The Old Mixer wrote:
Which brings me to a WTF concern I had when his malfunctioning suit lost power as he was getting to TN...since when does the movie IM's suit have a separate power supply that runs out of gas? I thought his suits were run by his palladium / IM2-ium chest piece? Even if they have separate power supplies that allow them to be operated remotely or worn by other people (as they clearly do), why couldn't he keep power going with his chest unit?
It really only made sense to use the heart-power-cell when no other options were available (in the cave and/or when he had not yet mass-produced the power cells). He was draining a vital function everytime he got in the suit, and it's probably not healthy to constantly be performing surgery on one's self.
Granted, the heart-power-cell did have the benefit of added security (limiting the ability of non-heart-power-cell-wearing individuals to use the suit), but it sounds as if Tony beefed up other types of security on the suits.
As for using the heart-power-cell as a back-up: it may have simply been a case of the new suit being incompatible with the heart-power-cell (at least, without heavy modifications or taking the heart-power-cell out of Tony's chest).