - Starter Cable is often only 25mm sq and takes 300 Amps for a few seconds quite happily.
The above figures relate to continuous useage.
 
Also, multicore wires have lower resistance than solid core (sum of resistancesin parallel), so a multicore wire will take more current than a solid. Take standard 15Amp solid core ring main - it will actually take a lot more than that but you need to apply a FOS to the maximum rating. Take the same as multicore wire and you can pull up to 50&#37; more power before it starts getting a bit warm.

Now then, if the cores are 7n purity PC-OCC copper, you get into a whole different ball game ;)
 
**** and i always just looked at the accessory or wot evva and thought ..mmmmmm!! that size wire will do..
so far i int had any burn up .
although i did once have to put a big arsed fuse into a leccy power steering pump circuit cos the silly bitch insisted in holding the wheel ovva on full lock fer ages, instead of backin orf a touch as instructed
 
slob said:
**** and i always just looked at the accessory or wot evva and thought ..mmmmmm!! that size wire will do..
so far i int had any burn up .
although i did once have to put a big arsed fuse into a leccy power steering pump circuit cos the silly bitch insisted in holding the wheel ovva on full lock fer ages, instead of backin orf a touch as instructed
Click to expand...

I'm with you Slob.
There's a lot of nonsense getting fed in here ... I mean, the guy was asking about cable for a blooming winch on a Landy, not wires for carrying current from a hydro station in Scotland down to Penzance.

We are using very low voltage direct current here chaps, not 440,000 volts AC, and almost invariably we are using COPPER wire, because copper wire is best by far, due to it's very low electrical resistance. However, as Slob points out, all wires do have some resistance, and that means that all wires WILL heat up when current passes through them. If the correct wire size is used, and no excess curent passed, the warming effect will be so slight we won't notice, BUT .....

.... as a wire heats up, even just a little, its resistance increases, and if we continue to try to draw a heavy current, the wire heats up more and more, and the resistance goes on increasing, until something melts, hopefully the fuse, but if not it will be something else, probably very expensive.

A fuse "blows" because the little link inside it has a resistance, and quite simply it MELTS damn quick if the current goes OTT, and breaks the circuit, which stops the current, and the rest of it survives till you use a six inch nail instead of the proper fuse.

There may be a moral there .... but as Slob says, have a look, think about it, check the current load, and pick the fattest quality cable you can lay hands on.

CharlesY
 
 
Geez but that looks like the way to go!

Get proper fittings for all the ends, crimp them AND solder them.

CharlesY
 
CharlesY said:
Geez but that looks like the way to go!

Get proper fittings for all the ends, crimp them AND solder them.

CharlesY
Click to expand...

There is NO need to solder and crimp. If the correct crimp tool is used for the fittings, not only is soldering unnecessary, but can actually weaken a crimp joint because it does not allow the wire to flex at the interface with the connector, and can cause a high stress point.
 
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