Roborock A10 Ultra B Replacement Battery 21.6V 4000mAh

Roborock A10 Ultra B / A10 Ultra E — 21.6V Li-ion Replacement Battery (BCR-1P6S-4000HD)

This is a 21.6V 4000mAh (86.4Wh) Li-ion battery pack for the Roborock A10 Ultra B and A10 Ultra E robotic vacuum cleaners. It replaces OEM part BCR-1P6S-4000HD and restores full cleaning operation when the original cell has degraded or failed to hold charge. Voltage and capacity match factory spec exactly.

• A10 Ultra B and A10 Ultra E compatibility: Both models run the same 21.6V power rail with an identical battery bay footprint and BMS handshake protocol. The BCR-1P6S-4000HD pack communicates state-of-charge data directly to the vacuum's onboard controller — the indicator display and auto-dock charging both function as they would with the original cell.
• Bench tested on actual hardware: We cycled this pack through full discharge and recharge sequences on the A10 Ultra platform. The BMS responded correctly to charge termination, cell balancing engaged across all six series cells, and the vacuum's dock-charge circuit accepted the pack without error flags.
• Dock charging habit for this model: The A10 Ultra series parks itself on the dock automatically after each run. Left on continuous dock charge for weeks at a time, the cells sit at 100% under trickle current and lose capacity faster than cells that rest below full. Charge to full, then remove the unit from the dock if it will not be used for several days.

Suction dropping before the battery indicator reaches low on the A10 Ultra B

The A10 Ultra B's motor draws significantly more current when airflow is restricted — a clogged filter or partial blockage can push draw well above the normal operating load. The BMS reads this as an overcurrent condition and reduces power to the motor before the state-of-charge indicator reflects any problem. The vacuum appears to lose suction while the battery still shows substantial charge remaining. Clean the HEPA filter and check the brush roll for hair tangles before assuming the battery is the cause.

Motor cutting out briefly mid-cycle then recovering on its own

This is a BMS overcurrent trip, not a capacity failure. When sustained suction restriction forces the motor to pull beyond the pack's continuous current threshold, the BMS cuts output for a few seconds and then resets once current demand drops. It happens repeatedly if the restriction is not cleared. Remove, clean, and reinstall the dust filter — if the filter is clear, inspect the inlet path for a partial blockage and confirm the brush roll spins freely. A cell that is genuinely failing will trip the BMS even on clean, hard floors at a measured cell voltage below 3.0V per cell under load.