Leisure battery - wire melt?

[poolhallrichard]

Just returned from a few days in Norfolk in our T25 and experienced a severe wire melt of the black negative wire from our newly installed leisure battery while driving along. Luckily we became aware of it early on alerted by the smell/smoke and were able to stop and disconnect the battery before too much damage was done. Bit scary to say the least though.

Not being electrically minded, I've no idea why this happened. I had previously hooked up the new battery to the existing leisure battery wiring behind the passenger seat and had had no problems prior to that. We were running the fridge through the Zig unit at the time but it still worked fine after we'd disconnected the leisure battery so presume it ran from the main battery while driving along after that.

Can anybody point me in the right direction and suggest what might have caused this problem and save me hours of trawling the net looking for a possible reason and how I can fix it and prevent it from happening again??

Thanks

[VWCamperfan]

How long had you been driving before you noticed the wire melting? If i'm going to take a guess I would say not long!
I bet you used the electrical stuff while parked up too.
Probably what has happened is you have used quite a bit of battery power and starting the engine has begun recharging the battery but the battery is drawing quite a large ampeage because it's low on power. This could have been enough to melt the cable.
Ideally your cable from the battery should be similar to the earth lead on you main starter battery. Anything smaller could mean problems.

[poolhallrichard]

Thanks for responding.

Yes - we had been only driving for a short time but we hadn't used any of the electrical stuff while parked. I'll check out the size of the cable as I'm going to have to replace it anyway.

[pionte]

You can buy the correct thickness one from Halfords, about £5 IIRC, I have just fitted all new leisure battery wiring and was surprised just how much Amperage could be expected to flow into/out of the LB. The kit I bought was rated at upto 85 ah batteries, and the charge wire from the starter to the LB was protected by a 50 ah fuse!

I would check the condition of all your earth strap points, not just the one from the LB but from the starter Batt to, and also the gearbox/ engine earths.

Martin

[Mocki]

if you fill your profile in with your location, it may help .
someone might be near to you to have a look?

sounds like you dont have a fused system.......

dont reconnect the battery untill you know why it happened........