When people read about this, one of the first questions that inevitably comes up is: "can you just use a solar panel?"
Short answer: not really (for reasons of cost & potential aerodynamic penalties).
If you drive a normal amount, it will cost you a
lot of money to get enough panels to keep your battery topped up, and you'll probably destroy your car's aerodynamics mounting them on top
.
The only reason I can get away with solar recharging is because I don't use my car very much (less than 200 miles in May). It could easily take a couple of days for my panel to replace the electricity I use from the battery in half an hour of driving.
The panel I have is equivalent to a 1 amp trickle charger, and it cost $160 CDN (I got it to keep a boat battery charged):
http://tinyurl.com/fw77y
A typical electric battery charger "trickle" setting is 2 A (twice the power of my panel), and they cost a fraction of what solar panels cost.