Originally Posted by
CatFan
A battery that is at 12.5V after charging, regardless of whether surface charge has been removed or not, is junk. 100%. The excess internal resistance and low specific gravity results in dramatically reduced capacity and charging issues.
If a battery can’t reach its designed full charge voltage, it has suffered chemical or physical damage. Battery full charge voltage doesn’t decline with age. Even a very old battery with very little remaining capacity will still reach and hold its full charge voltage if it’s not been damaged from neglect or abuse.
It’s even worse than junk, because the lower voltage results in charger current and voltage remaining high leading to bubbling electrolyte for far too long resulting in extreme water use, heavy gassing and acid damage to the area around the battery. These are the batteries that explode because they are run dry.