Building a Working Robot Step-by-Step

Without a power source, Asimo is just a complicated sculpture. Currently, its power source is a rechargeable, forty-volt, nickel metal hydride battery that lasts for thirty minutes on a single charge. However, the battery takes four hours to fully charge, so additional batteries are necessary if Asimo is to operate for a long stretch. The weight of the battery, stored in Asimo's midsection, helps create Asimo's center of gravity, keeping it stable and balanced.