Based on constant current/constant voltage single cell charger chip CN3065, this board is intended for usage in solar powerd projects. It can charge battery while powering the system and it can charge baterry while connected via micro USB connector.
Input voltage 12 V, output volatage 4.2 V, max. charging current 2 A, PWM switching frequency 300 KHz, working temperature -40 °C to +85 °C, dimensions 45x20x9.5 mm.