Originally Posted by Vartha
Rhodey had an ARC in his Armor. Watch IM2 again. Just before Hammer walks in to "arm" Mark II, Rhodey takes it out
All of the suits of armor Tony built after the Mark VI had their own ARC reactors, if I'm not mistaken. There's no need to power them off the reactor that's keeping his own heart beating. The suits were able to fly on their own because of their reactors, otherwise they couldn't have come to Tony & Rhodey's assistance. Also, individual pieces of the suits have their own power sources because they can fly independently of the whole.