Is it possible to control the charging voltage? As far as I know the regulation of battery charging is done inside the phone. The typical method of charging lithium cells is constant current charging followed by constant voltage charging where you shouldn't let your battery voltage go over 4.2V.

However it seems my charger keeps pushing the maximum possible current and increasing the voltage far beyond 4.2V. At 100% the voltage gauge is at 4.4V and if I remove the charger it's going down to 4.25V, which is again above the safe levels.

So it seems my charger is killing my battery. Is it possible to somehow tell the system to stop increasing the voltage above 4.2V or preferably 4V?
The battery voltage is controlled at a hardware level, not natively controllable via any Android APIs. Depending on your device &amp; firmware, there may be apps that can control the manufacturer specific features, but that's very unlikely.

Try looking into Voltage Control on the Play Store, it can under-clock the CPU, maybe even the voltage - Voltage Control


  Voltage Control Extreme (developer name sulph8), features include: 
  - Support more than one profile
  - CPU history display
  - overvolting support (+50mV and 1500mV limit) 
  - undervolting up to -250mV (lite version limited to -200mV)