MagnusXL
You'd think giant mech-things would at least use batteries.
Extension cords are lame and inefficent.
...in that case, anyways.
Well, that's sort of the point. The power supply is their limiting factor. Otherwise, they'd be completely unstoppable. And when a protagonist becomes unstoppable, they are no longer interesting.
And, if I might add, they did have internal batteries. That's what keeps them going for another five minutes. The idea is that they just consume so much energy that not even a highly advanced internal power supply can support them for long.