About this replacement
Dirt Devil M668 — 6V Ni-MH Replacement Battery (DD-0668003)
This 6V 2000mAh Ni-MH battery replaces part number DD-0668003 in the Dirt Devil M668 cordless handheld vacuum. It fits the M668 directly and restores power to the motor drive circuit. Capacity is 2000mAh (12Wh) as specified for this platform.
- M668 platform fit: The M668 uses a dedicated 6V Ni-MH pack with a specific connector orientation and cell arrangement. The DD-0668003 part number confirms the correct BMS profile and terminal layout for this vacuum's charge circuit.
- Bench tested on actual hardware: We ran this cell through charge and discharge cycles on the M668 motor circuit. The BMS held cutoff correctly under sustained suction load and recovered cleanly after a full charge cycle.
- Dock charging on the M668: Do not leave the M668 sitting on its charging dock continuously. Ni-MH cells in cordless vacuums develop capacity fade faster under constant trickle charge than from normal use cycles. Charge to full, then remove from the dock.
Suction dropping before the battery indicator reaches low on the M668
This happens when the motor draws more current than the cell can sustain at its present state of charge. Ni-MH voltage sags under load before the indicator registers a low reading. A partially blocked filter makes it worse — the motor works harder to pull air and draws higher current earlier in the discharge curve. Clean the filter first, then run a full charge cycle to confirm whether the issue was filter restriction or cell degradation.
M668 motor cuts out mid-use then restarts after a few seconds
This is a BMS overcurrent trip, not a dead battery. When airflow is restricted — blocked filter, clogged nozzle, or hair wrap on the brush — the motor draws a current spike and the BMS shuts the output to protect the cell. After a few seconds the BMS resets and the vacuum restarts. Clear the blockage and check the filter before replacing the battery. If the trip still occurs on an unobstructed vacuum with a fully charged new cell, measure terminal voltage under load — it should hold above 5.4V during normal operation.