Here's another option for those who might find themselves stranded by a dead or low battery somewhere, without anywhere to plug in the tender. I bought 2 of them last year, and so far, the one I've actually used to keep my lawn tractor's battery charged through winter, has worked flawlessly.
Amazon product ASIN B07Y5TKMZ4On a good "sun" day, 20W will produce just over 1A of current to the battery, and it's got a built in charge controller, and is waterproof. I will be keeping one of them in the C8's frunk, JIC. As a follow up, is the "always hot" 12VDC outlet in the frunk, the only one of it's kind on board? I looked through and searched the OM, but couldn't find it, or simply couldn't get the right keywords for the search.