The iPhone 6 is expected to sport a number of upgrades, including a better battery. However, Apple Inc. (NASDAQ:AAPL) fans may be disappointed this year, as the battery improvement might not be much of a boost from the battery of the iPhone 5S.

Apple iPhone 6

iPhone 6 battery smaller than expected

Reports from Chinese media citing unnamed “foreign media sources” claim that the 4.7-inch iPhone 6 will have a batter of between $1,800 and 1,900 mAh and that the 5.5-inch model will have a 2,500 mAh battery. Although these batteries are slightly better than the 1,560 mAh battery that’s in the iPhone 5S, the larger displays are going to need much of that extra power to run the bigger displays and offer a performance that’s similar to that of the smaller iPhone 5S.

Also those numbers keep Apple firmly behind competing handsets of similar sizes. Samsung Electronics Co., Ltd. (LON:BC94) (KRX:005930) included a 3,200 mAh battery in the 5.7-inch Galaxy Note 3. And higher resolutions use more battery power, so if Apple bumps up the resolution as well, users may not see the battery last much longer than the previous model.

Why Apple may keep the battery small

According to Mac Rumors, some are speculating that Apple is sacrificing battery size in order to keep the iPhone 6 ultra-slim. Also it’s possible that significant improvements in iOS 8 will further stretch the battery life of the smartphone. Also Apple’s next-generation A8 chip will play a role in exactly how long the batteries last.

Apple is expected to unveil and launch the iPhone 6 in September. The company might show off both models on the same day or hold back the larger of the two for a later launch. In addition to a better battery and the next-generation A8 chip, the smartphone is expected to feature Apple’s Touch ID fingerprint scanner and possibly look like the iPod Touch. It’s expected also that Apple will charge about $100 more for the 5.5-inch model.