Kärcher EF426 Replacement Battery 25.2V 4500mAh BV 5/1 Bp

Karcher EF426 / BV 5/1 Bp Series — 25.2V Li-ion Replacement Battery (6.654-183.0)

This is a 25.2V, 4500mAh lithium-ion battery for Karcher cordless tools including the EF426, BV 5/1 BP, T 9/1 BP, and BR 30/4 C BP. It replaces OEM part numbers 6.654-183.0, 6.654-255.0, 6.654-284.0, BV 5/1 Bp, and T 9/1 Bp. The pack uses the same connector and BMS handshake as the original, so the tool recognises it immediately on insertion.

• EF426 / BV 5/1 Bp platform compatibility: These models share a 25.2V six-cell rail and the same physical connector housing. The BMS on each expects the same charge termination voltage and current profile, so one pack runs across the entire platform without firmware conflicts.
• Bench tested on actual hardware: We cycled this pack under load conditions that replicate suction motor inrush on the EF426. The BMS held the overcurrent threshold without nuisance tripping and recovered full voltage within seconds of each load spike.
• Motor inrush conditioning on first use: On first use, run the tool at reduced load for two full discharge-charge cycles before sustained high-power operation. This lets the BMS log the motor's inrush current profile and set accurate overcurrent thresholds before you push the tool to full draw.

BMS overcurrent trip on trigger pull — why the EF426 cuts out instantly

The EF426 suction motor pulls a sharp inrush current spike the moment the trigger fires. If the BMS on a new or cold pack has not yet profiled that spike, it can read the surge as a fault and cut the output rail before the motor reaches running speed. This is not a defective battery — it is the protection circuit responding to an uncalibrated threshold. Two conditioning cycles at partial load teach the BMS where normal inrush ends and a genuine fault begins. After conditioning, trigger-pull cutouts on a healthy pack should stop entirely.

Charger blinking red and refusing to accept the pack after storage

Lithium-ion packs stored for several months can drop below the charger's minimum acceptance voltage — typically around 2.5V per cell, which is roughly 15V at pack level for a 25.2V six-cell unit. Most Karcher chargers will blink red and refuse to enter bulk charge mode if the pack arrives below that threshold. The fix is a short recovery charge using a bench supply set to 25.2V and a current-limited output of around 0.1A for 10–15 minutes, which brings cells back above the acceptance floor. Once cell voltage is above the threshold, re-insert the pack into the Karcher charger and it should enter normal charge mode.