>If the battery is 'floating' the shield of the cable >gets connected to the frame (metal) of the bus.

Hey Russel and all ..

I wonder what ever falls EMI on the shield would get shunted to the metal Frame which it self is floating will this really happen , I wonder say if the Bus (on wheels) moves on hills where there are charged cloud the Frame potential would elevate , show me how exactly the EMI *SHUNTING* takes place when the shield potential varies . Am I getting over Engineered sorry .