OK here's the point i mean, im not being argumentative btw Gman, just clarifying the point, IF the circuit is broken, its broken. It doesn't matter if you break POSITIVE or NEGATIVE, the circuit is incomplete, therefore, no matter what you touch to the car body, whether it be the Positive OR Negative terminal makes no difference, so long as the battery has been isolated, ie. 1 lead is removed... UNLESS you still have the NEGATIVE connected then short the positive battery terminal to the car body, in essence your placing the spanner across the battery (now a welding rod)... If you touch the positive lead to the body, you will get a spark which is just residual current left over in the system, IMO shouldn't cause any damage...
So disconnecting the Negative first is a wise choice, as for re-connecting, doesn't matter so long as you don't do it backwards!!!
As for Voltage Spikes - Impossible. Surge, maybe but doubtful... A spike in general would mean 'Over-Voltage' which cannot happen unless your regulator/alternator is rooted & passes AC thru with the engine running because your rectifier is shot (4 diode matrix inside the Alternator). Remember - a car battery is a 12v cell, so, you can't get more than 12v from it!
The other point worth a mention... 'Conventional Current flow' is indeed Positive to Negative,
but, 'Electron Flow' is from Negative to Positive... Confusing i know
Hope that clears things up, i think we both mean the same thing but are saying it differently???
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