1.5V "button cell" battery changes polarity???

The cell failed then was reverse charged by the other cells in the battery

RonUK

OK, could this in any way be the fault of the key itself, or is it more likely to be a cheap battery?

If all the cells are just in series, then cheap battery

Ron

Its a natural phenomena ! You are never going to get four batteries to have identical voltages and deliver identical currents ! So at some point, one of the batteries is going to become depleted first. Then the current through it causes it to become charged in reverse.

This also applies to rechargeable batteries as well. Its a particular problem with the sort of battery packs used in things like electric drills ! Never let them become completely discharged for this reason !

This is why you will see manufacturers warnings to replace all the batteries at once with new ones.

I have a remote control that uses four AA cells and at some point it stops working. I then test the cells that I take out, throw the bad one away and use the other three in things like my wall clock or other remote that uses only two batteries.

Thank you both. I'm glad that it's not the key that's doing it!

This happened to me a few years ago with the N cells in an HP calculator.

The odd thing (to me, at least) is that although such button cells can't be charged once they're dead, they can apparently be reverse charged.

Having a "charge" and having a "polarity" are pretty much two separate things.

So what do YOU call it when a cell's voltage polarity becomes reversed?

Reversed Polarity. cuhulin

well, you can often recharge them in the positive direction, but they're not designed for it, so bad things might happen, like they build up internal pressure and leak. chemically, though, all these electrochemical reactions are reversible unless one of the products is a gas or something and goes away.

z wrote in news: snipped-for-privacy@n75g2000hsh.googlegroups.com:

Not just leak. Explode. Spread toxic chemicals.

This can happen if they are reverse charged, overcharged or charged too rapidly. I stuck one into a 'universal battery charger' and forgot about it until I hear a loud bang a few minutes later! Made one heck of a mess.

Attempting to charge a mercury cell has additional hazards because heated mercury out-gasses enough mercury vapor to be fatal.

Actually, they can.

I had a situation a couple of weeks ago where the button cell in a guitarist's pickup was dead, with no spare and no real option to put a microphone in front of the instrument, I held the dead cell across the terminals of a PP3 until it became 'quite warm'. The resultant charge held for the first half of the show after which I 'recharged' it again for the second half.

Ron(UK)

an explosion is just a real fast leak.

With shrapnel.

-- aioe.org is home to cowards and terrorists

Add this line to your news proxy nfilter.dat file

• drop Path:*aioe.org!not-for-mail to drop all aioe.org traffic.

conversely, a leak is just any explosion where you can run away from it.

Try that with a high pressure steam leak and get back to me, if they find all the pieces.

z wrote in news:a62ea883-f6a8-413c-bbfd- snipped-for-privacy@f63g2000hsf.googlegroups.com:

You could say that a leak is a sssslllloooooowwwww explosion.

Slow as molasses in January. :)

But that reminds me....

Have you heard of the 'Great Molasses Disaster'?

heard of it? I've actually smelled it. (did not dealt it, however)