# What CR2032 open circuit voltage is considered "dead"



## geepondy

I bought some CR2032s off of Amazon and my Pedometer is chewing right thru them. Normally they should last six months, these are only lasting two weeks. I just measured the open circuit voltage of a spent cell and it's reading 3.01 volts. Is this considered "dead"? Being a 3V cell, I would think that is still an acceptable voltage so I'm wondering if my pedometer is bad. Tonight I will measure the open circuit voltage of a new cell. Approximately what should that read for a fresh non defective cell?


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## afdk

geepondy said:


> I bought some CR2032s off of Amazon and my Pedometer is chewing right thru them. Normally they should last six months, these are only lasting two weeks. I just measured the open circuit voltage of a spent cell and it's reading 3.01 volts. Is this considered "dead"? Being a 3V cell, I would think that is still an acceptable voltage so I'm wondering if my pedometer is bad. Tonight I will measure the open circuit voltage of a new cell. Approximately what should that read for a fresh non defective cell?



Hello,
The only way to reliably check/test a cell, is with some kind of a load. You can either make one yourself or buy the excellent ZTS pulse load cell/battery analyzer. Measuring a cell/battery with no operational load doesn't tell much. The open load of a new CR2032 could measure 3.1-3.2 volt, as you can see, you can't really tell about the cells you bought.


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## Russel

Take a look at the Energizer CR2032 product data sheet. (150kb download) Notice the pulse characteristics chart, they use 100Ω load to test the cell for 2 seconds. The depleted 2032 cells that I've tested will measure 3V open circuit, but drop drastically when loaded with a 100Ω resistor. You can't really check the state of charge of these cells using open circuit voltage, you need to load them.

You can make a short jumper with alligator clips at each end and a 100Ω resistor in the middle. If you take one alligator clip from this load jumper and clip it to the positive probe of your multimeter and the other alligator clip to the negative probe you can test the voltage of a 2032 cell under load.


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## 45/70

As has already been pointed out, with the exception of Li-Ion cells, you can't really estimate the remaining capacity of cells without applying a load and measuring the voltage at the same time.

That said, for lithium button cells, I think at 3.0 Volts OC, the cell is probably "dead" concerning most applications that I use these cells for. Of course, the lower the current drain of the device, the more usable capacity that may actually remain, and the higher the current drain of the device, the less capacity that may actually remain.

Dave


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## Lynx_Arc

I just tested some of my 2032 that are a few years old unused (new) and they measure 3.34v with no load applied. I would say below 3.2v (no load) batteries are definately not 100% capacity for sure.
I would contact whoever sold you those batteries as they are bad, I have some 2016 cells that I bought from china that half of them went bad in a few years just sitting around, I suspect they were already "aged" to begin with as there is no way the manufacturing date can be determined on unpackaged 2032 cells so you could buy some that have been sitting in a hot warehouse for 5-10 years and not know it.


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## bleagh

Stat sheets that I have seen say lithium 2032 button cells are usable down to 2 volts. But recommendations I have seen say to replace them when they get down to 3 volts or less.


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## Russel

bleagh said:


> Stat sheets that I have seen say lithium 2032 button cells are usable down to 2 volts. But recommendations I have seen say to replace them when they get down to 3 volts or less.



Usable down to 2 volts under a load, or 2 volts open circuit?


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## BoarHunter

There is no rule, as long as one can measure some voltage, there is energy left. As for usability it all depends on the device powered. I use 2032 in red dot gun sights and OK till 2.8V.
True these 2032 are generally overpriced but I wouldn't trust the crapware sold in bulk for peanuts.


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## Russel

BoarHunter said:


> There is no rule, as long as one can measure some voltage, there is energy left. [...]


 
I've got several devices that use 2032 cells, when the devices don't work anymore due to the cell being depleted I can still measure 3V (open circuit) from the cell. If I load it at all the voltage drop to practically nothing. The voltage of new replacement cells measure 3.1 volts or so and will maintain voltage under a reasonable load.

Heck, I've gotten the new cell and the old one mixed up before and couldn't tell which was which by open circuit voltage. I had to use a load to tell which cell was the depleted one.


