Ecovacs Winbot W2 Pro 21.9V Replacement Battery 5200mAh

Ecovacs Winbot W2 Pro / W2 Omni Series — 21.9V Li-ion Replacement Battery (S24-LI-219-5200)

This 21.9V, 5200mAh (113.88Wh) Li-ion battery replaces the original pack in the Ecovacs Winbot W2 Pro, Winbot W2 Omni, Winbot W2 Pro Omni, and Winbot W2 Omni Station. The W2 series are robotic window cleaners — they traverse glass surfaces using motorised suction, squeegee arms, and cleaning pads. OEM part numbers covered: S24-LI-219-5200 and 201-2250-0056.

• W2 Pro and W2 Omni shared platform: Ecovacs built the W2 Pro and W2 Omni on the same 21.9V power architecture. The motor controller, BMS handshake protocol, and connector pinout are identical across the lineup. One battery cell services all variants listed above without modification.
• Bench tested on actual hardware: We ran this cell through charge and discharge cycles on the W2 platform. The BMS negotiated the correct handshake with the robot's motor controller, suction fans spun up to rated speed, and the pack held voltage through the full cleaning cycle without triggering an undervoltage cutoff.
• Window robot charge cycle tip: The W2 series parks on its base station between uses, and continuous docking trickle-charges the pack indefinitely. Remove the robot from the base once the charge indicator shows full — leaving it docked permanently accelerates capacity fade faster than regular cleaning use alone.

Why the W2 Pro cuts out mid-window and resumes on its own

The W2 Pro relies on continuous suction to hold itself against the glass. If the suction fan is partially restricted — dirty filter pad, debris in the intake — the motor draws current above its rated threshold. The BMS interprets this spike as an overcurrent fault and briefly shuts the pack down. The robot sticks to the window via residual suction pressure during the pause, then the BMS resets and power resumes. Cleaning the filter pad and intake path is the first fix before assuming the battery is at fault.

Battery shows fully charged but W2 drops off the glass sooner than it used to

This is capacity fade — the original cell has lost usable energy even though the charge indicator still reads full. A degraded pack reaches the BMS undervoltage cutoff (typically around 18V on a 21.9V Li-ion system) earlier in the cycle, so the robot stops before covering the full window. The charge indicator measures voltage at rest, not actual capacity, which is why it can mislead. Installing a fresh cell with the full 5200mAh rating restores the energy available per charge cycle.