Is it OK to use low voltage recovered cells

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B8rez 2g4

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Jun 21, 2021
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For example, if a cell tested below 3V . I would toss them in a separate pile. And focus on good cells.

After spending time separating good cells, I come back to find these cells below 3V test at low IR. They have discharged fine, and held charge fine with no significant self discharge.

Would these be fine to use in a pack with a similar cell that tested above 3V upon opening the package.
 

Wolf

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Sep 25, 2018
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Absolutely.
That being said it does depend on the cells spec for cutoff voltage. Many cells have a cutoff voltage of 2.75V to as low as 2.0V (in rare occasions).
I find that if a cell is as low as 1V and the IR is good and the date code is within 3 to 4 years I will give it a recovery charge at 100mA to 3.5V and then charge at 1A to test. The theory is if a cell is not that old it hasn't spent much time in a low voltage state and the chemistry has not degraded to the point to increase the IR or decrease the SOH. Your mileage may vary and no guarantees but 99% of the time the cell will recover and perform just fine. Obviously a SD check after 30 days is necessary with an additional IR check.
Wolf
 

B8rez 2g4

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Jun 21, 2021
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Thanks for your reply Wolf.

Some of these cells initially tested as low as 0.1V

But they seem fine
 

Wolf

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Some of these cells initially tested as low as 0.1V
Um at that low of a voltage <1V I would be very cautious. Although as you say they seem alright and I have similar experience with <1V cells.
I do recharge them but I usually will eliminate them from my powerwall build and consider them for more of non critical use.
Wolf
 

jon218white

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Jul 18, 2019
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Yes seen a few you tube vids on cells that have been revived, charge at low current to max volts 50ma, they probably have been damage a bit but will still work
 

daromer

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Oct 8, 2016
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First of all the definition of low voltage. Belo 3v is not low voltage. Manufactures state that down to 2.5 for many of them is totally fine.

Below 2.5 is where you should be cautious. I would not

1. Care about 0.1 or 0v cells any more. The yield is very very low unless its manufacturer error
2. I would only take cells below 2v if i can determine if they where discharged below last months basically.

With that said you can recover below 2.5 without issues but below 2.5 is where they start to change. This is also why the manufacturer disable batteries going below that. So its basically up to you if you want to accept that risk.
 

winny

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Jan 28, 2019
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If the self discharge is still within specification (or your own quality requirements) and capacity is good, it's impossible to tell from the outside that the cell has been severely discharged. That being said, most bad Chinese no-name cells will turn into junk (very low capacity) or have enormous self-discharge after being discharged too deeply. The other side of the spectrum would be some Panasonic cells I recovered from 0.00 V for at least weeks if not more, which charged fine and jumped back to full capacity with minimal self-discharge.
 
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