If you’ve ever short-circuited a 12-volt battery, you’re not likely to make the mistake again. Maybe you were lucky and only got your surprise of the month. Maybe you weren’t so lucky and got a nasty shock, or a burn, or both. It can be worse than that, too, if just the wrong set of circumstances are gathered around. So marine professionals who deal with DC electrical systems develop ironclad habits when working around batteries.

Potential short circuit

On the left, a very bad situation. The nut loosens suddenly, the wrench swings down and hits the positive lug, and you have your hand in the middle of a big direct-current discharge. On the right, a rag covers the positive terminals, preventing a short and reminding you to be careful.

One mentor told me only to work with one hand, but I’ve never found that very practical. I prefer another bit of advice, given to me by my friend Herman, who works a lot on megayachts, where there are often mortally high doses of electrical current flowing here and there, and plenty of switchovers between DC and AC: Always keep a rag in your toolkit, and any time you work on one battery terminal, use the rag to cover the other. It’s a simple solution, and it works – both to shield you from shock and to give you a visual reminder of what you’re up to.

I’m one of the ones who has had the misfortune (OK, let’s call it the stupidity) of shorting a 12-volt battery. So I was actually wincing when I took the photo on the left, above. You might think there’s nothing wrong in that photo, but there is. Let’s be safe out there!

Do you have any other battery safety tips? Share with us in the comments.