BST 275600 Emergency Light Replacement Battery 2.4V 2000mAh

BST 275600 — 2.4V Ni-Cd Replacement Battery

This is a 2.4V, 2000mAh Ni-Cd replacement battery for the BST 275600 emergency lighting unit. It fits the internal battery pack in emergency exit signs and evacuation lights that require standby power during mains failure. Voltage and capacity match the original cell exactly at 2.4V and 2000mAh (4.8Wh).

• BST 275600 fitment: Emergency lighting units in this range share a fixed 2.4V Ni-Cd charging circuit with a float voltage set for this cell chemistry. Swapping to a different chemistry or voltage rating trips the charge controller out of its acceptance window and the fitting reports a fault.
• Bench tested on actual hardware: We cycled this cell through a full charge and load test on the bench. The BMS accepted the cell without fault, the charge indicator stepped from red to green within the expected window, and the cell held load through a full rated duration test.
• First test cycle after installation: Hold the test button for the full rated duration within 24 hours of fitting. This confirms the new cell accepts load and lets the charge controller register cell capacity before the next compliance inspection. A fresh Ni-Cd cell at storage charge may not pass a duration test until this conditioning cycle is complete.

Charge indicator staying red after new battery installation

A Ni-Cd cell sitting in storage for several months drops to a resting voltage below the float acceptance threshold of the BST 275600 charge controller. When the controller sees that low incoming voltage, it holds the fault or charging state and keeps the LED red. In most cases, leaving the fitting connected to mains for 12 to 24 hours allows the controller to bring the cell up into the acceptance window and switch to green. If the LED does not step to green after 24 hours, check the cell voltage directly — it should read at or above 2.4V.

Emergency light dims partway through a duration test

A new Ni-Cd cell that has not completed a full conditioning cycle will show lower available capacity than its rated 2000mAh. The cell voltage sags under load earlier than expected, and the fitting dims or cuts the lamp circuit before the test duration is complete. This is not a faulty cell — it is an unconditional one. Run the manual test cycle immediately after installation, allow a full 24-hour recharge, then run the test again. The second test result reflects the cell's actual rated capacity.