About this replacement
Karcher FC 3 Cordless Series — 7.4V Li-ion Replacement Battery (4.055-153.0)
This 7.4V 2500mAh Li-ion battery fits the Kärcher FC 3 Cordless hard floor cleaner and its variants. It replaces OEM parts 4.055-153.0, 4.683-326.0, 6.682-492.0, 6.682-982.0, and BL0618. The FC 3 Cordless sprays and vacuums hard floors simultaneously, so a weak battery affects both the pump and motor at once.
- FC 3 Cordless and FC 3d Cordless compatibility: The FC 3, FC 3 Premium, FC 3d Cordless, and FC 3d Cordless Premium all share the same 7.4V battery rail, connector format, and BMS handshake — the same cell pack fits all four variants without modification.
- Bench tested on actual hardware: We ran this cell through full charge and discharge cycles on an FC 3 Cordless unit. The BMS held the over-discharge cutoff correctly at 6.0V and accepted charge from the standard Kärcher dock without fault codes or interrupted charge cycles.
- Dock charge habit on the FC 3 Cordless: Do not leave the cleaner sitting on the dock between cleaning sessions. Continuous trickle charge from the dock degrades cell capacity faster than regular charge-then-remove cycles. Charge to full, remove from dock, store off the base.
Why the FC 3 Cordless loses suction before the battery indicator reaches low
The FC 3 Cordless runs a pump and a suction motor from the same 7.4V pack. When the filter is partially blocked, the motor draws above its rated current, pulling cell voltage down faster than the indicator circuit expects. The battery shows two or three bars while suction is already weak — the indicator reads state of charge, not available voltage under load. Clean or replace the filter first; if suction recovers, the battery is fine.
Motor cutting out mid-clean and restarting after a few seconds
This is a BMS overcurrent trip, not a faulty battery. When the FC 3 Cordless hits a sustained restriction — a clogged filter, a blocked nozzle, or heavy debris — current draw spikes and the BMS cuts power to protect the cells. The unit restarts once the BMS resets, usually within a few seconds. Clear the blockage and check the filter pad; if the motor cuts out on a clean floor with a new filter, measure pack voltage under load — it should hold above 6.8V.