The MultiPlus-II will prevent overload of a limited AC source, such as a generator or shore power connection. First, battery charging will automatically be reduced when otherwise an overload would occur. The second level will boost the output of a generator or shore side supply with power taken from the battery.

In the event of a grid failure, or when shore or generator power is disconnected, the inverter within the Multi is automatically activated and takes over the supply to the connected loads. This happens so fast (less than 20 milliseconds) that computers and other electronic equipment will continue to operate without disruption.