An optical network terminal (ONT) battery backup unit (BBU) battery voltage alert system (BVAS). This alert is provided as a supplement to an audio alarm which sounds when the backup battery is discharging because that alarm may not be heard in sufficient time if the alarm is remotely located relative to its customer, e.g., in the customer's basement or outside. A battery monitoring facility, located in a telecommunication service provider's centralized serving office, or remotely located elsewhere, monitors the voltage of each of a plurality of batteries deployed in customers' premises within the geographical area served by that centralized serving office. That battery monitoring facility receives packets via a communication network from each such customer's premises, each of those packets representing a battery voltage measurement. That battery monitoring facility stores these on-going measurements thereby creating a trending database to point to any potential future battery failures. The battery monitoring facility alerts a particular customer via the communication network when its battery is about to fail by email/text, fax, telephone or other similar mechanism.