It's not a stupid question.

When disconnecting the negative side of the battery, it doesn't matter
if your wrench its the metal around the battery (as they are both
ground.)

If you haven't yet disconnected the negative side, and are wrenching
on the positive side, you risk making a circuit to ground with your
wrench. A wrench can take an immense amount of current, but you are
likely create a weld (melt metal) wherever you touch with it. It is
also very likely that the wrench will get hot.

On Aug 4, 2008, at 8:02 PM, Jere Hawn wrote:
>
> The manuals (all the auto manual that I have seen in my life) say to
> disconnect the negative terminal from the batter before performing..
> X, Y,
> Z,. etc.  Why the negative and not the positive one?  Does it
> matter, is
> negative more dangerous that the +?
>