drained alkaline battery flips polarity

[PhotonWrangler]

Sitting on my keyboard at the moment is an Energizer AAA battery that was run into the ground by an MP3 player. What's amazing is not only that it flipped polarity, it's showing a no-load voltage of almost a volt! It seems this could damage some digital devices if accidentally inserted the correct way.

Have you seen this as a common occurrence? Does the Energizer bunny run backwards?

 

[Led_Blind]

It wont damage you devices as it can deliver almost no current then the polarities reverse.

 

[Illum]

I've had Duracell Cs and Ds change their polarity before...its kinda strange at first,, but after awhile I begin to think of it as normal occurrence...in a few cells

 

[lctorana]

Amazing.

It's a rather common occurrence in radios etc, but your MP3 player is, I presume, a single-cell device.

Just how this happened has got me.

 

[half-watt]

Sitting on my keyboard at the moment is an Energizer AAA battery that was run into the ground by an MP3 player. What's amazing is not only that it flipped polarity, it's showing a no-load voltage of almost a volt! It seems this could damage some digital devices if accidentally inserted the correct way.

Have you seen this as a common occurrence? Does the Energizer bunny run backwards?

the "pole reversal" phenomenon is NOT unique to alkaline battery chemistry. it also occurs, based upon my first-hand experience, with NiMh and NiCd battery chemistry. in my limited experience, it is far more common in NiMh cells, probably due to the 50% greater self-discharge rate of NiMh cells as compared to NiCd cells. so, when i didn't get to using or recharging them for a period of time, the NiMh were more likely to have self-discharged to the point of pole reversal than the NiCd cells during that same period of time - assuming that they were all at 100% SOC at the same T-zero. while i haven't seen it first-hand, i've read that Li-ion cells and primary Li cells can do the same thing.

a common cause of pole reversal is allowing rechargeable cells to remain in storage or unused in a device for long periods of time and undergo self-discharge. i had this happen to a number of NiCd and NiMh cordless power tool batteries. i usually just read a couple of hundred millivolts reverse polarity on the batteries that i have had that have undergone pole reversal.

on rarer occasions, i've taken cells (both old, near out of date, alkaline cells and newer NiMh cells) out of a light that haven't run for very long, but the light is already performing poorly, only to find that one of the cells has undergone pole reversal.

i have a charger that purports to be able to recover such pole reversed NiMh cells. it worked in four out of six pole reversed AA NiMh cells that i attempted it on. how well do the cells perform afterwards? frankly, i don't know. i foolishly failed to mark them as "recovered" cells so that i would be able to track their usage and performance subsequent to the "recovery". wish i had.

now, every two to three months, i take a couple of days and start recharging the batts in all of my power tools, as well as the individual cells used for other purposes.

 

[PhotonWrangler]

Thanks for the input everyone. Looks like it's a somewhat common phenomenon that spans multiple battery chemistries. I'm making a mental note to keep my rechargeables recharged after long periods of being idle.

BTW, it was in a single-cell MP3 player so there were no other forces (such as other batteries in series) working on it. Stranger than friction.

 

[Illum]

NEVERMIND, OT

 

[SilverFox]

Hello Half-Watt,

A point of clairifacation...

When NiMh cells first were introduced, their self discharge rate was greater than NiCd cells, and it was a major disadvantage. Over the years the NiMh chemistry has been improved to the point where the current cells actually have a lower self discharge rate than NiCd cells.

Unfortunately, the literature has not kept up with these changes. You can still find high self discharge listed as a major disadvantage of NiMh cells when they are compared to NiCd cells.

NiCd cells have a discharge rate of 1 - 1/5% per day. The modern (healthy) NiMh cells have a self discharge rate of around 0.7 - 1% per day.

As far as storage goes, NiMh cells, like NiCd cells, perform better when stored empty. If you charge them up and let them self discharge over a few months, your performance will suffer and cells in a pack will become unbalanced. If you store them empty, or with a minimal charge, they will perform better and last much longer.

Tom

 

[half-watt]

Hello Half-Watt,

A point of clairifacation...

When NiMh cells first were introduced, their self discharge rate was greater than NiCd cells, and it was a major disadvantage. Over the years the NiMh chemistry has been improved to the point where the current cells actually have a lower self discharge rate than NiCd cells.

Unfortunately, the literature has not kept up with these changes. You can still find high self discharge listed as a major disadvantage of NiMh cells when they are compared to NiCd cells.

NiCd cells have a discharge rate of 1 - 1/5% per day. The modern (healthy) NiMh cells have a self discharge rate of around 0.7 - 1% per day.

As far as storage goes, NiMh cells, like NiCd cells, perform better when stored empty. If you charge them up and let them self discharge over a few months, your performance will suffer and cells in a pack will become unbalanced. If you store them empty, or with a minimal charge, they will perform better and last much longer.

Tom

SF, good to know.

i did know about the improvement in NiMh rates. however, i didn't know about NiCd getting worse SD rates now then in earlier times. At least that's what it sounds like you're telling me if i understand your numbers correctly.

