Avoid shorting battery terminals

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Jan 13, 2005
This isn't very techie and is probably ho-hum to some folks, but I thought I'd share this little tip. I've been meaning to write this for some time, but kept forgetting to snap photos.

When you remove wires/links from battery terminals, has your wrench accidentally touched another terminal or another battery or some grounded metal? If not, you either don't check/clean your battery connections very often or you're way more careful than yours truly. Next time I'm at the coach I'll snap a photo of a burn mark on the (grounded) metal case of a solenoid adjacent to one of the batteries.

It was actually the golf cart batteries on our boat that finally made me think of this simple solution. In this case, I have 10 batteries which I check regularly for electrolyte level, but some links between adjacent batteries get in the way of removing the fill caps. The fix was to buy a small socket wrench with a rubberized handle and to use a deep socket. See the attached photos (I just noticed that I ignored my new-found photography knowledge and didn't pay attention to depth of field).

  • The deep socket keeps the wrench handle high above an adjacent terminal.
  • The rubberized handle prevents accidental grounding on the adjacent generator box.


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And always remove the ground cable first, and replace it last, when working on the batteries.
The worst that can happen is the battery explodes when a firm short exists.  This really does happen.  One acquaintance blew up a new 6 volt battery (mounted under the passenger floor in a 1940 Chevy pickup) when replacing a plugged gas line.  Another blew up a diehard in his twin screw Chris Craft.  No serious injuries, but there could have been.
That's why it's a good idea to remove the ground cable whenever working around the batteries.  Covering the batteries with a plastic sheet would also help to prevent shorts while working on other things in the vicinity of the batteries, but I would still remove the ground first.
I also automatically turn off the battery isolator, although it won't help with accidental grounding of a positive battery terminal unless you also remove the ground wire as Ned suggested.

While your idea is great, in the Dutch Star I am lucky to be able to get a box end wrench and my hand in there to work on anything.  I put electrical tape on the wrench except for the actual box end.  If you have a straight wrench with only one end, shrink tubing works even better.  VBG

I work most electrical stuff hot up to 220 Volts AC or DC.  Carefully!  VBG
I've had a few of those and find the "round out" easily and I am rather "ham handed".  VBG  The military furnished a lot of them to me and frequently replaced them too!!
"The worst that can happen is the battery explodes when a firm short exists."

Maybe, but a friend of mine started a fire in his boat by shorting out the cables.  Actually he hooked them up wrong. Fortunately little damage was done but it could have been "good-by" boat.
James Godward said:
I work most electrical stuff hot up to 220 Volts AC or DC.  Carefully!

We used to work up to 415V AC and 400V DC hot. When it came to 10KV and up, I insisted on tripping the breaker and physically cranking it out away from the bus bar. I'd let someone else work on the 32-66KV stuff  ;D

As I recently told someone, a boat only burns to the water line. (That always gets their attention).

In 1954 I was working 12,000 hot for the first time.  I decided then and there I was going back to school.  Of course I had lost my deferment, Korean war at the time, so it was 3 years later before I got there.  220 is my limit!! Most of the time it is less than 24 volts AC or DC.  VBG 
Jim, working hot on 12KV, you're a braver man than I.

I went back to school too, in order to get away from the high voltage stuff in terrible working conditions. Next thing I knew I was figuring out how to measure sub-picoamps. That was a long time ago, but it got my foot in the in the high tech door.
LOL Karl. I'm going to start counting your typos  ;D
Another option is to dip the exposed, unused portion of your favorite battery wrench in Plasti-Dip a couple times. It will put an almost indestructible insulating coating on it. Available in most hardware/home supply stores for about $6/can.
Good idea Karl. I have a can of that stuff in the garage, but didn't think to use it  :-[
Tom:  Don't know how else to say this.  Your batteries are lovely.  Neat.  Clean.  Cables not corroded.  What are those white things on top of them?

Pat, those white things are the filler caps. Actually, they're the quick-fill quick-cap style that allows me to remove/replace 3 caps at one time. Sure helps speed things up when I have 30 cells to check. The old set of golf cart batteries didn't have the quick-fill style caps, so it was a bit of a chore. On the flip side, the new battery configuration is different from the old one which, coupled with those quick-fill caps, resulted in some of the battery straps being in the way of removing the caps. Thus the frequent need of the wrench.

[edit]Corrected name of filler caps.[/edit]

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