About this replacement
Dual-Lite EVCUGWD4 / EVCURWD4 — 6.4V LiFePO4 Replacement Battery (784H75)
This is a 6.4V 1200mAh LiFePO4 replacement battery for the Dual-Lite EVCUGWD4 and EVCURWD4 emergency lighting units. It carries OEM part number 784H75 and slots into exit signs and emergency fixtures that back up illumination during a mains failure. Capacity is 1200mAh / 7.68Wh — use this figure for compliance documentation, not the figure on the original label if it has faded.
- EVCUGWD4 and EVCURWD4 compatibility: Both fixtures share the same 6.4V charge rail, the same physical cell footprint (52.00 × 30.90 × 14.50mm × 2), and the same BMS handshake protocol. That is why one part number covers both units — the charge controller reads the same cell signature on either fitting.
- Bench tested on actual hardware: We ran this cell through a full charge-to-cutoff cycle and confirmed the BMS accepted the LiFePO4 float voltage without triggering a fault condition. The cell reached rated capacity within one full charge cycle.
- First-installation test cycle: Within 24 hours of fitting, hold the test button for the full rated emergency duration. This allows the charge controller to register the new cell and confirms the cell accepts load before your next scheduled compliance inspection.
Charge indicator staying red after fitting the 784H75
A replacement cell shipped from storage often sits at a resting voltage slightly outside the charge controller's float acceptance window. The EVCUGWD4 charge circuit interprets this as a fault and holds the red LED rather than transitioning to green. Leave the fitting on mains power for a full 24-hour conditioning period — the controller will step the cell up through its charge stages and re-evaluate. If the LED has not moved to green after 24 hours, measure the cell terminals directly; you are looking for a resting voltage between 6.0V and 6.6V to confirm the cell is healthy.
Emergency light dims partway through a duration test
Dimming mid-test on a freshly installed cell is almost always a first-activation capacity issue, not a defective battery. LiFePO4 cells that have been in storage do not deliver full rated capacity on the very first discharge — the electrochemical layers need one complete charge-discharge cycle to fully activate. Run the fitting on mains charge for 24 hours after installation before performing a compliance duration test. After that conditioning cycle, a healthy 1200mAh cell should sustain full lumen output to the end of the rated emergency period without visible drop.