16.8 V 40A series 4 lithium battery protection board with AUTO Reset function Scope of application: lithium batteries with nominal voltages of 3.6V and 3.7V (including 18650, 26650, lithium polymer batteries) Features Product size: 46 * 60 * 3.4mm Weight: 10.3g Continuous discharge current (upper limit): 40 A (if the 'heat dissipation environment is not good, please reduce the load current to use) Charging voltage: 16.8 V-18.1V Continuous charge current (upper limit): 20A Standard version: suitable for electric drills with starting current lower than 60A and power lower than 100W. Upgraded version: suitable for electric drills with starting current lower than 80A and power lower than 135W.  Balanced version: suitable for electric drills with starting current lower than 80A and power lower than 135W Note 1 : the correct start of the electric drill requires 4 x 15C-20C power batteries or 8 x 10C-15C power batteries (normal 18650 can't start electric drill !!). Note 2 : wiring 0V, 4.2V, 8.4V, 12.6V, 16.8V strictly according to the diagram, do not intentionally short circuit. Note 3 : For brush motor loads, try connecting a capacitor non-polar in parallel with the positive and negative terminals of the motor (voltage ne resistance greater than 25V, capacitance 10uF-100uF) to prevent the reverse peak voltage generated by the motor interfere with the protection board or Break the MOS tube. Note 4 : When connecting 4 groups of batteries in series, please make sure the voltage of each battery group is the same. If they are not the same, please charge each battery group separately and then use them in series. . . During the discharge test, the battery with the fastest voltage drop is a defective battery.