After Apple Japan’s offer to replace any suspected overheating first generation iPod Nano batteries almost 5000 have been swapped in the first 3 weeks.

Apple was put under pressure to make the free battery replacement offer by the Japanese Ministry of Economy after there was 27 complaints about the Nano overheating. A few cases of overheating had caused minor injuries.

The announcement was put on Apple’s Japanese website and in August Apple replaced over 5000 batteries for the device. Apple blamed the battery problem on an unspecified battery supplier.

Figures from the Japanese Ministry of Economy said that over 1.8 million first generation iPod Nanos were sold from September 2005 to September 2006.