The main source of power for these power bank is the magnet, as long there is continuous flow of magnetic flux in the magnet, it can last you for weeks.
For you to start up this project, all the listed materials should be made available.
You need to get 2 south pole of magnet, USB cord, charger head, copper wire, wood. This are the only material you are required to get.
first cut the wood into any desire shape but you can as well cut it to a rectangular shape. Place the south pole magnet side by side on the wood. You can make use of your super glue so it can hold for a long period of time.
Place the charger head at the middle of the magnet, then connect the copper wire ( negative and positive) part to the charger head then attached it to the magnet.
Connect your USB cable to the charger head, then plug it to your phone, then watch as it charges. This can last you for weeks.