Lithium battery not included! only for people who are familiar with battery performance and have practical experience in battery assembly. The PCB protection board with voltage detection to prevent overcharge and over discharge, safe to use. Help to repair and assemble battery pack. Place 15 18650 power lithium batteries, But this is a plastic shell, there is no battery inside. No Cell, DCB609 Plastic Case For 20V 60V FlexVolt lithium Battery DCB612 Preparation before assembly: 1. If using a core, please note: (1). Please use 18650 power lithium batteries with small internal resistance, the same model and the same parameters, do not use ordinary lithium batteries for energy storage (2). Please test the voltage of a single 18650 battery and charge the single battery so that the voltage of each 18650 battery is the same. 2. If repairing an old battery, please test the voltage at both ends of each battery. If the voltage is different, please charge each battery to the same voltage value. Very important: Make sure the voltage of each 18650 battery is the same before soldering the PCB. Due to different batches, there may be differences in product appearance, color, and printed text, which not affect the use. Colour:Yellow Material:Plastic Package Contents: 1 * Case Kit Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.