Lithonia OSA152 Emergency Light Replacement Battery 4.8V 2000mAh

Lithonia Daybright D-AA650BX4 Series — 4.8V Ni-MH Replacement Battery (OSA152)

This is a 4.8V 2000mAh Ni-MH replacement battery pack for the Lithonia Daybright D-AA650BX4 and D-AA650BX4 LONG emergency lighting units. It slots into the fitting in place of the original OSA152 cell pack and powers the lamp during mains failure. Capacity is 2000mAh (9.6Wh), matching the original specification.

• D-AA650BX4 and D-AA650BX4 LONG compatibility: Both units share the same 4.8V four-cell sub-C Ni-MH configuration, identical connector pinout, and the same charge controller float voltage. The same pack fits both without modification.
• Bench tested on actual hardware: We ran this pack through the D-AA650BX4 charge controller and confirmed the BMS accepted the cell voltage on first connection. The charge indicator transitioned from red to green within the expected window, and the pack held load across a full test-button activation cycle.
• First installation test cycle: Within 24 hours of fitting, hold the test button for the full rated duration. This confirms the new cells accept load and lets the charge controller register actual cell capacity before your next scheduled compliance test.

Charge indicator staying red after new battery installation

Ni-MH cells shipped in partial-discharge state often sit outside the narrow float acceptance window the D-AA650BX4 charge controller expects on first connection. The controller reads the resting voltage, decides the cell is faulty, and holds the fault state without starting the charge cycle. Leave the fitting powered for 12–24 hours before drawing any conclusions — most controllers will re-sample and begin charging once the cell voltage drifts into range. If the indicator is still red after 24 hours of continuous mains power, measure the pack voltage directly; a healthy starting voltage should be at or above 4.0V.

Emergency light dims or cuts out partway through the duration test

A new pack that has not completed a full charge cycle will show rated voltage at rest but sag quickly under the lamp load during a test. This is not a cell defect — it is a shallow initial charge from storage. The fix is straightforward: allow a minimum 24-hour uninterrupted charge on mains before running the duration test. If the light still dims after that conditioning period, check the charge controller output with a multimeter; the trickle charge voltage to the pack should read between 5.4V and 5.8V across the terminals.