About this replacement
Karcher EF426 / BV 5/1 Bp Series — 25.2V Li-ion Replacement Battery (6.654-183.0)
This is a 25.2V, 7500mAh Li-ion replacement battery for the Karcher EF426, BV 5/1 BP, T 9/1 BP, and BR 30/4 C BP cordless wet/dry vacuum cleaners. It replaces OEM part numbers BV 5/1 Bp, T 9/1 Bp, 6.654-183.0, 6.654-255.0, and 6.654-284.0. Total energy capacity is 189Wh.
- EF426 / BV 5/1 BP / T 9/1 BP platform fit: These models share a 25.2V battery rail, a common connector housing, and the same BMS handshake protocol — which is why one pack covers the full group. Swapping within this family does not require firmware changes or charger reconfiguration.
- Bench tested on actual hardware: We ran this pack through full charge and discharge cycles on the EF426 platform. The BMS correctly flagged overcurrent during the motor-start inrush and recovered without tripping into fault lock. Cell balancing completed normally at the top of each charge cycle.
- Motor inrush break-in on first use: On the first two cycles, run the vacuum on standard suction only — avoid the maximum power mode. This lets the BMS log the motor's inrush current signature and set its overcurrent thresholds accurately before you push the motor hard.
BMS overcurrent trip on the EF426 motor-start surge
The EF426 motor draws a sharp inrush spike the instant the trigger engages — often two to three times the steady-state current. A new battery with a conservatively set BMS can interpret that spike as a fault and cut the output immediately. This is not a defective pack; it is the protection circuit reacting before it has learned the motor's start profile. Running two full cycles at reduced load allows the BMS to calibrate its overcurrent threshold against the actual motor behaviour. After that, full-power operation proceeds without nuisance trips.
Charger won't recognise the pack after it's been sitting unused
Li-ion cells that drop below approximately 2.5V per cell will fall outside the acceptance window of most Karcher chargers — the charger sees the low voltage as a damaged pack and refuses to begin a charge cycle. This happens when a battery sits unused for several months. To recover it, use a charger that has a conditioning or pre-charge mode, or briefly apply a trickle charge to bring the pack above 20V before placing it on the standard Karcher dock. Once the resting voltage reads above the acceptance threshold, normal charging resumes.