I want to make a power bank for my cell phone(cell phone's Li-ion battery capacity = 2070mAh). The AC adapter of the phone has an output rating of 5V dc and 550mA. Hence, it has a constant output. Now a power bank consists of a dc battery. So it's voltage and current will vary with time. So how is it that both the power bank and ac adapter are able to safely charge the cell phone battery when one provides a constant input while for the other it varies?
Also how is the battery capacity(2070mAh) related to its charging?
Also how is the battery capacity(2070mAh) related to its charging?