Perhaps you’ve heard about the “million-mile battery” — the latest buzz phrase electric vehicle proponents hope will energize public interest in buying EVs.
If you haven’t, Elon Musk will make sure you do on Tuesday, when Tesla goes online for what it’s calling Battery Day. Musk is expected to detail a million-mile battery project — along with, he teased on Twitter, other “exciting things.”
Musk’s teasers don’t always pan out. But the idea of a million-mile battery offers real promise.
“[I]t would eliminate one of the big negatives associated with electric vehicles,” said Donald Sadoway, a materials chemist and battery expert at the Massachusetts Institute of Technology: the car owner’s fear that the battery will die and require costly replacement.
But because the battery industry is loaded with start-ups and inventors promoting their wares, often before they’re ready for prime time, Sadoway suggests some skepticism is in order.
What is a million-mile battery?
A million-mile battery does not mean you can drive a million miles between recharges. It means a battery that will last for 1 million miles or more before it can’t hold a charge strong enough to power an electric car anymore. Regular recharges every few hundred miles would still be needed to keep a car or truck powered.
Today’s batteries face limits on the number of times they can be recharged. Right now, most car batteries are rated to handle about 1,000 full charges total. Manufacturer warranties on car batteries top out at about eight years and 150,000 miles — which is proving conservative, as car batteries in general are outlasting their warranties. A battery that lasts 1 million miles could handle 4,000 full recharges or more.
So what makes it a big deal?
No car is likely to last 1 million miles. It would fall apart long before that. But it’s possible to design cars so that batteries can be swapped in and out. Individual car owners, theoretically, could keep their batteries and install them into new car bodies. A long-lasting battery could increase a car’s resale value.
Perhaps more important, swappable batteries could power long-haul trucks, city buses and driverless robotaxis, all of which log many miles a day, every day. The same batteries could also pump energy into the electric grid when the vehicle’s not being used, with less worry about battery life degradation.
For those applications, “this would totally change the game,” said Shirley Meng, professor of nano-engineering and materials at UC San Diego.
Tesla, which has aspirations to build electric semi trucks and deploy fleets of robotaxis while attempting to build a grid energy battery storage business, plans to begin manufacturing batteries itself. It currently buys batteries from Panasonic and LG Chem.
Do any million-mile batteries exist?
Maybe. China’s battery manufacturing giant, Contemporary Amperex Technology Ltd. (CATL), said in June it is “ready to produce” a battery that will last 16 years and 1.2 million miles but hasn’t said much more about it.
The battery would cost 10% more than the typical battery CATL sells now, company Chairman Zeng Yuqun told Bloomberg in June. No detail has been provided on the battery’s inner workings, its weight, range, energy or power, and no carmaker has yet announced an interest in buying it.
No battery maker beyond CATL has made a million-mile claim. If Musk announces he’s ready to produce one, it would raise eyebrows throughout the industry.
Battery Day “certainly creates some buzz,” Sadoway said. “But remarkable claims require remarkable proof.”
If Tesla has an edge, what is it?
It’s not clear yet that it has one. A research paper released last September by Tesla-funded scientists at Canada’s Dalhousie University reported they’d created a million-mile battery in the lab. The team was led by Jeff Dahn, a major figure in lithium-ion battery research who began working with Tesla in 2016.
The three-year project showed that by using specific combinations of cathode and electrolyte materials, charge-recharge limits could be pushed from about 1,000 cycles up to 4,000 cycles, a major step toward longer-lasting car batteries.
A big question for Musk on Battery Day is whether his manufacturing plans are getting ahead of the science. Some leading battery experts express scientific skepticism. It’s one thing to show results in a lab, quite another to develop manufacturing lines and turn out large volumes at a profit.
“Dahn is very famous, he’s very good, he’s committed to his work,” said Vince Battaglia, who heads the Battery Storage Group at the Lawrence Berkeley National Laboratory. “This is interesting. Who knew you could do so many cycles?”
Yet he calls some of the methods and findings “different from my own.”
Battaglia noted the batteries Dahn’s lab tested were far smaller than the cells that would be used in electric vehicles. “I don’t know what’s going to happen when you make those bigger cells and the temperature gets a little hotter inside. You’ll maybe get back to an eight-to-10-year life,” Battaglia said. Dahn said he stands by his findings.
The website Electrek, which sometimes gets advance looks at Tesla’s plans, last week published pictures of unusually large battery cylinders it said Musk might introduce. The cells in Tesla’s current cars look like slightly larger AA batteries. These look like junior-size beer cans.
Perhaps Tesla will reveal convincing data to show those cells can boost energy density and cost efficiency to reach a million-mile cycle life, Battaglia said — but it’s a tall order.
What about the cost?
“The big question here is how it’s going to increase cost,” said MIT’s Sadoway.
“The battery price I think will go up, because dollars per kilowatt-hour will go up,” Battaglia said. “Maybe Tesla buyers will spend extra on a battery that will last longer.”
Meng, of UC San Diego, said such a battery could be considered an asset for the car buyer. If the battery can be swapped into other vehicles and last 1 million miles, it will retain a certain value, said Meng, who drives a Tesla herself. How much that might be is unknown. “It will take some economists looking into this to show how the equations will be changed,” she said.
So can Musk be trusted?
Musk created a new and significant market for electric cars. His SpaceX sends rockets into outer space and lands them on barges. He has pushed the envelope with driver-assist technologies. He has accomplished much.
Yet his promises in recent years have far outreached performance. A semi truck unveiled in 2017 has yet to be produced. He predicted 1 million driverless robotaxis by the end of this year; so far, Tesla is on pace for zero. (The company doesn’t make self-driving cars, never mind 1 million robotaxis.)
A solar roof project announced with a nonfunctional prototype in 2016 remains an experiment. Grand plans to solve traffic problems with underground tunnels have amounted to a single tourist attraction in Las Vegas.
Musk has overpromised and underdelivered on battery technologies too. In 2013, he put on a show to demonstrate a plan to build a network of stations to swap batteries for Tesla owners and relieve range anxiety. Only a single station was built. Little used, it was dismantled, but not before the California Air Resources Board gave Tesla extra emissions credits for the effort, which it later sold at a profit.
Musk has set a high bar for himself on Tuesday. In a conference call with stock analysts in 2017, asked about a Toyota solid-state battery project, he said this:
“You know, I could give you a PowerPoint presentation about teleportation to the Andromeda Galaxy. That doesn’t mean it works,” he said. “When somebody has like some great claim that they’ve got this awesome battery, you know what, send us a sample. Or if you don’t trust us, send it to an independent lab, where the parameters can be verified. Otherwise, [shut up].”
Lawrence Berkeley’s Battaglia said Musk could silence the critics with one simple statement. Tesla’s battery warranty is good for eight years and 150,000 miles. “Musk could extend the warranty to 15 years,” Battaglia said. “You think he’ll do that?”