Reported by Nikolaus Schaller, Jul 22, 2019

The % display is almost correct, but calculations of remaining time 
are wrong, because the bq27xxx does not know exact battery capacity. 
It should be provided by DT through the driver to Flash inside the 
bq27xxx but isn't.

Another effect is that we have reduced End Of Charging voltage of 
the bq24297 by 50mV to 4.15V (because it could make the modem turn 
off due to overvoltage in some situations). This means that the 
battery is never charged to 100%.

This effect is not properly handled by the bq27xxx setup.