isabelll wrote: You wrote above that "the voltage [12.5V] a few hours after charging the battery is correct", now that after 96 hours from charging it was 12.96V relatively new, and the half-good voltage was 12.54V. (you wrote above that "it had a voltage of 12.4V an hour after charging", that is, according to the new information, for a further 95 hours the voltage increased by 0.14V).
Please read my statements again carefully. It had 12.54V after being charged with a rectifier outside the car and left for 96h "on the shelf".
12.4V had an hour after the end of charging with the alternator in the car.
isabelll wrote: I would like to know why the batteries are now charged "to 14.72V", I always charge, if I charge with current, up to 14.4V. Is this an error and the battery is not fully charged?
14.72V was for charging with a rectifier. The fact that I charge this way with a rectifier does not mean that you cannot charge up to 14.4V or (with low current) up to 15.2V. In the car, the alternator charges me from 13.6V on hot summer days to 14.5V on cold winter days. Such a "modern" technique to prevent excessive electrolyte loss> the higher the temperature of the electrolyte, the lower its gassing voltage.
isabelll wrote: What about the battery, which in the car had 12.9V after a few days when loaded with a computer and a clock? and after putting aside for half a year in a charged state - 0.1V? - went to scrap.
Active mass lost? Got a short circuit? - without an autopsy, it is impossible to determine the cause because a good battery (whatever I mean by that) had no right to fall. You might as well ask why a young athletic footballer who played the last match without any effort has not been injured, has not been fouled, and after a few days he suffers a heart attack that he does not survive.
isabelll wrote: What to judge about a battery that has 12.6V a few hours after being charged, but spins the starter five times in the car and then sneezes.
This is a typical symptom of a significant loss of capacity / sulphation of the battery, but it is necessary to clarify what we mean by "spin the starter five times" - five times 2 seconds with several seconds breaks or 5 times "chews" for 6 seconds with several seconds breaks? The second case indicates that the capacity loss is less than the first.
isabelll wrote: It is true that I do not have a variable load that would consume a constant current, but I am curious if the 11V voltage on the battery was present when the current of 6.4A was drawn from it.
I have an "ordinary" 2? / 75W resistor (measured with a 1.9? ohmmeter

that is, the current was not constant and it slowly decreased with the voltage drop, which of course I took into account when calculating the capacity. In the initial phase of discharge, reading every 15 minutes, in the middle (linear characteristic) every 1 hour and in the final phase (below 11.5 V under load) also every 15 minutes.
At 11V, the current consumption was 5.5-5.8A depending on the resistance we choose. It is not an exact measurement but according to my estimates the error does not exceed 10%.
I also noticed a significant difference in the slope of the linear part of the characteristic U = f (t) for the new (120 mV / h) and the old (145 mV / h) battery. Both Centra Futura 64Ah batteries, old one purchased on May 10, 2010. new 23 November 2016 replacement in early December.