Second capacity test?

Iker138

Iker138

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Joined
Jan 16, 2019
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Hi everyone!! Its necessary to make a second capacity test to each 18650? Thankyou!!
 
Yes, if the cell was stored for a long time. Second test's result gonna be closer to it's working capacity.
 
Another question,can it happen that when taking a cell out of a laptop, it gives me a capacity for example 1800 and that later with the second test it gives me more capacity? Does that happen? Did havean explanation? Thank you!!
 
Yes, it is possible, and quite common. The longer the cell has sat without any charge/discharge cycles, the more likely you'll get a better result on the second test. I'm not sure "why" it happens, just noting that several others have had it happen.
 
I checked all mine at 500mA. Then again at 500. Then I checked at 1000. With rests. Then I did the whole 4 wire kelvin thing. Mind you, I am just learning. BUT it certainly sorted the crap ones out. My next batch will be the 4 wire, then a 500 then 1000. Some cells were a lot better after testing. Also better results at 500 than at 1 amp. I think there is quite a bit of banter about exact testing methods. Depends on how you are going to use them.
 
Thank you korishan and thunderheart!!

Yeah i was surprised because in the second capacity test i obtain like 100-150 mAh more. It was a laptop battery that was so many year without any charge.
 
I dont do 2nd. The first one determines the capacity and all above are bonus. Takes to long time to test them a 2nd time.

The only time i do 2nd is when they fall slightly under my capacity limit.

Have it worked out? yeah i have packs used for over 3 years still working perfectly fine.
 
I don't do a second test. However, I do test each parallel pack before assembly. I also ignore internal resistance.
 
I dont think its needed, but ..

I certainly have benefitted since changing my methods to include more than one capacity test. NB i harvest extremely old 18650's and vast majority of them come to me at <1V ... some retests are rock solid. wasted time? nope because some of the retested cells end up completely dead by the third cycle. its kinda an either or thing in my experience, either the retest results are same as initial, not many dip up or down substantially, excepting those that end up pretty dead.
 
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