Additional Functions; Load Shedding - SMA SUNNY ISLAND 6048-US Technical Description

12 Additional Functions

12 Additional Functions

12.1 Load Shedding

If the loads connected to the Sunny Island use more energy over an extended period than the energy
produced by the generators connected, 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 automatic shutdown of the Sunny Island, the loads are
not supplied with current and the generators connected to the Sunny Island cannot charge the battery.
In off-grid systems in which generators are connected directly 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 "Accessories", page 224).
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 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).
102 SI4548_6048-US-TB_en-13
SMA America, LLC
Technical description