Submitted by grega on February 24, 2014
There's a lot of talk about battery swaps and why bother when a supercharge only takes 30 minutes or quicker. There's also talk of Metal-Air batteries with slow charge times but extended range.
If you put that all together, it makes for an interesting option.
Lots of assumptions here… but… What if the car comes with 3/4 of a LiON battery pack, and 1/4 metal-air battery. The metal-air might double the car's range, but rarely get used - and when it is used an overnight charge would top it up, just not a supercharger. A battery swap then would purely focus on replacing a smaller metal-air battery. The car might even be smart enough to book the battery swap ahead of arrival, and with that knowledge deplete the metal-air battery (charge the LiON battery) before arriving at the swap station, so that the car gets a quicker supercharge of the LiON at the same time as the metal-air is being swapped over.
The smaller size could also mean the same swap batteries for Model S and for Model E cars. It also allows for new battery configurations - the smallest configuration could be a 40Kwh LiON battery and a placeholder for a metal-air battery (of the same weight), so when you plan a long trip you swap in a metal-air battery when you leave etc.
Would that make more sense?