Possible earthing problem

Good one, not sure, but maybe we can work it out.
If everything that is connected to the 2nd battery connected like this?
Does everything do this?
If yes, and it is earth, is the 2nd battery earthed to the car or the 1st battery?

Not likely to be an earthing issue as there shouldn't be any significant current flow through the earth path...yes the body is the appropriate place to earth - use a star washer to cut through the paint if you like. First thing to do is to put a voltmeter across the aux battery and UHF when starting and see what's going on. Casper

Personally, I never earth anything through the body - I run a two core cable, and get the earth directly back to the battery. Never had any problems since I started doing this.

Cheers
Andrew

Aux battery is not earthed at all!

Best way is to earth the aux to BOTH the motor and the body - just like the manufacturer did with your starting battery. If you only earth to the body, then recharging of the aux may slow down.

I wired up most of our 'add ons' with dual core cable. Including drive light, HF & UHF Radios, fridge, inverter, compressor, fresh water pump etc.
All these are supplied through an add on sub- fuse panel (10 fuses)- with power linked from aux. battery.
The earth return to a common earth strip (brass thingy with positions for 10 wires) located next to the add on fuse block. Then a fatter wire to the engine block.
All the harnesses then run thru black split flexible conduit. The fuses & earth blocks are all labelled.
I guess I'm a bit parenoid about tidy wiring- trying to avoid a spagetti mess.
Touch wood...I've had no elec. probs. yet -

There really is no earth on a car as such, the body is just being used as a convenient "negative" wire back to the battery ??

The main batt is "earthed" to the motor as the starter motor takes a lot of power, and seeing as the starter motor has no negative terminal, it is "earthed" to the block of the motor.

The aux should be joined ( negative ) to the main batt. That way anything you run off the aux batt and you hook the negative to the chassis the current can get directly back to the "aux" batt. In other words, while the chassis will make do most of the time, its a better electrical connection if the negative runs back along a wire to the batt. ie; you wouldn't let a winch run its negative thru the chassis ? would you ??

Well forumites, I was looking forward to the great tyre debate, alas I will just have to make do with the collective brains trust fixing my earth problem.

thanks to all that responded, invaluable information. I have re-earthed the body to a new position that seemed to make a better contact , and earthed the engine as well. Problem solvered. Down the track I may earth the aux battery back to the main, but for the interim all looks well.

cheers and have a great weekend

Mike