Abstract: An automatic monitoring system of storage batteries housed at an application site which includes an A.C. power source at the site, a mechanism to interrupt the A.C. power from its source and generate an alarm, a battery plant to provide D.C. power when the A.C. power is interrupted, a mechanism to automatically detect and measure the voltages generated from said battery plant, a mechanism to measure the midpoint of the D.C. battery discharge voltage by measuring the rate of change of said voltage over time and halving the difference between plateau and end of life voltages, a mechanism to generate an alarm message (a) if said midpoint has been reached, (b) if a predetermined low battery cutoff voltage has been reached, (c) if the battery plant is being overcharged or undercharged, and/or (d) if A.C. power is interrupted.