From memory- I put an earth from the battery to one of the starter motor mounting bolts and another one from there to the inner wing mounting bolt.
I'm not keen on only earthing through the gearbox, as aluminiumium is not as conductive as steel.
No. Alluminium has 60% of the efficiency as copper where steel is only 20% as efficient (at conducting electricity).
Steel has a conductivity of 10.1 x 10⁶ Siemens/m; alumimium 36.9 x 10⁶ Siemens/m; so aluminium is more than three times as conductive as steel.
This is helpful. Any recommendations on where on the chassis? I suppose I could route a cable out of the battery compartment along with the earth to the gearbox?
Sorry I should have explained my picture better.
Top cable goes straight to the negative pole on the battery battery.
Fat cable with yellow tape goes to the winch (neg).
Lower cable (which comes towards the camera) is alttached to the chassis just by the camera.
The fat cable coming from the top left and going forward is from the isolator to the winch.
The winch cables are overkill (700A) the others are 400A.
The Red (+) cables exit the battery box forward into the engine bay and can't be seen in the picture.
The engine and the gearboxes are somewhat isolated as they sit on rubber mounts.
The gearbox mounts to the bellhousing (Al) which mounts to the engine using an enormous cross setion of steel and alluminium, i'm guessing this is likely rated at several thousands of Amps.
An M10 steel bolt is rated around 230A.
There are much fewer mated, painted surfaces from the engine block back to the gearbox which will provide an easier return path than from the starter motor bolt to the inner wing.
However.
The current rating of that inner wing path is still greater than 'needed' so it isn't a problem, but the gearbox and chassis is 'better'.
