Symptoms

• When phone is turned on, my LG G3 would not charge beyond 30%.
• When phone was turned off, my LG G3 could charge to 100%.
• Phone would power off randomly at 10%.

Treatment (rooted phone)

I am rewriting the steps given in the AndroidPit article to be a bit easier to read.

1. Phone On. Discharge the phone to 0%.
2. If your phone can turn back on
   1. turn it back on
   2. let it turn itself off again.
3. Repeat sub steps below.
   1. Turn Phone Off.
   2. Charge to 100%.
   3. Unplug charger.
   4. Turn Phone On.
   5. Charge to 100%.
   6. Restart phone.
   7. Continue to next step if battery = 100%. Repeat otherwise.
4. Install Battery Calibration app
   1. Restart phone.
   2. Launch Battery Calibration
   3. Recalibrate the battery
5. Phone On. Discharge to 0%.
6. Phone Off. Charge to 100%.
7. Turn on phone. Battery percentage is reset!

Results

My phone’s battery is fixed. It charges to 100% and shuts off at 0%. Battery life is still good, obviously not as good as day one, but what you would expect from a older phone.

Sources

• https://www.androidpit.com/how-to-calibrate-the-battery-on-your-android-device