I came aross a battery hazard I hadn’t thought of before. I asked one of my team members to remove the pigtails (power cable and plug) from an old battery. I’m sure the battery still had charge to it.
She enterprisingly recruited another team member to help, and I saw that each had a wrench on the battery - one on the positive erminal and one on the negative. I immediately asked them to stop. If there’s a wrench on each terminal, and the wrenches touch one another, they will short the battery!! Any piece of metal will conduct electricity, not just a wire and not just copper.
FYI, I could envision this happening, especially in a pit if two people change or just tighten connections and are in a hurry. Only one wrench on a battery at a time!
As well-intentioned as this is, just how would the two wrenches contact each other while contacting the terminals? Wrenches aren’t exactly as flexible as wires.
Gimme a large pair of open-end wrenches (uninsulated, naturally) and some electrically-insulated reaching devices and I’ll show you. Wrenches slip, wrench ends meet, “nice” shower of sparks.
Or, the human body can conduct electricity. Two students working contact, and the resistance is low enough, not only do you have sparks, but you have two shocked students, literally.
It’s not hard to short a battery with two wrenches, or a single screwdriver. I warned our students about the dangers several times before they assembled batteries to cables. It’s a serious business. Please be careful and think about what you’re doing.
garyk,
the greater danger here is that if the two wrenches touch while both contacting battery terminals, the chance for welding currents to flow is very high. Once the wrenches weld together and to the battery terminals, they will go to several hundred degrees rather rapidly depending on the state of charge. That temperature is also reflected in the battery which causes a rapid pressure rise that can lead to case failure, electrolyte leakage and possible explosion. It is for this reason, all battery terminals must be insulated at all times. Only work on one terminal while the other is insulated. The voltage is low enough that it can’t force enough current through your body to be felt unless it is across a very sensitive (read that packed with lot’s of nerves) area that is wet like with sweat or salt water.
Max,
The batteries are sealed so that you can use them upside down. The seals will not hold and likely will not be able to vent enough gas in abusive situations like shorted battery terminals. Case failure is the result.
Well, they’re sealed so that you can tip them and nothing will spill… But sealed batteries brought to a boil create pressure that will eventually (and in the case of a terminal short that doesn’t burn up whatever is shorting them like a fuse, very quickly) rupture the case, allowing the pressurized badness within to escape at high velocity…
I can tell you from experience ::ouch:: that a sealed battery will almost defiantly blow up during a fault, actually a non sealed battery probably will too under the proper conditions. And there is usually quite a mess to clean up after.
Put some care into working with batteries* everyone*. Use insulated tools or wrap regular wrenches and drivers with electrical tape. Same goes for test probes for meters and such, as little exposed metal as possible.
I know for a fact that one screwdriver is enough to short a battery if the person is not paying attention. Thats why we have a black burn mark on our famed orange-handled screwdriver now. The kid wasnt paying attention and shorted the battery and got shocked in the process. 2 Wrenches could easily short a battery and shock 2 people instead of just 1.
12 volts isn’t really enough to shock anyone unless it goes through wet skin. The person is likely to be startled (and perhaps slightly stung) by the sparks that fly upon initial contact.
The immediate hazard is from extreme heat as current flows unimpeded through the metal tool. The slightly less immediate but more dangerous hazard is from shrapnel and acid from an exploding battery.
Not to mention the sharp and tiny bits of lead and plastic, coupled with globs of strong sulphuric acid. More than enough to ruin your day, week, month and year in a flash.
I, too, have seen the aftermath of a battery explosion. You too would never forget it.
Last year, I accidentally shorted one of the 2010 batteries with a hacksaw. The gigantic shower of sparks was startling enough, I was lucky the hacksaw didn’t end up welded to the terminals :eek: