If your iPhone 5s needs charging all the time, it turns out you're not alone. A relatively small number of users have reported that their brand new iPhone 5s battery drains abnormally fast. As it turns out, some iPhone 5s batteries are not performing as they should due to a manufacturing issue, and Apple is moving to correct the problem.
Apple did not specify exactly why the larger capacity 1570 mAh power pack was experiencing the problem in some units, however they are contacting affected customers about the issue. Of course, if you suspect that battery life on your iPhone 5s is substandard, the device is covered by a one year AppleCare warranty. Apple can test the device to confirm there's a problem before issuing a replacement or taking corrective action.
While this particular problem might be new, it's not the first time that iPhones have experienced battery life issues. Major updates to iOS have significantly decreased battery life for some users running older hardware in the past. Apple has issued patches to help resolve these problems as they are discovered. The iPhone 5s manufacturing problem does not involve a defective battery and is not being caused by iOS.
Apple spokesperson Teresa Brewer issued a statement to the New York Times:
We recently discovered a manufacturing issue affecting a very limited number of iPhone 5s devices that could cause the battery to take longer to charge or result in reduced battery life. We are reaching out to customers with affected phones and will provide them with a replacement phone.
In the meantime, there are several iOS 7 battery saving tips that can help reduce power consumption until your iPhone 5s is replaced.