AA Cell Changes Polarity!!!!

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AA Cell Changes Polarity!!!! Empty AA Cell Changes Polarity!!!!

Post by Guest on Thu Mar 21, 2013 12:21 pm

I was listening to a portable radio today which is powered by 4 AA cells. After a few minutes the radio went silent and I thought the cells might be weak. I decided to test the cells and 3 were fine but one cell caused the needle to move left! I had to check and make sure I didn't have my leads reversed! Well I didn't and I reversed them to now be wrong. To my surprise the needle went to the right but showed a weak cell.


I have never seen that happen before! Shocked


Last edited by MEZLAW on Fri Mar 22, 2013 10:13 am; edited 1 time in total (Reason for editing : correct from battery to cell)

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Post by 75X11 on Thu Mar 21, 2013 10:47 pm

I've not seen that happen before. No chance that cell was reversed in the radio, was there?
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Post by Guest on Fri Mar 22, 2013 7:40 am

75X11 wrote:I've not seen that happen before. No chance that cell was reversed in the radio, was there?

I don't think so......the cells were in the radio for about 6 months and I don't use it often. I turned on the radio and tuned in an AM station and after listening for about 10 minutes walked away. When I came back the radio was silent! I thought the cells were just old and weak. when I removed and test them, 3 were just fine but the one actually measured in reverse. I replaced the one cell and continued listening to the radio. That one cell now reads dead.

I have never seen a cell reverse it's polarity before! confused

Since I really don't remember one cell being reversed (I think I would have noticed, but I am getting old) I will try to duplicate this by inserting one cell reversed and see what happens.

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Post by willy3486 on Fri Mar 22, 2013 8:33 am

Seems like I remember someone who let a car battery to go completely down. They reversed the leads and charged it the wrong way. It charged fine and worked. They reversed the leads so it would start correctly. They did that so if someone stole their battery they would mess up their car they put it in. Its been over 25 years since I heard that and I don't know if these new crappy batteries could be charged that way. As far as that battery goes I wonder if it was weaker or some kind of defect in it. And when it sat it went completely down. Then when the current went through it the thing got a reverse charge somehow. Odd.

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Post by 75X11 on Fri Mar 22, 2013 9:35 am

In a lead acid battery, it's construction is such that the charge current from zero could be reversed and accepted and that was sometimes done to correct plate sulfation. The alkaline cell though, is constructed in such a manner as to maintain a singular polarity. That is why I wondered if the temporary reversal may have caused the temporary polarity reversal before discharge state.

http://electrapk.com/alkaline-cell/
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Post by Guest on Fri Mar 22, 2013 10:10 am

I just tried installing one cell in reverse. All I got was motorboating out of the speaker. I tested the cell afer it was removed and the polarity was fine. I don't know what happened. The bad cell still has a little reverse kick to it. I wonder if Energizer will know what it is?

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Post by 75X11 on Fri Mar 22, 2013 10:43 am

I'd ask them. Most battery suppliers have QA departments that track all defects in their products.
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Post by easyrider8 on Mon Mar 25, 2013 5:44 pm

This is quite common when you have cells in series.

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Post by Guest on Mon Mar 25, 2013 5:59 pm

easyrider8 wrote:This is quite common when you have cells in series.

Dave

Well......this is new to me, but I'm glad you posted so members won't think I'm crazy! lol!

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Post by atwater10 on Thu Mar 28, 2013 4:01 pm

Just like Dave says: "Quite Common w/cells in series"

This can happen if cells of different capacity/or freshness are used in a series string. When the weakest one discharges to zero, the remaining cells will present a reverse current through it and force a reverse charge on it ... Then Wah Lah, lots of heat generated and a leaky goo all over the place Mad
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Post by terrydec on Thu Mar 28, 2013 4:46 pm

Did you ever hear of heating batteries to charge them up? If I hadn't seen it with my own eyes I wouldn't believe it. But this guy did it. The batteries were regular alkaline, and they were dead, I checked them my self. He put them in a frying pan for a few seconds and the voltage was restored. It was only temporary but powered a radio for about half an hour.
I've never tried it. Exploding alkaline is not my thing. Also, I think this guy might have been inhaling an illegal substance. But it did work.
Weird!
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Post by 75X11 on Thu Mar 28, 2013 5:06 pm

In my salad days, trying to wring each last bit of power from a battery, I had read that a part of a batteries failure was due to poor electrolyte contact on the cathode and anode. a small amount of charge can be restored by taking the battery and lightly rapping it straight down on a soft surface, like a chair arm. Heating and liquifying the electrolyte bearing material would probably have somewhat the same effect. I'd prefer not heating them in such a manner. One other thing about doing this, it speeds up the onset of post-charge leakage.
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Post by Guest on Thu Mar 28, 2013 7:15 pm

atwater10 wrote:Just like Dave says: "Quite Common w/cells in series"

This can happen if cells of different capacity/or freshness are used in a series string. When the weakest one discharges to zero, the remaining cells will present a reverse current through it and force a reverse charge on it ... Then Wah Lah, lots of heat generated and a leaky goo all over the place Mad

It was 4 cells in series but all out of the same package. This happend in the matter of 15 minutes, the radio was playing, then it went silent. A check of the cells showed three very good and one reversed. I believe all cells leak after time and take them out when the item is not in use.

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Post by atwater10 on Thu Mar 28, 2013 9:27 pm

It was 4 cells in series but all out of the same package. This happend in the matter of 15 minutes, the radio was playing, then it went silent. A check of the cells showed three very good and one reversed. I believe all cells leak after time and take them out when the item is not in use.

I suspect that one of your batteries may have been defective or failed prematurely and was it that probably started the process … I’ve had brand new packages of batteries opened and found a dead one in the lot … especially those bulk packages from the large box stores. Cool
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Post by terrydec on Fri Mar 29, 2013 12:16 am

I ALWAYS buy Duracel. They have a new battery with a blue band. It lasts 3 times as long as any other. I have an MP3 player hooked up to my house transmitter that plays 12 hours a day. The regular battery lasts 12 hours, the new one lasts 3 days.
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