Anyone see a battery go negatively charged before? 6-2-05

[dmcowen674]

I've been around Electronics/Electrical nearly all my life and have never seen this before.

Last year around October Lightning hit and knocked the Digital Answering machine out. It still worked but the display was messed up and didn't make any sense and couldn't change anything.

So left it alone until yesterday. Figured it couldn't hurt to change the batteries even though it was still working. So took out the batteries and it went dead as expected.

I started to check the batteries and found 3 out of the 4 AA batteries to be perfectly fine.

The fourth battery is the kicker. It reads negative .5 volt!

I replaced that battery and powered the unit back up and was able to program it.

Apparently the circuit did not like the one battery with a negative charge.

So my question or questions are;

How come the negative charge of the one battery did not affect the other batteries in a bad way?

What the heck happened to the battery putting out the negative charge (yes apparently the lightning did it)?

What exactly was the reason of the battery config with the one negative battery had on the circuit?

Should I hang on to the negative charged battery for further testing?

 

[jongyoo]

are you sure you didn't get the polarity wrong when you used the multimeter?

 

[phisrow]

It is possible for batteries to be run in reverse like that. Often happens to the weakest cell in a battery pack, especially in somewhat abusive applictions like RC cars, planes, helicopters, etc. The battery is probably worthless now.

 

[f95toli]

Yes, I have also seen it several times in lead-acid battery packs, sometimes this polarity reversal makes a few batteries "explode" which can be pretty messy.

 

[MobiusPizza]

How come the negative charge of the one battery did not affect the other batteries in a bad way?

I an answer this one.
If you put two oposing voltage in series the electro motive force just cancels out
If you have 3 1.5V battery and a -0.5V battery you will get 4.0V
Current would be still in the right direction, so really the -0.5V battery takes the most daage because current in its perspective goes the wrong way

 

[CrispyFried]

It does happen, I race radio control cars and if you run the pack way down in abusive situations the weakest battery reverses. Its junk now.

edit oops I just noticed that I said what phisrow said.. need more coffee...

 

[dmcowen674]

Originally posted by: AnnihilatorX

How come the negative charge of the one battery did not affect the other batteries in a bad way?

I an answer this one.
If you put two oposing voltage in series the electro motive force just cancels out
If you have 3 1.5V battery and a -0.5V battery you will get 4.0V
Current would be still in the right direction, so really the -0.5V battery takes the most daage because current in its perspective goes the wrong way

Thanks for all the replies guys.

Perhaps the above explains the strange behavior of the circuit while that battery was present.

 

[TStep]

Hmmm....never knew this. Learn something new everyday.