Line 1 is the first metro line of Nanjing,was put into operation in 2005.Every station computer room use 2 units VRLA battery,24x12V cells in every unit as the UPS power.They maintain the battery manually and take 20 minutes for a station UPS detection. With the use of DLT_B8500 battery monitoring system,the real-time monitoring of battery is available,the failed battery can be found on time,make sure the battery working stably.Till now the system working stably and help to find the internal resistance in maintainence,which cut the cost and avoid the accidents caused by battery’s failure.