Cell self discharge


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ChrisD5710

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Sep 13, 2017
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How much cell self discharge do You consider OK?

We all have our own "self approved" procedure when we sort our harvested li-ion cells.

My question to You out there is, how much voltage loss/week do You tolerate?

ChrisD
 

daromer

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image_ynbbdb.jpg


I basically let it be above 4.05 after 1-4 weeks.
 

Charly144

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Nov 22, 2017
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I do sort out when they are below 4.15 after 3-4 weeks...
 

daromer

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Most cells will sit at 4.15V directly after charge or an hour after. Normal when charging to 4.2 is that they instantly bounce to 4.15-4.18 ;) Also note that charging with opus or others they stop all between 4.1 and 4.25....

So i would recommend to redo all your tests unless you crosschecked that after 2 hours they were at 4.2V
 

jdeadman

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Mar 28, 2017
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I write the ending voltage of each cell on itself. Then after on month or more of sitting I rechek the voltage right before I use it in a pack and if it's more than .1 lower than it's listed voltage it does not go in my wall.
 

ChrisD5710

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Sep 13, 2017
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jdeadman said:
I write the ending voltage of each cell on itself. Then after on month or more of sitting I rechek the voltage right before I use it in a pack and if it's more than .1 lower than it's listed voltage it does not go in my wall.

Thanks :)

If I understand You correctly themax self discharge You tolerate is 25mV/week.

I have just recorded 120 cells. (4.109 - 4.189) I will check after one week and see how this corresponds with Your suggestion.

Chrisd


Charly144 said:
I do sort out when they are below 4.15 after 3-4 weeks...

That was also how I used to do it (min. 4.130v) but as mentioned I received a bunch of cells charged with an OPUS charger that was already below 4.12v. Therefore, unless I was prepared to scrap a lot of seemingly goodcells, just for reading below 4.12, I had to come up with another way to determine how to pinpoint the bad cells. (If a cell reads 4.109 volts coming out of an OPUS charger, and that cell maintains say 4.107v 2 weeks later it is obviously OK.)

If You have not scrapped Your, below 4.15 v cells , for good, You mayconsider testing a few to see how much they actually loose say in 14 Days.

Thanks for the feedback :)

ChrisD
 

daromer

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Cells will discharge the most the first week or 2. If you look at the Voltage vs capacity you will see that at the top and bottom you dont have much capacity therefore the voltage drop after or closer to 4.1 or even 4.05 should slow down ALOT. Thats where you see self dischargers. Not the first day :)
 

Charly144

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Nov 22, 2017
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I always recharge them to full once they are below 4.15. i hsve experienced that the opus stops between 4.10 and 4.15. tp4056 often stops at 4.10. i fully charge cells with my liitokalas and let them sit for a while...
 

jdeadman

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Mar 28, 2017
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Not per week just in total. they may sit there for 1 month or more. my min is 1 month for waiting time
 
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