On Thu, 01 Sep 2016 12:28:19 +0100, Capitol wrote:

Or a small solar panel on the dash (depending on which way it's
facing
of course). ;-)

IME these don't charge sufficiently.

Worked for me. At least the car was quite happy when I came to unlock
and start it up after being left for a month. I don't intend to
perform the opposite test leave it a month without the solar panel. I
might see if I can measure how much draw there is once it's been
"off" overnight as cars tend to have several sleep states.

But even if the solar panel is only providing half of what is taken
that doubles the lenght of time it takes for the car to go into a
coma.

--
Cheers
Dave.