Multiple times I have had my iPhone shut itself off due to low battery at percentages above 5%. Today it happened at 17% - either iOS BLOWS at calculating battery percentage, or there's something wrong. I have not been performing intensive tasks when the battery dies, i.e. mostly due to texting, etc. As a side note, my iPad mini often goes down to 1% without dying. Anybody else frustrated by this iPhone issue? Or do I have a problem with my battery?