Elon is clearly psyched and I'm really curious what it'll end up being.
I think it's a new take on battery swapping. Here are two alternatives I came up with:
1) A big hurdle with battery swapping is that you don't want to end up with battery that's been abused in your daily driver. Since you don't take road trips often, you don't want to drop off your pristine, well-cared for battery only to get an abused battery during a road trip that you end having to keep. But, since you don't take road trips often and since you come back the same route you took the swap is setup to give you your original battery back, as follows:
a) Drive towards your destination. You might have only the small battery pack, so about 100 miles out of town is a swapping station.
b) You swap your mostly empty small battery for a big, fully charged battery.
c) You drive to your destination. Maybe you swap again if it's far.
d) You charge at your destination. You start the drive home.
e) On the way back, you're last stop is the first battery swap station. They have your personal battery waiting for you, all charged up.
f) You get your original battery back and drive home.
This gets you quickly up and running, the batteries are charged with sunlight, and you can swap for a big battery for road trips but get your original pristine battery back for months of commuting. You don't need to buy a big battery pack except if you want it for performance or do a lot of miles on a regular basis.
2) Elon talked a lot about leases in the last conference call. What if you bought the car, but only leased the battery? In that case, you could swap your leased battery for another leased battery at any time and all that matters is that you pay every month for the lease and that they guarantee the range you'll get from that leased battery. As long as you're making payments you can swap batteries for the cost of charging and swap labor. The big advantage here is that you no longer worry about residual value losses or having to replace the battery. Like leased solar is sold based on the payments being less than utility electricity, batteries would be leased by the month, with the cost being less than gasoline.
I came up with these pretty quickly. I'm sure there are other creative ideas.