1: Get 4 different razor blade of the same product.
2: Get a carton cut it according to the size of the razor blade.
3: Get a bowl and add a non concentrated Sulphuric acid.
4: pick up the carton you cur and soak it very well in the acid.
5: attach the shaped carton to the blade and a thin shit of zinc or led or aluminum to the carton itself.
6: Attach the remaining carton with the same procedure, and tie it up all together.
7: then attach a red and black wiring (Position and negative)
8: Get a spare USB cut it and attach it to the carton and blade
9: connect it to your phone and watch it charge well