What are the primary energy sources for humanoid robots? What is their typical operating duration or endurance?

Ha, that's a pertinent question, and it's one of the biggest headaches for all robotics companies right now. Let me break it down for you.

Main Power Sources:

Simply put, current humanoid robots primarily rely on two types of energy sources: one is "self-contained," and the other is "tethered."

1. Lithium Battery Packs (Self-Contained) This is definitely the mainstream approach. The batteries are essentially the same technology as those in your phone or electric car—lithium-ion batteries. Inside the robot's body, usually in the torso or back, a large battery pack is installed.

   • Pros: Convenient, no wires to restrict movement, allowing the robot to go anywhere freely. It also looks the coolest, most like something out of a sci-fi movie.
   • Cons: Heavy! And energy density has its limits. The larger the battery, the heavier the robot; the heavier the robot, the more power it consumes for walking and working, creating a dilemma. This is partly why many robots walk cautiously—to conserve power.

2. External Power Supply (Tethered) Many robots being tested and developed in labs or on factory assembly lines are often seen with a thick cable connected to their back.

   • Pros: Unlimited energy! As long as the power grid is operational, the robot can work and be tested 24/7 without engineers worrying about recharging it every hour.
   • Cons: Severely restricts range of motion. It can only operate within the reach of the cable, like a pet on a leash, unable to truly navigate complex real-world environments.

Some future directions currently being explored include:

• Fuel Cells: Such as hydrogen fuel cells, which generate electricity through the reaction of hydrogen and oxygen. They offer much higher energy density than lithium batteries, and "refueling" with hydrogen is faster than charging. However, the technology is still complex and costly, so it's rarely used in humanoid robots currently.
• Hybrid Power: Similar to hybrid cars, a small internal combustion engine might be used to charge the batteries. But this makes the robot's structure more complex and noisy.

Battery Life:

As for battery life, there's a huge variation, and there's no single standard answer, as it largely depends on what the robot is "doing."

You can think of it like your phone:

• Standby Mode: If the robot just stands there, barely moving, only maintaining balance, it can last for a long time, possibly several hours.
• Light Use: For example, slow walking or performing simple hand movements. This is like browsing the web on your phone, and battery life might be between 1 to 3 hours. This is a relatively common endurance level currently.
• Heavy Use: If the robot is running, lifting boxes, or performing high-intensity dynamic actions, the power drains rapidly. This is like playing a graphically demanding game on your phone at max settings; it might run out of power in 20 minutes to half an hour.

So, when you see cool videos online of robots doing backflips or dancing, understand that these are "extreme operations" that consume a lot of power and can usually only be sustained for a very short period.

In summary, for mainstream battery-powered humanoid robots performing meaningful, continuous work, battery life is generally still quite short, typically in the range of 1-2 hours. The ultimate goal for all companies is to enable robots to work continuously for at least 8 hours, like humans, but this remains a huge challenge until significant breakthroughs in energy technology are achieved. Everyone is trying to figure out how to make them "eat less and run further."