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Battery safety Answered

Hi guys, I was wondering if it's dangerous to touch two wires hooked up to a 9v battery to each other. They heat up really quick, could they make the battery explode or do something else bad if left like that for any long period of time? I tried to search for the answer, but couldn't find it.



9 years ago

Just a few words of caution...
Battery technology has improved a lot in the last few decades. It used to be pretty difficult to hurt yourself with standard (AA-C-D-9V) batteries. But nowadays with alkalines and rechargable batteries, it's a lot easier. You can easily burn yourself short-circuiting a battery with a wire. You might generate enough heat in the wires to cause fires. You might be able to cause a battery to overheat to the point where it "bursts." This is usually a pretty trivial event; MOST battery technologies still are based on water as a main internal ingredient, so that when they burst the effects are limited to a small pop, a leakage of rather caustic chemicals, and the stoppage of normal battery function. I've also seen high-voltage "shocker" type circuits that say "this is safe because the battery cannot provide enough current to reach dangerous levels at the output", and I wonder just how safe they are with modern batteries...

However, the "Lithium Ion" and "Lithium polymer" batteries used in many modern rechargable devices (cell phones, lap-tops, mp3 players, cameras, etc) need to be mentioned. In these batteries, the internal liquid is flamible, AND there are some other chemicals that react violently with each other at high temperatures. Given suitable mistreatment, these can "vent with flames" rather spectacularly (though it's not quite an explosion.) The most common mistreatments that cause this behavior are improper charging or physical damage, leading to short circuits INSIDE the battery, but its rumored that external shorts are bad news as well. A rechargible battery PACK usually contains numerous protective devices designed to prevent such incidents, but your experiments might lead you to, say, taking apart "broken" battery packs and using the internal cells. In which case the level of care you take needs to go upward a notch or two...


that is actually known as "short circuting", and its not really safe, but i read that in an old book, so it could be safe today. It drains the battery fast....

Hi, Adrian. What you've described is precisely a short circuit; in fact, it's the very first example in your Wikipedia link :-)

You've connected the postive and negative voltage terminals with no load. The wire and the battery will heat up, for sure (since it has non-zero resistance and you're sucking lots of juicy current through it). A regular electrolytic or alkaline battery won't explode, but you will drain it to zero voltage pretty quickly.

Oh. Haha, I'm an idiot. Sorry, DJ... I see, thank you for explaining it! I noticed I could make cool sparks and even some kind of apparent magnetic effect if I touched both wires to an altoids tin. But it stopped working suddenly. Musta drained it as you said.

Magnetic effect? If you got sparks at the same time, it's more likely you created a small weld (either with actual welded metal, or with oxidised patches overlapping).

That's exactly what it is, a 9V has the current capacity to do so, most things do, I saw this effect a lot during some recent experiments, I couldn't tell if it was welding or oxidation but the bond can be quite strong so welding of tiny proportions could be it...

Linux already did it, not only that but it's useless in reality because it's a very weak weld most of the time, plus I'm not actually sure it's a weld or if it's oxidation with two metals, like just being glued by oxidation...

Really? I'll have to see what he did... Hmm. I'm experimenting with more batteries, maybe that will help-I'm not giving up quite yet, not because I don't believe you, just because I want to see for myself.

I tried it with various power sources... It happened notably on 50V at less than an amp, currents what matters here so a lantern battery might work better... At one amp and 12V I could stick magnesium together with wires... (I was trying to make something I had a notions about work, now I know why the lamps don't exist.)

Check first - it's more likely to be fused oxides (=useless), but if you do create an actual weld, it may be too small to be useful.

Unless you're welding tiny things?

Maybe 9V soldering?

Okay. How do I check? I was holding two paperclips to an altoids tin...so not much visible. That'd be cool if it was welding though!


Touch the clips before you connect the battery - do they still stick?

If nothing happens without sparks, then it's probably oxidisation rather than welding.

If you get a better, firmer join if you run the current for longer, then maybe it's a weld (assuming that longer = hotter = more melted metal).

By the way (for others reading this discussion), this is what we call Science -- observe something you don't understand, formulate hypotheses, then come up with ways to confirm or disprove those hypotheses.

Many thanks to Adrian and Kiteman for an excellent off-the-cuff demonstration!

>suffers flashback to staff pantomime, executes deep curtsey

My flashback is to the Mr. Science, and Bill Nye the Science Guy series... :-)

We got it in my area on PBS for the longest time, but I haven't seen it for awhile (might be because of my shift too).

Okay, I tried it with another battery because I lost the first. No sparks on the metal, but still the same "sticking" thing. And it leaves little marks! I can't really tell if it affects it when I leave it longer. It seems to be very fragile though. I must experiment further. Also, for some strange reason, when I move the wires closer together on my tongue, the shock hurts way worse. I even think I made sparks in my mouth!

This is very cool :-) You can tell that smart folks are interested. If you have the patience and interest, take pictures as you play with the wires and tin. Try other metals (aluminum foil should behave the same way as the Altoids tin, a soup can might be different). If you feel like you can time things with some accuracy (at least of order seconds), then do so. This is good science you're doing, here :-)

I'll do that! I'll go get more batteries and hope to post more pictures today or tomorrow. Thanks for your interest-I hope this works. If not, I guess I still have an interesting way to play with batteries. :D >This is good science you're doing, here :-) Thank you! That means a lot, especially coming from you.

I thought Altoids tins were steel?

Duh. All I needed to do was check with a magnet...

If you could come up with a 9v powered pocket sized welding unit, you would make a million. I know I'b buy one!

. Welding depends on current not voltage. A transistor battery is not going to put out enough current to do any real welding. Might work for "watchmaking" size stuff, but I have my doubts. If you want to pursue it very far, you will need an inert gas (eg, Argon, Nitrogen, CO2 might work) blanket to inhibit oxidation.

I have a horrible feeling that oxidation is all that's happening, but it's worth checking, no?

. Most certainly yes. ;) I'm with kelseymh - it's a great experiment.

Yeah, that might up the danger as Adrian doesn't appear to be experienced in electronics at this point.....meaning only she could hurt herself if not careful and updated.

Haha-it'd only be dangerous if I could actually manage to connect a capacitor to the battery. :D You're right, I'm not experienced with electronics.

I suppose if one day I just leave with absolutely not a word to anyone, ya'll will know what happened... =D

There are plenty of good tutorials online if you are interested, and quite a few of us here are always willing to help in any way we can.

Could the tin have been acting like a coil ?

not at the low currents that are here (i think so)

Speaking of magnetism, I touched two magnets to the side of my smaller TV, and BOY did it mess with the picture.

Don't do this too often, especially with a CRT monitor, as it will mess up the orientation of the electron gun and you will get either distorted pictures or weird colors.

That's EXACTLY what I got. I now need a degaussing agent.

Go in to settings and look for degauss, doing that several times may restore the picture a bit, other than that time will eventually fix it if it's not completely buggered.

. Gee, you're old. Most modern CRT TVs/monitors have a degauss function built-in. Some require manual initiation, but most will auto-degauss every so-many times you turn the TV on (often every time).

Monitors have a manual degauss along side the auto one aswell, not all of them but ones aimed at commercial use definitely, you get quite a good noise from it if it's been on for ages...

that is news to me :-) I just knew I had never seen it on my TV drop down menu :-) it is only about 4 years old

. It's probably doing it every time you turn on the TV and you just don't notice it. My Trinitron monitor makes "bhhhuuungggg" sound when I turn it on.

All I hear is the gun warming up high pitched whine that is severely irritating and the crinkle of static when the picture comes on...