MP4.2+6.0

Well gee, maybe if you had been in this specific forum for a while, you would know that's what a variety of posters prefer and regular practice here--look below. Some (actual owners) have even asked for it. Or similarly that older forum construct of threaded responses a few of us still used helped minimize this, but AW didn't continue with it. I bent my pick on that as well as some here know, and as posted contemporaneously in Feedback Forum. In other specific recent cases like the tranny fluid change thread, confusion over what was being responded to led to some unnecessary hurt.The style here is also somewhat different than Q5 arena FWIW since you are there a lot. Plus honestly, there enough questionable information in your post, that well it helped to see what was being addressed. So that's why substantively since you chose to lead with that critique.

Walmart: How about next time take a look at the materials referenced? You said:Rather than "last I heard," I provided a very detailed underlying source table. Had you looked at it, you would have found much better info. Since table was last updated Nov 14, 2015 I'll take it as pretty current as well. It was referenced in my more definitive post linked in reply 13, but here is the table again: Lead-Acid Battery Manufacturers and Brand Names List 2015

Here is the excerpt, which also ties into some of post response experience earlier in overlapping threads: Overlapping thread here: https://www.audiworld.com/forums/a8-...ttery-2892290/ There if you sort it to EverStart MAXX in particular, you get the answer. More so if you tie it to the poster's description of the outer case details, often a definite good set of cues for identifying who made it. MAXX-H8 - Walmart.com For others and per that Walmart thread, H8 is what they show just by on line catalog; H9 "big boy" size is either in many of our cars like mine, or chosen by owners anyway. You are parachuting late into a thread here, so knowing others posted in close proximity or even earlier parts of this one would have been better informed...

Biggest picture and back to an earlier point for owners to keep in mind...analysis paralysis. It's a $130ish to $200 part that goes for some years, typically highly reliably almost no matter where it's from. These are not rocket science. And when they go, they can leave you or a loved one stranded in the dead of night in who knows what unfortunate circumstances. Leading to other simple advice, when it gets at all dubious with no other reasonable explanation (lights on carelessness, too much VCDS work, (low failure rate) alternator, etc.) change it out.

Shark_V8

One Fluke is measuring two batteries. Both batteries are 12.55-12.6 volts. They read same voltage in or out of the car. Readings are taken with minutes (during the battery swap-out and coding) Gothca?

VCDS readings from HEXNET, before battery is removed and after new battery installed:
Old battery in A8 (12.55) - VCDS reads 12.4 and falling rapidly, caution box etc.
New battery in A8 (12.6) - VCDS reads 12.75 and steady.

I'm OK with it. The ENERGIE GENIE is one smart chick, voltage at the terminals ain't worth squat really for assessing battery performance/condition. There needs to be a load applied. However, my spare NAPA battery (for the boat, boosts etc.) fully charged punts out a solid 13 V.

For me it was not analysis paralysis. I'm in a remote location, stuck in fact (can't drive due to eye operation), and wanted to understand, how old the battery I had was, & what was going on with the behaviour of the car and it's power management system. What Audi has is a smart charger built in with rudimentary battery monitoring technology designed to increase battery life, manage all the electrical loads (load shedding), and prioritize vehicle starting, so the alternator can take over. In the mean time VCDS showed up at the my door and I've learned what I need to know.

Onto networks now

Redd

MP-
I have no idea who Bill Darden is, for all I know he's the world's leading battery expert. But I guy a do know, who wires up pricey yachts and "fixes it once and fixes it right" has the connections to know who actually supply the sellers that don't make their own batteries, and he's found the suppliers can, do, and HAVE changed from year to year. They bid on contracts. The bid can be for a "D3 we can sell under $200" or a "D3 that's identical to yours" and the two products will look the same--but often WEIGH differently, and that's usually a sign of plate changes. Some prefer more empty space in the bottom for crud to collect as it precipitates out. Others prefer more lead for more power. Both choices can be valid. Do you think WalMart's great guarantee is from the goodness of their heart? Or from something they are doing differently, perhaps?
I don't know. But when someplace like Consumer Reports occasionally actually tests these things, they almost all come out differently, regardless of maker versus label.

And when someone (no offense, Shark) posts that his battery shows 13VDC? That's a red flag that either the equipment is not calibrated, or he's reading float charge. Because normal lead-acid chemistry, AGM or wet, just can't hold a 13V charge.

Testing under load is best, sure. But in less than five minutes you can burn off a float charge, although it may take 24 hours for the electrolyte in a wet battery to equalize out (mix evenly all the way through) and a battery really should stand for arguably 4-24 hours to settle down to a "real" even charge. You can argue that carbon pile load testers and internal resistance load testers give different results, one or the other aren't valid.

If there's one thing you can say about batteries, it is that the lead engineers (and I've spoken off the record to two such people) disagree about all the subtle mysteries. Three-stage charging has gone the way of the buggy whip, and no one is in full agreement about all the finer points these days.

Bear in mind that lead is also expensive to ship. What you get in Wal-Mart in Maine, may not come from the same supplier that stocks Seattle. Or Louisiana. And most battery makers will actually put in a different electrolyte for northern climates, versus hot ones. Even new England versus Florida, they'll ship different products, without telling anyone about it. Audi? I don't know, maybe they do ship one battery worldwide. But locally sourced replacements, will vary. With both time and place.
Sorry, but I've seen it, and the folks who make it have told me directly. What you found online is probably true--for a given place and time. What I find in the store, this week or next month? On this coast or the other one?
Hey, in New Haven they don't put red sauce on a pizza unless you ask for it, and a Chicago deep dish pie isn't to be found in NY's Little Italy. You tell me, which pizza is "right".(G)

Shark_V8

OK -- The 13V reading was just coming off the Bosch smart charger. My "boat" batteries, which are the smallest I could buy (due to lightweight) are sitting at 12.8V and 12.7 after, well a week off the charger.

I could just bring my meter to the refinery and compare against the instrument shop units. Those guys will have calibrated theirs. Engineers aren't supposed to have meters, or tools on-site

Redd

12.7 and 12.8 are not unusual, although not all chemistries (battery makers) will hit them, even brand new. The metal mixture in a battery, aside from "thin plate pure lead" (TPPL) types always has some secret sauce to make the plates harder, less vulnerable to sulfating, or sometimes simply cheaper from less refined scrap recycled lead, and that will affect the voltage.

13V off the smart charger means either it is trickle charging, or it is in error. Not a big error, and if you are just comparing "my gas gauge says full, not empty" then it really doesn't matter what the numbers are, as long as they are consistent. We had an old cheap analog voltmeter on a boat that could be calibrated "right" at 11.5V (dead battery) or 14.4V (full alternator) but if you set it correctly for either one, the other could be 1/2 volt off. Not ideal, but "does it say full or empty?" was repeatable consistently, as long as you ignored the numbers.

I haven't found any reasonable source for "mass market" or consumer grade calibration sources, but working with 12V systems, I needed something besides sending meters out for calibration, and wound up rolling my own, built around dedicated "calibration source" IC's.

Whatever you use, if you use anything at all to calibrate it beats nothing. Or Horror Fright.(G) Used appropriately, a calibrated voltmeter can tell you just as much about a modern battery as a hydrometer ever will. And without any risk of acid burning your clothes!