The motive battery (DC) in an EV needs the external V2G inverter connected to the Chademo/CCS connector to make 240v 50Hz AC. They are so expensive because they are a low-volume manufactured product that required a lot of certification for connection to the grid and contain a lot of expensive protection and inversion kit.
The car has an on-board charger to charge the motive battery, it only works one way - taking mains AC power and charging the battery.
The other converter in the car takes high voltage DC from the motive battery and converts it to charge the 12v auxiliary battery.
You wouldn't want to connect solar panels directly to the motive battery. You should have dedicated DC solar charging equipment to do that.
The car has an on-board charger to charge the motive battery, it only works one way - taking mains AC power and charging the battery.
The other converter in the car takes high voltage DC from the motive battery and converts it to charge the 12v auxiliary battery.
You wouldn't want to connect solar panels directly to the motive battery. You should have dedicated DC solar charging equipment to do that.
