wow, I was very skeptical about battery swaps, but it's starting to seem quite possible given everyone chipping away at it here as well as Capitalist Oppressor's remarks.
I could see a system within economic range (though some remaining logistical hurdles).
I think it would brilliantly complement the Supercharger Stations. It would satisfy those out there who think they'll never be okay wainting 40 minutes to charge. Perhaps more importantly, during holidays when the SuperChargers would otherwise run into log jams, customers would have another option, swap out their battery for hold until they return. Just like rental cars, Tesla could require a reservation at these times to help manage the system.
Why not just more Super Chargers to help at the high traffic times instead of complicating the system with battery swapping? Because unlike capex for Supercharger capacity well beyond everyday use, the battery inventory necessary for high volume time would NOT be extra expense.
Here's how all those batteries for the rare high volume times will not require underutilized capex: charge per mile of use on the rented battery. If Tesla can make an 85kWh battery for $25,000, and it has 125,000 useful miles to it, that comes to $.20/mile, or 20 mpg if gas is selling for $4/gallon.
So if Tesla charges customers $.20/mile used on the "rental batteries", once the battery has been used up, it's also been paid for.
How does this look to a Tesla customer?
20 mpg isn't far off from other cars in Tesla's class.
but here's the big kicker- the $.20/mile you pay on your "rental" battery would be entirely offset by the $.20/mile you would have depreciated on your own battery had you logged those miles on it instead of the rental.
(While this may not be 100% of how depreciation is calculated, for the battery usage is the basic driver in the calculation.)
Can they afford all the capex of all the swapping stations? I think so. If they basically had 1 or 2 swapping bays at or very close to Supercharger locations they could cover very high volumes. Two at locations in high traffic corridors, one in less populated, would mean roughly 150 of these bays, at $500K each, $75 million. Two shifts of modest costing labor would add $10 million per year (no need for 24/7, off peak hours with far less volume, if battery swap is out of order, you just deal with Supercharger. Not perfection, but big improvement.
So for roughly $85 million in year 1, and $10 million ongoing they could pay for this. I think 10X that spent in advertising wouldn't do them nearly as much to convince people to buy the cars. And it wouldn't hurt to have two shifts of staff available to help with any Supercharger glitches as well.
Edit: I overestimated that savings of $.20/mile on depreciation on your old battery... that's the cost of using up your existing battery, the cost of replacing those miles of use when you buy a newer more advanced battery will be as much as half as cheap depending how far off in the future you'll be replacing).