Long term storage of Li-ion batteries?

I use my MC3000 that discharge the li ion at 3.7 volt for storing purpose.

However the fridge thing make sense IMHO if you have a lot of batteries.
If I have to start worrying about the li ion in the fridge (did someone put oil on them? or added to the salad?), and their humidity/rust, it has to be for some expensive battery.
Today you can buy cells for less than 4€ each, and remember that every year that passes the cells you have in the fridge will still decay, while the ones you can buy should be not only new, but also with improved performances due to constant research.

That charger (VC2) doesn’t have a discharge function, which is the only real way to determine capacity.
It shows how many mAh is put into the cell, which does give a fair guide on healthy newer cells but maybe not so much on older ones.

3.8v should be a fine rested measurement for storage of cells though.

Don’t worry about it too much, you’ll be wanting to replace cells every 3-4 years anyway.

Maybe the Opus BT-C3100 V2.1 would be better for you.

Thanks guys. Looks like I’ll be getting that Opus charger.

Yeah, noobs do stuff that just doesn’t make sense! OK, I’m discussing myself. I didn’t have a clue, but I don’t want to just destroy these batteries either. I simply don’t need so many charged batteries.

I live in an earthquake and fire danger area and I keep all my 18650 and 26650 batteries charged and check them every three months with a static voltage measurement. Batteries are stored in a cool, dark, and dry environment.

I have been following this procedure since 2012 without problems. From my reading and listening to people on lithium ion battery safety and battery efficiency there is no absolute method for storage.

What is needed is an evaluation of battery needs and requirements without regards to the time and external power needed to charge lithium ion batteries.

Old thread…but still relevant and came up in Google today while searching on “Storage of Lithium batteries”

Didn’t HJK say the MC3000 is by far the more versatile charger?
I have one…it most certainly does have a Discharge function and also Refresh, Cycle and many other customizable functions.

Oh, here it is……

Of course the MC3000 is far more versatile . I was refering to the VC2 BrianK linked, not the MC3000 :wink:

I store them fully charged at around 16 C.
The temperature is good and requires nothing to keep it there.
Storing them fully charged may not be the officially recommended practice, but that way I can quickly detect in time if any of them have problems (voltage drops significantly instead of just a little over a long period).

Same here. I suppose keeping my Go-bag in the refrigerator might slightly improve their longevity, but I can live with recycling and replacing cells every three or four years. I already have to do that with the alkaline cells.

Most everyone says to store at cool temperatures, but this was on the web months ago:

“Lund Instrument Engineering: July 19 2018. https://www.powerstream.com/Storage.htm:
Cadex’s recommendations are to store below 15° C (59 F) at 40% of full charge…. Our experience is that with cells stored at room temperature for 3 years that the non-recoverable capacity did not decrease, so this is probably manufacturer dependent.”

I am not sure about the wording there, but assume they meant to say they could recover capacity about the same as with the Cadex recommendation? Anyway, after reading that my extra refrigerator space has been dedicated to beer, LOL. But each to his own, do whatever seems right to you.

Calendar aging strongly depends on time, SOC and temperature.

Thank you, docware for the info.

Apparently another factor is manufacturer (chemistry) since they seem to have said they had good experience with their batteries (Panasonic if I remember correctly) after 3 years at room temperature. Some of the information on the web is not dated and we seldom know the latest manufacturing schemes, but we can hope quality is improving with added research. Do you know what years the graphs you posted represent and the battery or batteries tested?

Still, the statement I quoted was removed from their website, so it might not have been totally accurate. I am not trying to argue, but just find cell data to be hit and miss. That is one of the reasons BLF is so useful, so thanks to all who share their analysis of lights and cells.

The study is dated 19.4.2017, cells are Panasonic NCR18650PD. You can read the whole study here :

Calendar aging - page 43 till page 71.

Different chemistry, manufacturer, electrolyte additives, …… may have little bit different results, however the statement from this study is in general valid for all cells : calendar aging strongly depends on time, SOC and temperature.

Thanks for the link, docware, I’ve saved a copy of that :+1:

Yes, thank you. Very informative study.

The graphs you show and the ones on page 69 seem to indicate storage at 10C (50F) and 25C (77F) might be acceptable depending upon ones needs. It is very high temperatures and high SoC that are problematic. Cells stored at 3.7V for 15 years are thought to exhibit a capacity fade of 6% at 10C and not quite 10% at 25C. Maybe this is why Lund Instrument did not find temperature to be a major problem for 3 years. Since I do not intend to store my batteries for 15 years, the beer wins the extra space in my refrigerator, not my batteries.

Stored at 4.1V at 25C they are estimated to lose 16% capacity in 15 years, which is much better than one would think. But it is not inconvenient to store at lower voltage, so that is where I will focus.

Please correct me if my thinking is in error and thanks again for providing the study. It can help anyone can see the impact of various factors on their storage decisions.

Generally for long term storage is better lower temperature as well as lower voltage. Definitely recommend to use voltage bellow 50 % SOC which is bellow 3,7 V for majority of the cell. Good to remind that all producers from BIG FOUR (Panasonic/Sanyo, LG, Samsung, Sony) are sending their products to distribution at 3,5 V. Values in the chart are informative only, not absolute numbers, especially at low SOC end :

I love this forum :)

This very informative study shows a higher degradation of their NCA cathode material at higher voltages, leading to increased internal cell resistance. Don’t have time to look it up now, but it is in the study. Sorry, I read that and then forgot it before my last post.

And thanks for the chart, it is quite helpful. This is real information; I appreciate this forum too.

Yes, excellent information. I’m curious to know what long-term effect is on internal resistance. i.e, are high-discharge cells still good for high-discharge after 15 years, even when the capacity is still good?

Good question. This study utilized Panasonic NCR18650PD cells with the highest discharging current presented in the data sheet of 10 amps (page 16 of the document). There might be differences with other batteries, or maybe not much, I would not know. They did not test high discharge rates in this study. Let us know if you find out.

Concerning the difference in cells from different manufacturers (and the same cell from the same manufacturer produced later) the study sheds light on the changing landscape:

The cells were all of the same type but stemmed from two different production lots. The cells from the first lot were used in the first calendar aging study and in the cycle aging study on driving operation; the cells from the second lot, produced about six months later, were used in the second calendar aging study and in the cycle aging study on charging protocols….

As these cathodic side reactions are not observed in the second study, it is assumed that slight changes in the functional materials, such as modifications of the electrolyte and its additives, have reduced the cathodic side reactions of the cells examined in the second aging study, which were produced several months later.