The voltage allowed, the time spent at higher voltages, and battery temperature will have the biggest effect on water usage.
And overcharging does more than just use more water, it causes positive plate erosion.
As batteries age they will use more water, but usually this is only apparent on batteries that are deeply cycled and recharged properly. If they are not recharged properly, then one will not get to notice water loss as they will be replaced before that becomes necessary.
A voltmeter and battery temperature sensor, both on the battery itself, would go a long way to determining if the battery in question is being overcharged, but I would certainly clean the connectors on the back of the alternator and the main battery to firewall ground and battery to engine ground and engine to frame ground, if one exists.
Simple visual inspection of grounds is not adequate. Unbolt, wirebrush mating surfaces and threads shiny, retighten, and perhaps smear some grease over it to inhibit oxidation.
Caig deOxit D5 or D100 is a wonderful contact cleaner. Other electrical connector cleaners do nothing about contact oxidation, but are great for flushing out detritus and old crusty dielectric grease.
Too many people tend to thing the presence of dielectric grease means the contacts inside any given connector are still just fine. It does not. Stuffing an electrical connector with grease then connecting it might be able to part the Pin socket mating area, or reduce it substantially, so less surface area is making contact and passing the required current. As a result there is more heating and more oxidation on that part of the limited surface area.
I'd clean all grounds, and put a voltmeter on the battery terminals visible to driver when driving. A voltmeter in a 12v outlet on the dashboard will read voltage similar to the battery terminals, but not the exact same. it depends on how much current already is on the copper between battery and 12v power port. But the 12v powerport voltmeters are convenient and can give a better idea than an Analog dash gauge where one cannot differentiate between 14 and 14.5v.
Hot batteries should get reduced charging voltages.
