Battery Management SMA Solar Technology AG
98 SI5048-TB-TEN110340 Technical Description
13.2 Start Options
If the battery is replaced in a plant, the battery management system must be restarted and
reconfigured. This can be done using the "Quick Configuration Guide QCG" (see section
8.2”Starting the Quick Configuration Guide (QCG)” (page57)).
13.3 State of Charge / SOC and SOH
The Sunny Island has a very precise internal state of charge calculation (display value
"120.01 BatSoc"). The procedure for calculating the state of charge is based on balancing the
ampere hours. This means that all currents flowing in and out of the battery are accumulated and
referred to the nominal capacity. In order to take into consideration faults caused by self-discharge
and charging losses caused by gassing, these losses are already internally extracted. Unlike other
operations, no fixed charging factor must be set.
When the full charge states are reached, the battery state of charge is reset to values of 90 %,
95 % or 100 %, depending on how full battery was actually charged. If default settings are not
changed, a state of charge of 80 % after boost charge, 95 % after full charge and 100 % after
equalization charge is reached.
Since full charge states are generally only rarely achieved during a grid failure, the operation used
here can also utilize the battery voltage during constant discharge phases with low discharge currents
to recalibrate the state of charge. Compared to the ampere-hour balancing method, the operation
used here exhibits a high level of stability over the long term when recalibrated at regular intervals.
Both the ampere-hour balancing method and the recalibration procedure, which is performed via the
voltage, automatically adjust to the connected battery over time (depends on the number of grid
failures).
The estimated state of charge error (display value "120.11 BatSocErr") will provide you with
continuous information on the accuracy of the battery state of charge currently calculated. The
average error will continuously diminish as the adjustment to the actual battery state of charge
increasingly improves.
Only when the battery is new does its usable capacity correspond to the capacity specified by the
battery manufacturer. As the battery ages and as a result of frequent insufficient charging, the battery's
usable capacity may decrease considerably on a permanent or only temporary basis.
NOTICE!
Possible damage to the battery as a result of faulty temperature measurement
If the battery temperature sensor is defective or missing, the Sunny Island continues to run,
assuming the battery has a temperature of 40 °C. This can result in insufficient charging of
the battery in the long run.
• Observe the corresponding warnings of the Sunny Island.
• Connect the battery temperature sensor.
• Replace the defective battery temperature sensor.
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