It's not quite as easy as changing batteries on a Walkman, but you can change your generation 3 iPod's batteries yourself.
For more about why you might want to replace your iPod's battery yourself and what your other options are, see "Replace Your Generation 1 or 2 iPod's Battery" [Hack #15] . If you think you want to try the operation yourself, be sure to also read the disclaimer at the beginning of that hack.
Here's what you'll need for this hack:
A thin, flathead screwdriver; I use a 2.5-mm flat blade made by Wiha of Germany (http://www.wihatools.com)
The PDA Smart plastic disassembly tools
A guitar pick (the hard plastic kind, not the newer rubberized kind)
A new iPod battery
Far and away, the best tool for the job is the one supplied by PDA Smart, because it's plastic and won't scratch or mar the original case. Since I'm of the school that a ding here and there adds character to an item, I just use a screwdriver. A guitar pick is easy to get hold of and will get the job done, but it's a pain to work with.
The iPod batteries are all standard off-the-shelf units, so it doesn't matter where you buy them. PDASmart.com (http://www.pdasmart.com) and ipodbattery.com (http://www.ipodbattery.com) are both good sources. PDASmart.com also provides the plastic disassembly tools noted previously.
The G3 metal case backs are much tighter than the G1 and G2 iPods' case backs and contain some limited electronic components (the audio port hardware is soldered onto the metal case back). Thus, the metal case half is tethered to the main component board by a very delicate ribbon cable that you should not disconnect; the cable is extremely delicate!
Turn off the iPod and place the hold button on (so orange is showing).
Start on the left side of the iPod. This is very important, because there's another ribbon cable on the right side that you can easily damage when you insert your prying tool between the case halves. I've found that the best place to insert the tool is right next to the Back button (perhaps known as the Rewind button for those of you joining the iPod from analog land) on the iPod's front.
Once you've inserted the tool, pry it up and unclip the middle of the five clips on the left side that are holding the two case halves together. Once that one is unclipped, the other four will come undone rather easily. With the left side free, the two case halves will also come apart easily.
Be careful with the tethered connection between the two halves! Do not stress that ribbon cable too much. I disconnected it to make photography easier, but laying the metal half on a book or just holding it while you perform the rest of the procedure is much safer.
With the metal case half unclipped, lay the iPod on a flat surface so the LCD display is facing down and the metal half is to your left. The large metal object you're looking at is the PCMCIA-based hard disk. It is surrounded by a blue Delrin (a high-tech rubber material) shock isolator and is sitting on another blue Delrin shock isolation pad. That second isolation pad has a ribbon cable on it that connects the hard drive with the main board.
Carefully reach under the bottom blue Delrin pad and disconnect the low profile connector for the hard drive. The drive and Delrin pad will still be connected. Figure 1-47 shows a G3 iPod with the main board detached from the main enclosure half.
The battery is the black plastic rectangular object in the upper-right corner of your iPod. It is not glued in or attached in any way other than by the battery cable. Disconnect this with the needle-nose pliers, and slip the connector cables under the corner of the main board.
Put the fresh battery in place, work the connectors around the main board cable, and plug them in.
With the drive out, as shown in Figure 1-48, you can now easily see the shock isolation pad mentioned earlier; it's the big blue thing hanging off the hard drive. The easiest way to get the drive back in is to unplug this pad from the drive itself so you can reconnect the extremely low-profile PCMCIA connector on the main board. Just grab the copper connector on the drive and gently pull it off. Being a PCMCIA connector, it is fairly robust; don't be afraid to tug a bit.
The low-profile hard drive connector (in the upper-right corner of Figure 1-48, surrounded by black insulating plastic film) and the connector (in the lower-right corner) should not be disconnected.
Once the drive and isolation pad are apart, connect the ribbon cable on the isolation pad back onto the main board. If you flip the pad over, you will see an extremely low-profile, black, 40-pin connector (yup, I counted!) that will snap into its mate in the lower-right corner of the main board. Snap these two connectors back together. It can be a bit tricky, so just take your time and pay careful attention to the feel; it should positively snap into place. Press it down to ensure a good connection; you don't want to snap the case halves back together only to discover that you didn't connect the drive properly. It's a delicate job, but the low-profile connector is fairly robust, so don't worry about damaging the pins as you blindly slide the two connectors together trying to get them to mate.
With the ribbon cable reconnected and the isolation pad installed, slide the hard drive back onto the copper pin connectors. The iPod does not utilize all of the PCMCIA interface pins, and the connector lines up with a block on the lower right.