Plate mossing (Dendrites) is certainly possible to explain the weaker older battery.
Battery manufacturers have insane power bills. The bill for a small manufacturer said twenty-one thousand dollars when I read it and that was more than twenty years ago. The consequence is manufacturers charge their batteries as little as possible and still not put out a defective product.
Curing the plates will definitely get the new battery off to a good start. If you doubt this point, pay attention to the point that OEM's claim the battery will reach full-potential after several perhaps a dozen cycles.
5-amperes into each 100-amp hours until the battery reaches 15.0 volts is the best way to get the battery off to a good start. You can load test an out of the box fully charged battery, then top-charge it, let it sit for half a day then retest and see a significant improvement.
I tried this with a Lifeline and saw zero improvement. After a phone chat, I learned Concorde treats every single battery they make to Mil-Spec post charging. Rolls & Surrette does the same and I would believe other premium line OEMs like Fullriver, and Crown do the same. I also suspect Trojan does it to their premium lines. BTW Concorde uses Mil-Spec quality assurance and raw materials vendor record keeping on every battery they make.
The economics of battery manufacturing is bare-knuckle brutal. Any time I can use three cents worth of electricity and receive even a minimum improvement in battery lifespan I will do it.
