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Alkaline battery reverses polatirity - cause?

In my many years of dealing with electronics I've never seen this phenomena . I am curious as to a) the cause and b) the chemistry behind this. I have a remote control that has four AAA alkaline batteries in series that power the remote control. For a period of time, before the remote became inoperable, the LED activity indicator would not illuminate when I pressed a key but the correct behavi or would happen on the devices the control talked to, e.g. the relay would go on/off accordingly. BTW, the remote control is a 310MHz rf transmitter.

Recently, I pressed the on button and the relay clicked on but the off butt on would not turn the relay off. I replaced all 4 batteries and the contro l behaved normally. I measured the voltage of each battery: 1.4vdc, 1.35 vdc -0.35 vdc (Yes, th e polarity of the battery reversed) and 0.75 vdc. I put a 470 ohm resistiv e load and measured the batteries again: 1.33vdc, 1.28vdc, -0.31 vdc, and

0.71 vdc. A slight drop as expected and the polarity on the one battery w as still reversed.

I let the reversed charge battery rest for a few days and measured it again . It measured -0.22 vdc. I considered putting the battery in my self desig ned programmable battery charger (I can vary voltage, current, charging int erval and duty cycle, etc.) and doing some experiments but have not had any time.

I've never seen this before. The two low voltage cells were at the bottom of the series string with the reverse polarity battery being second from t he bottom. I can theorize that the bad battery has a (chemical) defect. There is no visible leakage on any of the batteries.

Any battery chemists in the crowd can shed some light on this? Anyone see this behavior before? Thanks

Reply to
three_jeeps
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At a guess I'd say the odd battery is not the same date code/manufacturer/etc as the others.

That battery was weaker than the rest and so when it went to zero volts out the batteries 'above' it in the circuit reverse charged it as it was in the way of the common negative connection.

John :-#)#

Reply to
John Robertson

This can happen to the weakest cell in a series battery and has been known over a century. Eventually all the stronger cells and the load circuit end up impressing a reverse polarity on the weakling. Hence the instruction to always replace with fresh cells from the same batch.

I can't help with the cell chemistry - no doubt others will ...

piglet

Reply to
piglet

Here you are fifth google result...

piglet

Reply to
piglet

TJ-

I'm no chemist, but it seems obvious that one cell reached zero before the others. Current continued to flow from the other cells, which caused the one cell to reverse-charge.

Fred

Reply to
Fred McKenzie

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Thank you for the ref and to the others for their thoughts. I must have a mental block on this - I am trying to visualize charge flow through the 3 s eries batteries with the middle one being weakest. Eventually what ever is producing the positive voltage dies out, taking the voltage potential of th e cell to zero. Got that. I dont get how the reverse charge in that cell is formed. The battery below it has , for example at 1.5vdc potential at its + terminal. The middle battery - terminal would see 1.5 volts (the + p otential of the bottom battery) and the top battery - terminal would effect ively have zero volt potential (being connected to the middle battery + ter minal which went to zero). Wouldn't the positive potential of the bottom ba ttery attempt to distribute itself via charge flow through the middle batte ry and reach the - terminal of the top battery, effectively making the volt age potential = 1.5 v? so how does the reverse polarity occur across the middle battery? The middle battery effectively is a short and supplies no additional charge from its - to + terminals

I noted that the voltages in the cited paper (thank you!) are similar to th e voltages on my batteries.. J

Reply to
three_jeeps

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a mental block on this - I am trying to visualize charge flow through the 3 series batteries with the middle one being weakest. Eventually what ever i s producing the positive voltage dies out, taking the voltage potential of the cell to zero. Got that. I dont get how the reverse charge in that cel l is formed. The battery below it has , for example at 1.5vdc potential a t its + terminal. The middle battery - terminal would see 1.5 volts (the + potential of the bottom battery) and the top battery - terminal would effe ctively have zero volt potential (being connected to the middle battery + t erminal which went to zero). Wouldn't the positive potential of the bottom battery attempt to distribute itself via charge flow through the middle bat tery and reach the - terminal of the top battery, effectively making the vo ltage potential = 1.5 v? so how does the reverse polarity occur across t he middle battery?

ge from its - to + terminals

the voltages on my batteries..

If you can picture the cell voltage going to zero, then what happens if the current continues to flow? The cell voltage will go negative. Isn't that pretty logical? That cell is not a short. The current still has to flow through the chemistry of the cell, only it causes some reaction that produc es the opposite voltage to grow.

--

  Rick C. 

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Reply to
Rick C

The fact that one was +1.4 and one was +0.75 indicates that they didn't start out equal. That was the cause.

The order of the string makes no difference. Any type of components in a loop can be in any order.

Reply to
Tom Del Rosso

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