The Studer Xtender can be used as a smart boost for a current limited AC source. In the above example the generator or grid is only capable of supplying 9 Amps AC at 230V. If the electrical consumers in the house (or boat) draw more than the max 9 Amps a brown out or problem with the generator will result. The additional short term 3 Amp demand (12 Required minus the 9 available) will be automatically provided by the battery bank. 

The Xtender constantly monitors the incoming current flowing from the grid or generator and as soon as it starts to equal and pass the 9 Amp limit it starts taking power from the batteries. When the peak demand has passed the Studer Xtender uses the AC input to recharge the batteries.