I ruined the battery (for the second time) on my Volvo due to lack of use so needed to carry a portable starter for fear of a flat battery.
No access to power from the house, so bought a solar charger for £10 from Maplin and it works.
Battery remains charged - damaged or not and will start even after a week of being parked up - problem solved.
Car is not garaged and I had to connect directly to the battery - 12v not live.
Panel sits behind rear seat head rests(battery in boot).
You know it makes sense! 
