After sitting for a week the magic pixies in my truck were a bit lethargic, dancing around at 12.53 volts. Not terrible, it would certainly start at that voltage but not ideal either. So I flipped switch connecting the solar panel to the starting battery, a loud clunk under the hood occurred and now I have have those magic pixies dancing around at 13.7 volts. This was when I turn the key in a bit those magic pixies will be at their maximum happiness level.