AEG QX 9 1 50 IB Replacement Battery 25.2V 2000mAh

AEG QX 9 1 50 IB Series — 25.2V Li-ion Replacement Battery (4055478301)

This is a 25.2V, 2000mAh (50.4Wh) lithium-ion battery for the AEG QX 9 1 50 IB cordless stick vacuum and related QX91 models. It replaces OEM part numbers 4055478301, 4055542544, and PANGU 7C-C. The battery slots into the same housing as the original and connects to the vacuum's motor controller without modification.

• QX91 series compatibility: The QX 9 1 50 IB, QX 9 1 ALRG, QX 9 1 ALRS, and QX91 ANIM all run the same 25.2V cell stack with an identical connector and BMS handshake protocol. One battery cell fits all listed variants because the motor controller expects the same voltage rail across the range.
• Bench tested on actual hardware: We ran this cell through full charge and discharge cycles on a QX91-series vacuum. The BMS maintained stable voltage delivery under sustained suction load and engaged thermal protection correctly at rated cutoff thresholds.
• Dock charging habit on QX91 vacuums: Do not leave the vacuum sitting on the charging dock continuously. AEG QX91 chargers do not cut off cleanly after a full charge — trickle current keeps flowing. Remove the vacuum from the dock once the charge indicator shows full to avoid accelerated capacity fade over time.

Suction dropping before the battery indicator reaches low

This happens when the motor draws more current than the BMS expects, triggering a voltage sag before the cell is actually depleted. On the QX91, a partially blocked filter is the most common trigger — restricted airflow forces the motor to work harder and spike current draw. The BMS reads that as an undervoltage condition and reduces output. Clean or replace the filter first, then retest with the new battery before assuming the cell is at fault.

Motor cuts out mid-clean and then recovers after a pause

This is a BMS overcurrent trip, not a dead battery. It occurs when sustained airflow restriction — usually a clogged filter or blocked brush head — pushes current draw past the BMS cutoff threshold. The BMS shuts the motor down to protect the cell, then resets after a short cool-down. Clear the blockage and check the filter condition before reinstalling the battery. If the motor trips again on an unobstructed, clean vacuum, verify the charger output is at 29.4V before suspecting the cell.