There is disclosed an instrument for the continuous monitoring of emergency stand-by batteries during operation of the batteries. The invention monitors the emergency batteries during all discharge operations and records the usage and conditions of the batteries as well as alerts the operators when the discharge voltage of the batteries falls below the minimum required for the particular application. The instrument includes voltage, current and temperature sensors which generate signals that are applied through gain amplifiers to an analog to digital converter and then to a central processing unit. The central processing unit receives a reference voltage and has an independent emergency power supply. The central processing unit outputs signals to a liquid crystal display as well as to a printer and receives commands from a key pad. The central processor unit is supplied with a software operating program which is recorded on a ROM and has system RAM for non-volatile storage and a clock. The instrument is programed to record battery usage in total accumulated numbers of battery discharges of greater than one or more preset durations, total accumulated time (duration) of battery discharges, total accumulated battery discharge power (KW Hours) as well as recording charging information such as the battery float voltage, the ambient temperature of the batteries, and the recharge current and voltage during the initial recharge periods. This information is printed every 24 hours and after every battery discharge.