My AC Delco AGM (made in Germany by Varta) is coming up on 6 years old and I plug it into a Granite Digital "Save a Battery" battery tender most evenings. It has an anti sulfation program built into its algorithm, but the battery has slowly started to lose CCA on my tester in the past year. Rated at 900CCA it was always testing over 1000 for several years. But this year it has slowly dropped and a month ago was showing 874 CCA. It goes on the tender almost every evening when I get home since the pandemic in 2020...about 4 or 5 times a week I would guess.
Out of curiosity, after seeing the 874cca reading, I started using my Battery Minder 128CEC2 on the 2 amp flooded setting per the user manual instructions. Using my same testing protocol, it is now consistently reading 909 to 914cca. So one month of using the Battery Minder seems to have improved the battery condition.
Save a Battery tender keeps a battery around 13.1vt to 13.2vt during maintenance whereas the Batter Minder is around 13.50vt depending on ambient temperature of course.