More news.
Raised Float to 13.8, also raised Boost Reconnect - don't remember the value because Epever software froze on the laptop. Upon restarting the software it became unruly, stopped recognizing the "station" (in other words, custom profile including data of the controller and solar array). I deleted the "station" and it's now refusing to add a new "station" and configure Port COM - Windows seems to dislike this software.
Whatever settings are in the custom profile, are buried in the controller memory for good. I can't communicate with controller, can't see or change custom profile.
Meanwhile controller itself works, quietly doing Boost at 10A, as I can see on its built-in display. Only I don't remember the latest settings and can't be sure they are still what I set.
Will try and return Epever and get Renogy Rover Li, it can't be much worse. Rover also requires a laptop and software for custom profile BUT at least it has a preset Li profile accessible (though not modifiable) directly through controller interface.
