Upgrading from Lurker to Poster

Hi, I've been lurking for probably 2 years now. Finally made a post! I guess there's no reason to hide anymore!

It's been extremely slow building a powerwall. I guess I'm in no rush.After testing and sorting something like 1500 genuine cells, I never got anywhere. I'm retesting some cells that have sat for a year now and have been finding that self-dischargers, even the ones that don't seem to self-discharge after 2 months, but drop a lot of voltage after a year, end up losing half their capacity or more. But ones that stay above 4.1, even after a year, seem to not lose capacity at all.

Then I had an opportunity to buy new-old-stock chinese generic laptop battery packs. Like a lot. I honestly haven't counted, but I wouldn't be surprised if I had 7000 genericcells. And I think I paid less for those 7000 than the 1500 genuine ones.

Besides that, I'm in the Chicago area. Its going to be -13*F/-25*C for a high temperature on Wednesday, I'm itching to do a cold weather charge test at 1A with a TP4056 to see what happens.

Anyway, that's me. :-D

Welcome!

Greetings! Yeh, no reason to hide

My build has been slow and long drawn out as well. So you're not alone there. Patience allows one to be absolutely sure of what they are doing and helps to drastically minimize errors or mishaps. Life is too short to make a mistake that could take out your house, or your life.

Welcome mate

Greetings,
"But ones that stay above 4.1, even after a year," - avoid leaving cells in a fully charged state (I would say >3.95V) for a long period of time as this will accelerate the calendar aging of the cells / capacity loss.. especially when it is warmer, less so when it's -25C !
Extreme is to put them in the fridge (warmer than outside for you !) if your keeping them for a long time without use.. this slows the calendar aging chemical reactions, although I would love to see the look on the wife/girlfriends face when they open a the door on a fridge full of 18650 cells... lol.

completelycharged said:

Greetings,
"But ones that stay above 4.1, even after a year," - avoid leaving cells in a fully charged state (I would say >3.95V) for a long period of time as this will accelerate the calendar aging of the cells / capacity loss.. especially when it is warmer, less so when it's -25C !
Extreme is to put them in the fridge (warmer than outside for you !) if your keeping them for a long time without use.. this slows the calendar aging chemical reactions, although I would love to see the look on the wife/girlfriends face when they open a the door on a fridge full of 18650 cells... lol.

Click to expand...

I agree, I think I've done some permanent damage to my cells by leaving them in the fully charged state! At first, I was only going to leave them like that for a month to weed-out the self-dischargers. But they stayed at full charge due to my lack of a roadmap for my project. With my generics, I'm testing them for capacity to weed-out the poorly manufactured ones, and then pulling them out of my Opus when they reach3.74V (which drops down to 3.70V at rest). It takes more time and attention, but I can store them this way for a long time without a problem.