Please note: Single BMS boards may be shipped via USPS First Class Large Letter, so a tracking number may not be available. Description: This BMS balance board is used for a lithium battery pack to equalize voltage and protect the cells. This module charges, discharges, balances, and acts as a low voltage/over charge cutoff. This model contains the same BMS and heatsink as the preassembled model. The buyer will have to apply the self adhesive heatsink to the BMS board. Instructions are below and will be sent with the package. Kit assembly instructions:1. Remove the protective film from the back of the heatsink self-adhesive thermal pad.2. Place the heatsink thermal pad side down on to the main MOSFET group.3. Hold for 15 seconds. The thermal pad and heatsink is rated for long-term usage at 120 C. Battery compatibility: Voltage of 2.5V - 4.2V lithium battery (18650, 26650, LiPo, Li-ion)Charging input voltage: 12V - 16.8VMaximum starting current: 80ADischarge current: 40A Charge current: 20ABoard Size: approx. 46*60*7.4mmPackage includes: 1 x Lithium Battery Protection Board 4S 16.8V 40A Li-ion LiPo Lithium Battery Charger Balance BMS Protection APEX. Condition is New. Shipped with USPS First Class.