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We know that you can start a fire with a battery. the better prepared you are the easier it is going to be.

I am not prepared and all I have in my pockets is my car keys, which includes a keyless entry fob that has a '3v Lithium Coin Cell Battery' is it possible to start a fire with this battery? All I have is the metal key ring, finger nail clippers, and a couple of other keys on the ring.

I don't have a tiny screwdriver to get the battery out, so I am going to have to use a rock to break the key fob. I suspect that banging two rocks together would be a more effective fire starter, but I might be wrong.

Can I start a fire with my key fob battery?

James Jenkins
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2 Answers2

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With just the right equipment in a laboratory setting, you can use the energy in a key fob battery to cause a spark. You can then use that to start a fire under the right conditions.

However, that's not going to happen in any realistic back country conditions. The voltage and current capability of a key fob battery are just too low.

The reason you can sometimes use a car battery for starting a fire is because a car battery can deliver a massive amount of current. When shorting the battery with a small wire, the contact point gets so hot that some of the metal is vaporized, causing a spark. Sometimes small amounts of molten metal are also shed off. A key fob battery just doesn't have the oomph to do that.

In addition, it's not easy to start a fire with just a electric spark unless you have ignitable vapor. A few drops of stove fuel on tinder, then letting that vaporize for a few seconds can work, but trying to light solid tinder directly is very difficult. The reason this is sometimes successful with a car battery is due to the molten metal resulting from the high current, not the spark itself. With a car battery, you can even get small wire to glow, and then melt. A key fob battery isn't capable of that.

Olin Lathrop
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A bit more than a comment on Olin's answer:

I've done an experiment, and no, you can't.

I took:

  • a brand new CR2025
  • some steel wool to make it easier; this is a nice firelighting filament with bigger batteries
  • a tissue

I shorted the cell using the steel wool, held in a pad of tissue to provide tinder and keep the heat in. It got fairly warm for a couple of minutes, even through the tissue, but when it cooled and I opened the tissue it wasn't even blackened. If I couldn't get close with the contents of a house and garage at my disposal, you're not going to be able to do it in the field.

imsodin
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Chris H
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