SMA SI 4548-US - Manual (Page 102)

12 Additional Functions SMA America, LLC
102 SI4548-6048-US-BE-en-20 Operating Manual
12 Additional Functions
12.1 Load Shedding
If the loads connected to the Sunny Island consume more energy over a longer period of time than
the generators connected produce, the batter can deeply discharge. The Sunny Island shuts down
automatically if the state of charge of the battery is too low. This way, the Sunny Island avoids a deep
discharge of the battery. Due to the automatic shutdown of the Sunny Island, the loads are not
supplied with electricity and the generators connected to the Sunny Island can not charge the battery.
In off-grid systems in which generators are connected directly to the battery via DC-to-DC converters,
these generators charge the battery, even if the Sunny Island automatically shuts down. When the
battery reaches a particular state of charge, the Sunny Island can carry out an automatic restart after
the automatic shutdown. After the automatic restart, the generators connected to the Sunny Island can
also charge the battery.
You can prevent the Sunny Island from automatically shutting down by installing a power contactor
for load shedding. The power contactor automatically switches off the loads in the off-grid system
when the battery charge level is low. The Sunny Island continues operating and can charge the
battery.
Install an external (AC or DC) power contactor between the Sunny Island and the loads (see
Section 21 "Accessory", page 225).
Rapid battery electric discharge in the event of missing load shedding
Premature failing of the off-grid system.
• Install an external load shedding contactor as soon as the off-grid system on the AC
generating side is coupled to PV arrays or wind generators.
• If there is overload due to low energy production or very high energy consumption, you must
be able to switch off loads.
• Always switch off the loads, never the energy generators (e.g. Sunny Boy).