How to make my iphone 4 battery last about 5 days?

I'm going to reading festival an i really need my phone the whole time and iphones literally run out of charge in like a day and a half at most! Is there anything you can buy, maybe like a portable charger thing, that would keep you battery going for about 5/6 days?

You could always buy two or three spare batteries and take them with you fully charged then when one runs out just change the battery

External battery or an external battery case is your only option. Google it.

Buy an external battery like this one http://www.ebay.co.uk/...1511396251

Okay. So This is what I recommend.
1.) Keep your phone on airplane mode. It charges 3x faster and saves your battery.
2.) Keep your phone on lowest brightness possible.
3.) KILL YOUR APPS! When you're done using an app click the home button twice and if you have iOS 7 then your apps will show up and you put your finger on them and swipe up. If you have iOS 6 you click the home botton twice and a 'multitasking' bar will show up at the bottom with the apps you have recently used. Hold them down as if you were going to delete them and click the X button on the top left corner and that kills the app.
4.) Slide your Wi-Fi off & Location Services off.
Hope this helps

-Put your phone on airplane mode
-Disable all unused apps
-Put on Power saving mode (If you have one)
-Buy a portable charger (Basically a battery you connect to your phone with a usb cord)