The Dangers Of A 9V Battery

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Most people don't realize how quickly a 9V battery can start a fire. Read on to learn how to safely handle and dispose of 9V batteries.

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A 9 Volt battery is such an innocent looking thing. We don't use them in many devices, the most common being a smoke detector which is designed to save lives. So what could be so dangerous with a 9V battery?

The battery itself, as it sits in its packaging or being used in a device is just as safe as any other battery. It's when a 9V is out in the open and loose that it becomes a potential fire hazard.

A typical battery like an AA, AAA, C, or D cell have the positive (+ side) terminal on one side and the negative (- side) on the other. The chances of something, like a wire or piece of metal, connecting both sides of those batteries together is slim.

With a 9V battery, the positive and negative terminals are located on the same side of the battery. They're also right next to each other, just milimeters apart. If a conductive material (any metal) connects both terminals together it shorts the battery out.

When a battery shorts out heat will be generated. Picture an old incandescent light bulb and the fillament inside. When you apply electricity it creates heat and light. It's enough heat to start a fire but it's safely contained inside of the glass bulb.

Imagine tossing a 9V battery into a drawer and it bumps up against a paper clip (for example). That paper clip now acts like that light bulb filament. It heats up instantly as it shorts the battery terminals.

We all know the three things needed to start a fire, right? Heat, fuel, and oxygen. Oxygen is in the air and we just added heat from the paper clip shorting the battery. The fuel will be anything nearby that can burn. Papers, cardboard, the wood the drawer is made out of, you name it.

Many house fires are started from 9V batteries. The most common way is when you replace your smoke detector batteries (which you should do yearly). Most people take the old batteries and toss them in the trash. Imagine if two batteries touched together and shorted in your trash. It could burn your entire house down.

So how do you deal with 9V batteries? It's so easy! Put the old batteries back into the plastic package from the new batteries and seal that packaging back up with tape.

If you don't have the packaging then wrap tape around the battery and terminals. Use duct tape or electrical tape or something thick and go around the battery a few times. Scotch tape isn't a good tape for this type of thing.

Note that this can happen with any type of battery. It's most common with 9V style because of their design. But any battery can short out so you should be using these tips for any battery as well as recycling your old batteries and / or disposing of them properly (which is not in your house trash).