GE Industrial Solutions Pulsar Plus Controller - Manual (Page 164)

Pulsar Plus Controller Family
Issue 7 December 2011 164
Low Temperature Compensation
This feature is disabled by default, and can be enabled only if Temperature Slope Thermal Compensation is
enabled. The following are the associated parameters.
Low Comp Limit: Low temperature thermal compensation can be set from -5°C to 20°C. The factory default
setting is 0°C.
Increase: The low temperature slope (rate of increase) can be set from 1mV to 10mV in .1mV increments.
The factory default setting is 3mV.
The controller has a flexible Thermal Compensation feature which provides voltage compensation from that
level established by the Plant Float Set-Point (fsp) or Boost Set-Point (bsp), dependent on the highest
temperature monitored by the QS873A VT-Probes attached to the system batteries. Thermal Compensation
should be used in a plant containing sealed or valve regulated maintenance free batteries. Note that
Thermal Compensation is automatically enabled from the factory when Valve-Regulated Lead Acid batteries
are the system battery type. The feature is not automatically enabled upon detection of a VT-Probe. Refer to
the Installation Instructions for more details on wiring and configuring this feature.
Thermal Compensation lowers plant voltage from the fsp for monitored battery temperatures which are
above the ideal temperature established during configuration as the Battery Thermal Slope Nominal
Temperature (ntt). (The items in parenthesis are the user configurable points referred to in the graph shown
below.) Lowering the plant voltage helps to keep the batteries at their optimum state of charge while
protecting them from thermal runaway. Thermal runaway is a complex sealed battery phenomenon where,
for one or more of a number of reasons, one or more cells in a string are unable to dissipate the internal
heat generated by their charging current and experience an increase in internal temperature. By lowering
the float voltage as cell temperature increases, the float current is lowered to a point where this destructive
behavior can be avoided. If a cell failure is imminent and the cell temperature continues to rise above the
threshold configured for Battery Thermal Step Temperature (stp), plant voltage drops in a single step to a
level which keeps the remaining cells in the string from overcharging and being damaged. Refer to Figure C-
1 for a graphical view of Battery Thermal Compensation and the relationship of its various set points.
The controller can also increase plant voltage above that set by the fsp or bsp for colder environments, again
seeking to keep batteries at their optimum charge state. Batteries will lose capacity as the battery
temperature drops below their optimal operating temperature. Increasing the plant voltage with decreases
in battery temperature will cause more current to flow into the batteries. This results in electrolysis of the
water in the batteries. Since this reaction is exothermic, it also serves to keep batteries warm. This feature
results in an increase in plant voltage, and is required to be enabled during controller configuration.