The way to tell is with an hydrometer to see if they are at "baseline" (as new after your initial overcharge) SG when you are at your idea of "full"
On full- time solar in the summer months I have the controller set to 14.8v which the 6v batteries get to after lunch sometime, then it drops to 14.4v the rest of the day.
If that subsequent time at 14.4 is long enough, the Trimetric AH count gets back up to zero and then goes "over" into positive numbers. If the sun is still out that keeps going till it is about 10AH "over" and then the SG is up to baseline. I reset the AH counter to zero after dark.
If the AH count does not go "over" by at least that much, then the SG won't be all the way up that day, and I do not reset the Trimetric. To make up for those days it does not get that high, once in a while I do an equalize to 15+, but that is not often needed.
If I want to use the inverter when the voltage is over 14.9, I just turn off the solar for a minute (switch between panel and controller so you don't have any time with panel on controller with no battery connected), which brings the voltage right back down, start the inverter and then turn the solar back on.
