On June 14, 2016, four researchers at the Jet Propulsion Laboratory were preparing to ship a waist-high, ape-like robot named RoboSimian off-site. They had built the bot to rescue people from dangerous situations that human rescuers can’t hack. The scientists swapped one lithium-ion battery for a fresh one, then left for lunch to let the new power supply charge.

Left alone in the lab, RoboSimian’s battery did what such batteries famously do: went boom. Plumes of smoke vented from the robot’s exposed torso, followed by a burst of flame. Fire filled the room, then stabilized at the size of a toxic campfire. Gather round the burning bionic monkey, everybody. (Don’t.)

Exploding lithium-ion batteries are not new news. Last year’s hottest Christmas present, the hoverboard, was a bit too hot. You can’t take an e-cigarette on a plane because it might combust in the cargo hold. And if you have a Samsung Galaxy Note 7…well…better luck in your next phone pick.

But the magnitude of RoboSimian itself–and that of other lithium-powered NASA projects–set its battery fire apart. “In general, a single lithium ion cell is dangerous, but it can’t cause a gigantic explosion,” says Jay Whitacre, a Carnegie Mellon professor of materials science and engineering who used to do battery science at the Jet Propulsion Laboratory. Cell phones typically have a single cell; RoboSimian had 96. If you’ve seen what a Samsung device can do to your hand, imagine what this robot could have done to the rest of you.

And because NASA builds lithium-loaded vehicles that also go to space–sometimes, someday taking people up there–this fire may feel like cause for concern. The huge sets of cells that live inside robots, spacecraft, and robotic spacecraft? “That’s a lot of energy that’s released very quickly, and it can be fatal,” says Whitacre. “The more you put in one place, the more you have to look at it.”

Pay your interns

According to a presentation that Lynne Lee, the laboratory’s mishap program manager, made earlier this month to senior management, RoboSimian’s boom packed the power of a stick of dynamite. “If you notice where that fire came out, it was exactly where our researchers were standing,” Lee said, as she prepared to share lessons learned as the October Safety Message. “It could have been a very bad day.”

After the initial battery burst, an intern from the next lab over climbed through a window and sprayed RoboSimian with a CO2 fire extinguisher. But the fire persisted–he needed water to quench this combustion, despite NASA’s safety protocol, which called for a Class D extinguisher (no such extinguisher was around, anyway).

Another intern called the fire department. Firefighters, with the benefit of breathing masks, eventually rolled RoboSimian outside by a handle, like some kind of Mad Max Radio Flyer, and killed the fire with water.

So what actually happened here? The final report on why the fire erupted in the first place isn’t ready, says Brett Kennedy, head of the RoboSimian project. But they do have some details about The Incident.

Lithium-ion batteries have a positive side (anode) and a negative side (the cathode), separated by a liquid electrolyte, which is highly flammable. When the battery is charging, ions move from the positive side to the negative side. “When you charge a battery, you put a current through it,” says Whitacre. “And you do it until the battery hits its max voltage. When it hits its max voltage, you should stop that current.” If you don’t halt that flow, the battery can fail and, sometimes, explode.

Kennedy says the battery itself, as a whole, was not overcharged. “There was a monitoring system in place that continuously monitored the overall battery voltage and current,” he says. “Had either the voltage or current to the battery moved out of specification, the charging would have been shut down.”

But based on initial analysis, one cell of the battery was damaged and sent misleading information to the monitoring equipment. As a result, individual cells became overcharged–and kablooie.

While Whitacre couldn’t confirm or deny a specific hypothesis–his evidence coming only in the form of this non-forensic video–he did notice one thing: It all happened fast, not in the slow-burn way of many battery fires.

“Battery packs are made up of a number of smaller cells. It’s common for one of the cells to go a little haywire first,” he says. That cell damages its neighbors, and then they go nuts, and the mess cascades. “This one is a little bit different,” Whitacre continues. “It looks to me like almost everything went at the same time or like one of the cells got very, very hot very quickly.”

A booming industry

Lithium-ion batteries are “an essential part of power in NASA,” Lee said in her presentation. They’re on the Curiosity rover, the OSIRIS-REx craft that just launched itself to an asteroid, the Juno Jupiter mission, and the space station, as well as other current and future ventures.

Plus, adds Whitacre, they’re incredibly common in the aerospace sector generally and satellites in particular.

