A system for and method of for detecting a non-functional battery back-up unit (BBU) of an optical network terminal is presented. The system and method may include receiving power outage data associated with a plurality of customer sites, receiving, from each of the plurality of customer sites, discharge time data associated with a battery via a network, calculating a mean discharge time based on the discharge time data, comparing the discharge time data associated with each battery to the mean discharge time, determining that each battery that is associated with discharge time data that indicates a discharge time value that is less than the mean discharge time is faulty, and outputting a data signal that indicates that a battery is faulty.