The iPhone 5 differs in this regard to some extent, and has an improved battery life over previous models. However, it is really expensive. You can also consider used models. Both new and used iPhones have similar battery life if you are purchasing them from reputed stores. The good thing is that unlike the new models, there is no heavy price associated with used models, and you get all the same features. So buying a used Apple iPhone 4 or any other model may be more feasible for you.

Nevertheless, the battery life of any iPhone can be improved in certain ways. So before purchasing a new model or buying a used Apple iPhone 4, you should be aware of these tips.

• Screen Brightness: Set the brightness to a lower value if you are comfortable with it. The dimmer the screen, the longer the battery will last.
• Auto Brightness: iPhone features a light sensor which automatically adjusts the screen's brightness according to the surrounding light so that the screen can easily be read at all times. The screen becomes dark in less light, and becomes bright when there is more light. You should turn on this feature so that your battery consumes less power.
• Bluetooth: If you use wireless headphones or earphones, then you will need to use Bluetooth. Try to use wired accessories because turning on Bluetooth at all times uses up a lot of the battery's power.
• 3G: 3G networks are characterized by fast data speeds and high quality calls. No one really likes slow connections, but you should turn off 3G if you want the battery to last longer. You can use EGDE instead. You can even switch between the two networks from time to time. This would save some power.
• Wi-Fi: Wi-Fi is faster than 3G but it may not be available in all regions whereas 3G is everywhere. If you can access a hotspot in your location, Wi-Fi should be your foremost choice. Many people keep Wi-Fi turned on in hopes that a hotspot might become available. But this utilizes battery, so switch off Wi-Fi Even when there is no hotspot nearby. You can easily turn it back on later.
• Location Services: iPhones have a built – in GPS. You can use this for navigation, directions and even for finding nearby restaurants and attractions. But once again, turn off this feature if you are in your native land and do not need additional information.
• Apps: Many people find it difficult to turn off so many features. So for these people, specialized apps are available that automatically switch off unused programs and save a lot of battery power. If you are buying a used Apple iPhone 4 or another model, download this app as soon as you can.