Bay Area researchers discover longer battery life in EVs, meaning more miles for drivers

PALO ALTO, Calif. (KGO) -- We have a look under the hood at a study that's generated a lot of buzz for people considering an electric vehicle.

Bay Area researchers recently estimated that electric vehicle batteries last far longer than first believed.

The winding roads around Stanford are the perfect place to test drive an important discovery. Our wheelman is Professor William Chueh, Ph.D. from the SLAC National Accelerator Laboratory.

"Can I give you a jolt?" Chueh said, smiling as he pressed the accelerator of his Tesla.

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Chueh is demonstrating the real-world driving conditions that may help EV batteries last much longer than even the manufacturers estimate. But first, it might help to tap the brakes and take a look at why those battery life projections are so different. To do that, fellow researcher Alexis Geslin braved the cooling fan noise to take us into a testing lab at the SLAC-Stanford Battery Center.

"So, here we have a room full of cyclers and environmental chambers to cycles, meaning charging and discharging batteries to study how they age," Geslin said.

And, he said the team used a row of small oven door chambers to study how the EV batteries age, but in a new way. Instead of just draining them at a constant rate, like the smooth graph at the top of the screen, they also introduced variables--electronic starts and stops that more closely mimic actual driving conditions.

"So, more realistic representative of real driving. And, you can see both the voltage response of the battery and the current are very dynamic," Geslin said.

It was dynamic and unexpected. They say the data suggests average EV battery life may be roughly 40% longer than estimated. It is a result that's the opposite of what the team theorized.

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"And our hypothesis was, if you use the battery in the real environment--where there is a lot of frequent charging, frequent discharging--that the battery would have a shorter lifetime. We were blown away when the result was exactly the opposite, that when we use the batteries in a real fixed setting, the lifetime was much longer than expected," Chueh said.

Back on the road, Chueh demonstrated what they believe is going on. First was the effects of drifting downhill on our winding road.

"So, now we're going downhill. So, now you're continuously charging the battery, and I'm not breaking. The act of going downhill regenerates the battery slight," he said.

Next, he pointed out the power that's recovered by the friction of the brake pads. It is a technology known as regenerative braking.

"Now, with the braking. Here we go, and we're recharging the battery, just a little bit," he said.

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And they say all those starts and stops add up to more potential battery life than projected. While technologies are constantly evolving, the SLAC team is hoping the findings will help manufacturers update their battery management software. It would potentially save owners money and make electric vehicles an even more attractive option.

"So, I completely agree that affordability drives social acceptance. And in this case, a battery time lifetime is an implicit cost driver. So, it's not something you can put a dollar amount to it on day one. But, if you knew that the battery was going to last 10 years rather than five years, then that's going to be a significant driver for adoption," Chueh said.

It also, perhaps, creates a smoother and more affordable road ahead for millions of EV owners.