The iPhone is fast becoming one of the most used phones in the United States. After being released in in 2007, it has gone through two rounds of upgrades, with the most current being the 3GS. The original iPhone had a talk time of eight hours, and 250 hours of standby time; the new 3GS boasts a talk time of 12 hours, and 300 hours of standby. The problem is that the iPhone is so versatile in what it can do (Wi-Fi or 3G internet, various applications, music, etc.), that it can be difficult to know exactly how long your battery will last. Luckily, there are a few applications that can help you answer that question.
Open the "Settings" application. Once the application is open, click on the "General" tab. Click on the "Usage" tab and turn on the "Battery Percentage" button. This will enable the percentage to be displayed in the top-right corner, next to the battery icon.
Download the "BatteryTime" application (See the link to the Apple Website in the References section). This is a free application that you can download from the App Store; Battery Time gives you more information about your battery: It gives you, for example, detailed information about how much battery time you have remaining and how long it will last for each of the various activities the iPhone is capable of.
Download the AppBox Lite or the AppBox Pro application (See the link to the Apple Website in the References section). The Lite version of this application is free, and the Pro version is $.99. This application is similar to the BatteryTime application, in that it gives you detailed information about how long your battery will last for each type of activity you do with your iPhone. What makes this application potentially better than the BatteryTime is that it also offers other uses in addition to the battery gauge: currency converter, loan calculator, flashlight and more. The Lite version has nine applications, and the Pro version has 18 applications you can use.