It’s pretty easy to tell when your flashlight batteries are on the brink. The light will falter a bit; you’ll get a sad, dim beam from those double-A’s as they shuttle their last few ions around.

Electric car batteries, though, are a whole different story.

Dan Steingart, Ph.D., is jointly appointed to Princeton University’s mechanical and aerospace engineering department and the Andlinger Center for Energy and the Environment. He currently works on a project, which receives guidance and support from ExxonMobil, examining electric vehicle (EV) batteries. Steingart explains why the matter isn’t so simple.

“For automakers to guarantee reliability on the road, EV batteries are considered ‘old’ when their capacity decreases to 80 percent. At that point they’re removed from the automobile and replaced with a brand-new battery.”

Imagine. Hundreds of thousands, eventually millions of nearly new batteries, instead of being used up, are deconstructed and recycled.

“Those batteries will have been exposed to such a variety of elements that the exact amount of power they’ll provide or energy they’ll hold is unclear,” says Steingart. “That makes it impossible to market them for powering anything that requires a quantifiable, reliable amount of energy.”

So the first challenge isn’t determining a use for old batteries, it’s figuring out how much energy they have left. And that’s precisely what Steingart’s team has done. Instead of plugging in batteries to gauge their lifespans, they listen to them.

“We put a sound wave through the battery and listen to how it changes that sound,” Steingart explains. “Once we’re able to determine the accurate amount of energy batteries retain, we’ll be able to sort them for the right application,” Steingart says.

That day will come, but first they’ll have to figure out how to scale the unique technology, as right now it’s too expensive to perform the acoustic test on each individual battery.

Until then, scientists will keep listening to them for signs of life.


Sources: There are more than 2 million electric vehicles on the road around the world


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