Robot mower displays E11 and refuses to start; often after battery replacement or long storage.

Safety first: Disconnect the charger and remove the battery according to the Parkside manual.

• Verify battery type: Ensure you are using the correct Parkside robot mower battery pack model and voltage. Generic packs without the proper communication lines can trigger E11.
• Inspect connectors: Check the battery plug and the mating connector in the mower for bent pins, corrosion, or melted plastic. Clean lightly and straighten pins if needed.
• Reseat battery: Reinstall the battery firmly, ensuring it clicks or locks into place and the connector is fully engaged.
• Measure voltage: Use a multimeter to confirm the battery voltage is within the expected range (typically 18–25 V for a 20 V class pack). Extremely low voltage may indicate a tripped BMS.
• Try original pack: If you have the original Parkside pack and E11 disappears with it, the replacement battery's BMS is incompatible or faulty.

When to replace: Replace the battery pack if the BMS is defective or if the pack will not communicate with the mower despite correct voltage.