Help with choosing proper converter amperage

I did/do get by. But one reason which kinda spurred on my thoughts about choosing a larger amp converters was that I remember reading somewhere that some quality (size and quality is unknown in the discussion) are capable of bringing a bank of batteries up to ample condition in relatively low time periods. So thinking that was an option kinda led me to this whole thread.

You'll also see back in one of my initial posts that I did try and research solar but once again simplistics was not part of the responses whereby trying to establish something less formidable, and discovering the overall costs wouldnt be cheap, I sort of gave up.