On Tue, 19 Nov 2019 16:12:30 +0000 (UTC), danny burstein
wrote:

In Roger Blake writes:

On 2019-11-19, M. L. wrote:
Could you elaborate on that solar cell setup? Where can I buy one?

This one will keep a charged battery topped up, but does not put out
enough to charge a flat battery:

https://www.harborfreight.com/15-wat...ger-62449.html

While yes, it will certainly work for "topping up", just a general
note that you should take any of the solar panel output labels
with a great deal of skepticism.

(Not just Harbor Freight).

also, of course, keep in mind that the (what used to be called)
cigarette lighter might, or might not, be cut out when the
car is turned off...
In MOST cars today that is "programmable" on the fuse panel by
simply moving the fuse - a 3 terminal fuse slot.