Aiming at the phenomenon that the online detection device for battery power in meteorological observation equipment is almost blank, the battery AC injection method detection, Internet of Things (IoT) and other technologies are comprehensively used to inject AC crosscurrent signals at both ends of the battery, and the battery power is calculated by the phase angle and internal resistance of the battery. Experiments and improvements are made of the detection process in practical applications; the Kalman filtering is added to reduce interference; and the reliable direct online measurement of battery power is achieved. According to this method, the specific realization of the hardware circuit is given, which has been applied in actual operation and has high operability, accuracy and consistency.