These batteries make good aerospace solutions because they pack wallops of energy relative to their size, hold a high amount of charge over their lifetime, and don’t lose that charge quickly when left alone. That’s exactly what you want in a space battery, which has to live long and prosper in the vast, empty off-Earth.

And so on systems that actually fly, NASA’s batteries undergo tons of oversight, from procurement to test after test after test. If a battery had inherent flaws, says Whitacre, engineers would know long before it went to space. “I’d be surprised if we ever saw this kind of thing occur in a flight project,” he says.

But if a battery cell or its management system happened to fail–or, as in RoboSimian’s case, failed to foresee a problem because of one cell’s faulty readings–a spacecraft may have inadequate shielding to contain the potentially resultant explosion. Shielding is heavy and every ounce counts when you’re trying to heft stuff to space.

RoboSimian is a non-flight technical project, and JPL is currently looking at how it can be used to “assemble orbital structures, like super big telescopes,” says Kennedy. If future ape-y robot ever went to space, it would go through the full zoo of tests. But because this particular robot wasn’t meant to fly, it–and all other ground-based NASA projects–was subject to less rigor. On top of that, some agency protocols are out-of-date, Lee said in her presentation, before stating that the agency needs to improve and update.

Because you know what they say: With great power comes great responsibility.


  1. Still safer than those tiny nuclear reactors they sent to the moon. Now those could really cause some damage if they exploded.

  2. Thanks for setting me straight. I guess I was born a hundred years too late. πŸ˜‰

  3. You and your modern 13th century definitions. πŸ˜› The original 12th century meaning was “small monastery, subordinate monastery”, it only came to mean the small room later.


  4. It’s fun to rant about hardware, but statistically -for example- the edge 7 is quite present on our websites.

  5. Jeramiah Johnson

    Because Apple is having a Media Field day with Samsungs problems. Using the media make Mt Everast x10 out of a few Samsung Phones that have had an issue.

  6. Nope. A cell was the small room a monk lived in. Some monasteries were quite large.

  7. It’s a double standard. If you put out negative news about Apple, they won’t invite that media outlet to Apple’s next product launch event.

  8. BobbyBobertson

    Any time you try to cram a lot of potential energy into a small area you are looking at the risk of explosive results…

    My solution? The gasoline powered cell phone. Sure… gas is flammable… but we have a lot of experience with internal combustion.

  9. Jeramiah Johnson

    *Shrug* I was thinking the same thing πŸ™‚

  10. Why no mention of the iPhone 7’s catching fire now? Just had a fire in San Jose, CA airport from a random iPhone 7 and a car burning to the ground in other news, and quite a few other stories of it happening

  11. Jeramiah Johnson

    I agree no one is advocating it. Yet the media takes a insignificant (not to the ones it happens to) statistical probability and goes into a feeding frenzy. IF Samsung gave me a Note 7 I would have no fears or concerns with it.

  12. I don’t think anyone is advocating to stop using Li batteries. It is kind of odd though that they’re so useful people are willing to put up with the fact they can occasionally explode in your pocket.

  13. Hypotenus Love Triangle

    Would be nice if they could tell us the Lithium chemistry they used in the battery, that would narrow the investigation a whole bunch. Most likely some form of Lithium Metal Oxide.

  14. Frederick Murre

    Good. Gravy.
    That is the most energetic/awesome lipo failure I’ve ever seen.

  15. Beat me to it. For example, “cell” used to refer to a small monastery.

  16. Bruce Curtis

    The meaning of words can change over time. It’s that queer?

  17. Jeramiah Johnson

    I think the media is having a field day on all of this scaring the crap out of people and derailing perfectly good items reputation.

    Samsung 7’s Fires 112 Unit’s in use 10M +

    Lithium Batteries in use …. I dont know BILLIONS.

    Point is our Tech needs Power and Lithium batteries are the way the majority of them get that power. What we forget the days of Cell Phones needing to be charged every few hours or left permanently on charge?

    NONE OF THIS indicates these incidents should not be investigated to the max to determine product improvement and usage.

    BUT to kill entire product lines for the media feeding frenzy? How does that help? That media feeding frenzy cost jobs, increases product cost.

    *Shrug* we get what we deserve and apparently the majority of us deserve to get the cost of sensationalism, dragging the rest of us with them.

  18. The term “Battery” implies two or more cells. Often folks call a single cell unit a ‘battery’, but that’s not quite correct. The term comes from navy and army history, where you might have one big gun, or a battery of big guns, to defend a fort.

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