Elon Musk, the CEO of electric vehicle builder Tesla Motors, sent out some tweets today announcing the launch of a pilot Model S battery-swap program:

Pack swap now operating in limited beta mode for SF to LA route. Can swap battery faster than visiting a gas station. Tesla blog out soon. — Elon Musk (@elonmusk) December 19, 2014

Tesla fast battery swap details http://t.co/4XWWUlOeQE — Elon Musk (@elonmusk) December 19, 2014

An entry on the Tesla blog today notes that "[s]tarting next week, we will pilot a pack swap program with invited Model S owners. They will be given the opportunity to swap their car's battery at a custom-built facility located across the street from the Tesla Superchargers at Harris Ranch, Calif. This pilot program is intended to test technology and assess demand."

Tesla revealed that the Model S was battery-swap-ready last year.

The battery swap will only be available by appointment and will cost the EV owner "slightly less than a full tank of gasoline for a premium sedan." The swap will take approximately three minutes to complete, a task complicated by the recent addition of titanium safety plates on the bottom of the car. The firm looks to lower the swap time to less than 1 minute.

In May of last year, the wildly ambitious EV battery-swapping firm Better Place closed shop after raising almost $1 billion and pinning the hype meter to eleven. The demise of that firm seemed to put an end to the idea of battery-swapping in favor of Tesla's integrated batteries. Renault's Fluence electric sedan was the only car built which complied with Better Place’s battery-swapping system, although fewer than 1,500 were deployed.

If this were a contest between two schools of thought on the future of automotive infrastructure, then swappable batteries have lost and integrated batteries like those Tesla uses have won.

But the battery-swap concept will live on if Tesla sees a demand for the service.

Commenters at the Tesla blog note that the "Supercharger network is far more useful to those of us with bladders, children and/or a love of coffee, to have a respite from the bleariness of highway travel while we Supercharge than to sit in astronaut diapers while a battery swaps out." Tesla already has a worldwide Supercharger network of 312 stations with more than 1,748 Superchargers.

Another commenter suggests, "With the build-out of the incomparable Supercharger network, I think battery swap is an idea whose time has already passed."

The battery pack is the most expensive system in the car. Concerns about the reliability of the swapped battery pack would be allayed if the original pack was retrieved at the same swap station, fully charged, on the return trip.