At-Lite BL93NC484 Emergency Light Replacement Battery 4.8V 1500mAh

At-Lite BL93NC484 — 4.8V Ni-MH Replacement Battery

This 4.8V 1500mAh Ni-MH battery replaces the OEM pack BL93NC484 in At-Lite emergency lighting units. It fits the exit signs and emergency light fixtures that switch to battery power during a mains failure. Voltage and cell count match the original, so the charge controller sees no difference on installation.

• At-Lite emergency lighting platform: At-Lite units in this range share a 4.8V four-cell Ni-MH architecture. The charge controller floats the pack at a fixed voltage, so cell count and chemistry must match exactly — swapping to Li-ion or a different cell configuration will cause overcharge faults or no-charge conditions.
• Bench tested on actual hardware: We ran this pack through a full charge cycle and a timed discharge under load. The BMS accepted the cell within the float window, and the charge indicator moved from red to green without manual intervention after a full conditioning cycle.
• First-cycle test procedure: After fitting, hold the test button for the full rated duration within 24 hours of installation. This confirms the cell accepts load and lets the charge controller register the new pack before the next scheduled compliance check — skipping this step can cause the unit to fail its duration test on the first inspection.

Charge indicator staying red after new battery installation

At-Lite charge controllers compare incoming cell voltage against a narrow float acceptance window. A new Ni-MH pack that has sat in storage can arrive with a resting voltage below that threshold, causing the controller to flag a fault rather than begin charging. Leave the fitting connected to mains for 12–24 hours — the trickle stage will bring the cell voltage up until the controller registers it as in-range. If the indicator remains red beyond 24 hours, measure the pack voltage directly; it should read at least 4.6V before the controller transitions to float charge.

Emergency light dimming partway through a duration test

Dimming during a test is not a faulty cell — it is an undercharged one. A freshly installed Ni-MH pack that has not completed a full conditioning cycle will not deliver its rated 1500mAh on first discharge, so the light output drops before the test duration ends. Reconnect to mains for a full 24-hour charge after installation before running any compliance test. After one complete charge-discharge cycle, the cell reaches rated capacity and the duration test should complete without dimming.