The best setup would be a small DC microgrid that stays in your van. The car charger you have would risk running out your car battery. Here's a short list with most of the things needed to set one up.

-24V 9.6Ah lifepo4 battery

-Victron 100-20 MPPT solar charger

-24V solar panel

-Roof cable inlet

-24VDC PSU

-24VDC to USB-C charger