A 200 watt panel connects to a charge controller. The controller connects to the batteries providing a charge. The more solar panels the more charge. You can purchase a portable 200 watt solar panel with a built in controller and connect it to the batteries. My friend has one. He boondocked at the beach and only started his gen to use the coffee pot and microwave.
https://www.renogy.com/200-watt-12-v...5&gad_source=1
If you add an inverter you'll be able to run a small device such as a TV while the solar continues to charge. As stated above, start with the battery bank. The more amp hours the better. Lithium prices have come way down, so highly recommend. I have the 400 package with lithium and an inverter. I only run my gen for the microwave and AC. Keystone has some great videos to help understand the benefits.
https://www.keystonerv.com/solarflex_landing
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Tony & Donna
2022 Montana HC, 295RL, Solar Flex 400, Onan 3600 LPG, 2K inverter, 200AH Lithium. 2020 GMC Denali 2500 6.6 Duramax, Demco 21K Auto Slide