I purchased a Mophie Gold Battery Case for my iPhone 5S which is supposed to recharge my 5S at 100% once I deplete the battery charge from my 5S at 0%. The one I purchased sold for $99.99. The Mophie Case for $79.99 charges at 80%. Months ago, I purchased one at Best Buy and it only charged at 60%, so I returned it. Because I really like the case, I repurchased the exact same case at Nordstrom a couple weeks ago. But it will only recharge my 5S at 62% when I deplete it to 0-1%. Obviously, there's consistency of only a 60% charge for both cases. Do you think I'm losing 40% charge from these battery cases because it takes me 3-4 days to utilize the charge after I deplete the charge from the 5S? I'm not a huge data user, therefore I can go without charging my 5S for 3-4 days.