I was thinking about electric cars, and their recharging times while on the occasional road trip. The solution seemed obvious in my head, but couldn’t think of a reason why it doesn’t exist already.Say an electric car comes with a small sealed and fixed battery that gives up to say 100 miles of range. This is sufficient for most uses (to work and back, may be getting around the city, grocery trip etc). Another slot in the car that is usually empty may be “filled” with a battery along the highway while on a road trip. Reaching the end of range? - just swap out the “filled” battery.This way, a customer gets to buy a cheaper car(smaller battery means lower cost). Buyer need not worry about getting stuck with a “aged” battery swapped with their good battery because swapping only occurs on the secondary battery that they don’t own.Environment feels a little better - users don’t hoard Lithium batteries that they do t need all the time.Businesses have a new way of earning money by selling subscriptions to such swap batteries.The swap battery stations may be easily setup everywhere easier than full-on charging stations. The batteries themselves may be charged with renewable energy in huge factories and distributed to remote swap stations.What am I missing?