Best way to revive/restore AA 1.2V NiMH rechargeable battery

Thread Starter

Themusicman

Joined Apr 2, 2017
48
Hi All

I have all of a sudden come across 8 of my AA 1.2V Duracell NiMH batteries that have each failed to hold any reasonable amount of charge.

Sadly, I discovered this the hard way as I had put them in my camera bag as spares for my flash unit and when I placed them inside the flash ready to use, I found they fired for only 10%'ish of the time they used to. Nothing major, only a hobby shoot, but nonetheless, I was surprised.

So, having read a little on t'interwebby about how to recover these batteries, I'd like some advice from the experts on here if I may, please. Is there a way and if so, what might that be - to recover these battery types?

Thanks.
 

ian field

Joined Oct 27, 2012
6,536
Hi All

I have all of a sudden come across 8 of my AA 1.2V Duracell NiMH batteries that have each failed to hold any reasonable amount of charge.

Sadly, I discovered this the hard way as I had put them in my camera bag as spares for my flash unit and when I placed them inside the flash ready to use, I found they fired for only 10%'ish of the time they used to. Nothing major, only a hobby shoot, but nonetheless, I was surprised.

So, having read a little on t'interwebby about how to recover these batteries, I'd like some advice from the experts on here if I may, please. Is there a way and if so, what might that be - to recover these battery types?

Thanks.
Apparently you can revive them with pulse charging - I had huge success with Ni-Cd cells but not so much with Ni-Mh. Obviously I haven't cracked that one yet.

There are commercial units - but I looked at the price and decided not to bother.
 

crutschow

Joined Mar 14, 2008
30,105
NiCds had a memory effect that caused a reduction in capacitance that could be recovered by specific discharge and charge cycling.

NiMH do not have that memory effect so when they lose capacity it's more likely from a basic degradation of the battery that you may not be able to recover from.
 
Last edited:

ian field

Joined Oct 27, 2012
6,536
NiCds had a memory effect that caused a reduction in capacitor that could be recovered by specific discharge and charge cycling.

NiMH do not have that memory effect so when they lose capacity it's more likely from a basic degradation of the battery that you may not be able to recover from.
That's one of the reasons I didn't want to take a chance on the price of a commercial unit.

Some of my own experiments produced negative results - which didn't make me any more likely to start peeling off folding money.
 

tcmtech

Joined Nov 4, 2013
2,867
Unfortunately unless it for personal learning experiences the odds are the time effort and money you may spend on trying to regenerate a AA NiMh cell will be worth far more than just tossing it out and buying a new one.

Contrary to what the battery purists (nazis) say batteries are a consumable item with a finite life span.

What temporary recovery you may think you gained will just irritate you with the cold hard reality that whatever you did wont last plus it will likely fail every time you need it most. :mad:
 

ian field

Joined Oct 27, 2012
6,536
Unfortunately unless it for personal learning experiences the odds are the time effort and money you may spend on trying to regenerate a AA NiMh cell will be worth far more than just tossing it out and buying a new one.

Contrary to what the battery purists (nazis) say batteries are a consumable item with a finite life span.

What temporary recovery you may think you gained will just irritate you with the cold hard reality that whatever you did wont last plus it will likely fail every time you need it most. :mad:
Pretty much with Ni-Mh - but the results I got with Ni-Cd were something of a contrast.
 

takao21203

Joined Apr 28, 2012
3,702
Duracell gives astonishing results but all NIMH suffer from degradation especially so if used for high current + deep discharge as such would be the kind of use for photo flash.
 

tcmtech

Joined Nov 4, 2013
2,867
Pretty much with Ni-Mh - but the results I got with Ni-Cd were something of a contrast.
Well I have at least half a 5 gallon bucket of dead NiCad sub C cells from cordless tool battery packs you can have for the price of shipping if you think your methods work that well. ;)
 

ronv

Joined Nov 12, 2008
3,770
Hi All

I have all of a sudden come across 8 of my AA 1.2V Duracell NiMH batteries that have each failed to hold any reasonable amount of charge.

