The other day I was changing the nine volt battery in my Multimeter pulled the old one out that would no longer light the display might have been in the meter 5 years or longer.

Installed the new one did a few tests to make sure every thing was working

In the course of moving things around I smelled something hot thinking it might be a light ballast or something on the AC unit I checked nothing was hot

Here I had bumped the old 9vdc battery up against a bolt enough to cause a dead short. Being it was only 15 or 20 minutes I can`t say if in 30 minutes something would have caught fire or the battery would have drained better safe then sorry.After it cooled down I checked the voltage it was just under 6VDC

I might try a controlled experiment to see how it would play out

 

I've seen one of those survivalist dudes make fire with some steel wool and a 9 volt battery.

 

Within certain limits, it's not the voltage that makes those 9V batteries what they are, it's the current they're capable of producing. They're a relatively high current battery, especially for their size.
For example, using a piece of wire, and short a D cell battery. If the wire is much bigger than 14ga, it won't burn the wire, or overheat and burst the battery.
As you saw, short a 9v battery, and it can really heat things up. At best, the battery will burst. Or burn the wires they use inside to couple the cells inside it. Due to the design of a 9v, with several cells added together to make it 9v, it can make some decent current, for a battery.

Yes, a 9v will cause a small wad of steel wool to heat up to the point it'll start some punk, maybe even some tinder, on fire in a survival situation. I keep a 9v and some steel wool in my grab-n-go pack. I also keep some home-made lifeboat matches, and some fire starter units I make my self. Put a bunch of sawdust in a used egg carton, and pour in some paraffin. A small piece of hemp cord for a wick helps. Just make sure it soaks up some paraffin.

Watch those 9v batteries. Keep the little plastic contact protectors, and put the new battery's onto the old one, for safety.

Have fun all!
Pat☺

 

Tape the contacts on these buggers. Even a simple spark from a piece of conductive fod can light up some plastic, paper, oil, or other accelerant nearby.

Also, fun fact: If you open up a 9v (it's safe), there are 6 AAAA batteries inside. It's an obscure size, but the same as buying 6 from the store.

 

The older 9 volt batteries from the '50s and 60's were built of six flat rectangular cells stacked one on another.

I guess it's been a long time since I dissected one

. Never seen one made of cylindrical cells before.

 

Just one of those rare things that happen. When my neighbors wife came to the door as i turned to talk to her I can only guess I bumped the old battery.

Knowing what can happen with a shorted battery of any size .

This was the first time since I was able to change my own batteries did this happen besides with larger batteries in vehicles which I tend to short freeze or explode most any time just be looking at them.

If it saves a visit from the Fire department for someone as is good.

 

Same here. The ones I saw were the flat stacked up cells in the outer metal case. Never saw the AAAA cylindrical cell type, but hey, things change. The AAAA type probably make more current than the old flat cells. Maybe not for as long, but more per unit time.

Anywho, a good idea to wrap a couple layers of electric tape around the battery, over the contacts, then down and back up. Especially if you're going to dispose of it in the garbage. Or strip off the metal case, as Wyo did above, and snip the wires connecting the cells together. That's the REALLY safe way. A single AAAA cell is pretty safe, six of them all connected in series that way, as he found out, not so much.

Have fun, all!
Pat☺

 

Same here. The ones I saw were the flat stacked up cells in the outer metal case. Never saw the AAAA cylindrical cell type, but hey, things change. The AAAA type probably make more current than the old flat cells. Maybe not for as long, but more per unit time.

Anywho, a good idea to wrap a couple layers of electric tape around the battery, over the contacts, then down and back up. Especially if you're going to dispose of it in the garbage. Or strip off the metal case, as Wyo did above, and snip the wires connecting the cells together. That's the REALLY safe way. A single AAAA cell is pretty safe, six of them all connected in series that way, as he found out, not so much.

Have fun, all!
Pat☺
Edit: Sorry for the double post. Not sure how it happened, nor real certain how to make the duplicate disappear. Any help greatly appreciated.