Possibly you came across as having a rigid approach strategy to this? And that you possibly don't actually need any help?
Generally speaking, most people posting here are professionals, and from my perspective, if you come on here asking us to solve your problem for you, you'll meet with reluctance.
If you came on here instead with, <here>'s the panel I have, and using <this> charger with <this> battery, and given I want to do <this>, but I'm having trouble with <issue>, do you the community have any suggestions to improve/help solve this or better/alternative approaches in general? You might have more responses. i.e. DIY not DIeevblogforum.
If it were my project, I'd use a small embedded micro with a small point to point RF link. All it really is, is something that shouts "CAR". Run off a replaceable coin cell.
I'd also consider if simply running cable was not a better idea...
My $0.02