Some first gen iPod nanos have defective batteries
Apple warned customers via email that: In very rare cases, the battery in the iPod nano (1st generation) may overheat and pose a safety risk. Affected iPod nanos were sold between September 2005 and December 2006.
The company also said that the risk of overheating increases with age, and since the models included in the replacement program are already more than five years old, that likelihood is ramping up for at least some owners.
Apple isn’t saying how many iPod nanos it expects to replace, although there are plenty of reports coming in from users saying they have one that’s eligible for replacement. Two iPod nanos The Mac Observer checked — purchased several months apart — both qualified for replacement.
Apple’s website includes a page where first generation nano owners can see if their unit is eligible for replacement. The replacement process, however, isn’t quick because Apple is saying turn around from sending defective units in to replacement delivery is about six weeks.