Easily replace the battery back up with a genuine APC replacement battery, model RBC17 (sold separately) 1 GB network dataline protection, 6' Power Cord, right-angle 3-prong wall plug (NEMA 5-15P ...
The UPS still needs to have a case ... which can automatically patch between incoming line voltage, and the battery backup. He already had one of these switches in place for use with a generator ...