SMA
Solar Technology AG
Battery management
Technical Description
SI2012_2224-TEN082311
121
12.2 Start Options
If the battery or individual cells are removed from the battery bank in a system, the battery
management must be restarted and configured. This can be done using the "Quick Configuration
Guide QCG" (see section 9.2 "Starting the Quick Configuration Guide (QCG)" (Page 76)).
12.3 Charge State/SOC and SOH
The Sunny Island has a very precise internal charge level calculation (display value "120.01
BatSoc"). The operation for calculating the charge level 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 deducted. Unlike in case of other
procedures, a fixed charging factor does not have to be set.
After full charge has been reached, the charge state value is reset to 90 %, 95 % or 100 %,
depending on how fully the battery has been really loaded. 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 fully charged states are only rarely achieved, the operation used here can also use the battery
voltage during constant discharge phases with low discharge currents to recalibrate the charge
state. Due to these recalibrations at regular intervals, the procedure used here exhibits a high level
of stability over the long term compared to the ampere hour balancing method.
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 charge state error (display value "120.11 BatSocErr") will provide you with
continuous information on the accuracy of the battery charge state currently calculated. With
increasingly better adaptation to the actual battery state of charge, the average error is
progressively reduced.
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 useable 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 a battery temperature of 40 °C. This can result in insufficient charging of the
battery in the long run.
•
Please observe the corresponding warnings of the Sunny Island.
•
Connect the battery temperature sensor.
•
Replace the defective battery temperature sensor.
