About this replacement
ELRO NV52 — 3.6V Ni-MH Replacement Battery (ELRD3SC1500)
This is a 3.6V, 2000mAh Ni-MH replacement cell for the ELRO NV52 emergency lighting unit. It fits directly into the NV52 fitting and restores backup illumination when mains power fails. Capacity is 7.2Wh, matching the original specification.
- NV52 fitting compatibility: The NV52 uses a 3.6V Ni-MH cell on a continuous trickle-charge circuit. The cell must match voltage and chemistry exactly — substituting a different chemistry breaks the charge controller's float voltage window and triggers a permanent fault LED.
- Bench tested on actual hardware: We ran this cell through a full simulated mains-failure cycle. The charge controller accepted the cell without faulting, the BMS held stable under load, and the fitting exited test mode cleanly at the rated cell voltage.
- First-cycle activation on NV52 fittings: Within 24 hours of installation, hold the NV52 test button for the full rated duration. This confirms the new cell accepts load and allows the charge controller to register cell capacity before any scheduled compliance test.
Charge indicator staying red after new battery installation in the NV52
A replacement Ni-MH cell shipped from storage typically sits at 1.0–1.1V per cell, well below the NV52 charge controller's float acceptance window. The controller reads this as a fault and holds the red indicator rather than entering charge mode. Leave the fitting powered on mains for 12–24 hours. Once cell voltage climbs into the acceptance band — typically around 1.2V per cell — the controller transitions to charge mode and the indicator shifts to green.
Emergency light dims and cuts short during a duration test after battery replacement
A new Ni-MH cell does not deliver full rated capacity on its first discharge cycle. The cell needs one complete charge-discharge cycle to reach the 2000mAh specification. If the fitting dims or cuts out early during a post-installation test, this is expected behaviour — not a faulty cell. Run a second full test cycle after the cell has completed a 24-hour charge, and the output will stabilise at rated capacity.