Numbers i've come across are about 20% per month for NiCd and 30% per month for NiMh. NiMh used to have about 45% per month (i.e., 2% of remaining charge each day, so starting at 100% and substracting 2% of the remaining charge per day would give us about 55% degradation - check me on that estimate please)

This puts the NiMh more or less in line with your numbers, but the NiCd values are different and lower than the figures you are suggesting. NOT saying yours are incorrect however. What would puzzle me a bit though is the way NiCd's would be getting worse SD rates now according to your numbers. Any idea why?

Thanks again - always an education reading your Posts.

 

[SilverFox]

Hello Half-Watt,

I don't think NiCd chemistry has changed. It is generally rated at 1%/day. This means that after 30 days you have about 75% left, and after 60 days you have about 55% left.

NiMh cells at 30 days have about 82%, and at 60 days have about 66% left.

At 180 days, NiMh cells are supposed to be at around 28%, but some tests with some good Energizer 2500 cells found them at around 37%. I guess the estimates may be a bit off, but I don't have a lot of data at 180 days.

Tom

 

[half-watt]

Hello Half-Watt,

I don't think NiCd chemistry has changed. It is generally rated at 1%/day. This means that after 30 days you have about 75% left, and after 60 days you have about 55% left.

NiMh cells at 30 days have about 82%, and at 60 days have about 66% left.

At 180 days, NiMh cells are supposed to be at around 28%, but some tests with some good Energizer 2500 cells found them at around 37%. I guess the estimates may be a bit off, but I don't have a lot of data at 180 days.

Tom

Right i didn't think so either, hence my making a somewhat veiled statement in my previous Post in an attempt to elicit a reply. The range of numbers you gave me in the first reply does indicate that, however.

Many sources have NiCd at ~20% per month 25% is fine by me too = that's the 1% per month figure, but would be a less then the oft found 20% figure, putting them only on par with newer NiMh cells. Hence my conclusion that you were attempting to communicate that NiCd had gotten worse (20% but now only 25%). In fact, according to some sources NiCd cells have improved too - now only 10% per month, but i haven't personally tried to verify this, so i went with the 20% figure.

You first said 0.7%-1% for NiMh. That's also *up to* 25% for the first month - not too different from the 30% figure i found in many places. I'm typically getting 20-40 percent loss from my newer NiMh (including the latest 2700's and 2900's) using a simple pulse load test. Nothing like the 2% per day of my older VersaPak batteries for some B&D cordless tools, or my old Radio Shack cells.

Are you using your no load/open circuit voltage measurement again for NiCd and NiMh? I've measured up to 89% off-the-charger voltage on my newer NiMh after a 30d storage at room temp (70F), but performing a pulse load test on them indicated less than 80%SOC (but more than 60%SOC). Performance sure indicates that it's nowhere near 89%. That's the difference b/t resting voltage and pulse load testing, as i'm sure you are aware.

Just like with Li-ion cells your numbers for NiMh and NiCd differ markedly from those published elsewhere in some sources (can't say "all" as i certainly haven't seen ALL published sources). Where are you obtaining your numbers?

Are you sure you're not just mixing up the numbers between the two and giving the NiCd percents to NiMh, and vice versa? Your numbers would be closer to other published sources if you were simply confusing the two.

My NiMh cells are essentially dead by six months for any reasonable current draw. Glow a filament, they might be up for that task. BTW, that NiMh six month 28% figure, i'm guessing is just an extrapolation of your 0.7% per day SD rate, or a simple open circuit no load voltage measurement. Am i right? I can see the appeal of taking a simple daily voltage measurement on a battery. Performing a daily load test of some sort drains a bit from the battery and changes it's internal resistance. That coupled with the change in internal cell resistance from SD affects working voltage when a load is applied. So, even coulomb counting alone the pulse loading isn't even sufficient to keep track of %SOC as available capacity will still depend somewhat on load when the cell is actually put into service. Though coulomb counting, coupled with some other parametric data comes close to actual tested %SOC.

All this i'm sure that you are more than aware of.
i only mention this for any other reading this exchange who might not be familiar with battery characteristics.

I wonder what the six month storage conditions were for those 37% Energizer 2500 cells? Do you know? LOX (no..., not the fish!!! sorry, a weak attempt at humor) [aka LOx] immersed or liquid nitrogen immersed?

Thanks again for taking the time to educate me.

 

[SilverFox]

Hello Half-Watt,

The numbers are based on test results. The testing is done on a battery analyzer. The cells are charged then discharged to determine their actual capacity. They are then charged back up again and left to self discharge at room temperature for a period of time. At the end if the time period, they are once again discharged to determine their remaining capacity. The difference in capacity divided by the time in days gives a loss per day.

Other than ending the discharge at 0.9 volts, voltage is not used in determining the self discharge rate of NiMh and NiCd cells.

Tom

 

[half-watt]

Hello Half-Watt,

The numbers are based on test results. The testing is done on a battery analyzer. The cells are charged then discharged to determine their actual capacity. They are then charged back up again and left to self discharge at room temperature for a period of time. At the end if the time period, they are once again discharged to determine their remaining capacity. The difference in capacity divided by the time in days gives a loss per day.

Other than ending the discharge at 0.9 volts, voltage is not used in determining the self discharge rate of NiMh and NiCd cells.

Tom

very good method. many thanks for the explanation.