Traditional vehicle alternators charge at 14.4 Volts. Sometimes 14.7. I think the 1996 Ford F150 drops down to 14 Volts when warmed up, which is a design that’s better than it could be, unless the alternator regulator is going bad and it’s an unintended feature.
If you leave a car battery on an unregulated charger it’ll stay at 14.4 to 15 Volts. After about 6 months and adding water, the battery will be ruined from over charging, but this time period is highly temperature dependent, as the current varies with temperature. A lead acid battery can be over charged by about 30 times its rated capacity before it is ruined. At engine compartment temperatures, a battery left on the charger would be ruined in about 3 months, or 2160 hours.
2000 to 3000 hours is typical for car batteries, just as expected from the over charging caused by 14.4 Volt alternators, which is similar to the unregulated battery charger. 14.4V is actually worse is southern climates because it has practically unlimited current and won’t reduce the charging Voltage as the battery gets hot and takes more current. That’s why batteries used in cars in the south sometimes last only half as long as cars in northern climates.
Over charged batteries often fail suddenly by going completely open circuit without warning. Usually there is a reduction in capacity first, but it goes unnoticed by people who start their cars every day and no not leave stuff on.
It seems that since 2010 or so vehicles have reduced the charging Voltage quite a lot. Some vehicles, like BMW, even have current sensors at the battery terminals. I’ve seen it on Ford and Mazda do this with battery Voltages at 13.5 Volts while running. There may be a brief 14.4V part of the charge cycle, but I didn’t monitor it enough. I’ve been involved in replacing two batteries that still worked but were just not being charged up enough, or wouldn’t take a charge like a new one presumably due to sulfation, the condition caused by under charging lead acid batteries. I put an 9 year old Panasonic Mazda factory battery in an older 14.4V car and it has been doing fine. 13.5 Volts just wasn’t enough anymore.
Unlike VRSLA and true deep cycle, the flooded lead acid vehicle and marine deep cycle batteries do need to be charged at 14.4 Volts for 4 hours to fully charge and not sulfate. This should be done every few weeks if the battery is in storage, and within a couple days of being discharged, such as use with a trolling motor. Nobody seems to know why this is, since other types of batteries, such as non automotive sealed lead acid, and some deep cycle such as 6 Volt golf cart batteries are able to fully charge at a lower Voltage. I learned this about marine deep cycle the hard way. I didn’t realize that 13.6 Volts won’t charge it up all the way no matter how long it charges. 14 Volts is the absolute minimum.
I wonder if manufacturers have been doing this to avoid the safety issue of batteries that suddenly go completely open circuit without warning? This way they slowly sulfate over time and may develop a shorted cell, allow the replace battery warning to work, but are less likely to fail suddenly and leave you stranded.