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I have power tools that use Lithium-ion batteries, and i have power tools that use Nickel Cadmium (NiCad) batteries. I only use these power tools maybe 5 times during the summer months. What is the best way to store these batteries to preserve them?

(1) Lithium-ion
I talked to two different manufacturers of the Lithium-ion battery operated power tools i own.

The first one said; "We recommend charging the batteries fully before storage. When storing for extended periods of time, every two months check to see if the batteries have depleted at all, if less than half charged, I would advise to recharge them back to full. This is important as it will keep the cells active to ensure proper run times for the next season"

The second one said; "It's best to store your lithium-ion batteries at around a 40-50% state of charge.... You may go back to put on the charger every 2 months to make sure its not completely dead...You can store it fully charged or dead... A Lithium-Ion battery's average life span is 2 to 3 years or 300 to 500 charge cycles."

So, i asked why not just charge the li-ion battery ONLY when i need them to run the power tools? And he seemed okay with that idea.

(2) Nickel Cadmium
The manufacturer of the power tools i own which use Nickel Cadmium batteries posted on their website; "After the last use of the product of the season, take the batteries off the product and store them off the charger. The batteries do not have to be charged up before storage, and can be stored at any level of charge."

I read that NiCad batteries can be charged 1,000 times or more.. but that they have a "memory effect" which i think means that if you don't fully discharge them before charging them they may loose some of their charge capacity but then later i read that this "memory effect" was a myth..?

i used a multimeter to check a 20volt NiCad power tool battery i kept in the charger for over 10 years and the voltmeter reads 20 volts...so does that mean its still fully charged?

TLTR: What is the best way to store Li-ion & NiCad (power tool) batteries so that their charging capacity & life is preserved?

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    I would not trust the "store fully charged" opinion for lithium chemistry batteries. Even Electric Vehicle manufacturers suggest no higher than eighty percent state of charge for longer life. For storage, the fifty percent value is more valid. For years, the radio control community has acknowledged a partial SOC for storage is best.
    – fred_dot_u
    Commented Oct 6, 2023 at 0:06
  • NiCad is pretty old tech, I'm surprised it isn't NiMh. NiCad can actually be "restored" by high voltage spikes 2-3 times the battery's voltage, but it isn't something manufacturers officially support.
    – Nelson
    Commented Oct 6, 2023 at 1:02
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    For the use case described, it's not really going to matter much how charged or flat your Li-ion batteries are when stored. If they are frequently charged and drained, like a phone, then it's best to hover in the middle 50% to get more like 500 than 300 charge cycles. If you only have 5-10 cycles a year, the 3-5 year "shelf limit" will catch up with you long before the charge cycle decay will significantly reduce your capacity.
    – dandavis
    Commented Oct 6, 2023 at 4:32
  • @dandavis - thank you for your reply. so then no matter what i do, after 3-5 years, i will have to buy new batteries? That really s*cks because these batteries are hundreds of dollars , infact, they are more expensive then the actual power tools :-(
    – Jeffrey
    Commented Oct 6, 2023 at 13:34
  • Yeah basically, batteries are consumables, which indeed sucks. I still prefer boring corded tools (except my light duty drill/driver); cheaper, more power+runtime, and lifespan; decades-old tools still work. With a jackery/ecoflow or inverter+lifepo4 you don't need long extension cords. Now, if it's a tool you use daily for a living and move around a site with continuously, cordless can make sense as the time savings can recoup the battery overhead. Eg. a battery angle grinder makes sense for a locksmith or plumber, but not an accountant. At 5 yrs, and 5 uses/year, you pay >$5/job...
    – dandavis
    Commented Oct 6, 2023 at 20:10

2 Answers 2

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Lithium batteries should not be allowed to tun flat, which can happen during a long period of storage. Ideally, charge to around 80%, which is less stressful on the battery than 100%. At that level of charge, it should go for many months in storage, and still have some charge when you take the battery out again.

NiCds are less fussy, and can be stored flat if need be. The memory effect does happen. You prevent it by running the battery almost flat from time to time (it doesn't have to be every time you use it).

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  • Memory effect forms when the battery has a charge, so the longer it stays fully charged, the more pronounced the memory effect. This effect can actually be reversed but it isn't something manufacturers support.
    – Nelson
    Commented Oct 10, 2023 at 3:19
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Yes, the answers are different for Lithium vs. NiCd. The advice you've gotten for each is pretty typical, as a websearch would show.

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