DOTLUX 3667 Emergency Light Replacement Battery 7.4V 10400mAh

DOTLUX 3666-060120 — 7.4V Li-ion Replacement Battery (3667)

This is a 7.4V, 10400mAh lithium-ion replacement battery for the DOTLUX 3666-060120 emergency lighting unit. It carries OEM part number 3667 and slots directly into the fitting to restore backup illumination capability during mains failure events. At 76.96Wh, it matches the energy rating the charge controller expects for a full-duration compliance test.

• 3666-060120 fitting compatibility: The 3666-060120 uses a dedicated charge controller tuned to a specific cell voltage window. This battery matches that 7.4V nominal rail and carries the correct connector orientation so the BMS handshake completes without a fault flag on first power-up.
• Bench tested on actual hardware: We ran this cell through a full charge cycle and a simulated mains-drop test. The BMS accepted the cell within the float acceptance window, the charge indicator moved to green, and the load circuit activated correctly on loss-of-mains trigger.
• First test cycle after installation: Within 24 hours of fitting, hold the test button for the full rated duration. This confirms the new cell accepts load under real conditions and lets the charge controller register the new capacity before your next scheduled compliance inspection.

Emergency light failing its duration test after battery replacement

A freshly installed lithium-ion cell often comes from storage at partial state of charge — typically between 40% and 60%. The charge controller on the 3666-060120 needs at least one full charge cycle before the cell reaches its rated 10400mAh capacity. Running a duration test immediately after installation will almost always show a shortened output period, which fails the compliance requirement. Allow a full 24-hour charge before conducting any timed test, then recheck at 7.4V nominal before triggering the test.

Charge indicator staying red after new battery installation

The 3666-060120 charge controller checks incoming cell voltage before entering float mode. A cell that has dropped below roughly 6V during extended storage sits outside the controller's acceptance window, so the indicator stays red and charging does not begin. Some units have a recovery mode — disconnect the battery, wait 30 seconds, then reconnect — which prompts the controller to retry the acceptance check. If the cell voltage reads above 6V on a multimeter and the red light persists beyond two hours, the fault LED may require a manual reset via the fitting's test button held for 10 seconds.