Can a 9-volt battery start a fire in your RV?

Yes it can, and it's much easier than you might think!

Dear Mike,

I recently read where a 9-volt battery thrown away in a trash can can started a fire in a garage. Can this really happen? What do we have to do to keep safe in our RVs? —Donny F.

Dear Donny,

In a word, YES, a 9-volt battery can start a fire. So let’s explore why a 9-volt battery can be a fire hazard, and under what circumstances.

But first, a short personal story about why I know this. Perhaps 25 years ago I was doing a big sound gig outside for the Maryland Symphony Orchestra on the 4th of July. So it was hot and sunny, and I was crawling around on stage setting up 60 microphones. Some of my wireless mics used standard 9-volt batteries, just like the ones you’ll find in most smoke detectors and many transistor radios. You know the ones that look like a little rectangular cube with a pair of contacts on the top.

And those contacts are uninsulated, which is why I literally had hot pants that day. You see, I had stuffed a new 9-volt battery in my pocket, along with some loose change. I didn’t think about this until I noticed my leg feeling hot. At first I assumed it was the hot sun beating on my leg since I was laying on the stage under some chairs running cables. But the heat soon got unbearable and I reached down to feel my pants, which were REALLY hot.

When I jumped up I noticed my jeans were smoking. Yes, literally hot pants. What had happened was the 9-volt battery in my pocket was shorting out on the quarters in my pocket and were now too hot to touch. A few more minutes and my pants could have caught on fire. Of course the other guys in the crew thought it was pretty funny, and I was amused if a little burned.

So why did this happen and can it happen to me?

Well, a standard 9-volt battery has a lot of energy in it. After all, it can power a smoke detector for a year or more and run a transistor radio for dozens of hours. And if that energy is released quickly, it converts into a lot of concentrated heat. So any metallic object bridging the terminals on the top of the battery will create a short circuit which quickly causes the cells inside the battery to overheat and catch on fire in minutes.

Normally when these batteries are sold they’re packaged so the terminals can’t contact anything metallic. But throw a 9-volt battery in your junk drawer and anything metallic can accidentally come in contact with the terminals as your RV is driving down the road. If that occurs, you can have a fire start inside your RV in a few minutes, and there are few things more scary than a fire in an RV, especially if you’re driving down the interstate.

What to do to keep safe?

Well, many industrial-duty batteries like the one above have a little plastic insulator on the top you remove before installation. This prevents them from shorting out by making accidental contact with anything metallic. You should always “cap” any 9-volt battery that’s not installed in a piece of gear. Even when they’re “dead” there’s still enough power left in a 9-volt battery to start a fire. And don’t do like some of the churches where they go through a bunch of batteries every week and just throw the used ones in a bucket. That’s a sure invitation for a fire to start.

If you don’t have a plastic cap on your battery, then a simple wrap of electrical tape over the top of the battery will protect it from short circuiting and catching on fire.

We always put a wrap of black tape around any “dead” batteries during a show so we know they’re not to be used. And some of my stage crew put a wrap of green tape on any new batteries so we know they’re brand-new and ready to be put in Beyonce’s mic (or whomever). 

Don’t believe me… Read this!

Duracell, a manufacturer of 9-volt batteries, and the National Electrical Manufacturers Association, a trade group that represents battery makers, provided these tips:

• Always keep all batteries in their packages before use.

• Don’t carry 9-volt batteries in your pocket – keys and coins can short the battery.

• Cover the terminals of all loose batteries with electrical tape.

• Never store or dispose of batteries near flammable substances.

• Follow these tips with other batteries as well. All batteries can short circuit.

It’s a simple solution, it only takes a minute and it could potentially save your life. And here is a video of one house that went up in flames when a homeowner put a bag of “dead” batteries in the garage. Don’t let this happen to you in your RV.

Let’s play safe out there… Mike