Storing Li-Ion battery ?

[928'er]

I just followed this link

http://toolboyworld.com/eBay/Ryobi_Batteries.htm

which claims that Li-Ion battery packs can be permanently damaged if allowed to drop below a certain level and that they "self discharge" over time.

I have A LOT of Li-Ion batteries (Ryobi, Nextec, Hitachi) that get used infrequently (once a week - once a month - etc.), so I normally rotate them and throw them on the charger to top them off after use - or check them before use.

I also tend to stock up on batteries when can I find a deal. So, I have a pair of 18v Ryobi P108 4Ah batteries still in their plastic clam shell packaging that I bought over a year ago. I also have ~6 12v Nextec NIB batteries sitting on the shelf.

After reading the above link, I thought maybe I should check all my NOS batteries and maybe start rotating them through my charger.

I just checked the two P108 Ryobis (still in their packaging) and the both show a 3 out of 4 bar charge - after sitting on the shelf for over a year. Not sure how long I've been hoarding the Nextec batteries, but just grabbed two at random and they both read 11.2v.

I've read before that Li-Ion batteries are shipped at something like ~3/4 charge - so, it seems that the NIB batteries I've been storing are still (pretty much) holding their "as shipped" charge.

So, what is the best practice for storing Li-Lion battery packs? Putting them on the shelf and ignoring them seems to have worked - so far....

 

[American Locomotive]

Lithium-Ion batteries have extremely low self discharge, ~1-2% per month, add a percent or two more if its a "smart" battery with charge level indicators. So they can hold a reasonable charge for years.

Lithium-Ion batteries can be irreparably damaged if they get over-discharged, which is around 2.8-3.0 volts per cell. Most modern tools turn off before the battery gets that low.

Conversely, it's also not good to keep Lithium-Ion batteries on the shelf fully charged - which is around 4.2 volts per cell. Keeping them at their fully charged voltage reduces their life span. For long term storage you should keep them at their "nominal voltage", which is 3.6-3.7 volts per cell, or roughly 1/2-3/4 charged.

 

[ChaseDE]

i said the same thing the other day, about 75% charge for long term storage and was quickly shouted down here.

there are a million links online to a million different studies and white papers about this topic.

i have been using all kinds of li-ion batteries for all kinds of devices for many years, i store my batteries around 75% or so if it is long term storage.

 

[Infinia]

After reading the above link, I thought maybe I should check all my NOS batteries and maybe start rotating them through my charger.

I just checked the two P108 Ryobis (still in their packaging) and the both show a 3 out of 4 bar charge - after sitting on the shelf for over a year. Not sure how long I've been hoarding the Nextec batteries, but just grabbed two at random and they both read 11.2v.

No don't charge them up! when I buy brand new 18650 batteries I just stash them away in the closet. Probably the worst way is store them is after a fresh full charge (max voltage ~4.2 V / cell) and higher temps.

For long term storage you should keep them at their "nominal voltage", which is 3.6-3.7 volts per cell, or roughly 1/2-3/4 charged.

+1
yes 3.75-3.80 V is closer to 50-60% charged. This voltage is also what the OEMs ship them out as. Monitor the voltage periodically and charge as needed. see www.batteryuniversity.com

 

[cajunfirehawk]

So to clarify, should we keep all of our batteries on chargers full time or not?

 

[American Locomotive]

No. For maximum longevity you shouldn't leave the batteries on the charger, or even let them sit on the shelf fully charged. If you feel you won't use the tool often (say you won't touch it for weeks or months at a time), you should charge the battery, and then use the tool a bit to run the battery down to about 75% capacity.

Some higher-end devices that use lithium-ion batteries actually have an option to only charge the battery to 75% capacity. Some Lenovo Think-Pad laptops have this feature, as it helps preserve the battery if the laptop is going to spend most of its time plugged in.

 

[Infinia]

So to clarify, should we keep all of our batteries on chargers full time or not?

no I wouldn't do that esp. for days on end. Li-ion life times are impacted by sitting at max charge. Anticipate usage, then start charging the backup while you use up the last 50-70% the main is stored at.
Note Most modern laptops have smart features that ask you if want to keep the battery at 70% or 100%. Always best to pick 70% unless you need the max run times.

 

[TomB19]

No don't charge them up! when I buy brand new 18650 batteries I just stash them away in the closet. Probably the worst way is store them is after a fresh full charge (max voltage ~4.2 V / cell) and higher temps.

+1

Less charge is best but if you store them empty, they will be useless when you need them. I'd keep them at 1/4~1/2 charge so they have enough charge to be useful, when it's time for them to be used.

If you have a shelf full of rarely used LiIon batteries, you are probably a good candidate for corded tools.

If you use a tool twice per year, after 5~7 years it will have been used 10~15 times and the batteries will be degrading from age. The odds of replacement batteries being available will become increasingly low over time. How many total uses will you get out of that device before batteries are NLA? None of these battery systems will be around in 25 years and it's pretty unlikely many/any will be around in 10.

 

[Infinia]

None of these battery systems will be around in 25 years and it's pretty unlikely many/any will be around in 10.

are you talking to me? I do use mainly corded tools.
No the 18650 cell form factor will be here a very long time, even if The Tesla EV switches to another. The chemistry inside will change over time, but the charging balance electronics is understood and maybe transparent E.g. built in the "systems".

 

[Ktmrider83]

I'm glad I joined this forum, I have been keeping my batteries topped up the last 2 years..