1. The is for 5 series Li-ion batteries, mainly used for electric power tools It uses special IC for 5S lithium batteries as processor to detect real-time voltage. 2. charge and discharge current and ambient temperature of each battery Stable protective functions for charging and discharging, such as overcharge protection over-discharge protection and short circuit protection. 3. Low power consumption,the working current is about 25uA and quiescent current is about 6uA. Choosing the correct protection board and applying it appropriately is vital to the your batteries 4. Charge Voltage: 21V Single Cell Charge Voltage 4.25V Current Continuous Discharge Current 8-20A Overcharge Protection Overcharge Single Cell Detection Voltage 4.25V Name:Battery Plastic Case Type:10 cores Suitable for Power Tool Note:(18 650)battery cell core is NOT INCLUDED in the kit Colour:As Shown Material:Plastic+Metal Package Contents: 4set x battery shell 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.