The Fronius Checkbox 500V ensures reliable operation of the Fronius Energy Package with LG Chem RESU H, even in exceptional situations. Since the battery is designed for 500 V and the inverter for 1000 V, the Fronius Checkbox 500V measures the voltage and separates the battery in the unlikely event of failure. The inverter and battery cannot be connected directly, as overvoltage can occur in the event of a fault, leading to an unsafe state.