Hello all. I am having what I am guessing is a Parasitic Drain issue. I have a 2017 SV with just under 50k miles on it. Started having issues with the original battery not staying charged. Had it tested, sure enough bad battery. Probably not the best choice but I replaced it with the middle of the road Wal-Mart battery. (I have had good luck in the past with them years ago) After about a month started having issues with battery dying when parked. Car is not driven daily but at least once or twice a week. Had battery tested again and it was bad. Battery was under warranty so was able to exchange it. Tried to upgrade and pay the difference but they did not allow it. Now after 2 weeks issues again. After 4 days since last driven, was barely enough juice to unlock the car. I tried to conduct a Parasitic Drain test with my multimeter by testing each fuse in the fuse panels after the car was asleep. Could not locate any MV drain. Car was driven and after 20hrs battery charge went from 12.6V to 12.03V. When starting the volts went from 12.3V to 9.14V then up in the 14V when started. Since it jumps up to the 14V range can I assume the alternator is good?

I am obviously no mechanic and just a car owner trying to fix the issue myself if I can. Reading and many YouTube videos has been my way to try and learn things.
Any thoughts on this issue or testing advice? Could this still be a battery issue by trying to save money? Or could there be something going on that is destroying batteries?
Thank you in advance.
E.