Controller displays F07 Low Battery Voltage; generator may fail to crank or cranks slowly.

Safety first: Turn the controller to OFF and disable auto-start. Use insulated tools when working on battery terminals to avoid short circuits.

• Measure battery voltage: With a multimeter, check voltage directly at the battery posts. A healthy 12 V battery should read about 12.6 V at rest. If below 12.0 V, the battery is discharged or failing.
• Inspect terminals and cables: Clean any corrosion from battery posts and cable lugs using a wire brush and a baking soda solution. Tighten connections firmly. Check the ground cable from battery negative to the generator frame.
• Check battery charger: With AC utility power present, measure DC voltage at the battery with the charger connected. It should be around 13.2–13.8 V. If voltage does not rise when AC is present, inspect the Siemens battery charger module and its AC supply fuse or breaker. Replace the charger if it has no output.
• Load test battery: If the charger is working but F07 persists, have the battery load-tested or use a battery tester. Replace the starting battery if it fails the test or is older than the recommended service life.
• Clear alarm and test start: After correcting battery and charger issues, clear F07 and perform a manual start. Confirm that cranking speed is strong and the alarm does not return.