Blue Sky SC30 User Manual
Page 6
Blue Sky Energy – Sun Charger 30
5
2-STAGE CHARGE CONTROL
Certain battery types or system configurations may require 2-stage Bulk/Absorption charge control. The SC30 can be configured for 2-stage charge control
by setting the Float Charge Voltage to OFF.
OPTIONAL TEMPERATURE COMPENSATION
The charge voltage required by batteries changes with battery temperature. Temperature compensation of charge voltage enhances battery
performance and life while decreasing battery maintenance. Temperature compensation of charge voltage can be provided using the optional battery
temperature sensor (BSE p/n 930-0022-20). The default compensation factor of –30mV/
°C is typically appropriate for most lead-acid chemistry batteries
including GEL and AGM. If a proper temperature sensor signal is not detected the SC30 will operate as if battery temperature is 25
°C.
FACTORY DEFAULT CHARGE VOLTAGE SETPOINTS -VS.- BATTERY TEMPERATURE
FIGURE 2
EQUALIZATION
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WARNING: Not all batteries can be safely equalized. Equalization should be performed only on vented liquid electrolyte
lead-acid batteries. Always follow battery manufacturers recommendations pertaining to equalization. Equalization applies a
relatively high charge voltage producing significant battery gassing. Prior to performing equalization disconnect equipment that
cannot tolerate the high equalization voltage which is temperature compensated as shown above.
Equalization is essentially a controlled overcharge which applies a relatively high charge voltage to bring all battery cells up to the same specific gravity and
state of charge. The SC30 may be configured to perform either an automatic equalization on periodic basis, or a manually initiated equalization. Since sealed
batteries should not be equalized the factory default settings have Equalize Enable set to OFF to completely disable automatic or manual equalization. Equalization
may be enabled by setting Equalize Enable to ON as described in the Charge Parameter Settings section. When an equalization cycle is being performed the Float
and Absorption charge status LED’s will alternately blink.
With equalize enabled the SC30 will perform an automatic equalization at the factory default settings of 15.2V for 2 hours every 30 days which is typically
suitable for most flooded lead-acid batteries. When set for automatic equalization the cycle will begin when the set number of days since the last equalization has
elapsed, and the charge control system has switched to Float. When set for manual equalization (Equalize days set to 00) an automatic equalization will not occur.
Whether set for automatic or manual the process may be started or stopped manually by pressing the Display Select push-button for 20 seconds.
Once equalization has started the equalize timer will not count down unless battery voltage is at the equalize voltage setpoint which is temperature
compensated. Therefore obtaining a proper 2 hour equalization will require longer than 2 hours to complete depending on available charge current. Note that at
least 3.5 amps of net charge current per 100 amp-hours of battery capacity is typically required to properly equalize a battery. If equalization does not complete
during the charging day it will resume where it left off the next charging day, but will automatically cancel if unable to complete within 24 hours. The equalize day
counter is reset whenever an equalization cycle is started.
30 AMP CURRENT LIMIT
Should transient conditions be present where the PV modules are able to produce more than 30 amps of output current, the SC30 will automatically
limit average output current to 30 amps. It is possible for output current to briefly exceed 30 amps as the current limit control system responds to sudden
increases in PV current. Note that when current drops and the SC30 exits current limit it will first enter Absorption (for 20 seconds) on its way back to Bulk
even though battery voltage may be below the Absorption Charge Voltage setpoint.
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WARNING: Current limit should be thought of as transient PV over current protection and not a normal mode of operation. If
the SC30 enters current limit and/or delivers 30 amps of output on a regular basis it is possible that excessive PV power is
connected. Confirm that the PV modules do not exceed ratings shown in the Selecting PV Modules section. If necessary
remove some PV power to keep normal operation below 30 amps.