Kosnic BAT48LI1 Emergency Light Replacement Battery 3.7V 5000mAh

Kosnic UEM03 / UEM Pro Universal Emergency Module — 3.7V Li-ion Replacement Battery (BAT48LI1)

This is a 3.7V 5000mAh Li-ion replacement cell for the Kosnic UEM03 and UEM Pro Universal Emergency Module. It restores the backup power supply that activates the luminaire when mains power fails. At 18.5Wh, it matches the original BAT48LI1 specification for duration test compliance.

• UEM03 and UEM Pro compatibility: Both units share the same BAT48LI1 cell format, charge controller voltage rail at 3.7V nominal, and connector footprint. No rewiring or adapter needed — the BMS handshake runs identically across both variants.
• Bench tested on actual hardware: We cycled this cell through a full charge and simulated mains-fail discharge on the UEM Pro charge board. The BMS accepted load at 3.7V nominal, held voltage through the discharge curve without early cutoff, and the charge indicator transitioned from red to green within the expected window.
• Post-installation test cycle: Within 24 hours of fitting, hold the test button for the full rated duration. A cell shipped in storage state needs one complete charge-then-discharge pass before the charge controller correctly registers capacity. Skipping this step risks a false fail on the next scheduled compliance test.

Emergency light failing its duration test after battery replacement

A freshly installed BAT48LI1 cell arrives partially discharged from warehouse storage — typically between 3.3V and 3.5V. The UEM03 charge controller begins topping it up immediately, but a full charge from that state takes up to 24 hours at the trickle rate these fittings use. If a compliance test is run before the cell reaches 3.7V float, the luminaire will dim or cut out before the rated duration. Fit the battery, let it charge for a full day, then run one manual test cycle before logging it on any maintenance schedule.

Charge indicator staying red after new battery installation

The UEM03 charge controller uses the incoming cell voltage to decide whether to enter float or bulk charge mode. A cell sitting below roughly 3.2V — which can happen after extended shelf storage — may fall outside the controller's float acceptance window, keeping the charge LED red. This is not a fault with the cell or the fitting. Leave mains power connected for 12–24 hours; the controller will complete bulk charge and the LED will shift to green once the cell crosses the float threshold near 4.1–4.2V.