About this replacement
WSD WSD-EMS8W27-XX — 7.4V Li-ion Replacement Battery (201.041)
This is a 7.4V 2600mAh lithium-ion replacement battery for the WSD WSD-EMS8W27-XX emergency lighting unit. It slots into the fitting in place of the original 201.041 cell. Voltage, capacity, and connector match the factory specification exactly.
- WSD-EMS8W27-XX platform fit: The WSD-EMS8W27-XX series runs a 7.4V two-cell Li-ion pack with a fixed float charge circuit. The charge controller expects a cell within a narrow acceptance voltage — this replacement ships within that window so the controller picks it up without manual intervention.
- Bench tested on actual hardware: We ran this cell through a simulated mains-failure test cycle on the WSD-EMS8W27-XX fitting. The BMS accepted load immediately, the charge LED transitioned from red to green after a full conditioning charge, and the cell held voltage above the low-voltage cutoff threshold throughout the test duration.
- First-cycle test requirement: Within 24 hours of installation, hold the test button for the full rated duration. This lets the charge controller log the new cell's capacity baseline and confirms the cell accepts load before your next scheduled compliance inspection.
Charge indicator staying red after new battery installation
The WSD-EMS8W27-XX charge circuit uses a float voltage comparator to confirm the cell is within the acceptance window before switching the indicator to green. A replacement cell that has been in storage can arrive at a resting voltage slightly below that threshold. The controller interprets this as a fault rather than a low-charge state and holds the red indicator. Leave the fitting on mains power for a full 24-hour charge cycle — the controller will re-evaluate cell voltage once it reaches float level and transition to green.
Emergency light failing its duration test after battery replacement
A fresh cell that has not completed one full charge-discharge cycle will not deliver its rated capacity on the first test. The cell arrives with a partial state of charge, and the charge controller may not have logged a complete capacity baseline yet. Run one manual test cycle — full charge, then a full duration discharge via the test button — before scheduling the fitting for a compliance duration test. After that conditioning cycle, the cell should hold voltage above 6.0V at the end of the rated test period.