The APC by Schneider Electric Smart-UPS SURT192XLBP-IN external battery pack (XLBP) connects to select APC by Schneider Electric Uninterruptible Power Supply (UPS) models. Together these units provide extended protection for electronic equipment from utility power Blackouts, brownouts, sags, and surges. The UPS and the external battery pack together provide continuous power from the batteries until utility power returns to required levels or the batteries are fully discharged.