For what it's worth.
Found this.
Maybe it is helpfull, maybe not.
How to calibrate an Android device battery without root access
The old 'fully charge and discharge' approach stands as one of the simplest ways to 'recalibrate' your Android battery. We've warned you in the past about low voltage problems in lithium batteries and the negative impacts of fully draining a battery on its lifespan and the same holds true here. But, if your phone battery is causing you real problems, it's worth taking the risk.
Method 1
- Discharge your phone fully until it turns itself off.
- Turn it on again and let it turn itself off.
- Plug your phone into a charger and, without turning it on, let it charge until the on-screen or LED indicator says 100 percent.
- Unplug your charger.
- Turn your phone on. It's likely that the battery indicator won't say 100 percent, so plug the charger back in (leave your phone on) and continue charging until it says 100 percent on-screen as well.
- Unplug your phone and restart it. If it doesn't say 100 percent, plug the charger back in until it says 100 percent on screen.
- Repeat this cycle until it says 100 percent (or as close as you think it's going to get) when you start it up without it being plugged in.
- Now, let your battery discharge all the way down to 0 percent and let your phone turn off again.
- Fully charge the battery one more time without interruption and you should have reset the Android system's battery percentage.
Remember that it is not recommended to perform this process regularly. Even when your battery is so dead your phone won't even turn on, your battery still has enough reserve charge to avoid system damage. But you don't want to poke the tiger with a stick. Perform this process once every three months at the most. If it is required more often than that, you have bigger problems at hand.
Put plainly: fully discharging a battery is bad for it. Trying to overload a battery is also bad for it. The good news is that charging batteries will shut off automatically when they've reached their safe limit and there's always a little in reserve even if your phone won't start. Again: only do this when really necessary, because it does have a negative impact on battery life.
