Frustrating, Dealer, Low-Charge

Unless I miss my guess, today's charging systems are more accurate and efficient than those of yor. My 79 Toyota would put out 14.7 at idle, even if the battery was new and fully charged. Today's charging circuits have smarter feedback.

 

From Crutchfield:

Automotive voltage is neither 12 volts nor 14.4 volts

http://www.crutchfield.com/S-jlwiLxcZnzz/learn/learningcenter/car/cable_gauge_chart.html

And the 13.8? Yes, vehicles have a 12-volt electrical system, but we're assuming that the vehicle is running, which means its alternator is generating additional current, which typically bumps up the voltage to about 13.8 volts. This is a better real-world representation of the vehicle's electrical supply. Dividing by 12 results in a larger number, which could point to a larger wire gauge, but it's often in the same color range in the chart.

 

I meant off/acc, Idle, rev, driving etc.