[konut]

 Almost all cell phones have non-replaceable li-ion batteries. Some of us use lap-top computers in our audio set ups. Some of us use li-ion batteries to power remotes for audio gear. I recently read somewhere that in order to maximize the usable life of these batteries, it is optimal for longevity,  to maintain a charge of between 20% to 80%. I have always re-charged these batteries to 100%. Is the 20-80% recommendation really true?  Should I change my routine?

[FullRangeMan]

Just checked with AI and it confirmed the 20 - 80% suggestion.

[WGH]

My Pixel 7 smartphone charging options has two choices:

1)  Adaptive charging - finishes charging to 100% right before you normally unplug

2) Charge to 80% and stop charging

[FullRangeMan]

To make Li-Ion batteries last longer, it's ideal to *avoid extremes*. 0% and 100% stress the chemistry.

*Golden rule for maximum lifespan*

*Keep between 20% and 80% daily.*
Percentage What happens to the battery
**0% - 20%** High internal resistance, forms lithium crystals. Deep discharge degrades quickly
**20% - 80%** "Comfortable" zone. Less stress, less heat, less wear
**80% - 100%** High voltage = 4.2V per cell. Accelerates electrolyte oxidation. Ages even when stored
*If stored for months*

*40% to 50%* and in a cool place, ∼15°C.

At 100% stored, it loses 20% of its capacity in 1 year. At 40% it only loses 4%.

*In practice, how to apply*

1. *Cell phone/Notebook*: If you have "optimized charging" or "limit 80%" in the settings, activate it. iPhones, Samsung, Dell, and Lenovo already do this.

2. *Tool/Power bank*: Don't leave it 100% charged in a drawer. Use it until it reaches 40-60% and then store it.

3. *Tesla/Electric car*: Everyone limits it to 80-90% for daily use. 100% only for travel.

4. *Overnight charging*: The worst-case scenario is 100% all night in a hot environment. If you're going to charge it, unplug it when it reaches 80%.

*Myths*

1. *"Needs to reset to calibrate"*: No. Li-Ion doesn't have a memory effect. Reset only once every 3 months if the percentage gets out of whack.

2. *"Charging to 100% causes damage"*: It doesn't cause damage, but it ages faster. One 0-100% cycle wears down the battery the same as four 50-75% cycles.

3. *"Leaving it on the charger damages it"*: Modern chargers stop charging at 100%. The problem is staying at 100% hot, not the charger itself.

*Quick Summary*
Ideal Usage %
**Daily use** 20% - 80%
**Storing for months** 40% - 50%
**Need maximum autonomy** 100% is okay, but use it quickly. Don't leave it charging unused.
Batteries are consumables. Even with proper care, they lose 2-3% per year. But following 20-80% usage easily doubles the lifespan: instead of 500 cycles, you get 1200+ cycles before dropping to 80% health.

What device do you use it with? If you tell me, I'll give you the specific tip.

[JakeJ]

Yes.  My Samsung phone automatically shuts off charging at 80%, although I can run it down to zero, I cannot charge it above 80%.  Also of note, it lasts for three or four days on a charge and it's a tick over 5 years old.  My Motorola phones all had battery failures much earlier.

Also it is how the RC guys care for their batteries in general.  Reduces risk of catastrophic failures (think fire) and lengthens useful life.

Here is a LiPo battery guide from MIT

[konut]

Thanks for the great info!

[Tone Depth]

I had the Li-ion battery in my Pixel 4 phone replaced for about $100. I guess you could say it is on its second life.