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Half charging lithium ion batteries for longer life expectancy

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Siwastaja:

--- Quote from: Miyuki on May 30, 2022, 06:13:25 pm ---Temperature plays a huge role here
As the electrolyte is highly volatile and with limited stability at elevated temperatures
You can clearly see it on some EVs without proper cell temperature management, they have only limited life
It is a really narrow range when you can safely charge it without causing degradation
You want to keep them like 10-30*C
Phones and laptops can get really hot
Even storage at elevated temperatures shortens life significantly

--- End quote ---

This. Basically, you would want like +30degC during use, and as cold as possible during non-use. Low-ish discharge current, or very low charging current counts as non-use.

But the problem with smart phones is, they are "in use" most of the time, either discharging or charging, and only rarely is charge/discharge current insignificant or zero.

They heat up and might be always at temperatures optimal for battery charge/discharge, sometimes a tad over the optimal, but never optimal for storage.

But, storage degradation is something that happens all the time, even during use. And it's accelerated by high temperature. Combination of high state-of-charge and high temperature is the worst. Dropping from 100% to 80% might not help as much as people expect. Go to 60% and below for best lifetime increase.

And for products that have distinct and long non-use periods, you can even store the batteries in refrigerator or freezer. Or just at 30-50% SoC. Either gives very long storage life, possibly 10 years. Combined - who knows how long. There might be some special wear-out mechanisms that step into picture after 10-20 years, that we normally don't see.

james_s:

--- Quote from: Siwastaja on May 31, 2022, 06:57:10 pm ---And for products that have distinct and long non-use periods, you can even store the batteries in refrigerator or freezer. Or just at 30-50% SoC. Either gives very long storage life, possibly 10 years. Combined - who knows how long. There might be some special wear-out mechanisms that step into picture after 10-20 years, that we normally don't see.

--- End quote ---

I have quite a few LiPo packs for my RC airplanes and other toys. During the off season when I'm not using them I use the charger to get them to ~50% state of charge for storage and then I store them in a drawer in my refrigerator. Many of these packs I bought in 2014 and have flown hundreds of cycles and they are still in good shape despite the fact that I have almost always charged them rather rapidly at 4C. I know other guys that aren't as diligent that burn through batteries like crazy, they puff up and/or lose capacity.

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