Alternator Battery charging

eric.hurtig · Sep 23, 2025

Does anyone know if the alternator output is always ON and charging the battery in the 2018 Chevy Z71 3.6 V6 colorado?

I notice the "Battery Voltage" monitor in the driver display can vary anywhere from 12.4V up to 14.2V while driving. I am guessing if the voltage monitor display is between 13.3 to 14.4V the alternator is connected and changing the battery.

My question is If the voltage monitor is reading between 12.4V to 12.7V is the alternator disconnected because the battery is fully change and it is disconnected to prevent over charging the battey?

I am not sure if my alternator is working properly or could it be cutting on and off.

RJL1983 · Sep 23, 2025

Those numbers are normal, the alternator senses the batteries voltage and adjusts how much charging voltage to put out. You'll see it move around.

fourwd1 · Sep 23, 2025

Yes, the voltage will increase when the charging circuit senses a load increase on the alternator.

It's an attempt to increase mpg by 0.01 mpg or so by decreasing alt load on the engine as often as possible.

DieselDrax · Sep 23, 2025

This post explains it pretty well - https://www.coloradofans.com/posts/5438546/

gherbert · Sep 24, 2025

All seems very normal for a Smart Charging System which is what our trucks have

Alternator Battery charging

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