Feature: 1. APPLICABLE SCENES: The board is applicable to 3.7V lithium battery, can be used for massager, LED lamp, solar street lamp, display power supply, etc. 2. STABLE CIRCUIT: The battery protection board provides a high accuracy voltage detection circuit with good stability and less interference. 3. MULTIPLE FUNCTIONS: With over discharge, over current, over charge and short circuit protection, the battery protection board is convenient and practical. 4. CURRENT AND VOLTAGE: Including 4pcs lithium battery protection boards, the maximum current is 15A, the protection voltage is 2.8V, safe and reliable. 5. COMPACT SIZE: The battery protection board has compact size, with convenient installation, stable performance and strong practicability. Specification: Item Type: Battery Protection Board Charging Stop Voltage: 4.2V Over discharge protection voltage 2.8V Maximum Current: 15A Applicable Battery Type: 3.7V lithium ion battery, 3.7V 18650 lithium battery. Package List: 4 x Battery Protection Board1 x User Manual Note: 1. Before installing the protection board, the batteries should be well matched (the voltage difference of each battery should not be less than 0.05V, the internal resistance difference should not be more than 5mΩ, and the capacity difference should be less than 30mAh). The smaller the battery voltage difference, the better the working performance of the protection board will be.2. The batteries shall be connected in parallel and then connected in series, and the welding shall be correct (18650 battery shall be spot welded with brocade pieces, and other batteries shall be welded with soldering tin). Do not use screws to protect the IC of the protection plate, which is easy to burn.3. If the old battery is replaced, please note: please confirm whether the battery is normal before purchasing.