         
RVC Systems (Regulated Voltage Control) GM is using three different generations of RVC systems on a number of new models including Cadillac CTS, SRX, STS; Chevy/GMC full size trucks and SUVs; Chevrolet Cobalt and Uplander; Buick Lacrosse and Terazza; Pontiac Grand Prix and Montana SV6. Regulated Voltage Control is a new dynamic control of the vehicle’s system voltage. It regulates the alternator output, based mainly on estimated battery temperature and battery state-of-charge. Since the RVC system allows changes to vehicle voltage, up or down, under various scenarios –the battery state of charge and the vehicle’s present electrical needs are two conditions taken into account – the voltmeter may fluctuate. Conventional systems usually maintain a consistent reading of 14 volts. The fluctuation of the RVC system may range between 12 and 24 volts. This is normal system operation. There are two types of RVC systems used today – integrated RVC and stand-alone RVC (SARVC). Integrated systems use a battery current sensor to provide a body control module (BCM) the amount the battery is charging or discharging. Accurate voltage measurements are taken through the battery positive voltage and ignition 1-voltage circuits. The BCM then communicates information over serial data circuits for the ECM/PCM to directly control the alternator. SARVC systems do not use the BCM for operation. They have an alternator battery control module mounted to the negative battery cable, to interpret battery current, voltage, and battery temperature inputs. The battery current sensor is internal to the module. This module also directly controls the alternators L – terminal duty cycle instead of the ECM/PCM. The purpose of the RVC system is to maintain the battery state-of-charge at 80% or above and to support vehicle loads. Both types of systems have two types of corrective actions to ensure that the battery stays at an 80% state of charge. These include up to three levels of load shed and up to three levels of idle boost operation. The basic operation of the RVC system will be covered in next months technical bulletin. The six modes of operation including the charge mode; fuel economy mode; voltage reduction mode; start up mode; windshield de-ice mode; and battery sulfation mode will be discussed in further detail. 
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