The only effective way to monitor a battery's state of charge is to measure the specific gravity of the electrolyte. Voltage readings are nothing but a SWAG by people who don't understand much about battery functions. Sealed-top batteries with no way to monitor the acid concentration or add water are for people too lazy to test the gravity, so checking the open circuit terminal voltage is the only way to make a somewhat educated guess about what's going on. Depending on the strength of the acid when the battery was manufactured, a specific gravity between 1.250 and 1.265 is full charge. Continuing to force current into a battery once the gravity in all the cells stabilizes just evaporates water and overheats the cell groups.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!