We modified the battery box to allow taller Interstate GC2XHD 6v 230amp hour batteries, and placed two more above these. So 12v
batteries with 460 amp hours are maintained by two 125watt panels wired in series (to 24vdc) through an MPPT charge controller. We see up to 18 amps charging current on sunny days when we have some catching up to do.
How much solar should you install? I suggest you should first install a Trimetric 2025 or equivalent on your 12vdc system and learn how much you use, for what, and for how long. It will tell you all this and more. Then you know how much solar and battery to install.