Check your voltmeter on your car battery, see if it is ~ 3 volts too high there too.
Lead acid batteries at 77f pretty much never want to be brought above 14.8v
The highest voltage ever recommended for flooded lead acid batteries is 16.2v, which is called an equalization charge which is an intentional overcharge, after a regular 'full charge' has been applied.
EQ charges are done on deeply cycled batteries that don't get returned to a true full charge often enough. EQ charges are very hard on a battery, and should only be performed when the cell's specific gravity are 0.015 apart from each other or when the battery capacity is obviously much lower than expected.
Bringing the lead acid battery to 15.5 to 16.2v for the EQ charge needs to be closely monitored and the specific gravity measured often. When SG stops rising, accounting for rising electrolyte temp, or reaches previously determined maximum, terminate the EQ charge. This can be 10 minutes to 10 hours depending on the battery, and th elonger it takes is a likely sign the battery is compromised and is nearing the end of life.
Most starter batteries will not take kindly to an extended duration EQ charge, and once again the EQ should never be initiated until after amperage stops tapering at 14.4 to 14.8v first. Forcing a discharged battery to 16.2v when it is still undercharged is even harder on it. You will hear the battery fizzing like a recently opened soda, 6 of them. and lots of oxygen hydrogen and a sulfuric acid mist will be escaping the caps.