AEG QX 9 1 50 IB Replacement Battery 25.2V 3000mAh

AEG QX 9 1 50 IB / QX91 Series — 25.2V Li-ion Replacement Battery (4055478301)

This 25.2V, 3000mAh (75.6Wh) lithium-ion battery replaces the original pack in AEG QX 9 1 50 IB, QX 9 1 ALRG, QX 9 1 ALRS, QX91 ANIM, and over 30 compatible QX91-series cordless stick vacuums. It matches the OEM voltage rail and BMS handshake the AEG charger expects. Capacity is sourced from the product data — 3000mAh, the same spec as the factory cell.

• QX91-series platform fit: All QX91-series models share a common 25.2V (6S Li-ion) cell architecture, identical battery connector, and the same BMS communication protocol. That is why one replacement pack covers the full model range — the voltage rail and handshake do not change across variants.
• Bench tested on actual hardware: We ran this pack through charge and discharge cycles on a QX91-platform vacuum. The BMS accepted the AEG charger without a fault flag, cell balancing completed normally, and the motor controller received full voltage at startup with no low-voltage cutoff interruptions during discharge.
• Dock charging discipline for QX91 vacuums: Do not leave the vacuum sitting on the charging dock permanently. QX91 vacuums on continuous dock charge develop capacity fade significantly faster than units charged only when depleted. Charge to full, then remove the pack or vacuum from the dock.

Suction dropping before the battery indicator reaches low

This is a voltage-sag issue, not a capacity issue. When the filter is partially blocked or the motor is under sustained heavy load, current draw spikes and the cell voltage drops faster than the fuel gauge expects. The vacuum's motor controller reads that sag as a power shortage and dials back suction to protect the cells — even though the indicator still shows charge remaining. Clean or replace the filter first. If sag continues on a clean filter, the old cell's internal resistance has climbed too high and a fresh pack will restore rated suction immediately.

Motor cuts out mid-clean then recovers after a few seconds

This is a BMS overcurrent trip, not a motor fault. When airflow is restricted — blocked filter, clogged brush roll, or a sealed nozzle — the motor spins harder to compensate, drawing current beyond the BMS overcurrent threshold. The BMS disconnects the load to protect the cells, then resets once temperature and current drop back inside limits. The fix is airflow, not the battery. Check and clear the filter and brush roll first. If the trip recurs on a fully clear airway, the replacement pack's BMS resets to 25.2V nominal and the cutoff threshold returns to factory spec.