Tesla first toyed with the idea of battery swapping three years ago, only to walk away from the service less than one year later. Despite this, the electric-car maker may still have an eye on battery swapping, and a new patent filing is evidence of this.

In May of this year, Tesla filed to patent a mobile battery-swapping rig with the U.S. Patent and Trademark Office that would aid technicians in changing out a battery in roughly 15 minutes. The patent describes a ramp that Model S or Model X drivers would drive onto and the machine would then assist the technicians in the battery-swap process. From there, the driver would be on his or her way with a fully charged battery.

The goal of a battery-swap service would be to eliminate charging times and get Tesla drivers back on the road quicker with a fresh, fully charged battery. Tesla originally shelved its battery-swap pilot program in 2015 as its Supercharger network truly began to flesh out. One of the major problems with the service was its appointment-only structure, which was hardly as convenient as stopping at a charging station at any time to charge the battery. Only 4- to 5-percent of Tesla owners in the small beta test responded to the battery-swap program. That original program charged $60-$80 per swap and required owners to come back to get their original battery swapped back in.

The patent could have bigger solutions in mind, however. As Tech Crunch notes, Tesla CEO Elon Musk formerly said if the company were to pursue mobile battery swapping, it would be with commercial vehicles in mind. While the patent drawing shows a station sized for a Model X or Model S, it could be adapted for a big rig. Coincidentally, Tesla plans to reveal its all-electric semi truck in October. Originally, the Silicon Valley automaker planned for a debut this month but pushed the reveal back to a tentative October 26 date.