Electrolux PQ91-50MB Replacement Battery 25.2V 2000mAh

Electrolux PQ91-50MB Series — 25.2V Li-ion Replacement Battery (4055478301)

This 25.2V 2000mAh Li-ion battery pack replaces OEM part 4055478301 in the Electrolux PQ91-50MB and related cordless stick vacuums. It fits across the PQ91 range including the PQ91-ALRGS, PQ91-ALRGY, and PQ91-ANIMA variants. Voltage and cell count match the original pack exactly so the vacuum's motor controller sees no difference on startup.

• PQ91 series fit: Every model in this range shares the same 25.2V six-cell architecture, connector pinout, and BMS communication protocol. That common platform is why one pack covers the full PQ91 lineup without modification.
• Bench tested on actual hardware: We ran this pack through a full charge-discharge cycle on a PQ91-series unit and logged BMS behaviour under sustained motor load. The protection circuit responded correctly to overcurrent events and released without requiring a manual reset.
• Dock charging practice for PQ91 vacuums: Do not leave the vacuum sitting on the charging dock continuously. The PQ91 dock does not terminate charge at 100% — it trickle charges indefinitely, which accelerates capacity fade in Li-ion cells. Charge to full, then remove from the dock.

Suction dropping before the battery indicator reaches low on PQ91 models

This happens when the motor is working harder than rated — usually a partially blocked filter forcing the motor to draw excess current. That higher draw causes voltage to sag at the pack terminals earlier in the discharge curve, so the vacuum loses suction while the indicator still shows charge remaining. The BMS reads pack voltage, not motor load, so the indicator lags behind the real situation. Clean or replace the filter and retest — restored airflow typically drops current draw back into the normal operating band.

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

This is a BMS overcurrent trip, not a dead battery. Sustained restricted airflow — a blocked nozzle, clogged filter, or matted brush roll — makes the motor draw current beyond the pack's protection threshold. The BMS opens the discharge circuit, the motor stops, and the pack resets once current demand drops to zero. Clear the restriction first, then press the power button. If the cutout repeats on an unblocked machine, check that the replacement pack's rated discharge current matches the OEM spec of 4055478301.