4 Operating From a Personal Computer
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Operation Guide Flatpack MCU,
351300.013, v8-2006-07
4.10.7 Symmetry Measurement Configuration
Symmetry measurement provides a method of automatically detecting unbalanced battery blocks. There are two
methods in which this measurement can be made; Block and Mid-point monitoring. Five (5) inputs are available for
battery measurements. In either method, the individual measurements are made and the Flatpack MCU software
performs calculations based on the measured total battery voltage to determine if an unbalanced condition exists, based
on a user-defined Symmetry Tolerance value. Any individual measurement that differs from the calculated value by an
amount in excess of the tolerance will generate a Symmetry Alarm condition.
Block Measurement. Each 12 Volt block is monitored in a single battery string. This provides the most detailed
measurements, however only a single string can be monitored by the Flatpack MCU circuitry.
Mid-point Measurement. Each battery string is measured at its mid-point (or after the 2
nd
battery block for 60V
systems). This method allows additional battery strings (up to four) to be monitored, compared to Block Measurements.
Symmetry measurements may be taken continuously, or only during an actual discharge event. Because it is normal for
a battery to vary somewhat from nominal voltage values when unloaded (during recharge), it is recommended that
symmetry monitoring be performed under discharge conditions for the most accurate results. Furthermore, it is normal
for some unbalance to exist between battery elements during the beginning of a discharge cycle, and for this reason a
configurable discharge delay time is provided. This also prevents symmetry alarms during brief AC power outages,
when recharge and discharge conditions may exist within a short timeframe.
The following parameters are selectable:
Measurement Type – Block or Mid-point
Mode – Continuous or Discharge
Battery Strings – the number of monitored battery strings. In Block Measurement, this field is fixed at “1”.
Symmetry Tolerance – The symmetry alarm threshold, in volts
Discharge Delay – The delay time between when a discharge event begins and alarms are reported
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