Hey guys, I own a 2020 Blazer LT and have noticed the battery voltage fluctuates a ton. On most occasions, I remain at 12.5-12.6, but in recent times it has been going down to 12.3 and then up to 13.8-14. Why is this? Bad battery? Alternator going out? Or what? Please provide any advice, it would be greatly appreciated.
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Straight from the service manual:
The BCM (Body Control Module) goes into Charge Mode when any of the following happens:
- Windshield wipers are on for more than 3 seconds.
- The climate control requests voltage boost mode (like when the A/C is on, or the rear defogger, high-speed cooling fan, or high-speed blower are running).
- The estimated battery temperature is below 0°C (32°F).
- Battery charge drops below 80%.
- The vehicle speed exceeds 145 km/h (90 mph).
- There’s a current sensor malfunction.
- System voltage falls below 12.56 V.
When any of these conditions are met, the system adjusts the generator’s output voltage to between 13.9 and 15.5 V, depending on the battery’s charge and temperature.
If it’s hot out (A/C is on) or you’re driving fast, the battery will be charging. Also, consider the battery’s age. If it’s a 2020 model and no replacement has been made, it might be nearing the end of its life after almost 5 years.
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I am not sure if the battery has been replaced since I just got this vehicle from a dealership about three weeks ago, and it is not listed on the Carfax report. I have never owned a car with a built-in voltage meter, so seeing it fluctuate like this has me a bit concerned. It might be worth getting it checked out by a shop to make sure everything’s in good shape. We’re in Tennessee, so the A/C is almost always running right now. I have just never seen it drop to 12.3V when idling; it usually stays around 12.6V, which I have read is a full charge. Thanks for the advice.
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If you bought it from a dealership, you can ask to see the hard copy of the safety inspection repair order. That should show what was done to the car at the time. But honestly, in regular driving, the voltage being in that range is pretty normal.