It might be OK.
GM has a complicated charging scheme.
https://www.motor.com/magazine-summary/are-you-smarter-than-a-smart-charging-system/
https://www.motor.com/magazine-summary/trouble-shooter-july2015/
https://www.motor.com/magazine-summary/trouble-shooter-september2015/
Quote
There are two types of RVC systems in use-integrated RVC and stand-alone RVC (SARVC). Integrated systems use a battery current sensor to inform a body control module (BCM) how much the battery is being charged or discharged.
SARVC systems (found mostly on trucks) do not use the BCM for operation. They have a generator battery control module mounted to the negative battery cable, to interpret battery current and voltage and battery temperature inputs. The battery current sensor is internal to the module. This module also directly controls the generator 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 support vehicle loads. To accomplish this, it has several different modes of operation. Six common modes of operation are Charge Mode, Fuel Economy Mode, Voltage Reduction Mode, Start Up Mode, Windshield De-Ice Mode and Battery Sulfation Mode.
The PCM/ECM (generator battery control module on full-size trucks) controls the generator through the generator L terminal control circuit. It monitors the generator performance though the generator field duty cycle signal circuit. The signal is a 5V PWM (pulse width modulated) signal of 128Hz with a duty cycle of 0% to 100%. Normal duty cycle is between 5% and 95%. The ranges between 0% to 5% and 95% to 100% are for diagnostic purposes.
The control module enters Charge Mode whenever one of the following conditions is met:
Under WOT conditions and when the fuel rate (sent by the ECM/PCM) is greater than 21 g/S and the throttle position is greater than 90%.
The headlamps 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 SOC 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 15.5V (depending upon the mode of operation the system is presently in) at a rate of 8mV to 50mV per second.
The control module enters Fuel Economy Mode when the following conditions are met:
The calculated ambient air temperature is above 32°F.
The calculated battery current is less than 15A and greater than -8A.
The battery SOC is greater than 80%.
The generator field duty cycle is less than 99%.
This mode's targeted generator output voltage is 13.0V. The control module will exit this mode once the criteria are met for Charge Mode.
The control module will enter Voltage Reduction Mode when the following conditions are met:
The calculated ambient air temperature is above 32°F.
The calculated battery current is less than 2A and greater than -7A.
The generator field duty cycle is less than 99%.
This mode's targeted generator output voltage is 12.9V. The control module will exit this mode once the criteria are met for Charge Mode.
After the engine has started, the control module sets a targeted generator output voltage of 14.5V for 30 seconds (Start Up Mode).
The control module enters Battery Sulfation Mode when the battery voltage is less than 13.2V for 45 minutes. Once in this mode, the generator battery control module will set a targeted output voltage between 13.9 and 15.5V for five minutes. The control module will then determine which mode to enter depending on voltage requirements.
In RVC Mode, the control module bases the charging voltage on battery SOC, which is estimated during a key-off event every eight hours, after three voltage measurements every 24 hours thereafter, and then monitored constantly while the ignition is on. These voltage 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% SOC.