         
RVC Systems Regulated Voltage Control Part 2 Six Modes of Operation Charge Mode: The control module enters the charge mode whenever one of the following conditions are met. The headlights are on low or high beam. The wipers are on for more than 8 seconds. The electric cooling fans are on high speed. The rear defogger is on. The battery state-of-charge is less than 80%. When one of these conditions is met, the control module ramps up the voltage slowly to a level between 13.4 to 15.5 volts (depending on the mode of operation the system is presently in) at a rate of 8mV to 50 mV per second. Fuel Economy Mode: The control module enters the fuel economy mode when the following conditions are met. The calculated ambient air temperature is above 0 degrees C (32 F). The calculated battery current is less than 15 amps and greater than -8 amps. The battery state-of-charge is greater than 80 percent. The alternator field duty cycle is less than 99 percent. Its targeted alternator output voltage is 13.0 volts. The control module will exit this mode once the criteria are met for the charge mode. Voltage Reduction Mode: The control module will enter voltage reduction mode when the following conditions are met. The calculated ambient air temperature is above 0 degrees C (32 F). The calculated battery current is less than 2 amps and greater than –7 amps. The alternator field duty cycle is less than 99 percent. Its targeted alternator output voltage is 12.9 volts. The control module will exit this mode once the criteria are met for the charge mode. Start Up Mode: After the engine has started, the control module sets a targeted alternator output voltage of 14.5 volts for 30 seconds. Battery Sulfation Mode: The control module enters this mode when the battery voltage is less than 13.2 volts for 45 minutes. Once in this mode, the alternator battery control module will set a targeted output voltage between 13.9 and 15.5 volts for 5 minutes. The control module will then determine which mode to enter depending on voltage requirements. RVC Mode: The control module bases the charging voltage on battery state-of-charge (SOC). Battery SOC is estimated during a key off event every 8 hours, after three voltage measurements every 24 hours thereafter, and then monitored constantly while the ignition is on. These measurements are then compared to estimated battery temperature, as battery temperature vs. battery voltage directly corresponds to battery SOC. While the engine is running, the system uses both the battery voltage and estimated battery temperature to determine the battery current in and out of the battery. The control module then regulates the charging voltage to keep the battery above an 80 percent SOC. SYSTEM COMPONENTS Battery Current Sensor: (for Integrated RVC) The battery current sensor is a serviceable component that is connected to the negative battery cable at the battery. The battery current sensor is a three wire Hall-effect current sensor that monitors the battery current. It directly inputs to the BCM. It creates a 5-volt PWM signal of 128 Hz with a duty cycle of 0-100 percent. Normal duty cycle is between 5-95 percent. Body Control Module (BCM), Instrument Panel Module (IPM), and Dash Integrated Module (DIM): The BCM determines the output of the alternator and sends the information to the ECM / PCM for control of the alternator L-terminal control circuit. It monitors the alternator field duty cycle signal circuit information sent from the ECM / PCM that determines the alternator electrical load. It monitors the battery current sensor, the battery positive voltage circuit, and estimated battery temperature to determine battery state-of-charge. The BCM performs, or sends, commands to the ECM or other controllers to perform idle boost and load management operations. Electronic Control Module (ECM), Power Control Module (PCM): The ECM / PCM directly controls the alternator field control circuit input to the alternator. The ECM / PCM receives control decisions based on messages from the BCM / IPM. It monitors the alternator field duty cycle signal circuit and sends information to the BCM / IPM. On some vehicles, the ECM / PCM overrides the control decisions of the BCM when the following conditions are met. The engine cooling fans are on high speed. There is a high fuel demand. The calculated ambient air temperature is less than 0 degrees C (32 degrees F) Instrument Panel Cluster (IPC): The IPC provides a means of driver notification in case of a charging system failure. Battery Control Module for Stand-Alone RVC (SARVC): It communicates with the ECM, PCM, IPC, and BCM for RVC operation. It is a serviceable component that is connected to the negative battery cable at the battery. It directly controls the alternator field control circuit input to the alternator. It monitors the alternator field duty cycle signal circuit, its internal battery current sensor, the battery positive voltage circuit, and estimated battery temperature to determine battery state-of-charge. 
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