Battery Voltage

[RockMan]

Hey all!
What are you guys showing for battery voltage while driving?
I’ve got a 2019 GS. When I start it the voltage goes up to 14.5-7 volts. Then while I’m driving (no headlights or HVAC on) it will drop down to 12.5-6. Do our cars have a variable charge system of some sort or am I starting to see the early signs of a battery/alternator problem?

 

[cdnrx1]

Hey all!
What are you guys showing for battery voltage while driving?
I’ve got a 2019 GS. When I start it the voltage goes up to 14.5-7 volts. Then while I’m driving (no headlights or HVAC on) it will drop down to 12.5-6. Do our cars have a variable charge system of some sort or am I starting to see the early signs of a battery/alternator problem?

What you're experiencing is completely normal behavior from a modern ECM / BCM "Smart" computer controlled charging system. Output voltage is controlled in stages or modes (there are six of them on the C7) and is dependent upon the load / demand placed on the system at any given time. Things like ambient temperature and battery age / condition will also factor in. When demand is high and / or the state of charge of the battery is low the output will increase as needed resulting in a higher voltage reading. Conversely, as load demand decreases, the C7's computer controlled charging system will lower the output voltage accordingly and can even enter a "Fuel Economy Mode" which lowers the parasitic drag on the alternator and, supposedly, helps to improve fuel economy. I guess the GM engineers figured that any little bit helps.

As the charging system works to maintain the state of charge of the battery and manage vehicle's electrical loads, it is normal for the voltmeter in the instrument cluster or the system voltage display in the driver information center to fluctuate. This does not indicate a malfunction. Depending on the state of charge of the battery and the vehicle's electrical requirements, these values may be anywhere from about 12.2 V to 15.5 V. As long as you're not seeing voltage readings below 12.0 V for a sustained period you've got nothing to worry about.

Hope this helps.

Best regards
Ross

 

[RockMan]

What you're experiencing is completely normal behavior from a modern ECM / BCM "Smart" computer controlled charging system. Output voltage is controlled in stages or modes (there are six of them on the C7) and is dependent upon the load / demand placed on the system at any given time. Things like ambient temperature and battery age / condition will also factor in. When demand is high and / or the state of charge of the battery is low the output will increase as needed resulting in a higher voltage reading. Conversely, as load demand decreases, the C7's computer controlled charging system will lower the output voltage accordingly and can even enter a "Fuel Economy Mode" which lowers the parasitic drag on the alternator and, supposedly, helps to improve fuel economy. I guess the GM engineers figured that any little bit helps.

As the charging system works to maintain the state of charge of the battery and manage vehicle's electrical loads, it is normal for the voltmeter in the instrument cluster or the system voltage display in the driver information center to fluctuate. This does not indicate a malfunction. Depending on the state of charge of the battery and the vehicle's electrical requirements, these values may be anywhere from about 12.2 V to 15.5 V. As long as you're not seeing voltage readings below 12.0 V for a sustained period you've got nothing to worry about.

Hope this helps.

Best regards
Ross

You have no idea how much that helped.
Thank you so much for the detailed explanation of how it all works. My BMW had a similar charging system.