50 miles is more than enough for a car with a gasoline backup tank for most use cases. Average car users use below 50 almost every single day. Something like 98-98% of trips are under 50 miles. 95% of people commute less than 40 miles.<p>Adding more weight and room for only a small percent of rides is probably less efficient (economically and ecologically) than just popping into gas for 5% of trips.