o.k, thanks. I recommend doing just the opposite. During the summer, they are getting lots of solar, so much less likelihood they are not getting to full. But in the winter, they are clearly not getting the FULL charge they need.
You also need to verify that the batteries are indeed FULL, when the controller says they are. Trust what your batteries say, and nothing else, until all devices have been verified as being accurate.
You need to supplement the (lack of) solar with gen charging in the morning, if possible, followed by solar for the remainder of the day. In fact, one of the guys here does a gen charge both am and pm, to supplement his solar.
If you haven't already, you need to establish your baseline SG for those batts. To do this, they need a NEAR FULL charge at say 14.8v; followed by a TOP charge (to truly 100% FULL) at say 15.2v , followed by a short EQ at 16v, (or better, at 8v per individual battery). Take SG readings every hour, until SG no longer rises. Let them sit for a couple days with absolutely no loads, and take SG readings, as well as voltage readings, for each individual 6v batt. If all is well and equal, (cuz you can't spell equalize without 'equal'), this is your baseline for future reference.
--- It is very important that you keep the batts very well ventilated when doing Top and EQ charging ---
And I hate to say it, but you could have gone with a much less expensive pwm controller with those 12v panels... mppt is for 24v... and spent more on your innverter. But as BFL often says, you've got it now, so try to make use of it the best you can. :)