Sadly, I discovered this the hard way as I had put them in my camera bag as spares for my flash unit and when I placed them inside the flash ready to use, I found they fired for only 10%'ish of the time they used to. Nothing major, only a hobby shoot, but nonetheless, I was surprised.

So, having read a little on t'interwebby about how to recover these batteries, I'd like some advice from the experts on here if I may, please. Is there a way and if so, what might that be - to recover these battery types?

Thanks.
You could do the experiment for us. :D
There seems to be 3 categories:
Their time is just up
They are shorted
They have a memory problem.
People claim victory on the second by zapping them with a higher voltage. This seems to work but the little wiskers quickly grow back. So I wouldn't try that one.
The other is to deep discharge and then recharge. This seems to have some merit.
http://batteryuniversity.com/learn/article/how_to_restore_nickel_based_batteries
 

ian field

Joined Oct 27, 2012
6,536
Well I have at least half a 5 gallon bucket of dead NiCad sub C cells from cordless tool battery packs you can have for the price of shipping if you think your methods work that well. ;)
Those are usually cooked and unrecoverable by any method.

Most cordless tool chargers are deliberately designed to ruin the battery - a replacement is priced about the same as just buying a new tool.
 

tcmtech

Joined Nov 4, 2013
2,867
Those are usually cooked and unrecoverable by any method.

Most cordless tool chargers are deliberately designed to ruin the battery - a replacement is priced about the same as just buying a new tool.
So what you're saying is your recovery method only works on batteries that are in fact not really damaged and dead then. :rolleyes:
 

ian field

Joined Oct 27, 2012
6,536
NiCds had a memory effect that caused a reduction in capacitance that could be recovered by specific discharge and charge cycling.

NiMH do not have that memory effect so when they lose capacity it's more likely from a basic degradation of the battery that you may not be able to recover from.
The shaver I got on Freegle lasted about 5min per charge.

A few charge/discharge cycles got reasonable run time (eventually) - now I make sure to run it down all the way to stalling before I recharge it. Sometimes it carries on going for some time after the counter gets down to zero.

The original plan was to see if I could replace the battery, but I couldn't figure out how to open it without wrecking it - so I have no idea about battery type.
 

InWonder

Joined Mar 14, 2012
8
Hello,

I could revive some NiMh batteries using a reflex charger.
The NC2000 is an example.

Bertus
I read through most of the pdf you linked us and found no information on how to restore bad NMHydride or NICAD batteries. This description seems to be a rather old circuit design for a very sophisticated battery charger.
 

ian field

Joined Oct 27, 2012
6,536
I read through most of the pdf you linked us and found no information on how to restore bad NMHydride or NICAD batteries. This description seems to be a rather old circuit design for a very sophisticated battery charger.
My very successful Ni-Cd reviver was further development on a very ancient Scandinavian design for getting a few more discharge cycles out of zinc-carbon cells - it doesn't work if you run ZC all the way down, but allegedly also works on alkaline.

The original design was a suitable transforrmer with H/W rectifier and a current limiting resistor. The clever trick is a "leak" resistor in parallel with the rectifier. The theory behind "re plating" the migrated chemicals inside the battery is well documented if you know where to look.

My idea was higher pulse frequency might work better. A charge pump voltage doubler on one of the secondaries of an AT-PSU more or less approximates to a constant current source. Careful placement of Shottky barrier and fast recovery rectifiers can be arranged to put a sharp reverse pulse on the output. It wasn't much good for ZC cells - but the results with Ni-Cd were impressive.

There are commercial pulse chargers for Ni-Mh, but my attempts to build one never got to the results I was hoping for.
 

Rahulk70

Joined Dec 16, 2016
529
My very successful Ni-Cd reviver was further development on a very ancient Scandinavian design for getting a few more discharge cycles out of zinc-carbon cells - it doesn't work if you run ZC all the way down, but allegedly also works on alkaline.

The original design was a suitable transforrmer with H/W rectifier and a current limiting resistor. The clever trick is a "leak" resistor in parallel with the rectifier. The theory behind "re plating" the migrated chemicals inside the battery is well documented if you know where to look.

