Thread: Battery life: leave plugged in or let discharge
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Old 05-08-2019, 10:06 PM   #20
davidfor
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Quote:
Originally Posted by Readirect View Post
It is ABSOLUTELY FALSE that keeping a lithium-based battery at 100% will damage it. That's because ALL such batteries have a mechanism which turns off the charging once it becomes fully charged.

Here's a YouTube video from Dell which says just that (@ 1:20 of the video). It deals with laptops but it applies to all battery-powered electronics devices.
https://www.youtube.com/watch?v=aF6kfMsQxdQ
At 1:20 in that video, it starts discussing whether it is safe to leave the power plugged in. That has nothing to with what happens to the battery at different charge levels. In fact, there is nothing in that video about extending the overall life of the battery.

Now, you are correct, having a Li-Ion battery at 100% does not damage it. But, it can lead to an overall shorter life. And as you are pointing to laptop behaviour, a large number have a feature to stop charging at 70 or 80%. This is a battery saver function.

The 40% figure comes from the Battery University site. Specifically, this page. Which contains lots of details about how to treat Li-Ion batteries to make them last longer and why. But, a basic thing is that the more time a Li-Ion battery spends at the extremes of the charge level, the shorter the overall life.
Quote:
FWIW, that's a myth left-over from the last-gen batteries which where nickel-based.
No, the recommendations for handling Nickel-based batteries are different. The rule that carried over from NiCads was that the batteries needed to be fully cycled and not partially charged. This is not so with Li-Ion. The recommendation for Nickel-based batteries from the above site is the same as for Li-Ion, but doesn't really state there are issues if stored at other charge levels.

Having said that, overall, I agree with that video for treating Li-Ion batteries, especially in laptop. There things you can do to extend the life, but, they don't really have enough effect to worry about. Just use the battery as you need to, and charge it when you can.
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