When a battery is not cycled the night before, there is no reason for the solar charge controller to bring the battery upto absorption voltage the next day.
It really depends on the charge controller and if it is adjustable, and If not, how long it will hold absorption voltage before reverting to float voltage.
If the controller sees the battery voltage rise easily, as it will with a fully charged battery, and low amperage needed to attain absorption voltage, and then drops to float voltage quickly, then no big deal.
But if the controller decides that every day the already fully charged battery requires 2 hours at absorption voltage, then this in effect is overcharging the battery and will cause positive plate erosion and excessive water usage.
Now, with flooded batteries, there is the issue of stratification, where the more dense electrolyte sinks to the bottom of the cells, and being stronger acid, eats the bottom of the plates faster.
Some converter companies erroneously have named an 'equalization' cycle which they say bumps up battery voltage every 18 hours or so to the mid 14 v range, for 15 minutes to cause gassing, which mixes up the electrolyte and de stratifies it. A true equalization cycle is an intentional overcharge of a punch drunk battery to restore it to its maximum remaining capacity.
The rate at which batteries self discharge can vary widely. But in general the higher the temperature, and the older the battery, the faster it will self discharge, and an old abused battery can self discharge a significant amount each day.
My former flooded battery, which I have taken out of service and out of my Van at ~465 deep cycles, can accept 3.5 AH each and every day, and this is with zero loads on it. It is self discharging 3 to 5 % daily.
On the other end of the stick, my Northstar AGM battery does not seem to self discharge at all. It has a fully charged open circuit rested voltage of 13.06v. Over the Xmas holidays I left it unattached to my solar, but still attached to my engine computer, and when I returned 3 weeks later it still read 13.06v, much to my surprise.
So whether it is best to disconnect the battery or let the solar do its thing all day long has a bunch of variables that leave any recommendation kind of pointless without knowing how your charge controller responds to a fully charged battery.
Will it decide to hold it at Absv each day for 90 minutes? then disconnect the solar.
Will it see that the battery is already fully charged and drop to float voltage shortly after sunrise? then leave it connected.
Can you change the controller's absorption voltage and duration? If so, do so. When I left my flooded battery connected to my solar over those 3 weeks over the new year I lowered float voltage to 13.1v, and lowered absorption voltage to 13.8, and duration at 30 minutes, and the amp threshhold at 2amps per 100Ah capacity. Basically the solar would have the battery up at 13.8v a half hour after after sunrise, even if cloudy, and drop to float voltage.
This still leaves stratification as an issue, So I had my trained Gorilla come out of the shed and jump on the bumper for 15 minutes every day.
Thanks for that reply its helping me to decide I have the morningstar 60 amp MPPT charge controller and it does respond to less load by bring the battery up to float quicker which i think is correct according to the manual there are not a lot of adjustments i can make other than make equalise AUTO OR MANUAL the biggest draw i have on my RV system 650 watts is a 1 amp 110 -115 volt fridge freezer this i usually have on for approx 10 hours a day with the good AZ sunshine i am usually at Float by mid morning but do not have any load on the system untill around 2.00 pm
