iRobot Roomba S9 Replacement Battery 14.4V 3300mAh ABL-B

iRobot Roomba S9 / S9+ — 14.4V Li-ion Replacement Battery (ABL-B)

This is a 14.4V, 3300mAh Li-ion replacement battery for the iRobot Roomba S9 and S9+ robotic vacuum. It fits OEM part numbers ABL-B and 4650994, including the S955020 variant. Voltage and capacity match the original spec so the Roomba's navigation system and suction motor receive the correct power from the first charge.

• S9 and S9+ compatibility: Both models share the same battery bay geometry, connector pinout, and 14.4V power rail. The S9+ adds the Clean Base dock but draws from the same battery system, so one cell fits both.
• Bench tested on actual hardware: We ran this cell through full charge and discharge cycles on an S9 unit. The BMS communicated correctly with the robot's onboard charge controller — no error codes, no premature cutoff on the motor-start current spike.
• Dock charging discipline on the S9: The S9 is programmed to return to dock and sit indefinitely. Leaving the replacement cell on continuous trickle charge accelerates capacity fade. Charge to full, then lift the robot off the dock during idle periods of more than two days.

Suction dropping before the battery indicator reaches low on the S9

The S9's brushroll and suction motor are high-draw loads. When internal resistance climbs in an ageing cell, voltage sags under load even though the reported state of charge still reads mid-range. The robot's motor driver reads the voltage drop as a brownout and reduces power to protect the drive system. A fresh cell with lower internal resistance holds voltage steady through the full suction cycle, so the indicator and actual performance stay in sync.

Motor cutting out and recovering mid-clean on carpet

This is a BMS overcurrent trip, not a battery failure on its own. On thick carpet, a partially blocked filter forces the motor to draw sustained current above the BMS threshold, which triggers a protective cutoff. The robot pauses, the BMS resets after a few seconds, and it resumes. Clean the filter and check the brushroll for hair wrap first — if the cutout stops after that, the battery BMS is doing its job. If it continues with a clean filter, check that the replacement cell is fully charged to 16.8V before the next run.