halfords electrical cable

they are very helpful in store. Don't go too mad with the length of the leads and make sure they are fatter than the existing ones and it will be fine. If you have some mains cable off an old appliance like a heater or even an old hoover that will probably be fine, just check it is at least as big and preferably larger than the existing leads. If in doubt then just try it, if the leads don't heat up it will be fine.

That cable appears to be way too fat. If you are only going a couple of metres you can use just about anything, an old extension cable or lawnmower cable works just as well even if it's not the right colours. (red and black often don't match what's used on the car anyway!)

With some old *flexible* mains cable of a good few metres the volt drop will be next to nothing and even if you are passing 15A through it, it won't be for long so it won't get too hot, when it drops to 3 or 4 amps you can get away with much thinner wire.

For instance look at the wires for headlamps, they pass around 6A in an extreme environment surrounded by high temperatures and enclosed with other wires. Battery charger wires are in free air and bundled with other heat producing cables.

Thinner wire just gets hotter and drops slightly more volts than thicker wire.

Stephen submitted this idea :

The amperage rating will be essentially the same - what differs is the voltage rating, the insulation. You also need to keep in mind that the lower the voltage, the more significant is the voltage drop.

1.5mm flex will be fine for two or three metres, so basically any of the larger mains two core flexes - or use three core and double up on one of the wires, rether than cut the spare one off.

I myself have my charger fixed to a roof beam in the garage. I have a pair of brass bolts also attached to a beam, with a wire dropping down from that with a ciggy plug on the end. That plugs into the car, then I just clip the chargers crock clips onto the bolts - It makes it a quick job to put the car on charge as I park it, yet means I can quickly move the charger to the bench to charge other batteries when needed, or swap the charger for another one.

Thanks for the help. I think the ammeter on the charger goes up to 8A, so I just went to the next size up of cable just to be sure. I do have some mains flex about, so I could use that this time. It might be handy to get some of the "proper" stuff because I suppose that in cars you only need one conductor and the chassis is the other one. If I used flex, I'd have a wire or two flopping about unused.

Thanks, Stephen.

Thanks. That's a really useful link and proves my suspicions that Halfords were expensive.

There's a link on that page to thin wall cable, which it claims is superior. I am a bit puzzled by this. If you look at the first cable on each page:

standard cable: 14/0.30mm, 1mm2, 8.75amp. thinwal* cable: 16/0.20mm, 0.5mm2, 11amp.

thin wall link=

So the standard cable has a 1mm^2 CSA, twice that of the thin wall cable, and yet the thin wall version with only 0.5mm^2 CSA can carry a higher current. Why is this? I thought the current capacity was defined by the CSA?

Or is it that the thin wall version, as its name suggests, has thinner insulation so doesn't heat as quickly? If the difference is insulation thickness, why do they make standard cable with think insulation? Normally manufacturers cut corners wherever they can! Why make a version with more insulation than needed?

I haven't done the maths but to get the overall CSA is it a matter of finding he CSA of one 0.2mm strands and then multiply that by the number of them; in this case 16?

I think the prices of the thin wall were better, so is there any reason not to buy that?

Thanks, Stephen.

The standard cable is obsolete - so just provided for repairs etc on older cars. Thinwall is what you'll find on new. And yes, I'd guess the the heating effect of a cable at maximum capacity is the primary reason. Might also be better overload protection in modern cars - faster acting 'fuses etc - allows a less conservative rating. It could also be the more common use of some type of remote switching - like relays etc. So the high current cables are shorter.

I dunno. In a car loom, both are additionally protected for much of the run by some form of sleeving. For your app they won't be. The answer is I don't know which type of insulation stands up to mechanical wear better.

The thinwall's normally also got a higher permissible temperature rating for the insulation.