Robots run out of energy long before they run out of work to do − feeding them could change that
by James Pikul , The Conversation, June 2, 2025
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…Though most robotics research into the energy problem has focused on better batteries, there is another possibility: Build robots that eat.
Robots move well but run out of steam
Modern robots are remarkably good at moving. Thanks to decades of research in biomechanics, motor control and actuation, machines such as Boston Dynamics’ Spot and Atlas can walk, run and climb with an agility that once seemed out of reach. In some cases, their motors are even more efficient than animal muscles.
But endurance is another matter. …
The issue isn’t how robots move – it’s how they store energy. Most mobile robots today use lithium-ion batteries, the same type found in smartphones and electric cars. These batteries are reliable and widely available, but their performance improves at a slow pace: Each year new lithium-ion batteries are about 7% better than the previous generation. At that rate, it would take a full decade to merely double a robot’s runtime.
Animals store energy in fat, which is extraordinarily energy dense: nearly 9 kilowatt-hours per kilogram. That’s about 68 kWh total in a sled dog, similar to the energy in a fully charged Tesla Model 3. Lithium-ion batteries, by contrast, store just a fraction of that, about 0.25 kilowatt-hours per kilogram. Even with highly efficient motors, a robot like Spot would need a battery dozens of times more powerful than today’s to match the endurance of a sled dog.
And recharging isn’t always an option. In disaster zones, remote fields or on long-duration missions, a wall outlet or a spare battery might be nowhere in sight…
If robots are to play meaningful roles in society assisting the elderly, exploring hazardous environments and working alongside humans, they need the endurance to stay active for hours, not minutes…
Some researchers are building systems that let robots “digest” metal or chemical fuels and breathe oxygen. For example, synthetic, stomachlike chemical reactors could convert high-energy materials such as aluminum into electricity…
Other researchers are developing fluid-based energy systems that circulate like blood. One early example, a robotic fish, tripled its energy density by using a multifunctional fluid instead of a standard lithium-ion battery… [end quote]
I didn’t realize what a limitation battery power is for robots. Real-world applications from household robots to drones to swarms of tiny insect-like robots would be vastly expanded if the robot could quickly refuel.
Wendy
