The Apple iPod uses a rechargeable, lithium-based battery that can go between 10 and 36 hours between charges, depending on the model. You can charge your iPod using either an electrical outlet or your computer's USB port, but if you find that your iPod no longer takes or maintains a charge despite having the right connections, you should try some basic troubleshooting methods to restore the device's battery life.
Connect your iPod to a different USB port or wall outlet. If you use a USB port to charge your iPod, you may simply have a low-powered port, according to Apple. You can often resolve this by switching the cable to a different port, or using a wall charger (sold separately) to recharge instead. Charge your iPod for several hours. If you find your iPod completely unresponsive even as it charges, leave it plugged in for three or four hours and check again. If your battery life has been depleted completely, the iPod will need time before it can begin functioning again. Restart your iPod. A frozen or dysfunctional iPod may fail to charge, but a quick reset can fix basic functionality glitches. To reset a touch-wheel iPod, hold down the "Select" and "Menu" buttons until the gray Apple emblem appears on the screen. For iPod Touch, hold down the "Sleep" and "Home" buttons (the only two buttons on the device). Connect your iPod to your PC using the provided USB cable, open the iTunes software and click the "iPod" tab in the left column. Then click the "Update" button to search for and install the latest iPod software. Apple recommends keeping your software up-to-date to ensure that your battery life remains fully optimized. Purchase a new battery from Apple. If your battery fails to charge despite all your troubleshooting efforts, it may simply be too old and depleted to continue functioning. By taking advantage of Apple's iPod Out-of-Warranty Battery Replacement Program (see Link Below), you can send in your iPod and receive a replacement battery or replacement http://www.apple.com/support/ipod/service/battery/
iPod for a modest fee.