Leifheit 51000 Cordless Vacuum Replacement Battery 3.7V 3400mAh

Leifheit Drybox 51000 Series — 3.7V Li-ion Replacement Battery (56925/LEI2)

This 3.7V 3400mAh Li-ion cell replaces the original battery in the Leifheit Drybox cordless handheld vacuum. It fits the 51000, 51000 II. generace, 51002, and 51113 models, along with seven additional variants in the same family. Capacity figure is taken directly from the product specification — 12.58Wh.

• 51000 series fit: Every model in this group runs the same single-cell 3.7V architecture with an identical connector and BMS handshake protocol. That shared platform means one cell covers the full range without modification.
• Bench tested on actual hardware: We cycled this cell through the Drybox motor circuit under load. The BMS held voltage within spec across sustained suction draws and tripped correctly at the low-voltage cutoff threshold without false triggering.
• Dock charging habit for the Drybox: Do not leave the Drybox sitting on the charging dock between uses. This vacuum's charging circuit does not cut trickle current once full, so cells left docked continuously develop capacity fade faster than those charged only when depleted. Charge to full, then remove.

Suction dropping before the battery indicator reaches low

This happens when the filter is partially blocked. A restricted airflow path forces the motor to draw more current than rated, which causes voltage to sag under load even when the cell still holds a usable charge. The BMS reads that sag as low battery and reduces power to protect the cell. Clear the filter and check the intake path — if suction returns to full strength immediately after, the battery was not the problem.

Motor cutting out mid-use then recovering after a short pause

That pattern is a BMS overcurrent trip, not a dead cell. Sustained restricted suction — usually a clogged filter or blocked nozzle — pushes current draw above the BMS threshold. The BMS cuts the circuit, the motor stops, and after a brief cool-down the protection resets. Check and clean the filter first. If the cutout stops, the cell is fine. If it persists on a clean filter, confirm cell voltage sits above 3.5V under load using a multimeter.