Robot mower displays E9 and stops; this may occur randomly during operation.

Safety first: Turn OFF the mower before handling the battery. Lithium-ion batteries must be handled carefully; do not puncture or short the pack.

Steps:

• 1. Check charge level: Place the mower in the charging station and allow it to charge fully until the display or LED indicates 100% or solid green.
• 2. Inspect battery connections: Open the battery compartment. Ensure the battery plug is fully inserted and there are no signs of heat damage or corrosion on the terminals.
• 3. Look for swelling or damage: If the Yard Force battery pack appears swollen, cracked, or smells burnt, discontinue use immediately and replace it.
• 4. Temperature conditions: Ensure the mower is not charging or operating in extreme heat or cold. Move it to a shaded, moderate-temperature area.
• 5. Runtime test: After a full charge, start a mowing cycle and time how long it runs before E9 appears. A significantly reduced runtime indicates battery capacity loss.
• 6. Replace battery pack: If the battery is old (3–5 years) or fails the runtime test, install a new Yard Force-specified lithium-ion battery pack.

If a new battery does not resolve E9, the charging electronics or main PCB may be faulty and require professional diagnosis.