Help choosing the right converter/charger?

Thanks for the replies. It so happens, because my old charger had problems charging 4 batteries, I had taken 2 of them off for the time being. So with this new unit, it is charging 2 batteries. So I figured it wouldnt take so darn long. It ran all day and late last night. But kept blinking rapidly. I think it was putting out a charge. But not as good as I expected. I can't back it up since I don't have the equipment to check. And I suppose i need to get it. But for now, I tried turning on Boost for a few hours. And it remained in that mode. We also had some sun today, so the solar charger was likely working as well. After the few hours I dropped it back to Auto. So I really have no idea how much charging this new unit does. It seems kinda odd to me that the batteries would be that low considering they have been running everything pretty well up to this point.