Charge Mode
WARNING: This page is about a different car, the 2006 Chevrolet Monte Carlo and 2006 Chevrolet Impala. However, it is still accessible from the selected car via links, so may be relevant.
The BCM will enter Charge Mode when the headlamps are ON, low or high beams. The voltage is controlled to 13.4 volts if the system is below 13.3 volts or to 14.5 volts if the system voltage is above 14.6 volts.