I'm after a bit of advice re. solar power

I've bought a allpower 2000w powerbank and a 200W portable panel to charge it. I need it mainly so we're not tied to campsites abroad with ehu (tbh we only use the electricity for the fridge - waeco crx50 - and the hairdryer for the missus).
What I need to know is what is the best way to keep the leisure battery charged for the fridge (we've got a 1989 Westy California) - do I connect the powerbank to the battery via the 12v outlet or do I buy a mppt charge controller and use the solar panel?
Cheers in advance
bernard