T&B 12745 Emergency Light Replacement Battery 1.2V 1500mAh

T&B 12745 / NIC1056 Emergency Lighting — 1.2V Ni-CD Replacement Battery (850.069)

This is a 1.2V, 1500mAh nickel-cadmium cell that replaces the factory battery in T&B emergency lighting units, including models 12745, 012745, and NIC1056. It activates automatically when mains power fails, maintaining illumination for safe egress. Capacity and voltage match OEM spec exactly — no modifications needed during installation.

• Models 12745, 012745, and NIC1056: All three share the same charge controller circuit, float voltage threshold, and physical cell bay dimensions. One cell fits all three without adapter hardware or wiring changes.
• Bench tested on actual hardware: We ran this cell through a full mains-failure simulation. The charge controller accepted the cell within the expected float window, the fault LED cleared, and the output stage held voltage under load through a complete test cycle.
• First-cycle test after installation: Hold the test button for the full rated duration within 24 hours of fitting the new cell. This lets the charge controller register the new cell's capacity and confirms it accepts load before your next scheduled compliance test.

Emergency light failing its duration test after battery replacement

A freshly installed Ni-CD cell ships in a partial state of charge — typically 30–60% of rated capacity. If a compliance duration test is run before the cell has completed at least one full charge-discharge cycle, the light will cut out early and log a fail. The fix is straightforward: install the cell, allow 24 hours of uninterrupted trickle charging, then run a manual test cycle using the test button. After that full cycle, the cell reaches 1500mAh rated capacity and subsequent tests pass.

Charge indicator staying red after new cell installation

The charge controller in these T&B units monitors cell voltage before accepting it into float charge. A cell that has discharged during storage may present a voltage below the controller's acceptance threshold — typically under 1.0V — which keeps the fault LED red. To recover the cell, apply a low-rate charge externally at C/10 (150mA) until terminal voltage reaches 1.2V, then reinstall. The controller will then detect voltage within the float acceptance window and the indicator will shift to green within two hours.