The iPod uses a rechargeable lithium-ion battery. Unlike players that run on Duracells, you can't easily pop out the old battery and replace it when the iPod wears out after repeated charging and use cycles.
Which is not to say you can't replace the iPod's battery. It just takes a little more time and effort. If your battery is too pooped to power your ’Pod, here are some options:
You get a full year warranty on your iPod battery (two years with the optional AppleCare protection plan). But Apple itself offers an out-of-warranty battery replacement service for $59 at www.apple.com/support/ipod/service/battery.
Laptops For Less (www.ipodbattery.com), offers do-it-yourself iPod battery replacement kits for less than $20.
OtherWorld Computing sells high-capacity NewerTech iPod batteries for all models of iPods. The company has instructional videos on their Web site, but will also replace the battery for you if you send them your iPod (http://eshop.macsales.com/shop/ipod).