AccA is awesome! I used it to repurpose my decade old Samsung Galaxy Grand Prime as a custom wall clock and alarm.

I couldn't figure out how to power it without a battery, and If I had plugged it in all time I was risking an exploded battery.

Enter AccA, it remains between 50-55% all the time, along with prioritizing battery-idle mode (which means the device tries to draw power directly from the external power source).