How Does an Automotive Battery Engineer Work?

Mark Hughes cuts car batteries open to figure out what went wrong inside.

GM battery engineer Mark Hughes.

Photo illustration by Slate. Image via Jeffrey Sauger/General Motors.

On this season of Working, we left the East Coast behind and flew to Detroit. We’re speaking with eight people who are drawing on the city’s complex history as they work to create its future.

The automotive industry, which has arguably defined Detroit for generations, employs a dizzying array of professionals responsible for every aspect of car design and manufacture. For this episode, which you can listen to via the player above, we wanted to get a sense of one of one of the more eccentric jobs involved in that process. To that end, we visited the General Motors battery lab, where we spoke with Mark Hughes, a recent chemical engineering graduate from the University of California, Berkeley.

Hughes describes himself as a “cell technical specialist.” In essence, he conducts forensics tests on failed batteries, mostly for fully electric cars such as the Chevrolet Bolt EV, though he sometimes works on hybrid vehicles as well.* And while Hughes is primarily dealing with inorganic chemistry, some of the stories he tells us really do sound a lot like medical mysteries.

The lab where Hughes works is an enormous facility, coming in at around 85,000 square feet. It includes equipment that allows the company to put in-development batteries through their paces under unusual and extreme circumstances. (If your memory of how batteries work is, like mine, fuzzy, fear not: Hughes also clearly explains the underlying processes.) They can, for example, test how those cells perform under temperatures higher or lower than any driver would be likely to encounter.

“When those batteries fail … they’re then given to me, and then I perform what’s called a battery teardown,” Hughes tells us. “What I do is I literally cut the pouch that the battery is encased in. I open it up, and I look through the electrodes and try to piece together what happened in the chemistry of the battery during these extremely strenuous test environments.” He and his colleagues then try to create a report that can help the company and its suppliers ensure the next generation of models will function better.

Though Hughes also goes into detail about the other elements of his work, it’s the process of pulling apart a battery and inspecting the insides that clearly excites him most. “The teardowns are absolutely the most fun part of my job,” Hughes says. “Because teardowns are such nonstandard work, there really is no handbook for how to do a battery teardown. … Small variations could result in huge consequences throughout the battery.”

And though Hughes spends every working day examining batteries, he claims that he never gets tired of them. “It’s not even so much the novelty of it, the cool factor,” he tells us. “I like batteries because of the massive potential that I see these devices having.”

Then, in a Slate Plus extra, Hughes talks about his own relationship to cars—and tells us what he drives. If you’re a member, enjoy bonus segments and interview transcripts from Working, plus other great podcast exclusives. Start your two-week free trial at

*Correction, July 10, 2017: This page initially misstated the name of the vehicle the Chevrolet EV Bolt. (Return.)