Hmm, odd that this one has 84V output. That’s AFAIK beyond the typical 48V battery charging voltage.

The problem with converting back and forth is both efficiency and that you need a seperate buffer battery (or at least super-capacitor).

IMHO, maybe the best idea is to just buy a so called balcony solar kit to feed into your regular home power circut and then charge as usual from a regular outlet.