How much is the voltage of electric car's batteries? I was thinking about a DIY electric van (Mercedes Sprinter) with 3x200 watts solar panels on the roof. I'm not sure but let's say the EV batteries are 460 volts and solar panels are are there any inverters or battery charges that can charge 460 volts battery with 18-20 volts?
What really matters is the energy capacity of the batteries measured in kWh. The base Nissan Leaf has a 30 kWh battery.
With 3 x 200 W solar panels in optimum orientation and illumination would generate 0.6 kW. With 100% output and 100% inverter efficiency (both of which are impossible) you would charge the battery in 30 / 0.6 = 50 hours of continuous sunlight. Of course, since the Earth rotates this will take at least 100 hours.