Quote Originally Posted by Dan in NZ
What I need, is to connect the positive lead of the battery to the chassis, so that if someone touches the car it grounds through their body...
Eh, let me guess. You're a psychology major? History? Ancient romance languages? I KNOW you're not in any technical discipline!

Now seriously. Think about what you said here. You're proposing to connect the positive lead of the battery to the chassis of the car, which is already connected to the NEGATIVE lead. Um, seems to me that that's a prescription for AN EXPLODING BATTERY! IOW, ain't gonna work, Dan. Besides, 12V won't hurt a flea, though it wouldn't matter if you had a 100,000 Volt battery in there and had its posive lead connected to the chassis, there'd still be nothing making a complete circuit to ground, which is what I suspect you had in mind in the first place (give them a shock they'd remember?).

Now, on the other hand, I do remember once seeing a web site where a guy with the same problem you have cooked up a taser-like non-leathal high-voltage shocker that had a little pigtail that dragged on the ground to make the ground connection, and that energized the chassis to a fairly high voltage. Dunno how successful the idea was in practice (what happens when the tires got wet in the rain?), or whether he was able to defend himself from the reckless homicide charges that probably happened when some moron with a heart condition accidentally touched his car and fell over dead. Some time spent at Google will probably find the info on how to do this if you really want to pursue it.