About this replacement
Karcher KM35/5 — 18V Li-ion Replacement Battery (BD0810)
This is an 18V Li-ion replacement battery rated at 2500mAh (45Wh), built to the same electrical spec as Karcher part BD0810. It fits the KM35/5 compact push sweeper and powers the brush motor directly. When the original pack degrades and the sweeper loses power mid-run, this is the unit to swap in.
- KM35/5 platform fit: The KM35/5 runs its brush motor off an 18V rail with a specific connector footprint and BMS handshake. This pack matches that rail voltage, connector geometry, and communication protocol — the sweeper's onboard electronics will recognise it without any pairing step.
- Bench tested on actual hardware: We cycled this pack through repeated brush-motor start sequences and monitored the BMS response to inrush current spikes at startup. The protection circuit held within spec across all test cycles, and cell voltage balanced correctly after each discharge.
- Brush motor start cycling: Each time the KM35/5 sweeper starts from rest, the brush motor draws a short inrush spike before settling to running current. Avoid starting and stopping the sweeper repeatedly in quick succession — back-to-back cold starts stack inrush events and can trip the BMS overcurrent threshold prematurely.
BMS cutoff on brush motor inrush at startup
The KM35/5 brush motor pulls a current spike the moment the sweeper engages — this is normal, but a degraded or deeply discharged pack may trip the BMS overcurrent protection before the motor reaches steady-state draw. The BMS interprets the spike as a fault and shuts down the cell output to protect the pack. On a new replacement pack, this is unlikely unless the cells have dropped below the charger acceptance threshold after storage. Charge the pack fully to 18V before first use to ensure the BMS initialises correctly.
Charger light stays red and never switches to green
If the Karcher charger blinks or holds red when you connect this pack, the cell voltage has likely dropped below the charger's acceptance floor during storage — most Li-ion chargers will not begin a charge cycle if the pack reads below approximately 12–14V. This is a self-discharge issue, not a faulty battery. Some chargers have a recovery or boost mode; if yours does, activate it to bring the cells up to acceptance voltage. If the charger has no boost mode, a compatible Li-ion recovery charger set to 18V nominal will bring the pack back into the chargeable range.