I'm late to this party, but I read a LOT of heavy technical newsletters.
The battery industry gurus who make these things tell us to try and recharge them at 40% for maximum lifespan.
And, don't be trying to get them charged to 101% either. when the phone signals you at 98% ~ call it good enough.
High Temperatures are the enemy of battery life. Draining the battery to zero is horrible for the chemistry involved, and it results in high recharging temperatures because of the very long charge cycle times.
At 40%, you are trading off "all day use" for years and years of continued use of a battery.
I have a 6 year old Galaxy 'S' with the OEM battery in it.... I have practiced the above since it was new.
that phone is still working, it gets occasional use as a camera or WiFi device.
I keep it charged more or less...... extended non-use recommendations is to keep the battery at 40% to get the best "shelf life" for non-use.
that 40% number just keeps cropping up... don't it?
I use a Qi wireless charging coil in my phones. They charge at roughly 40% of the Maximum rate of the OEM charger wall warts.... I use an app to beep at me when the battery is 40% ( MacroDroid ) and when I hear that, I drop the phone on a Qi pad asap if possible.
If I am at my office desk, and I use the phone a lot with a BT headset, I just lay it on the Qi charging pad. It trickle charges while I am talking, then when the call is ended, it charges at about 40%..... life is good.
I don't have a spare battery for any of my phones.... have never needed one.
If 40% catches you mid-day, change to a spare battery, and move on.
Put the spare on a slow charger and it will be ready when the phone needs it.
