Juice Pack Helium is very different from the many alternatives that debuted at CES: Mophie is positioning Helium as a thinner and more refined sequel to earlier Juice Packs, rather than as the most powerful or affordable battery case around. On paper, it seems anemic for its asking price: there’s only a 1500mAh battery inside, which only promises to refuel an iPhone 5 to 80% of its initial capacity. This capacity falls below every other iPhone…