Brand new 12 volt battery not reaching 100% state of charge

You give the impression that this battery charged up from flat (discharged; 11.2 V) to full in a short time. This is not necessary a good thing.

Yes, do this, but no need to let it stay on trickle. Just remove the charger and measure the voltage when you disconnect the battery charger, and then measure it again after 2 hours. After this, apply a 60 - 100 W load for 15 mins and then measure the voltage again after the 15 min and while still under load. Finally remove the load and leave it to rest for 2 hours. Take a final measurement after resting for the 2 hours.

Note all those measurements and post here for comment. Also, mention what the load was (as in how many Watts load).

PS, if you don't have a load, let it sit for 24 hours instead of load testing and then measure before and after sitting 24 hours.

 

That is normal, it is called surface charge and will bleed of and stabilise within 2 hours. That is why I want you to wait 2 hours and then do another reading. Then wait for 24 hours to do the next reading.

 

This is not the Yellow Top battery I assume? Yeah drive the car for a day or two, then check the Yellow Top voltage first thing in the morning. In precisely that scenario, ours read about 12.75 volts. It was brand new, charged with CTEK 4.3, then a day or so later, with a bit of driving.

Note that O'Reilly is likely testing with an electronic load tester, a pro version of something like the Solar BA5 or BA7. These can read the voltage, plus: you enter parameters about the battery, whether it's AGM or regular acid-flooded type, the specificied Cold Cranking Amps, then test, and it tells you the actual CCA, and gives a verdict, either "ok", "charge", or "fail". I think the verdict is a combo of the measured CCA and voltage.

I have the Solar BA5, think it was around $70. The BA7 is more prevalent now, about the same price, and there are a number of other DIY level testers on the market now as well. The Solar product works but is fairly rudimentary, so maybe you would want to research.

I appreciate getting a DIY load tester is a bit of a stretch, but when you think about it, the myriad battery questions here invariably boil down to "what is the status of my battery". The voltage is part of the story, but these electronic load testers really clear up the mystery.

 

so far, so good!

 

Now that you've got the bug, I think you'll be needing a Solar BA5 or equivalent.

 

sounds fine.

 

There is something funny going on here.

You NEED to measure the voltage with the car "running".
It needs to be at least 13.4.

Also, you might have a loose or corroded cable connection at the OTHER end of one of the main battery cables.
You have switched the battery often enough that the connections AT the battery should be good......probably.

 

All of this has me thinking your battery is indeed a dud. A freshly charged brand-new battery should be reading over 13.0, due to "surface charge". After a bit of driving and a rest, it might settle down around 12.7~12.8. And an electronic load test (possibly what O'Reilly's did??) would test it's Cold Cranking Amps capacity, basically going beyond just measuring voltage, measuring the "health" of the battery, it's capacity.

Have you posted where you got this battery, was it local or mail order. I would get an electronic load test, either DIY with something like Solar BA5, or back to O'Reilly's (if in fact that's what they're doing), get some proof, even a photograph of the Solar BA5 displayed CCA and verdict for example, and get back to the seller, for a refund.

 

no point to doing all this measuring with the car on or driving. if it is holding 12.76 after 36 hours, then dropping way down with a load, it's toast.

 

Agreed. Your Yellowtop sounds like it the better one. Give that a good charge and the drop it in.

Also, check the connection of the negative cable to the car body (in the back) is clean and tight. Ensure the battery positive and negative connections are clean and tight too.