Controller shows F08 High Battery Voltage; DC voltage reading is above normal and alarms persist.

Safety first: High charging voltage can cause battery gassing and explosion risk. Keep sparks and flames away from the battery. Wear eye protection and gloves.

• Verify DC voltage: Measure battery voltage with a multimeter. If it exceeds about 14.5 V on a 12 V system during float charge, the charger may be faulty or misconfigured.
• Inspect charger settings: Some Siemens chargers have selectable battery type or voltage settings. Confirm the charger is set for the correct system voltage and battery type as per the generator manual.
• Check charger output directly: If possible, measure charger output at its terminals with the battery temporarily disconnected (observe polarity and avoid shorting). If voltage remains excessively high, replace the charger module.
• Inspect battery condition: A severely sulfated or shorted battery can cause abnormal charging behavior. Check for bulging case, excessive heat, or acid smell. Replace the battery if any of these signs are present.
• Controller sense wiring: If charger and battery are normal but F08 persists, inspect the DC sense wires from the battery to the Siemens controller for loose or corroded connections. A faulty sense circuit on the controller PCB may require controller replacement.