AEG AG408 Cordless Vacuum Replacement Battery 9.6V 2000mAh

AEG AG408 / ZB408 / ZB4108 — 9.6V Ni-MH Replacement Battery (36.071.399.18)

This is a 9.6V, 2000mAh Ni-MH replacement battery for the AEG AG408, ZB408, and ZB4108 cordless handheld vacuum cleaners. It slots into the original battery compartment and restores the vacuum's motor to full operating voltage. Capacity is 2000mAh (19.2Wh), matching the original specification.

• AG408, ZB408, and ZB4108 fit: These three models share the same 9.6V motor rail, identical battery connector, and the same physical housing format — which is why one cell fits all three. The BMS on each accepts the same charge profile from the original dock.
• Bench tested on actual hardware: We cycled this cell through discharge under a sustained motor load equivalent to carpet cleaning. The BMS held the cutoff voltage steady and did not trip under normal draw. No voltage sag was recorded at the mid-cycle point.
• Dock charging practice for this vacuum: Do not leave the AG408 or ZB408 sitting on the charging dock permanently. Ni-MH cells in this voltage class develop capacity fade significantly faster under continuous trickle charge. Charge to full, then remove the vacuum from the dock until the next use.

Suction dropping before the battery indicator reaches low on the AG408

This is a voltage sag issue, not a failed battery. When the filter is partially blocked, the motor has to work harder to pull air, and current draw climbs above the rated load. At elevated draw, Ni-MH cells drop terminal voltage early — the indicator hasn't caught up yet, but the motor is already running lean. Clean or replace the filter first, then retest. If suction recovers fully after filter cleaning, the battery is fine.

Motor cutting out mid-use and then recovering after a short pause

This is a BMS overcurrent trip, not a dead cell. It typically happens when airflow is restricted — a clogged filter forces the motor to draw sustained high current, and the BMS shuts down the cell to protect it. After a short rest, the BMS resets and the vacuum powers on again. Clear the filter and check the intake for blockages. If trips stop after cleaning, the battery is functioning as intended. If trips continue with a clean filter, check that the dock is providing a full charge cycle to 9.6V before each use.