What cable type for -ve earth?

[dsmith1974]

Hi,

I need to make up a new cable for my leisure battery to go from -ve to chassis. What strand/diameter/amp rated cable should I use? The connectors need to be a 6mm ring term at one end and a 10mm ring term at the other, should I crimp and then heat shield these?

Thanks,
Dunc

[dsmith1974]

I think these should do it:

http://www.12voltplanet.co.uk/extra-fle ... 0-amp.html" onclick="window.open(this.href);return false;
http://www.12voltplanet.co.uk/copper-tu ... cable.html" onclick="window.open(this.href);return false;

[California Dreamin]

As you are not pulling 'starter cranking amps' the cables used just need to exceed the maximum likely combined load/charge plus a margin. This would normally be 6mm2 or bigger (42 amp or higher) I would probably go to 7mm2 (50amp) as long as the earth cable length doesn't exceed 50cm. Baring in mind that 98% of the time the current flow is likely going to be well under 10 amps.
I would solder the ends.

Martin

[dsmith1974]

Thanks Martin,

In the end I went for one of these
http://www.thetoolboxshop.com/2-404-06- ... -6601.html" onclick="window.open(this.href);return false;

I guess it's overspec for a leisure battery at 110A but figured the extra capacity wouldn't hurt? It was the only one I could find with a 10mm internal eyelet (so I don't have to crimp or solder)

[California Dreamin]

I hope you didn't pay that much for one?

http://www.ebay.co.uk/itm/POSITIVE-EART ... 3aa60b4b9a" onclick="window.open(this.href);return false;

Martin

[dsmith1974]

Aw man! Are they 8mm or 10mm eyelets? Most places (Halfords etc) standardised on 8 but the rig in the van takes 10.

At least it's a pack of 5 so just a tenner each. The vehicle batt looks shabby too so I can replace that while I'm at it.

Found some good info and a voltage drop calculator here
http://www.12voltplanet.co.uk/cable-siz ... ction.html" onclick="window.open(this.href);return false;

Looks like the drop will be close to zero over 15cm.

[CovKid]

You can get a bagfull of eyelets in all sizes from Toolstation (located in many branches of Wickes) for very little - Just over £6 for 30.

[California Dreamin]

At least it's a pack of 5 so just a tenner each. The vehicle batt looks shabby too so I can replace that while I'm at

The earth cable on your starter battery is likely to be heavier than this. Even though its a short run, a petrol starter motor has the potential to draw up to 150 -160 amps on the coldest of mornings (a diesel even higher) so a 110amp strap will get a little warm.

Martin

[slowcoach]

Can you fit 2 on? I've not looked at the links mind..

[California Dreamin]

Not really as they go back to one soldered battery clamp.

Martin

[dsmith1974]

Electrics now fixed! Thanks guys.

[dsmith1974]

Well, almost fixed..

After using the stereo and lights for about one week the leisure battery no longer had enough charge to turn the stereo on. Took the leisure battery out and connected it to a battery charger overnight and it was fine again.

Did a voltage test with a multi-meter when the engine was running - on the vehicle battery it read 13.something (so the alternator seems fine) but on the leisure battery the voltage was 12.something (occasionally skipping lower, 10, 8, 5, ...)

There's a split charging box which (I think) uses a relay to divert the current to and from the leisure/vehicle battery - should I try replacing this next?

[ghost123uk]

As you seem to know the basics of using your meter, check the voltage going into the relay and compare it to the voltage coming out.

Basically, with the engine running, (working on what you say re the battery charging OK on a domestic charger) =
Low voltage going into the relay (ie less than 13.6ish) = wire, connection or fuse issue in the wire feeding the relay.
Decent voltage into the relay, but low voltage coming out (with leisure battery disconnected) - duff relay.
Decent voltage on both sides of the relay, but low at the leisure battery (with battery connected) = duff wire, connection or fuse in the wire coming out of the relay (to the leisure battery).

[dsmith1974]

Thanks, much appreciated. I took a quick look earlier tonight and the fuses are all fine. Problem seems to be zero volts input to the relay. The relay earth input comes from the vehicle batt negative post and the relay positive input comes from some zig unit (looks like a basic volt meter and rocker switch to test the vehicle or leisure battery).

Will see about removing the zig unit from the circuit at the weekend (can't see a need for it) and clean/make new connections everywhere.

[ScienceBoy]

I would solder the ends.

Martin

So would I