Segway-Ninebot · BMS (battery protection)
21 Segway-Ninebot error code 21
Battery (BMS) communication fault
Widely published – may differ by model/firmware
Note
Table published for Xiaomi/Segway-Ninebot scooters; may differ by model/firmware.
Possible causes
General, component-based causes – not a manufacturer-specific statement.
- Cell voltage outside protection limits
- Over-current or short-circuit protection
- Temperature outside the permitted range
- BMS or communication fault
Safe test steps
- Pack temperature (let it rest at room temperature, repeat).
- Manufacturer wake/reset (e.g. connect the original charger) per instructions.
- Cell-group voltages – trained technicians with insulated tools only.
Workshop reference values
- Balanced pack at rest: group spread typically ≤ 30 mV (workshop rule of thumb).
Repair approach
- Remove the cause (temperature, charge), then manufacturer reset.
- BMS replacement/repair only at a battery specialist.
Tools needed
- Digital multimeter (CAT III, fused inputs)
- Manufacturer dealer diagnostic tool/software (if available)
Safety
- Never bypass the BMS or revive deeply discharged cells with a normal charger.
This information does not replace manufacturer service documentation. Work on batteries and high-voltage parts only with the appropriate expertise.
Related fault codes
22BMS password/authentication error23BMS serial number error (default value)10Communication error between dashboard and control board11Abnormal current in motor phase A12Abnormal current in motor phase B13Abnormal current in motor phase C14Throttle fault / not in zero position15Brake lever fault / not in zero position