Tyco Electronics Galaxy SC Controller J85501F-1
Issue 13 February 2001 Feature Descriptions 7 - 64
is created. The alarm is retired after the batteries recharge. This alarm
can also occur if the plant load increases so that the battery reserve time
is less than two hours with a fully charged battery. A prediction is never
made if the plant load in amperes is not in the range from C/2 to C/32,
where C is the ampere-hour rating of the batteries.
For typical discharges, the uncertainty is ± 5% of the reserve time
remaining. The accuracy of the reserve time prediction improves as the
discharge progresses. The algorithm will provide accurate reserve time
predictions for the operational temperature range of the battery. In
addition, if battery sections are configured, a reserve time prediction
will also be calculated for each battery section.
Installation The reserve time prediction algorithm requires the universal battery
temperature probe to provide battery temperature information for the
algorithm. The thermistor on the temperature probe should be installed
on any terminal of any battery string in the plant. Since the thermistor
supplied is highly insulated (case-to-lead electrical resistance), the
thermistor can be mounted to any cell terminal in the battery string.
However, extreme caution should be exercised when installing the
thermistor to any “above-ground” battery terminal post, in order to
avoid shorting all (or part of) the battery string. Also, in multiple battery
string plants, it is recommended that the installer choose a cell in the
string that is anticipated to experience the lowest ambient temperature.
(Before deciding on thermistor placement, temperature measurements
can be taken at each string using a thermometer, or similar portable
temperature-measuring device, in order to determine which cell has the
lowest ambient temperature. This can be done as long as the battery
subsystem area of the plant is not currently experiencing any unusual
temperature variations.) This selection will lead to a more conservative
prediction of the remaining reserve time.
Reserve time for individual battery sections can also be predicted. This
might be used in a distributed power architecture. To accomplish this
prediction technique, the voltage, current, and temperature of each
battery section can be monitored using remote peripheral monitors.
Parameters The algorithm uses plant voltage, plant current, the rectifier float set
point, the sum of the rectifier currents, the battery temperature, the
battery type, the number of battery strings, the minimum allowable volts
per cell, and the number of cells per string to determine the remaining
reserve time.
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