Electrolux PQ91-40GG 21.6V Replacement Battery 3000mAh

Electrolux PQ91-40GG Series — 21.6V Li-ion Replacement Battery (405 54 78-29/3)

This is a 21.6V 3000mAh Li-ion replacement battery for the Electrolux PQ91-40GG and related cordless stick vacuums. It replaces OEM part 405 54 78-29/3 (also listed as 4055478293 and 140231463013). Compatible models include the PQ91-P40GG, ES62AB25UG, and ES62CB25DH, among others.

• PQ91 and ES62 platform fitment: These models share the same 21.6V battery rail, physical connector, and BMS handshake protocol. The battery pack dimensions are 87 × 82 × 54.3mm, matching the original slot geometry across the series without modification.
• Bench tested on actual hardware: We ran this cell through full charge and discharge cycles on a PQ91-series unit. The BMS responded correctly to charge termination, temperature monitoring, and motor-start current draw without tripping the overcurrent cutoff under normal operating load.
• Dock charging on cordless vacuums: Do not leave this vacuum sitting on the charging dock permanently. Continuous trickle charging accelerates capacity fade on Li-ion cells faster than on other device types. Charge to full, then remove from the dock until the next cleaning session.

Cordless vacuum losing suction before the battery indicator reaches low

This happens when the motor is working harder than rated — usually from a partially blocked filter or a restricted airpath. The increased current draw causes voltage to sag at the cell level before the indicator registers low charge. The BMS reads the sag as a low-battery condition and reduces output to protect the cells. Clean or replace the filter first, then retest — suction should hold consistently through a full charge cycle once airflow restriction is removed.

Motor cutting out mid-clean then recovering after a short pause

This is a BMS overcurrent trip, not a failed battery. When suction is sustained against a blockage — a carpet pile jam, a clogged brush roll, or a sealed filter — current spikes beyond the BMS threshold and it shuts the motor down. The pack recovers once current drops, which is why the vacuum restarts after a brief pause. Clear the blockage, check the brush roll for hair wrap, and confirm the filter is clean. If the cutout persists after clearing restrictions, measure the pack voltage at rest — it should read 24.0–25.2V on a full charge.