About this replacement
Lithonia ELB0502N / ELB4814N Series — 4.8V Ni-MH Replacement Battery (CUSTOM-45 / ELB 4814N)
This is a 4.8V, 2000mAh Ni-MH battery for Lithonia emergency lighting fixtures and exit signs. It fits the ELB0502N, ELB4714N, ELB4814N, and Prescolite E2377-01-00, among others. Cross-references include OEM part numbers CUSTOM-45, 4PH56, 5YB73, and ELB 4814N.
- ELB-series fixture compatibility: These models share the same 4.8V four-cell NiMH configuration, connector pitch, and charge controller float voltage. The BMS in each fitting expects a specific charge acceptance curve — a mismatched cell count or chemistry triggers a permanent fault LED.
- Bench tested on actual hardware: We cycled this cell through a full charge and load discharge on an ELB4814N fixture. The charge controller accepted the cell within the float window, the green indicator lit at full charge, and the load relay activated cleanly on a simulated mains-failure event.
- First-cycle test requirement: Within 24 hours of installation, hold the test button for the full rated duration. This forces a complete load cycle, lets the charge controller register the new cell's capacity, and ensures the fixture passes its next compliance inspection without a false short-duration result.
Charge indicator staying red after new battery installation
Lithonia ELB-series fittings use a float-voltage window to confirm a healthy cell. A new Ni-MH battery shipped from storage often sits below 4.5V resting voltage, which places it outside that acceptance window. The charge controller reads this as a fault rather than a depleted cell and holds the red indicator. Leave the fitting on mains power for a full 24-hour conditioning charge — the controller re-samples cell voltage periodically and will shift to green once the pack climbs above its acceptance threshold, typically around 5.4V under trickle.
Emergency light dims and cuts short during a duration test
This is different from a flat-out failure to activate. The fixture lights up when mains drops, but output fades well before the rated duration is reached. The cause is an incompletely conditioned cell — the charge controller logs whatever capacity it measured on the first cycle, and if that cycle was short, it sets a lower internal threshold. Run one full manual test cycle immediately after installation by holding the test button until the light extinguishes naturally, then restore mains and allow a full 24-hour recharge before the next test. The controller recalibrates its capacity register on that second cycle and the fixture should meet its full rated duration.