SMA SI 4548-US - Manual (Page 109)

SMA America, LLC 13 Battery Management
Operating Manual SI4548-6048-US-BE-en-20 109
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.
State of Health (SOH)
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.
The battery's state of health (display value "320.01 Soh") is a measurement of the present useable
capacity expressed as a percentage relative to the nominal capacity. 100% means that the entire
nominal capacity can be used. 50% means that only half of the original nominal battery capacity can
be used. The state of health of the battery is determined using a self-adapting procedure which takes
several charging cycles to collect accurate and reliable data.
The current capacity for the Sunny Island is automatically adjusted downwards for temperatures
below < 68°F (20°C) because of the significant drop in the usable capacity of the battery when
temperatures fall below the rated temperature.
For all lead-acid batteries, the nominal capacity is adjusted by a fixed factor of −0.6%/°F (−1%/°C).
For NiCd batteries, a factor of − 0.4%/°F ( − 0.75%/°C) is used.
Recalibration of the State of Charge
The Sunny Island recalibrates the display value for the state of charge of the battery to 20% as soon
as the battery voltage per cell has reached a limiting value that is dependent on the battery type and
the battery capacity. In addition, recalibration of the state of charge always takes place if one of the
following conditions is met:
• The nominal capacity is entered incorrectly.
• The battery cable resistance is too high.
• The battery is not connected correctly.
• Differing concentrations of acid in FLA batteries (if necessary, reset the parameters in the menu
"222# Battery Charge Mode).
• The battery has aged so much that the SOH is below 80%.