Dose anyone notice that with the charger case you never get what is being advertised.? I had the mophie helium case for the 5/5s. It would give me a charge but only 40% and that's half of what they advertise (80%). Now I have the belkin grip power with a 2000mAh pack for the 5/5s. It charged me up from 8% to 79%. Now the 5s battery is only 1440mAh. Should I be worried that the cases are defective or it's just false advertisement.