Red mark could be a burn. Move it to a new area on your body. Dr. Hulda's zapper page had something on how to treat electrical burns from zappers. She says they can be prevented by moving the rods or plates when you start to itch.
You shouldn't be able to get badly hurt from the battery. I would contact the manufacturer just to make sure.
I have had an unbelievable amount of sweating since I started zapping. But I'm doing it immediatly after the zapping not during. I think it means that something is dieing and I am throwing off the toxins. Man do I stink. I've been bathing several times a day because of this. At first I thought it was because of the Liver Flushes but I didn't have that after the first or second flush when I was just on herbals. If we drink more water it should help our bodies get rid of these toxins quicker. I also started kidney herbs today just in case.
Please post back if you find out anything more.