This is a solderless mobile power supply kit (circuit board+shell), not a finished product of the mobile power supply, excluding batteries, packaging, etc. The battery needs to be purchased separately with a 18650 (flat head) battery to be used. Please note that the capacity of the three batteries must be consistent. Do not place the batteries upside down as it will damage the motherboard. (The spring is the negative pole and the spring is the positive pole) Please place them correctly. There is no chance of secondary disassembly, and the shell cannot be disassembled again. Please fix them all at once!