Lithium ion batteries

Re: A UPS backed by a Lithium Ion battery - is it OK for the battery to be on full charge for months on end?


Yes that’s fine.

They recommend storing Lithium Ion batteries at half charge because it lengthens their life but for a UPS you sacrifice some battery life to make sure you have a full charge.


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I have read a number of articles at battery university. I find them useful and haven’t yet found one that has errors. They state that both undercharging and overcharging Li-ion will shorten their life. Recommended charge for longest life is 3.92V per cell, which yields about 60% of full capacity. Charging to 4.1V could diminish capacity by 30% in a couple of years. So after a couple of years the battery will yield similar charge anyway but the one charged to 4.1V will continue to deteriorate whereas the 3.92V cell will live on (they talk of 8 year life but that assumes the battery is being charged and discharged. On standby one one would expect longer). Link to battery university