How to Maintain the Life of Your iPod Battery
There are ways to keep your iPod battery healthy. Most important is a lean diet of topping off your battery whenever it is convenient. Using and recharging 100 percent of battery capacity is called a charge cycle. You can charge the battery many times, but there is a limit to how many full charge cycles you can do before needing to replace the battery.
Each time you complete a charge cycle (100 percent recharge), it diminishes battery capacity slightly. Apple estimates that the battery loses 20 percent of its capacity (meaning it holds 80 percent of the charge) after 400 full charge cycles.
Recharging your battery when it’s only half empty does not count as a full charge cycle, but as half a charge cycle. That means you can use half its power one day and then recharge it fully, and then use half the next day and recharge it fully again, and this would count as one charge cycle, not two.
It’s a good idea to calibrate the battery once soon after you get your iPod; that is, run it all the way down and then charge it all the way up (which takes at least 4 hours for an iPod touch or iPod classic, or 3 hours for an iPod nano or iPod shuffle). This improves the battery gauge so that the gauge displays a more accurate reading.
This calibration occurs anyway if you fully recharge the battery, but if you’ve never done that, you can calibrate by disconnecting the iPod from any power for 24 hours to make sure the battery is empty and then fully recharging the battery.
Lithium-ion batteries typically last 3 years or more, but are vulnerable to high temperatures, which decrease their life spans considerably. Don’t leave your iPod in a hot place, such as on a sunny car dashboard, for very long (don’t leave it out in the rain, either — water can easily damage it).
For a complete description of how Apple’s batteries work, see the Apple Lithium-Ion Batteries page.