From Tim Moynihan at Wired, a description of the third iteration of Honda’s Asimo robot:

“ASIMO has sensors everywhere: Force sensors in its fingers to make sure it’s not crushing things, sensors in its waist that help it climb up and down stairs, image sensors in its eyeballs help it gauge its environment and make decisions. It takes a lot of battery power to drive this complex humanoid: A 13-pound lithium-ion cell that takes three hours to charge.

That battery is stashed in ASIMO’s ‘backpack,’ and it can power about 40 minutes of continuous walking, according to Shigemi. When ASIMO senses it’s running low, it automatically seeks out its charging station and plugs itself in.

But even when ASIMO is still and silent, its ‘muscles’ are constantly working.”