Why has my PowerBank lower capacity then the nominal value?
----------------------------------------------------------
PowerBank capacity is necessary to measure at voltage of one cell (3V).
For example power bank with capacity 13.6Ah made by 3V cells has 40.8Wh of energy (13.6Ah x 3V).
If we charge / discharge at 5.1V: Capacity = 8Ah (40.8Wh / 5.1V)
If we charge / discharge at 12.8V: Capacity = 3.18Ah (40.8Wh / 12.8V)