After the pandemic started I was using my car about once a month or two and the battery was getting drained enough that the car would not start. This solar panel fixed that problem:
It is powerful enough to actually charge the battery instead of just maintain it, and it has a charge controller so it won't overcharge the battery. It did fail me once when we had a couple months of rain and overcast weather, but kept the car going otherwise. Eventually replaced the battery with an AGM battery and that plus the solar charger has worked very well.
https://www.amazon.com/gp/product/B07Y5TKMZ4
It is powerful enough to actually charge the battery instead of just maintain it, and it has a charge controller so it won't overcharge the battery. It did fail me once when we had a couple months of rain and overcast weather, but kept the car going otherwise. Eventually replaced the battery with an AGM battery and that plus the solar charger has worked very well.