The Electric: Humanoid Robots Are Cool—but How Will Their Battery Problem Be Solved?
Adam Jonas made his name as one of the biggest Tesla bulls. These days, people are flooding the Morgan Stanley analyst with questions about humanoid robots. The volume of calls has exceeded “the entirety of our [automaker], dealer and supplier coverage combined,” he said in a note Friday.
Tesla’s Optimus robots likely sparked the enthusiasm for humanoids among Jonas’ clients. At a Tesla event in October, a dozen or so prototypes operated by staff behind the scenes served drinks and gabbed with amused guests. CEO Elon Musk, presiding over the event, said Optimus would “basically do anything you want,” and that future sales of the robot would drive Tesla’s value to $25 trillion.
Jonas is not convinced. Robot sales are not part of his forecast demand model, which goes through 2040. Though he did not cite battery life as a reason, it’s a key problem.
Battery power, it turns out, is a primary limiting factor in the deployment of humanoids: A small number of humanoid robots now work in factories. They have a runtime of only about an hour and a half when they’re carrying stuff and moving around.
It then takes up to an hour to recharge them. That means a factory or warehouse would have to keep two or more robots on hand for each task, swapping them out for recharging. “It’s a major hurdle for humanoids to actually be a realistic tool for any business that is looking to add them to their operation,” said Steve Crowe, editor of The Robot Report. “They need to figure out how to make the batteries last longer.”
Roughly 4 million industrial robots were in operation globally last year, of which some 382,000 were in the U.S., according to the International Federation of Robotics. Almost none were humanoids. Instead, most sat in one place and remained plugged in, or they moved on wheels, which is far more efficient than walking around.
In the U.S., there is at least one humanoid robot working under a paid contract. Digit, made by Oregon-based Agility Robotics, can carry around 30 pounds of stuff in its arms. Some Digits are now moving merchandise around a Spanx apparel distribution warehouse in Flowery Branch, Ga.
Agility’s engineers have tried hard to maximize Digit’s battery life. They’ve packed as many cylindrical batteries as they could into the robot’s torso, Agility chief technology officer Pras Velagapudi told me. The batteries are nickel-manganese-cobalt with graphite anodes—among the densest chemistries in current lithium-ion batteries. Still, the robots can work for just one and a half to two hours on a charge. It takes 50 minutes to an hour to get them back to a full charge, he said
For now, Velagapudi said, his focus is on making the charging process as fast as possible: The goal is to get Digit to charge in, say, 10 minutes, and then work for 100 minutes. In that case, total runtime matters less. The robots could charge while humans take their breaks, he said.
The Digit drains its batteries most quickly when it is carrying heavy things. Some of that is offset by power generated when the robot walks and swings its arms. It’s similar to regenerative braking in an electric vehicle.
“It’s not necessarily about running forever,” Velagapudi said. “It’s about running for a long time with respect to how much you’re charging to get an overall good, useful amount of work out of the robot over time.”
Velagapudi gave limited details about Agility’s future strategy. When I asked whether the company planned to use silicon anodes, which would allow superfast charging and could also increase Digit’s working time, he said only that he’d consider anything as long as it doesn’t surpass the robot’s weight and mass maximums.
While the need is great, the battery industry has been slow to respond: Since the Tesla event, I’ve asked multiple battery startup executives about humanoid power requirements. Earlier this month, as we reported, SES AI CEO Qichao Hu released a prototype battery with silicon that he said could power robotics, though he did not mention humanoids; none of the other CEOs had reached out to robot developers to find out what they needed.
Battery developers have eagerly pursued other futuristic uses besides EVs for their products, including powering space-going satellites and flying electric taxis. With EV demand sluggish in the U.S. and Europe, automakers appear to be less interested in deploying next-generation batteries; the developers of silicon and lithium-metal batteries need new markets.
If Musk is right about future demand, humanoids are a rich new opportunity. Crowe, the newsletter editor, said some humanoid prototypes have three hours of uptime, but that that’s not enough either. It’s a major issue for the nascent industry. “A three-hour battery life is not really acceptable,” he said.