Google and get awakened about solar power. A 12 volt 15 watt panel under the most ideal conditions ( pointed directly at the sun all day long) will give you 1 (one) amp at best. For the early morning and late afternoon hours, it's less. If you have even a partially cloudy day, it's less. Even a 30 watt panel pointed straight south at roughly a 50 degree angle might get you 2 amps for a couple hours. Get snow on the panel, you know where this is going.