About this replacement
Lithonia Daybright D-AA650BX4 Squared Shape — 4.8V Ni-MH Replacement Battery (OSA152)
This 4.8V, 2000mAh Ni-MH battery replaces the original cell pack in the Lithonia Daybright D-AA650BX4 Squared Shape emergency lighting unit. It fits the D-AA650BX4 and compatible it Signs fixtures. Voltage and capacity match the OEM specification (OSA152 / CUSTOM-145-10) so the charge controller recognises the new cell without modification.
- D-AA650BX4 and it Signs compatibility: These fixtures share a 4.8V charge rail and the same four-cell NiMH sub-C configuration. The connector pinout and BMS float voltage are identical across the D-AA650BX4 Squared Shape and the it Signs range, so one cell pack fits both without rewiring.
- Bench tested on actual hardware: We ran this pack through a full mains-fail simulation on a D-AA650BX4 unit. The charge controller accepted the new cell, stepped through its inrush phase without tripping, and held float voltage within the expected 5.4–5.6V window. No fault LED triggered.
- First-cycle conditioning for compliance tests: Within 24 hours of installation, hold the test button for the full rated duration. A fresh cell from storage has not been through a charge-discharge cycle and will underperform on a compliance duration test until it has. One full test cycle lets the charge controller register actual cell capacity before a scheduled inspection.
Charge indicator staying red after new battery installation
The D-AA650BX4 charge controller checks incoming cell voltage before switching from bulk charge to float. A cell that has been in storage drops below the float acceptance window — typically under 4.2V open circuit — and the controller interprets this as a fault rather than a depleted cell. Leave the unit on mains power for a full 24 hours. Most controllers on this fitting will transition to green once the cell clears 4.6V and holds it for two consecutive sample intervals.
Emergency light dims partway through a duration test
Dimming mid-test on a freshly installed cell is a conditioning issue, not a cell defect. NiMH cells shipped from storage have partial crystalline buildup that limits current delivery until the first full discharge cycle burns it off. The cell voltage collapses under load before the rated capacity is actually exhausted. Run one complete test cycle — full charge, then full test-button discharge to cutoff — and recharge for 24 hours before the next compliance test.