Quick question, I have a few Molicel P26A 18650 batteries that are kept in long term storage in my closet (dry, cool place away from sunlight), kept for around 1 year since the last charge, when tested with a digital meter a few days ago, the readings show between 3.3V to 3.65V for all of them. Do I need to charge them up again? to around 3.8V to be safe or let it be?
By the way, I noticed that my Samsung 25R (18650) also kept together, are still hovering around 3.8V and 4V, that’s good right?
Long term storage for what? I guess you can buy 2x as many cells as you need, and keep them half charged, for double the “shelf life”, or run one set hard, then just replace it?
I keep my 2x and 4x sets together to ensure they’re matched, and singles get swapped between lights as and when I need, other than that, I don’t have time or inclination to obsess over tenths of volts.
If you’re desperate, 3.7, 3.8V seems to be what the “storage voltage” guys do.
I have sets of 4 ea. Moli M35A and Samsung 40T that I bought a year ago on sale, and haven’t touched them other than to measure voltage. They are still at the same voltage as they arrived (3.51 and 3.45, respectively). Yours seem to be in an acceptable storage range. Just monitor for drain.
Shipping and storage are somewhat different issues with some overlapping concerns. If you know they’re going to be parked for a year I would aim for 3.7v. Although I typically leave everything that I’m not using often at 4.0v
Aim for the nominal voltage for storage….3.7. But it’s not a huge deal. If you store them at 4v+ it may scrub just a little from their lifespan but most people aren’t going to notice that. One question I have is if they were all fully charged at 4.2v when you stored them. If so then discharging that far over a year and with significant differences now isn’t a great sign of quality/health, but also not a huge deal although it might indicate that you don’t want to use those cells together in any series configuration even if the driver has lvp.