Electrolux PQ91-50MB Replacement Battery 25.2V 3000mAh

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

This 25.2V 3000mAh Li-ion battery pack replaces the original power cell in the Electrolux PQ91-50MB and related PQ91 series cordless stick vacuums. It fits the PQ91-ALRGS, PQ91-ALRGY, PQ91-ANIMA, and over a dozen additional PQ91 variants. Voltage and capacity match OEM spec at 25.2V and 3000mAh (75.6Wh).

• PQ91 series platform fit: All PQ91 variants share the same 25.2V battery rail, connector pinout, and BMS handshake protocol. Swapping the pack across these models triggers no fault codes and no charge lockout — the BMS communicates identically to the original cell pack.
• Bench tested on actual hardware: We ran this pack through full charge and discharge cycles on a PQ91 unit, confirming BMS charge acceptance, motor start current handling, and cutoff behaviour under simulated blockage load. The pack held within 2% of rated capacity across five consecutive cycles.
• Dock charging habit on PQ91 vacuums: Do not leave the vacuum sitting on the charging dock continuously between uses. PQ91 models draw a low trickle current when docked even after reaching full charge. Over weeks, this accelerates cell degradation. Charge to full, then remove from the dock.

Suction dropping before the battery indicator reaches low on PQ91 models

The PQ91 motor controller reads pack voltage directly to manage suction power. When cells age, internal resistance rises and voltage sags under load — even if the indicator still shows a partial charge. The motor controller interprets this voltage sag as low battery and reduces power output before the indicator catches up. A new cell pack with lower internal resistance restores full voltage under load and eliminates early suction loss.

Motor cutting out mid-clean and recovering after a few seconds

This is a BMS overcurrent trip, not a cell failure. When the vacuum's filter is partially blocked, the motor draws significantly more current trying to maintain airflow. The BMS detects the spike and cuts power to protect the cells, then resets after a short cooldown. Before replacing any parts, clean or replace the filter and check the brush roll for hair wrap. If the cutout stops after clearing the restriction, the battery and motor are both fine — the trip was a normal protection response.