Hold on a sec. What 3s 5Ah 20C battery are we talking about here? Some may be rated for 20C, but they don't hold up to that in the real world. In reality, they should be realistically rated for something like 15C. And if that's the case, 5Ah won't be enough. If using cells that fall into this category, I would shoot for a 120A value or more to be safe.