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

Safety: Turn the generator to OFF and disconnect AC power to the battery charger before working on the battery. Wear eye protection and gloves.

• Inspect battery terminals: Remove negative then positive cables. Clean corrosion from posts and clamps with a wire brush and baking soda solution. Reinstall clamps tightly (positive first, then negative).
• Test battery: Measure open-circuit voltage (should be ~12.6 V for a fully charged 12 V battery). Load-test the battery with an automotive battery tester. Replace the battery if it fails load test or is more than 4–5 years old.
• Check battery charger: Restore AC power to the charger. Measure DC voltage at the battery with the generator off; it should be around 13.2–13.6 V. If voltage is low or zero, check the charger fuse and AC feed. Replace the Generac battery charger module if it does not output proper voltage.
• Look for drains: Ensure no aftermarket accessories are connected directly to the battery. Disconnect any non-OEM loads.