after reading of some people paying $4k to charge at home + tesla buying solar city... How has an stand alone solar (possible protable) charger been invented at whatever cost. Even $10k if you could fit it in your X during camping for instance. Set it up, suck up sun rays, charge at night. OR more practically set up some sort of panel at your house that stores energy to charge your car even half way. Is this somewhere and I'm not finding it? It seems to obvious.. Or would panel have to be to big?