1. Built-in IC detects each cell voltage. And remember the number of uses! 2. Detection battery status: Overheat, overvoltage , undervoltage, overcurrent, overcharge. 3. Stable quality and anti-vibration. It is the best partner of torque wrench and impact drill and angle grinder. DIY (semi-manufactured goods, No battery) Advance notification: (1). To use this product, you need to have some professional knowledge and experience. We do not that you can use it well. (2). It requires you to have assembly tools. If you do not have these tools, please do not place an order! (3). No-Original for PCB, but 100% New, Only PCB !!!!!! Preparation before assembly: 1. If a new core is used, please note: a. 18650 Power lithium battery core must be , b. A group of 15 cores must be equipped with resistance and capacitance to make their voltage the same. 2. If the old battery is repaired, please test the voltage at both ends of each cell. If the voltage is different, please charge each cell to the same