Tesla may have never followed through with the 90-second battery swap scheme it showed off in 2013, but that doesn’t mean the company still isn’t devising new methods to remove and replace its EV batteries.

Tesla received a patent on Sept. 14 for a “Battery Swapping System and Techniques,” which is a patent-office-friendly way of saying that Tesla came up with another way to swap car batteries.

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Whereas the 2013 version was meant as a standalone solution, this new one is mobile, potentially deploying from the back of a trailer. It won’t be entirely autonomous, either — technicians will monitor the system as it works and can also operate it manually. The 2013 swap station detailed a 90-second swap, whereas this latest patent describes a process that can swap batteries “in less than 15 minutes.”

Judging by the extended time period and the ability to be shoehorned into a trailer, it appears the two different types of battery swaps serve different purposes. The 2013 scheme focused on reducing range anxiety by providing quick swaps of fully charged batteries, while this new model seems to make more sense as a service-related job, in the event an owner’s battery starts acting up.

As Electrek pointed out during its deep dive of the Model 3’s battery pack, it’s not really built for quick swaps, with additional hardware that requires more work than the batteries in the Model S and Model X, which were designed with faster swaps in mind.

But as with every automaker patent, there’s no guarantee this will be used for anything. Automakers routinely file patents for technologies that they’d like to keep away from competitors. Then again, Tesla’s service departments have been pinged for long waits in the past, so adding a mobile battery swap station could take one more job out of the service bay and into the owner’s driveway, helping reduce service backlogs.