I guess Lithium batteries have been a hot topic lately. Well, here's my dilemma:
Basically, I have two Li-Ion battery packs for my Dell C-series laptop, and they are quite old I believe. They are rated 14.6V, 4460 mAh, and 66 Whr. Both batteries are functional and still hold *some* charge: I can get about 50-60 minutes run time while using Word or other office software, and about 30 minutes with software that uses the CPU more heavily. So clearly, their capacity has dropped quite a bit from what it was originally (my laptop states about 3 hours and 40 minutes with the battery fully charged… but of course, that time drops much quicker). I keep the batteries disconnected from my laptop almost all of the time and only charge them when I know I will need them – which is usually no more than a few times a year when I visit relatives. In the meantime, I keep the batteries stored in my room. I try to charge them to 60-70% every few months so that they don't go dormant. (Actually, one of the packs was originally dormant when I got it about 5 years ago and would refuse to charge at all. But after forgetting it in a spare laptop for a while one day, it suddenly decided that it will charge and has been working ever since.) They usually drop to 30-50% between those charges. Also, both battery packs are original Dell batteries with all of the proper safety marks (UL number on one is E73362, which points to Sony, while the other has E17935). Sticker on the bottom says Made in Japan for both, too. Cells inside are standard 18650s, I believe.
Anyways, my main question for you all is:
Is there any danger or risk of fire of using very old Lithium batteries, even if they are still somewhat functional?
And if not, do you have any recommended safer way to keep/store them?
Basically, I don't want them to catch fire and burn my house down (especially since houses here in the U.S. are all made from wood and OSB). Comments, questions, concerns? Please let me know.
Basically, I have two Li-Ion battery packs for my Dell C-series laptop, and they are quite old I believe. They are rated 14.6V, 4460 mAh, and 66 Whr. Both batteries are functional and still hold *some* charge: I can get about 50-60 minutes run time while using Word or other office software, and about 30 minutes with software that uses the CPU more heavily. So clearly, their capacity has dropped quite a bit from what it was originally (my laptop states about 3 hours and 40 minutes with the battery fully charged… but of course, that time drops much quicker). I keep the batteries disconnected from my laptop almost all of the time and only charge them when I know I will need them – which is usually no more than a few times a year when I visit relatives. In the meantime, I keep the batteries stored in my room. I try to charge them to 60-70% every few months so that they don't go dormant. (Actually, one of the packs was originally dormant when I got it about 5 years ago and would refuse to charge at all. But after forgetting it in a spare laptop for a while one day, it suddenly decided that it will charge and has been working ever since.) They usually drop to 30-50% between those charges. Also, both battery packs are original Dell batteries with all of the proper safety marks (UL number on one is E73362, which points to Sony, while the other has E17935). Sticker on the bottom says Made in Japan for both, too. Cells inside are standard 18650s, I believe.
Anyways, my main question for you all is:
Is there any danger or risk of fire of using very old Lithium batteries, even if they are still somewhat functional?
And if not, do you have any recommended safer way to keep/store them?
Basically, I don't want them to catch fire and burn my house down (especially since houses here in the U.S. are all made from wood and OSB). Comments, questions, concerns? Please let me know.

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