Battery icon flashes rapidly, and the unit will not start even after the charger was recently used.

Safety: Do not attempt to open the battery pack. Lithium-ion packs can be hazardous if punctured or shorted.

• Cool down the battery: If the pack feels warm, let it rest at room temperature for 30–60 minutes, then try again.
• Check charger behavior: Place the battery on the OEM Nilfisk charger. Confirm the charger LED shows normal charging (steady or slow blink). If the charger LED flashes an error pattern, the pack is likely defective.
• Inspect contacts: Examine the metal contacts on the battery and vacuum handle for corrosion or deformation. Clean gently with a dry cloth; do not use liquids.
• Try another battery/charger: If available, test with a second Nilfisk battery. If the second battery works, replace the original pack. If no battery works, the main PCB or battery connector in the vacuum may be faulty.
• Do not bypass BMS: If the error persists, the internal BMS has locked out the pack. Replace the battery pack through Nilfisk or an authorized dealer.