About this replacement
Dual-Lite EVCUGW / EVCURBD Series — 6.4V LiFePO4 Replacement Battery (784H73)
This is a 6.4V 600mAh lithium iron phosphate cell for Dual-Lite emergency lighting units including the EVCUGW, EVCUGWDI, EVCURBD, and EVCURW. It slots into the fitting where the original 784H73 cell lives. When mains power drops, this cell drives the lamp circuit to keep evacuation routes lit.
- EVCUGW and EVCURBD platform fit: These models share the same 6.4V LiFePO4 chemistry, physical footprint (50.70 × 31.50 × 14.30mm), and charge controller float voltage. Swapping between variants in this family does not require any wiring change — the connector and BMS acceptance voltage are identical across the series.
- Bench tested on actual hardware: We ran the cell through a simulated mains-fail activation. The BMS held output voltage stable under lamp load, and charge acceptance from the controller completed without a fault flag. Cell voltage at full charge sat within the LiFePO4 float window.
- First test cycle after installation: Within 24 hours of fitting, press and hold the test button for the full rated duration. This lets the charge controller register the new cell and confirms load acceptance before your next scheduled compliance inspection.
Charge indicator staying red after fitting the new 784H73 cell
A red charge LED after installation usually means the cell arrived from storage at a voltage below the fitting's float acceptance threshold. Dual-Lite charge controllers on this series expect to see the cell above approximately 6.0V before they transition out of fault mode. If the cell sat in a warehouse for several months, its resting voltage may have dropped enough to trigger this. Leave the fitting on mains power for 12–24 hours — most controllers will re-enter normal charge mode once the cell climbs back into the acceptance window.
Emergency light dims partway through the duration test after battery replacement
This happens when a freshly installed cell has not completed its first full charge cycle before the test is run. LiFePO4 cells do not reach rated capacity on the very first activation — the initial charge cycle conditions the cell. Running the test immediately after installation pulls the cell below its usable floor too early, causing the lamp to dim. Charge the fitting on mains for a full 24 hours, then run the duration test. If dimming still occurs after proper conditioning, check that the cell voltage under load stays above 5.4V.