Upon receiving the product, simply prepare 3 parallel-connected standard 21700 flat-head lithium batteries or 3 parallel-connected standard 18650 flat-head lithium batteries (note: without protection board, and definitely not pointed lithium batteries). Use a soldering iron to weld the positive and negative terminals of the batteries to the B+ and B- on the mainboard. This easy process allows you to assemble the 5V2A mobile power supply and indulge in the joy of assembly.