[notorious]

Goran, just in case you don't have a garage nearby:

Buy OEM Solar Sunroof and instead of connecting it to the blower motor just connect it to this CTEK device and you will have nice 33.6W charger that will trickle charge your battery free of charge. (that's 2.2A on sunny day). This is what I'm going to do soon myself.

The CTEK device you'll need:

http://www.ctek.com/gb/en/chargers/D250S%20DUAL
http://www.ctek.com/Archive/ProductP...%20DUAL_EN.pdf
http://www.ctek.com/Archive/ProductM...%20DUAL_EN.pdf