AceOfHearts

Hi,

Yes, another battery overheat issue. This time it I couldnt explain it at all. Basically, I had 4 AA battery in a standard case. I wrapped around some black tape to avoid the contacts touching any of of the other circuitry on my robot.

I had not connected the battery terminals to anything but when I was installing the battery pack onto the robot, all of a sudden I could smell a burning odour. I immediately checked my soldering iron if it was on but it wasnt. I had not suspected anything on the robot itself to be burning.

Then I noticed how the battery pack in on my robot was emitting smoke and the plastic case was melting right in my hand! Small molten plastic particles dropped on my hand (no injury) and I was sure this thing is way hotter then I would ever want it to be!

I immediately tried to unwrap the black tape, the end bits (connected to + and - were melting), so that I could take one of the cells out quickly.

A later battery case inspection reveals that most of the end terminals of the case had melted away with one or two intact.

This was an unusual phenomenon, and a dangerous one at that! Anyone else experienced the same? Any one know of reason/s why this could happen?


Thanks,
peace.

Nigel Goodwin

You'd got a short circuit across the batteries - as simple as that, nothing unusual about it!.

You must be VERY careful with batteries not to sort them out, and even more so with NiCd or Lead Acid - both of those have enough power to cause serious damage, and VERY quickly! (they can even explode!).

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AceOfHearts

Thanks Nigel for that. I may have indeed. These were Duracell M3 ones, so they have a lot of energy in them.

I did not know that shorting battery terminals could result in this. But lesson learnt.

So if I were to connect the + terminal to the - terminal of an AA cell, what would happen? Would it heat up dangerously? Or does there have to be certain number of these AA cells in series for it to happen (higher voltage)?

Thaniks again.

Nigel Goodwin

Yes, even one will heat up dangerously - but, whatever you do!, DON'T EVER DO THAT WITH NiCd - it will self destruct in seconds, if not less!, and can be VERY dangerous!.

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Gayan Soyza

If you do it in a high amperage battery or a battery pack the first thing you feel that the wire is getting hot & burning the outer insulation.Don't do that as earlier mentioned.It may the first step to attempt to a blast in your house.

Always use battery housings.Crocodile clips good to solder to wire ends that comes from battery terminals.If it is a fixed battery pack then I used to put some heat shrinks to avoid contacting with other parts also with heat shrinks it looks great.

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picbits

Just a thought - did you get your Duracel batteries from a reputable supplier ?

Reason I'm asking is that there are a hell of a lot of fakes out on the market at the moment and there have been reports of exploding and overheating fake batteries.

I thought I might have bought some fakes the other day - I paid £0.99 (around $2) for a 4 pack of Duracel AAs with a good date code on them. I got them from a discount store (everything is 99p) so they were about a third of the price they should have been.

Something just doesnt feel right about them but I've phoned Duracel and they dont seem to think they are fakes.

Krumlink

This site has a lot about batteries that you might want to know.

http://images.google.com/imgres?imgu...en-US%26sa%3DN

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kchriste

On some NICAD and NIMH batteries most of the cylinder part of the battery is part the negative terminal and only insulated by a thin piece of plastic sheet wrapped around it. There is a very small gap between the + & - near the + button. Also, if you connect them in series and form the "pack" in a square there is only a very thin layer of plastic between the first and last battery in the string with a 4.5V potential between them. If you slip when soldering them together it is very easy to penetrate the thin plastic and expose it to the danger of contacting the other battery or wiring.

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Super_voip

were these batteries connected via tags or nipples?

Hero999

It wouldn't make any difference, exactly the same current will flow if you connect up 1000 batteries in series as when you short one cell. The current if determined by the internal resistance of the battery which would be 1000 times greater with a 1000 cell pack than a single cell.

Always use a proper battery holder for your cells ad a fuse is a good idea too. I recommend poly switches or bimetal switch type circuit breakers as it saves replacing the fuse.

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