Tesla filed a patent application for a battery swapping device.

Tesla appears to be following up on a plan it revealed a few years back to swap out dead batteries for fully charged ones for owners of vehicles who don’t have access to a supercharger.

The California-based EV maker filed a patent application for a portable battery changer design that would allow technicians to make the swap in as little as 15 minutes. A quick scan of the diagram in the application shows many similarities to the model it demonstrated in 2013.

However, the version in the application appears to be smaller and portable, according to Electrek.com. This would allow them to be set up in areas that do not have superchargers. The company showed off its ability to swap the batteries in June 2013.

After tweeting plans to prove that possibility of a quick and simple swap, Tesla CEO Elon Musk invited journalists and several hundred Model S owners to the factory to demonstrate the new battery-swap strategy.

(Tesla demoed a 90-second battery swap four years ago. For the story, Click Here.)

They were shown a video of a Tesla employee filling up a car’s gas tank at what the South African-born executive described as “the fastest gas station in L.A.” On stage, a robotic machine automatically removed a Model S battery and replaced it with a fully charged one.

After just a minute and 33 seconds, the Tesla Model S drove off. Another sedan drove on, this one with Musk behind the wheel. His vehicle had required 96 seconds for the swap. The gas-powered vehicle was still filling up as he began to address the crowd.

The plan was to have battery-swap capabilities at the Supercharger stations, at a cost about $500,000 per facility to implement. Each station would have about 50 batteries in stock, and while they would all be new, initially, they could soon get plenty of use, Musk suggested.

(Click Here for details about Tesla’s string of setbacks last week.)

Tesla expanded its supercharger network, and is still adding more units, with the idea that no one would be more than 80 to 100 miles from a charging station. However, the battery-swapping stations didn’t get included in the plan.

Battery swapping is a concept that has been considered during recent years but seldom executed by the electric vehicle market because, while it might seem as simple as replacing the batteries in a flashlight, it is far more complex. In most electric vehicles, the battery pack is buried deep inside the car’s structure. In fact, in some products, it is part of the structure itself and essentially a permanent component.

Tesla, however, designed the Model S from the beginning to be removed and quickly replaced. The application showed a design for the Model S and Model X, but it looks like Model 3 owners will be on the outside looking in for the service.

(To see more about Tesla expanding its product portfolio beyond the Model 3, Click Here.)

It also doesn’t address how vehicles like its soon-to-be-revealed semi-truck might benefit from this kind of system. The truck is expected to have a 200- to 300-mile range when shown, which would be fine for regional runs, but would leave it out of the market for cross country trips. However, if a cost-effective way for swapping batteries could be developed for long-haul trucks, it would be revolutionary.