My idea was higher pulse frequency might work better. A charge pump voltage doubler on one of the secondaries of an AT-PSU more or less approximates to a constant current source. Careful placement of Shottky barrier and fast recovery rectifiers can be arranged to put a sharp reverse pulse on the output. It wasn't much good for ZC cells - but the results with Ni-Cd were impressive.

There are commercial pulse chargers for Ni-Mh, but my attempts to build one never got to the results I was hoping for.
I've had luck with some NI-Cds. But then again it depends on how well the Ni-Cd cells were treated in the past. If it was abused like leaving it to get overcharged and heated up resulting in gassing. Then a significant chance of recovery is lost.
 

Rahulk70

Joined Dec 16, 2016
529
Hi,

I've tried recovering all kinds of batteries. I've a bunch of them currently running fine for my various projects too. The battery chemistries that are most recoverable are undoubtedly Lead - acid cells(Flooded or SLA). If a cell is fully shorted or you hear powdery stuff moving around when you shake a dried up one it is junk else it 50-70% recoverable with 10-15 cycles. Second place goes to Ni-Cd. I have tried recovering a few fairly treated in past dead ni-cd cells by pulsing it for 2-5 sec with those old automotive 10A chargers at 6 and 12V and it managed to recover some of them unless the electrolyte dried up. But the worst part is the self-discharge is very high and unless u use it every day or two and recharge it. Recovered capacity is like 30-40% mostly. The internal dendrites will grow pretty fast and short it again. NiMH cells on the other hand, are like least recoverable and even if recovered like the Ni-Cd method have like only 20-30% of their capacity and pretty useless. Finally, Li-ions/Li-Po just throw it away. Messing with them is like taking a lighted candle to find a gasoline leak under the car.

Well in the end I can say that if you are lucky you might be able to recover some part of its capacity else it's better to just trash it. Its a lot cheaper to get a new one. Plus those dangerous methods to remove the internal shorts like welder or auto chargers means if the cell blows up you will have the corrosive potassium hydroxide electrolyte right on your face.
Cheers :) Good Luck!!
 

ian field

Joined Oct 27, 2012
6,536
I've had luck with some NI-Cds. But then again it depends on how well the Ni-Cd cells were treated in the past. If it was abused like leaving it to get overcharged and heated up resulting in gassing. Then a significant chance of recovery is lost.
I got years of use out of a pile of skip raided AA Ni-Cd cells - the capacity was at least published spec. But I have no idea of their previous history.

Over charged cells almost never recover to any noticeable extent. They get lazy if you don't give them the occasional regime of complete charge/discharge cycles - those cells can come up good as new............or even better.
 

ian field

Joined Oct 27, 2012
6,536
Hi,

I've tried recovering all kinds of batteries. I've a bunch of them currently running fine for my various projects too. The battery chemistries that are most recoverable are undoubtedly Lead - acid cells(Flooded or SLA). If a cell is fully shorted or you hear powdery stuff moving around when you shake a dried up one it is junk else it 50-70% recoverable with 10-15 cycles. Second place goes to Ni-Cd. I have tried recovering a few fairly treated in past dead ni-cd cells by pulsing it for 2-5 sec with those old automotive 10A chargers at 6 and 12V and it managed to recover some of them unless the electrolyte dried up. But the worst part is the self-discharge is very high and unless u use it every day or two and recharge it. Recovered capacity is like 30-40% mostly. The internal dendrites will grow pretty fast and short it again. NiMH cells on the other hand, are like least recoverable and even if recovered like the Ni-Cd method have like only 20-30% of their capacity and pretty useless. Finally, Li-ions/Li-Po just throw it away. Messing with them is like taking a lighted candle to find a gasoline leak under the car.

Well in the end I can say that if you are lucky you might be able to recover some part of its capacity else it's better to just trash it. Its a lot cheaper to get a new one. Plus those dangerous methods to remove the internal shorts like welder or auto chargers means if the cell blows up you will have the corrosive potassium hydroxide electrolyte right on your face.
Cheers :) Good Luck!!
On lead-acid; early stage sulphation is fairly easy to reverse - but the "disease" progresses very fast. Left flat - the battery can be unrecoverable after not much more than a week.
 
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