Self discharge can vary greatly, even Among batteries off thesame line, on same day.
Self discharge increases with temperature, and battery age/decliming health.
An older but retailed as new unused battery, if put on a charger which takes it to mid 14's for an hour or three, then floats for 24 hours, could easily test as well as a fresh battery.
It really depends on if the self discharge allowed battery below 80% state of charge, and for how long.
Watching a voltmeter and ammeter when charging, and discharging that first cycle, i find that every new battery behaves less well than expected, until it is discharged below 80%, then immediately recharged to true full.
Several high $ agms ive had refused to maintain the manufacturer specd full charge rested voltage, until it was cycled then recharged with no less than 25 initial amps.
I almost returned group 27 Northstar, as it seemed weak and cranked the engine slowly, until I cycle it deeper, then recharged with 25 amps initial current.
Tha voltage held that first deep discharge cycle was abymsal, i was so angry. As it was such a high$ agm which no doubt would not qualify for warranty replacement, Just because.it did not meet my performance expectations
After recharging it from a rested 12.2 volts, about 50% state of charge, then put on a 25 amp charger, the next day, 12 hours off the charger and restes, it still read 13.27v.
Obvious surface charge voltage,
but it was not showing this before, even after 12 hours on a charger when it was not cycled.
But it then it cranked my engine.to life faster than any battery, ever before.
The voltage held its second discharge cycle was nearly 0.25v higher than that first discharge, all factors being nearly equal.
That battery lasted 6 years which is no great feat, but it was deep cycled about 1200 times over that 6 year span, which is.
Best battery I ever had. And it performed so badly.on cycle number 1. I wanted to go throw it through door of the retailer and be the ugly entitled ignorant modern day consumer.
I contend all off the shelf batteries, whether factory fresh, or dusty, perform better after a discharge cycle below 80%, and a recharged to full with no less than 10 amps per 100ah of capacity, for flooded, and double that initial rate for agm.
Its kind of like breathimg exercises, to increase lung capacity.
Just slapping it in a vehicle and letting the vehicle treat it as it will, could very well have the battery underperform, until its potentially premature replacement.
My second Northstar agm, behaved the same way when new. Disappointing performance until.it was cycled deeply then hit immediately with 25 plus amps.
Id view a dusty 'new' battery, especially a flooded one that one could use a hydrometer to determine true full charge, as an opportunity, and acceptable, perhaps desirable, if it were discounted for its age. But no discount, and i demand as fresh as possiible.
I know i could get it performing as well as possible, with my charging sources , and vast experience deeply cycling lead acid batteries while watching voltmeters, ammeters and amp hour counters during discharge and charge cycles.
