Help me understand battery charging

[leeelson]

Eleven years after the fact I'm still trying to understand my system. I'm a novice.

I'm trying to understand how the batteries are charged. I have a pretty good understanding of how the Classic and Whizbang junior handle battery charging. What I don't understand is the role of the Xantrex. Battery charging is enabled (Gel batteries). Some specific questions (see attached diagram):
1) When the grid is up, what is the role of the Xantrex in charging the batteries? How does it work when there is ample output from the PV's? What about with no PV output?
2) When the grid is down and the PV's are producing full power, enough for protected circuits and some leftover for battery charging, who controls the charging, the Xantrex or the Classic?

TIA for any insights.

[ClassicCrazy]

It is going to depend what setpoints are programmed in all those devices. The Classic and Xantrex and SMA are all independent systems . Also it would depend if there is any controlling going on for example from the Classic Aux terminals to something else.
I think you would have to document all the charge settings and any additional controls in the setup to really understand how it works .
Larry