If you use a new core, please note Please use 18650 power lithium battery, with low internal resistance, same model with same parameters,Do not use ordinary lithium batteries for energy storagePlease test the voltage of a single 18650 battery, And charge a single battery to make the voltage of each 18650 battery the same. 18650 battery cell voltage should be above 3.7VIf the old battery is repaired, please test the voltage at both ends of each battery. If the voltage is different, charge each battery to the same voltage value.Make sure that the voltage of each 18650 battery is the same before soldering the PCB. Please make sure that the voltage of each 18650 battery is the same. 18650 battery cell voltage should be above 3.7Vcolour As shownMaterial ABSPackage Contents 1 x Battery pack shellOnly the above package content, other products are not included.Note Light shooting 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.