Got it. Sharing between 2 Classics only works when they current limit rather than OCP.
My sealed AGM cells have a 2.35 VPC bulk voltage limit, which on a 24V arrangement is 28.2 volts. I do exceed that occasionally because there may be some value in overcharging every few months, but routinely overcharging would generate gas which can escape rather than recombine. The user's manuals for my batteries are pretty explicit on the matter. The cells are sealed and should remain sealed for the life of the battery.
My cells should float at 2.25V per cell, and temperature compensation is allowed as long as the limit is not exceeded. Since the slope is 0.005V/C starting at 25 degrees Centigrade, then to make the difference of 0.1V I get:
25degC - (0.1v / 0.005 V/C ) = 5C
Well these cells are obviously designed to be stored indoors, but I have to keep mine outdoors (no room in the house and it would have a very long cable run if I did).
So in the winter months, about November to February, I can expect the temperatures to be below -10C so pretty frequently I would be overcharging the batteries if I allowed temperature compensation to rule the float or absorption voltage.
Next thing to bear in mind is that I have 2 charge controllers, one for wind diversion, one for solar. I set them differently from each other and at different times of the year. The diversion controller has no control over the float voltage, so with or without the temp sensor connected, it will divert at 28.2-28.3 volts anyway. But I may choose to turn the diversion voltage up a few notches for an "equalizing" charge sometimes. The solar controller needs the temp sensor disconnected in the winter. I also tweak the settings so that it floats higher, like 27.6v.
There were a few winters when I didn't do that - I had a special diversion load heating water for the horses and I WANTED the diversion to run, so I let the solar float voltage rise and set off the diversion heater. It was fun to play them against one another. I should get that hooked up again, but it was ad-hoc, and I went over the extension cord a few too many times with the snowplough.
![Roll Eyes ::)](https://www.fieldlines.com/Smileys/default/rolleyes.gif)