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## BoarHunter

Russel said:


> I've got several devices that use 2032 cells, when the devices don't work anymore due to the cell being depleted I can still measure 3V (open circuit) from the cell. If I load it at all the voltage drop to practically nothing. The voltage of new replacement cells measure 3.1 volts or so and will maintain voltage under a reasonable load.
> 
> Heck, I've gotten the new cell and the old one mixed up before and couldn't tell which was which by open circuit voltage. I had to use a load to tell which cell was the depleted one.


 
How much current from a 2032 via a 100 ohm R ? How much current drains say a pocket calculator ?


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## Lynx_Arc

BoarHunter said:


> How much current from a 2032 via a 100 ohm R ? How much current drains say a pocket calculator ?


 
if a 2032 starts with 3.2v then ohms law states I=E/R or current = 3.2/100 or 0.032A or about 32milliamps. As for the pocket calculator it depends on the calculator. LCD displays take very little current and calculators are similar too. I have a watch that takes a 2025 lithium battery that is still running 10 years after I bought it. It is broken (the place where the band attaches) so I don't use it and it sits in a box of watch parts. so divide 10 years into the mah of a 2025 cell... maybe 250ma? or 25mah a year?


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## Russel

BoarHunter said:


> How much current from a 2032 via a 100 ohm R ? How much current drains say a pocket calculator ?



My point is that even though a 2032 cell measures 3V open circuit it may still be too depleted to use. It really doen't matter what the current drain of a given pocket calculator is if the 2032 cell powering it is depleted and won't operate the calculator, but you may still be able to measure 3V from the cell open circuit.

This characteristic of 2032 cells had me scratching my head for a while when I first discovered it. I'm too accustomed to batteries that measure low open circuit voltage when they are depleted. I couldn't understand why I kept measuring 3V from depleted 2032 cells until I tested them under load. Then it dawned on me that with these cells open circuit voltage can't really indicate the state of charge. Of course, if your calculator doesn't stay on because the cell is depleted you have just load tested it's cell and confirmed that it is , for the purpose of powering your calculator, depleted.


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## BoarHunter

Russel said:


> My point is that even though a 2032 cell measures 3V open circuit it may still be too depleted to use. It really doen't matter what the current drain of a given pocket calculator is if the 2032 cell powering it is depleted and won't operate the calculator, but you may still be able to measure 3V from the cell open circuit.
> 
> This characteristic of 2032 cells had me scratching my head for a while when I first discovered it. I'm too accustomed to batteries that measure low open circuit voltage when they are depleted. I couldn't understand why I kept measuring 3V from depleted 2032 cells until I tested them under load. Then it dawned on me that with these cells open circuit voltage can't really indicate the state of charge. Of course, if your calculator doesn't stay on because the cell is depleted you have just load tested it's cell and confirmed that it is , for the purpose of powering your calculator, depleted.



My point is that you have to consider the equipement using the battery, that 2032 cells are low drain and that a 100ohm charge is high for them.
So if the battery shows 3.0V it may be unusable do drive a LED but perfectly OK for say a pocket calculator or a clock backup.


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## Russel

BoarHunter said:


> My point is that you have to consider the equipement using the battery, that 2032 cells are low drain and that a 100ohm charge is high for them.
> So if the battery shows 3.0V it may be unusable do drive a LED but perfectly OK for say a pocket calculator or a clock backup.


 
Good point. There is no point discarding a cell that may still be useful. If a cell is partially depleted you could simply use a load appropriate to the device you intend to power with the cell. If your calculator draws 10mA, for example, then you could use a 300Ω resistor, etc. For that matter, the calculator or clock themselves could work as a test load.

The original poster purchase some CR2032s batteries and because his pedometer was consuming them so quickly he was concerned that the cells were defective. He measured the voltage of one of the spent cells at 3.01V and was wondering if that could be considered dead. The answer is that you can't tell by the open circuit voltage alone. I suggested a 30mA load with a 100Ω resistor so that he could effectively test his other new cells to see if they were defective. For a new cell 30mA isn't an unreasonable test load.


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## daan_deurloo

makiyoung said:


> Here is the CR2032 date sheet,maybe it can help you.


you are replying to a old topic. Useless in my eyes.


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## peter yetman

daan_deurloo said:


> you are replying to a old topic. Useless in my eyes.




All information is useful.
P


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