18650 Lithium Li-ion 3.7V 4.2V Battery Charger Board DC-DC Step Up Boost Modu…
He module can be roughly judged by two LEDs and other status of the working state, CHRG is red light, STDBY is blue light. The following is the formula and examples. Charging current limiting resistor R = 1200/1 (l is the need to set the current), resistance value (K) 30, charging current (mA) 50.