Hi woody,are your cranking batteries connected in parallel or series? Isolation switches may be fitted between your earth lead and the chassis.I have just consulted my Hella catalogue and there are a number of units suitable for your application.They are of marine quality and for 6-36V systems with alternators or generators. Max load at 12 V is 500A for 10 sec while they carry a max continuous load of 310A at 12V or 155A at 24V.Available as a straight switch or with a key lock .Sorry I have no idea of price. Products are..2767 Marine Dual battery Switch and 2768 Marine Dual Battery Master Switch with a Keylock. Hope this is of help to you. Ian.

Yes, I purchased a similar el cheapo so that I could charge my start and aux battery at the same time in my Y62 but it was less than satisfactory.In a commercial vehicle with the current draw you would have something more substantial is required.

Dry land cropping patrol03 yes dry here but that's ok for this time of year if it rains during summer I like at least 30ml or it just costs money to control the summer weeds without putting much moisture down below .

Woody v

I have one in my truck. It was about $28 and works fine.I use it to insolate the starting battery from the storage baterys.Will post pic if you want. Bill