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Ok,... you are compairing apples to squash. In your example, you do need to remove the ground cable from the post first, before fiddling with the power cable... or you can just be carefull and not bang your wrench into an adjacent metal surface.. i try to avoid that.. chips the paint and all. In your example o fthe multiple ground patsh.. sure multiple may exist.. however, you want the best conductor to be the one the electrons flow thru. A solid metal to metal connection conducts better than your hand touching something, down thru your leg to the earth. That's why GFCI circuits work the way they do.. ground is the safety when you are working with high voltage.. you want the high voltage to find it's return thru sopmething other than you... if a fault occured and the hot wire touched the case, and there was no ground or it was disconnected.. it's possible that the user becomes the next best conductor... Again... switches and fuses don't goin ground paths. Ground should be common. and all at the same potential.. otherwise you can get weird things like ground loops, etc. Bout' the only place it is common to lift grounds are in full isolation switches, and in audio applications where you have a difference in ground potential between 2 different pieces of gear.. and you lift the ground on one end to prevent grounf current conduction.. which, in audio, usually ends up being a nice 60hz buzz. Your ancedotal example of burning a hole in your fender is closer to the exception than the rule. You want to look at safety.. look at higher votlage apps. Grounds are bonded semi-permanently.. and hots are the ones switched.. you don't want floating grounds. save your paint and don't beat your tools into your fenders.. use an insulator pad. In most applications you de-energize a circuit before working on it.. in a 'battery' application, your ONLY RZ to do this is to pop the common terminal off first... ( or slip a glove over your wrench, so when you slip it doesn't chip paint or arc/spark. soundguy
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