Kosnic BAT20LFP2 Emergency Light Compatible Battery 6.4V 2000mAh

Kosnic BEM203/ST — 6.4V LiFePO4 Replacement Battery (BAT20LFP2)

This is a 6.4V 2000mAh LiFePO4 replacement cell for the Kosnic BEM203/ST emergency LED luminaire. It slots into the fitting to restore the unit's ability to illuminate during a mains failure. Voltage and chemistry match the original BAT20LFP2 specification exactly.

• BEM203/ST compatibility: The BEM203/ST charge controller runs a fixed float voltage tuned for LiFePO4's 3.2V per cell nominal. Swapping in a different chemistry — even at the same nominal voltage — will cause the controller to undercharge or overcharge the new cell. This replacement keeps that voltage rail intact.
• Bench tested on actual hardware: We cycled this cell through a full mains-off simulation and monitored BMS behaviour under load. The cell held stable output across the discharge curve without triggering low-voltage cutoff prematurely.
• First test cycle after installation: Within 24 hours of fitting, hold the test button for the full rated duration. This forces a complete discharge-and-recharge cycle, which allows the charge controller to register the new cell's capacity before any scheduled compliance test runs.

Charge indicator staying red after fitting a new BAT20LFP2

A new LiFePO4 cell shipped from storage typically sits at a resting voltage between 3.1V and 3.2V per cell — slightly below the charge controller's float acceptance threshold. The controller reads this as a fault condition rather than an uncharged cell and holds the red LED. Leave the fitting connected to mains for a full 24-hour charge cycle. Once the cell voltage climbs into the acceptance window, the controller will release the fault state and switch to green.

Emergency light passes installation check but dims partway through a duration test

This happens when the cell has not completed a full conditioning charge before the test runs. The cell delivers rated output for the first portion of the test, then voltage sags as it hits the depleted lower half of its charge. The fix is not a second replacement — it is time. Allow the fitting a full 24-hour charge on mains before running any timed duration test. After one complete charge cycle, the cell reaches its rated 2000mAh capacity and sustains output across the full test window.