Battery-switching device promises more road time for Tesla, Leaf drivers

Nissan Leafs, which go about 107 miles on a charge, often don’t graduate beyond commuter car status due to battery-life worries. The mass-market, standard Tesla Model 3 can travel double that distance, which is still limiting on long road trips.

Both batteries could work about 50 percent longer with a device provisionally patented by Vanderbilt University’s Ken Pence, professor of the practice of engineering management, and Tim Potteiger, a Ph.D. student in electrical engineering. It reconfigures modules in electric car battery packs to be online or offline—depending on whether they’re going to pull down the other modules.

Tim Potteiger, a Ph.D. student in electrical engineering, tests his battery-switching device on a levitating electric vehicle in the School of Engineering. (Joe Howell/Vanderbilt University)

The two used Tesla’s open-source, high-density, lithium-ion battery to model their method of improving durability, adding a controller to each battery cells.

“We know there are some battery cells that run out of juice earlier than others, and when they do, the others run less efficiently,” Potteiger said. “We make sure they all run out of energy at the same time, and there’s none left over.”

With the current configuration of Tesla and Nissan battery, gauges display a worst-case scenario on remaining power so users aren’t stranded and commonly show empty with 10 percent or more power left, Potteiger said.

The older the batteries are, the more likely they are to experience problems making them less efficient, and the more useful the team’s device becomes, Pence said.

“They’ll have a longer useful service life,” Pence said. “Drivers won’t see the 50 percent return immediately, but they will later on in the life of the battery.”

Their device also can connect to electric cars’ software for a more accurate read that allows drivers to get the most out of a charge.

Tim Potteiger, a Ph.D. student in electrical engineering (left), and Ken Pence, professor of the practice of engineering management. (Joe Howell/Vanderbilt University)

The battery cell-switcher has its roots in Pence’s project management graduate class and, separately, Potteiger’s NASA internship, both in 2016.

In the class, graduate students succeeded in building a working, one-seat vehicle that levitates a few inches off a steel track using electrified magnets. A major challenge was batteries that ran down too quickly.

Potteiger returned from his fall 2016 NASA internship eager to use what he’d learned in real-time prognostics, such as the working efficiency of a rocket or surface-roving device and how much energy it has left. After hearing some teaching assistants talking about Pence’s levitation vehicle, he volunteered to make a gauge for it.

Instead, the duo pivoted and ended up with the battery switcher. They are working with Vanderbilt Center for Technology Transfer and Commercialization to get it to market.

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