Earthing a leisure battery + recommended cable size

[Moseley]

This should be a quick and easy one for someone with some electrical know-how! The PO of our bus was an electrician, and he has wired up a separate fuse box for the leisure battery. However, he has run both the positive and the negative to it with separate fuses for each pole.

Is there any reason why you would do this, and not just fuse the positives and run the negative to an earth point?

And another similar question - what gauge of cable is recommended from the LB? Is it just a case of working out the maximum current draw of everything that could be switched on together and then adding a bit on? We've got a 400w inverter, and hopefully a sound system with a couple of hundred watts RMS, so was looking at something around 8 gauge / 1000W.

 

[jonboylaw]

That is a strange one, maybe Sparkywig can chime in. No idea why you would consider running a separate earth for the LB. Was it grounded to the chassis at all? How would it charge ?


I run a common ground so the starer battery and LB both ground on the chassis ( also the hook up).
Also run a separate fuse box and as you suggested, calculate you max load and add extra ( I did 50% from memory.



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[Moseley]

Odd indeed, and if it weren't for the fact that he was an electrician, I wouldn't be questioning it! And even more bizarrely, the fuses used on the positive and negative side of each circuit are different ratings...

There are no earthing points from memory, although I will double check that as the charging thing has now got me stumped. It had a split charge relay installed when we purchased, but the wiring wasn't complete, so I have re-assembled it. The other day, the LB was flat and below 7V, so the trickle charger wouldn't kick in. I ran it for 15 mins or so until the voltage rose, and the charger could do it's thing, so it is getting juice somehow from the dynamo...?! :?