Abstract: A system and method to monitor and control a battery string in an uninterruptible power supply unit is provided. The present system and method aids in the prevention of thermal runaway conditions which may lead to battery damage and fire. Battery parameters are measured and compared to a given standard to determine if the measured parameter deviates from a range of acceptable standard range. A time delay is initiated if the measured parameter is outside the acceptable standard range and the battery parameter is remeasured. If the measured parameter is still outside the acceptable standard range, than an alarm is activated, which may include disconnecting the battery string from the charger and producing a perceptible alarm. False alarms are reduced and true runaway scenarios can be prevented at an early stage with the present system and method.