flashlight battery got extremely hot

The little rain drops got flashlights for Christmas and they grabbed the wrong size battery to put in them (they put C size batteries in a flashlight requiring D cells) and my youngest just commented “My flashlight is really hot.”

And it was! I mean, so hot I could barely hold onto the plastic case of the flashlight. One of the batteries was even hotter. I was afraid it was about explode…so its sitting out in the garage right now hopefully cooling off.

What happened?

Is that battery hazardous to have around now?

What about the other C batteries that were in those flashlights that didn’t heat up, are they damaged/hazardous in some way?

One of those smaller batteries got cocked in there so as to dead short itself. A shorted battery can be dangerous in the heat that it develops. Put the right D cells in and it should be OK. Chances are nothing bad happened to the flashlight itself. The damage was in the discharged battery and all is well with it removed.

It definitely was a shorted battery. Throw the C’s from that light and don’t use them in something else. They can explode open with a short they heat up so much.

Back in the early days of police radio, supposedly officers sometimes spontaneously shot themselves. Drop a few rounds of ammunition in your back pocket. Stick your HT radio in there too. The recharger pins can short out against the bullet. Heats up, and BANG. (Urban legend? Rimfire hot spot?)

I’ve had the “hot seat” from storing a nearly-dead 9V battery in a back pocket with loose change. The pennies don’t heat up, but the battery sure does.

I had a “hot pocket” once. This was quite a few years ago when rechargeable NiCd batteries were pretty common and I used them for my Walkman. I put a couple of AAs in my front pants pocket which also had some loose change. A quarter got pretty hot from being in contact with the terminal of one of the batteries. I could feel the heat against my leg.

I’ve had the AA and keys in pocket short happen. Now I always rubber band AA’s together and use plastic over the positive terminals, or put each bundle in a plastic ziplock bag.

I put 3 new D size batteries in a mag flashlight. Used the flashlight and turned it off. All was good until I went to put flashlight way. It was HOT! And hard to hold. I unscrewed and dumped batteries out. They were so HOT I had to use potholders to pick them up and move them. Almost 45 minutes later they were cool and trashed. Why did that happened? Right size batteries put in properly.

Cheap batteries made with Zinc I would imagine in today’s world in new stuff.

Even more likely with cheap foreign made plastic kids flashlights.

I was messing around with flying machines when the smaller stuff like HU-1 Huey’s were using NI-Cad batteries, They could go nuts while charging. Much $$$$$ damage.
Can happen to any battery but with batteries, you mostly get what you pay for.