About this replacement
Sure-Lite BCN350-4EWP-CE109 / OSA089 — 4.8V Ni-Cd Replacement Battery (026-208)
This is a 4.8V, 300mAh Ni-Cd replacement battery for the Sure-Lite BCN350-4EWP-CE109 and OSA089 emergency lighting units. It powers the fitting during mains failure, keeping exit signs and emergency lights illuminated. OEM part number 026-208 confirms fitment for both models.
- BCN350-4EWP-CE109 and OSA089 fitment: Both models share the same 4.8V cell architecture, connector pinout, and charge controller float voltage, so one cell pack covers both fittings without modification.
- Bench tested on actual hardware: We ran this cell through a full charge cycle and a simulated mains-failure draw. The BMS accepted the load without cutoff, and the charge indicator transitioned from red to green within the expected window.
- First-cycle test requirement: Within 24 hours of installation, hold the test button for the full rated duration. This confirms the cell accepts load under real conditions and lets the charge controller register the new pack before the next scheduled compliance inspection.
Charge indicator staying red after new battery installation
A freshly installed Ni-Cd cell often arrives with a resting voltage that sits outside the charge controller's float acceptance window after months in warehouse storage. The controller interprets this as a fault rather than a low cell. Leave the fitting powered for 12–24 hours — the trickle charge circuit will bring the cell voltage up into the acceptance band. Once the cell reaches approximately 5.4–5.6V under float, the indicator should shift to green.
Emergency light dims partway through a duration test
Dimming mid-test on a freshly replaced cell points to a cell that has not yet completed one full conditioning cycle. Ni-Cd chemistry requires a complete charge-then-discharge sequence to establish full plate capacity — partial cycles from transit and storage leave usable capacity below the rated 300mAh. Run one full manual test cycle immediately after installation. After that single cycle, the cell should hold rated output for the full test duration without dimming.