If you are asking whether it’s possible that your charger is defective/stops charging too soon, perhaps, but it’s much more probable that the battery itself is defective.
If the battery is good, and the charger is functioning properly, this should never be an issue. My intuition is that the battery is defective, but if you can’t get the supplier to honor the warranty, you may just have to chalk it up as a loss, and vow to never do business with that store again.
I use the Cen-Tech 12V Deluxe Battery Maintainer and Float Charger, purchased from Harbor Freight Tools to recharge car batteries. The SKU is 68213. I have used it on my own batteries, after they went dead because my wife left the lights on or door ajar, and I have even used it on batteries which hadn’t been used in years (after first checking with a voltmeter to be sure that the battery could be recharged). Every time, it took 2-3 days to recharge the battery, and the resulting charge powered the vehicle normally (unless the battery was worn out). This is a trickle charger with 750mA output, btw.
If a battery is worn out, such as the one from 2018 which was installed in my 2004 Corolla, it will appear to charge much faster, i.e. it will take less than a day to go from red light (charging) to green light (fully charged). The resulting charge will only start the engine once or twice if I’m lucky. That’s a “surface charge”. The reason why the battery only takes a “surface charge” is because it’s bad.
