Tefal Air Force Extreme TY8865KS Compatible Battery 25.9V 2500mAh

Tefal Air Force Extreme TY8865KS / 2D2 — 25.9V Li-ion Replacement Battery

This 25.9V, 2500mAh (64.75Wh) lithium-ion battery replaces the original power cell in the Tefal Air Force Extreme cordless vacuum range. It fits the TY8865KS / 2D2, TY8865KS / 9A0, TY8865KS / 9A2, TY8865HO / 2D2, and more than 30 additional Air Force Extreme variants. The battery slots into the same position as the original and connects to the same BMS circuitry.

• Air Force Extreme platform compatibility: These models share the same 25.9V battery architecture, connector pin layout, and BMS handshake protocol — which is why one cell works across the full TY8865 and TY8865HO range without modification.
• Bench tested on actual hardware: We cycled this battery through the TY8865 motor controller under both hard-floor and carpet-resistance loads. The BMS held voltage above the cutoff threshold through repeated sustained draw cycles and did not trip on motor start.
• Dock charging habit on Air Force Extreme vacuums: Do not leave the vacuum sitting on the charging dock permanently. The Air Force Extreme charges to full quickly, and continuous trickle current from the dock degrades cell capacity faster than normal cycling. Charge to full and remove it.

Battery fade from leaving the Air Force Extreme on continuous dock charge

Lithium-ion cells held at 100% charge under continuous trickle current experience elevated internal stress at the cathode. The Air Force Extreme dock does not drop to a true maintenance mode after the cell is full — it continues to push a low-level charge. Over months, this compresses the usable capacity window from both ends, and the battery behaves as though it has far fewer milliamp-hours than rated. Storing the vacuum off the dock at around 50–70% charge between uses slows this degradation noticeably.

Suction dropping off before the battery indicator shows low

This is not always a battery fault. When the Air Force Extreme filter is partially blocked, the motor works harder to maintain airflow and draws more current than the BMS expects at that state of charge. The BMS reads the elevated draw as a low-voltage condition and throttles motor power before the indicator reaches the low threshold. Remove the filter, wash it, let it dry completely for at least 24 hours, then retest — if suction holds through a full charge cycle, the filter was the cause, not the cell.