Its still a mystery to me on how my power bank which utilizes 3.7v battteries connected in parallel is able to charge my phone with an output voltage of 5v±..explanation please

 

They will use a switch mode step up regulator (Such as an MC33063) to convert the 3.7 volts to 5 volts. I think some of them use a special function IC that contains the charging regulator and the step up regulator.

Les.

 

Its still a mystery to me on how my power bank which utilizes 3.7v battteries connected in parallel is able to charge my phone with an output voltage of 5v±..explanation please

Although it sounds like you might be getting something for nothing, that is not the case. As the boost regulator raises the output voltage it lowers the available current. The output power available from a power bank is ALWAYS less than the input power. Sometimes it is much less.

Example: If your 3.7 Volt battery can supply 1 Ampere, you have 3.7 watts of input power. If the conversion is 80% efficient you will have 2.96 watts of output power. If the output voltage is 5 Volts, then the maximum output current will be 590 milliamperes. Do you see how that works?

The following article may illuminate some of the mystery.

https://en.wikipedia.org/wiki/Boost_converter