SMA America, LLC
Additional Functions
Technical Description
SI5048U-TUS121440
101
12 Additional Functions
12.1 Load Shedding
If, over an extended period, the loads connected to the Sunny Island use more energy than that which
the generators connected produce, the battery 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 Sunny Island's automatic shutdown, the loads are not supplied
with current and the generators connected to the Sunny Island cannot charge the battery.
In off-grid power systems in which generators are connected directly to the battery via a DC/DC
converter, these generators charge the battery even if the Sunny Island shuts down automatically.
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 avoid the Sunny Island's automatic shutdown by installing a power contactor for load
shedding. If the battery shows a low SOC, the power contactor disconnects the loads in the off-grid
power system automatically. The Sunny Island remains in operation and can charge the battery.
Install an external (AC or DC) power contactor between the Sunny Island and the loads (see also
section 21 ”Accessories” (page 215)).
NOTICE
Rapid battery electric discharge in the event of missing load shedding. Premature failing of
the off‑grid system.
• Install an external load-shedding contactor once the off-grid power system on the AC
generating side is coupled to PV generators or wind generators.
• If there is overloading 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)!
