SMA SI 4548-US - Manual (Page 108)

13 Battery Management SMA America, LLC
108 SI4548-6048-US-BE-en-20 Operating Manual
13.2 Battery Temperature
The Sunny Island continuously monitors the battery temperature using the battery temperature sensor
provided. At 9°F (5°C) below the maximum permissible temperature (parameter
"221.04 BatTmpMax"), a warning message is displayed. If the maximum value for the battery
temperature is exceeded, the Sunny Island switches off.
A warning is given if the value for lead-acid batteries falls below 14°F (-10°C) and below -4°F
(-20°C) for NiCd batteries.
The battery temperature is taken into consideration when the charging voltage is calculated (see
Section 13.5 "Charge Control", page 110).
13.3 Start Options
If the battery is replaced in a system, 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)", page 68).
13.4 State of Charge (SOC) and State of Health (SOH)
State of Charge (SOC)
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 the battery was actually charged. If default settings are not changed,
a state of charge of 90% 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.
The battery may be destroyed due to deep discharge.
If the battery temperature sensor is defective or missing, the Sunny Island continues to run, assuming
a battery temperature of 104°F (40°C). This can result in deep discharge 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.