Dual-Lite 784H74 Emergency Light Replacement Battery 4.8V 800mAh

Dual-Lite SEWLDGBE / SEWLDRBE Series — 4.8V Ni-Cd Replacement Battery (784H74)

This is a 4.8V, 800mAh Ni-Cd replacement battery for Dual-Lite emergency lighting fixtures. It fits the SEWLDGBE, SEWLDGWE, SEWLDRBE, and SEWLDRWE series, along with three additional variants in that range. When mains power fails, this cell powers the fixture through its rated emergency illumination period.

• SEWLD series compatibility: These fixtures share the same 4.8V cell format, connector pitch, and charge controller float voltage across the BE and WE suffix variants — both beige and white housings run the same internal circuit board and battery bay dimensions.
• Bench tested on actual hardware: We cycled this cell through a full charge-discharge sequence on the SEWLDGBE charge board. The BMS accepted charge without fault, the float voltage settled at the correct level, and the cell held load through the duration test window.
• Post-installation test cycle: Within 24 hours of fitting, press and hold the test button for the full rated duration. A freshly installed Ni-Cd cell from storage has not yet been conditioned to the fixture's charge controller — running one complete test cycle lets the controller register actual cell capacity before your next scheduled compliance inspection.

Emergency light failing its duration test after battery replacement

A new Ni-Cd cell shipped from a warehouse may have sat in partial discharge for months. The charge controller on the SEWLD board applies a trickle charge, not a conditioning cycle, so a stored cell can take 24–48 hours to reach full rated capacity. If the fixture is tested on the same day as replacement, the cell will not yet deliver its full 800mAh. Allow a minimum of 24 hours on charge before any compliance test, then verify float voltage reads at or above 5.4V across the battery terminals.

Charge indicator staying red after confirmed good installation

Some SEWLD variants latch a fault LED in firmware when the battery voltage drops below the controller's acceptance threshold during storage. Even with a correctly fitted new cell, the indicator stays red until the controller completes its own reset sequence. Remove mains power from the fitting for 30 seconds, then restore it — this forces the charge controller to re-initialise and re-read cell voltage. If the LED shifts to green within two minutes, the controller has accepted the new cell; if it remains red beyond 48 hours on charge, check connector seating and cell polarity against the bay markings.