How can you reverse the polarity of a normal Alkaline AA battery?

Question

In my company we are trying to understand how can you reverse the polarity of an alkaline battery and then come up with a solution for that. We have a product that uses three AA batteries (the brand is Energizer Industrial...but it's really a normal battery). The thing is that, in some cases, we have found that the customer gets it dead on arrival. When we get the product back for investigation and we test the batteries, we find that two are somewhere in the 0.8 V range, but there is one that is always like -0.2 V. And it's always the same one (the one at the bottom - the battery housing is vertical). Nobody has been able to really answer how is that possible. We called Energizer and they cannot figure that one out either. I checked in several forums an found that customers have also had the same problem with a certain model of Canon camera. So this proves that it can happen. But, how does it happen? Why does it happen? What could solve the problem?

Answer 1

I have no experience of the phenomena you describe in alkaline cells, but I do, however, with nicads.

If a nicad battery is deeply discharged, to much lower than a nominal 1V per cell, the actual voltage across each cell will be different.

Sometimes one or more cells, those with the lowest capacity, will exhibit a reverse voltage.

What happens is that during the discharge the terminal voltage of an affected cell drops to zero while the battery is still discharging, and current continues to flow through that cell which becomes reverse charged.

It is a well known effect.

I don't know the chemistry involved but I wonder if the same thing happens in a battery of alkaline cells.

The fact that you say it's always in the same cell position is very curious, but, unless there is an additional conductive path across that cell position (or possibly a localised magnetic field which affects it), common sense says that it is purely conicidental.

Answer 2

There is nothing wrong with reverse polarity, it occurs because this cell was the first to be depleted and then the other two cells caused reverse charging of the totally dead cell. The real question to ask is why are these cells dying on arrival. Doesn't your device employ an off switch? It sounds like some of your circuits are defective and they place a large drain on the batteries even when it's suppose to be off. Failure of the 1st cell may be random luck or it may be due to heat from some nearby device. Heat will affect rxn rate and may cause the cell to dry out and fail before the other two. Also, are you taking a voltage tap across the first cell? This would place a larger load across this cell and cause it to fail first. Are cells bonded together? Are they welded and not soldered? Solder can damage the cell due to heat.

Answer 3

i am shocked that your underwriters allow you to package batteries installed in the product prior to storage/shipping. this is a fire waiting to happen. most customers are savvy enough to be able to install a battery. while replacing an occasional dead cell might be a nuisance, having a warehouse full of delicate electronic equipment burn up would be a major expense. getting the batteries out of the gear is a more important imperative than discovering the cause of cell reversal.

Answer 4

I haveAA recharge able batteries, it says so on the battery and you can't recharge a normal battery at all. You buy a battery charger they are usually in the same place you buy the batteries. It takes 24 hours to charge them the first time after that it shouldn't be as long. The charger plugs in to regular outlet and you can't charge them through your USB computer port.

Answer 5

Just pulled 4 Rayovac AA Ultra Pro's out of a handheld unit, one has -1.3v ......