With more and more manufacturers opting for a non-removable battery in their smartphones, it's not too surprising that external battery packs have become more and more popular. Being able to charge your device without being tied to a wall outlet, is a pretty big deal. And Innori's 15,000mAh battery pack is also a big deal. That is about 5x the size of most batteries these days. And is currently on sale for just $29.99.