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Don't keep fully charged Li-Ion in long term storage, they tend to bulge
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james_s:

--- Quote from: RoGeorge on January 15, 2023, 09:46:55 am ---- NiCd or NiMH (AA or AAA) about 2-5 years, after that the internal resistance grows and make them unusable (for NiMH), while most of my NiCd grown internal short-circuits. 

--- End quote ---

They should last longer than that. I started buying Eneloop NiMH batteries not long after they came out, must have been 2006-2007. I just recently had a few of my oldest ones fail and really they're still usable for some applications, just the capacity dropped from 2000mAh down to ~1500mAh so I marked them and will use them in TV remotes and such.
thm_w:

--- Quote from: james_s on January 15, 2023, 07:16:07 pm ---
--- Quote from: RoGeorge on January 15, 2023, 09:46:55 am ---- NiCd or NiMH (AA or AAA) about 2-5 years, after that the internal resistance grows and make them unusable (for NiMH), while most of my NiCd grown internal short-circuits. 

--- End quote ---

They should last longer than that. I started buying Eneloop NiMH batteries not long after they came out, must have been 2006-2007. I just recently had a few of my oldest ones fail and really they're still usable for some applications, just the capacity dropped from 2000mAh down to ~1500mAh so I marked them and will use them in TV remotes and such.

--- End quote ---

A large percentage of the non Eneloop nimh batteries don't last long at all. Many people don't know to only buy Eneloop, and its often not available in local stores, or if it is, cost is high. Not to mention, Eneloop does not manufacture C or D cells at all.
Even within Eneloop, people have reported the China manufactured cells are not nearly as good. And that has been shown to be true at high discharge: https://www.candlepowerforums.com/threads/japanese-vs-chinese-eneloop-cycle-testing-results.392229/

So, it is very easy to buy the "wrong" nimh that dies after <5 years.
RoGeorge:
In EU there are other brands.  I don't recall seeing Eneloop other than on the Internet, they seem to be the preferred brand in US at least.  Maybe I should buy some Eneloop to test them, too.

So far all my NiMH were not that good.  Have tried many brands for a photo camera that uses 4xAA.  Tried so far GP, SONY, VARTA, DURACELL, UNiROSS, no name, etc.  All failed after 2-3 years.  The upper left bowl is full of failed AA.



Most common failure was high internal resistance.  In the camera they were good to deliver only small currents to take normal pics, but not able to deliver high current to charge the flash.

Since LIDL supermarket became a thing here, in Ro, they came with a new brand of NiMH, "TRONIC", advertised as "low self discharge".  They are indeed low discharge and seems very good for the price (about $1 per AA cell), size from AAA to C size and 9V too.

They last about the same, 2-3 years.  After that, they are good only for low current loads.  I've made a discharger for AA some years ago, and many of the old AA were not able to deliver the usual 0.2C current.  Voltage was dropping under 0.9-1V at 0.2C, though at about 10 times less current they were still able to deliver 50-80% of their nominal C.

RoGeorge:
Checked out of curiosity, Eneloop is available in EU, too, just that they are 3-4 times more expensive than the TRONIC ones from the LIDL supermarket.
https://www.emag.ro/brands/brand/eneloop
MadScientist:
Very low charge rates should be avoided , ie below 0.2 C as  very low  charging rates encourages SEI layer growth and hence leads to battery degradation.  Chargers at 0.5c then stop charging once full no float etc needed. Track SOC band restart charging at a point

Long term storage is best at 60-70 % SOC but really fine upto 80% SOC avoid very low Soc for storage or below 40% SOC

In essence short high current charge ( relatively high ) is best once the correct safety regime and a proper stop charge point is set
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