Hello dear softers and ballers, as we use in almost all of our projects USB powerbanks there has to be at least one blog article that should be dedicated to it.
Our customers are more proactively taking care of powerbank on their own, either from stash that thay have home for free or they buy new wanting specific capacity.
A typical powerbank has 5 Volts output and you can get them everywhere around the world, but is the real capacity of a powerbank the one wrote on the plastic shell?
Inside powerbanks are 3.7V batteries, but the USB standard is 5V. Between the battery and the USB socket is a conversion circuit which changes the 3.7 V into USB 5V. When converting voltage , you must also convert the mAh.
How to calculate theoretical USB output
A simple equation can be used to convert the 3.7V into 5V.
ACTUAL 5V mAh = 3.7 X Advertised mAh / 5
For a 10,000mAh powerbank – 3.7 X 10,000 / 5 = 7,400 mAh
So a 3.7V 10,000 mAh powerbank really only supplies 7,400 mAh output at the 5V USB connection.