Since rally season is coming up.

[Tom]

This solar panel may help those that do a lot of exploring and camping out.

"Perfect for the outdoors and for people who are on the go.  This rugged water proof solar power bank can handle anything you can throw at it.  Features a built in LED Flashlight and 2 USB ports for charging multiple devices.  The rubber casing is perfect for those annoying drops we all punish our devices with occasionally! This solar charger will charge your phone or tablet just by using the power of the sun or with the supplied USB cable!  So, load up anywhere the sun shines, and charge away! Can charge an iPhone 6 up to 100%-only needing 3 - 4 hours."

https://survivaladdicts.net/collections/all/products/sa-outdoor-waterproof-20000-mah-solar-powerbank?_ke=YXVjeWNsZXNAZ21haWwuY29t&variant=44784754067

[Guzzi Gal]

Hummm...  Trickle charge an ailing battery?

[Tom]

I carry a similar product to this on the road.  https://www.evine.com/Product/469-859  There are alternatives on Amazon.  Costco carried a line that they sold at a reasonable 2 pack price.  The one I bought was able to jumpstart 3 trucks in a row.  Great for back up 12v electrical demands.