I have a WF 5110 HP inverter in my 2017 Heritage Glen 5er for my fridge. It worked great last winter, stored over summer, put 2 new batteries in configured exactly as they were last year, and the screen shows a picture of a battery with the word "low". Yellow light is on when connected to shore power and green light is on when not. Fan runs. Is all of this normal, or am I supposed to have something other than "low" showing up? Obviously, I am clueless about how all of this works.