LED display shows F3 and vacuum will not start, often after long storage

Safety first: Do not attempt to jump-start or open the battery pack. Deeply discharged lithium-ion batteries can be hazardous.

• Step 1 – Attempt standard charge: Place the battery on the original Bomann charger for at least 3–4 hours, even if LEDs do not light immediately. Some BMS circuits need time to wake up.
• Step 2 – Observe charger LEDs: If the charger never indicates charging or shows an error pattern, the pack may be beyond safe recovery.
• Step 3 – Try a second charger (if available): Test with another compatible Bomann charger to rule out charger failure.
• Step 4 – Replace battery pack: If F3 remains and the battery will not accept charge, replace it with a new genuine Bomann battery pack. Recycle the old pack at an authorized facility.

Do not attempt DIY revival methods on lithium-ion packs. Always use approved Bomann batteries and chargers.