A battery group online monitoring system for back-up power of communication base station is designed and realized.Based on host-slave architecture of Modbus

the system message dispatch mechanism is used to manage the message transmission of the tasks and datas of single voltage

group voltage

current and temperature can be real-time collected

stored and processed.An Ampere hour battery method for capacity estimation based on BP neural network is designed for the series connection of base station battery group.Experimental datas show that the system has advantage of high estimation precision and of high efficiency and can fulfill practical application.