I have a 30 year old diesel camper van which we use once every few weeks. Being a mechanically injected diesel Toyota so it's pretty reliable, the only thing that lets it down is the battery, especially over the winter when it gets used even less frequently.
The obvious solution to this is a small solar panel to keep the battery topped up.
It had never occurred that I'd have to be very careful to park the van in an area where it has good direct sunlight (it's only a 10w panel so anything less than direct sunlight means it's barely producing enough to support the charge controller). The street in which I usually park is south facing but has tallish buildings on both sides.
The upshot of this is I can can't imagine how frustrating it would be if I was counting on the solar panels on the car contributing to its range.
