Originally Posted by
big john
A voltmeter can tell you if the voltage drops but it can't tell you why. An ammeter can tell you how much parasitic draw is on the battery. We like to see less than 50 milliamps. If it's under that number it shouldn't go down in a week. An inductive ammeter is expensive but cheap ones are available that connect in series. When checking for a draw you have to wait for all modules to go "to sleep". This might take 15 minutes. If the draw is intermittent, good luck.
I still think your problem is just crappy batteries.
The Duralast battery that lasted 22 months was guaranteed for 5 years. The point of the volt meter is simply to give warning about when it's time for a new battery. To prevent it going dead in an underground parking lot late in the day. It's something we will now plan for, rather than being blind-sided again.
This is our first new car since the 91 Corolla. A lot has changed.