percentage of charge indicated on a device in direct correlation with impedance of battery. fully charge level usually depend on battery chemistry and can be from 3.70 to 4.35V . it probably 30+ variation of chemistry compound in overall , only few in mass production. measure precise fraction are important, like 4.31V still has a percentage of let say 3.35V top level. (it means need at least 4.XXX on measurement device display, not 4.X - too uncerain )
usually it a single chip that responsible for charging , type and top voltage correlated to battery chemistry.
it possible that chip out of spec tolerance, or it shifted in time, so charging process are incorrect. ( we deal with 4.XX precision)
longevity of battery directly depend on charging cycles , charge \ discharge level, usage temperature.
amount of charging cycles usually limited by 300-400 full cycles , till battery lost 30-40% of capacity. with fraction of cycles , let say from 30% to 80% it can be even extended to 1000
charging current usually play the most role in longevity, so would be advisable do not use fast charging , or disable it.
but it direct correlation with battery capacity. so large tablets due to large battery capacity , and surface much more tolerable to the high current.
temperature also factor that can be overlooked, due to charging cycle it produce a heat that need to dissipate , do device pass the heat over the shell to the surface table cooling itself, but if it in enclosure it more difficult. so internal temperature are rising.
personally I.m use 5v 0.5A charger over night (or 5V 1A charger with long cheap cables) my S8 usually shows 4 hours to full charge. so current and temperature artificially limited. I don't bother to charge up to 90% - not big deal . but in extremely caution do not discharge below 20%, usually 30% - set to charge.
my tablet has magnet connector, it also limit current
