What percentage?

[Mooncatt]

So charging when you hit 50 or 60 is fine? That just seems kinda early.

Li-ion batteries prefer a happy medium. If you are willing to plug and unplug that often, that would be great for battery life. It would also be inconvenient for most people, and put extra wear on your USB port that may cause it to go bad. That's part of why the 40-80% guideline exists. If it were ONLY about the consideration of battery longevity and easily accomplished, holding it about 65-70% (around 4.1V) would be best.

 

[chyeo1979]

Believe you can charge anytime, just dun let your phone drained to zero and died from no juice

 

[chanchan05]

Letting it go to 20 isn't so great either. In terms of battery life longevity. I would stick with the 40-80 rule whenever possible. Regularly running your battery down to 20 and then charging it all the way back up to 100 will over time, may take a fair bit of time, impact your battery's health. I like more often smaller charges than once a day big charges. Just my opinion based on what I have read.

What I'm talking about is also based on what I read. In fact, in the research from around 4 years ago, a regular discharge of 100 to 0, then recharge of 0 to 100 would give you an average of 300-500 charge cycles (so 1.5 years) before it's max capacity is just 75% of original.

Samsung claims that their new battery technology retains 95% of original capacity after 2 years worth of discharge cycles (basically 1 cycle of 100 to 0 to 100 in a day for two years). Even taking that they're probably exagerrating, I would expect it to be fair to estimate that a discharge of 100 to 0 once a day would still give you 75% capacity after two years using the new tech, even better with 20% because the closer you are to 100% when you recharge, the more charge cycles you save. Charging when the phone hits 75% actually extends battery lifespan to 5x that of the lifespan of charging from <5% to 100. But charging at 75% is just kind of stupid. between 40-50% is sort of the best bang for buck in balancing longetivity and usability.

But as I said, watching out for 40% nowadays isn't as big a deal if you don't plan to keep your phone for too long. Maybe if you plan to resell it though, since it would be a consideration to the buyer.

 

[AndroidFan3420]

Actually I heard that about Google phones. They don't go to 100% or 0%. My mobility scooter battery is the same. It cannot run empty because the batteries don't deep charge.

It applies to everything with a battery. They never let it charge fully and never let it discharge fully. Batteries would explode. Samsung claimed that the s8 battery would degrade 5% with normal usage after 2 years.

 

[Rukbat]

Opinions are fine to be all over the place, but facts are still facts. It's been shown, in actual testing of many different brands of battery, that constantly allowing the battery to go below 40% shortens the life.

As for the other end, the only way to know when the battery is fully charged is by watching the terminal voltage (to about 3 or 4 decimal digits). When it stops going up, the battery is fully charged. That's how calibration apps that require root work. When you see the voltage no longer going up, you tal a button, and the app sets a file to "know" that voltage as 100%. And it is fully charged at that point. Further charging (for a significant amount of time, not a couple of minutes) can cause the battery to pop its safety cap and the electrolyte will boil off.

(Old saying - everyone is entitled o his or her own opinion, no one is entitled to his or her own facts.)