2011 Silverado voltage drop

[NARDA1]

I have a stock 2011 Silverado 5.3 with 6,300 miles on it. I just returned from a 1600 mile trip to Canada and back and noticed that at times the voltage would slowly drop to about 12V and stay there for a while (15-20 minutes) and then slowly climb back to normal. No adverse affects were noticed when this occurred several times during the trip. Any ideas as to what might be causing this?

[MikeNH]

Normal. GM trucks will vary voltage for efficiency and (supposedly) for battery maintenance. There are probably 200 threads on this topic that discuss this.

[NARDA1]

Normal. GM trucks will vary voltage for efficiency and (supposedly) for battery maintenance. There are probably 200 threads on this topic that discuss this.

Thanks