As we have no way to connect an external battery to the PMIC on the NanoPC T3 Plus, I was considering adding a suitable battery that would supply 5V at up to 3A to the 5V input on the GPIO connector and adding an I2C based charging IC that I could read the battery state from.

Has anyone looked at this or where to read this in the source code? Is it done at the Kernel level or within the Android source itself? I'd like to have the Android status show the real battery state.