Lithonia OSA052 Ni-CD Emergency Light Replacement Battery 12V 8000mAh

Lithonia A35241 — 12V Ni-CD Replacement Battery (OSA052)

This is a 12V 8000mAh Ni-CD battery for the Lithonia A35241 emergency lighting unit. It replaces OEM part OSA052 when the original cell degrades and the fitting can no longer sustain output during a mains failure. Rated at 96Wh, it matches the voltage and capacity the A35241 charge controller expects.

• A35241 compatibility: The A35241 uses a charge controller tuned to a 12V Ni-CD float voltage. Swapping to a different chemistry or voltage shifts the float acceptance window and the controller will fault. This cell keeps the circuit within spec.
• Bench tested on actual hardware: We ran a full load discharge cycle on the A35241 to confirm the BMS accepted the cell and the charge LED transitioned from red to green after a complete charge cycle. No voltage sag anomalies were recorded during the load test.
• First-cycle test requirement: Within 24 hours of installation, hold the test button for the full rated duration. This forces the charge controller to register the new cell's capacity baseline before the next scheduled compliance test — skipping this step can cause a false fail on your first duration test.

Why the A35241 charge LED stays red after a new cell is installed

Ni-CD cells lose charge during storage. If a replacement cell arrives with a resting voltage below the charge controller's float acceptance threshold, the A35241 will flag a fault instead of entering a normal charge cycle. The controller needs to see the cell voltage climb above approximately 1.0V per cell (12V pack = 10 cells in series) before it transitions to trickle charge. Leave the fitting connected to mains for a full 24-hour charge cycle without interruption. If the LED has not turned green after 24 hours, check the terminal connections and confirm polarity before suspecting a faulty cell.

Emergency light dims and cuts out partway through a duration test

This is not a faulty cell — it is an uncharged one. A new Ni-CD pack installed and tested within hours of fitting has not completed its first full charge cycle and cannot deliver rated capacity under load. The lamps draw sustained current the cell simply cannot sustain yet. Allow a minimum 24-hour mains charge before running any duration test. After that first full charge, the cell should hold steady output through the complete test period without dimming.