Lenovo ThinkPad and Edge battery recall

For some reason I just got the email about the recall today, I guess they imported some email addresses since the footer notes 'You were added to the system April 21, 2014.'.

If you have multiple batteries you can deinstall the program and run it again, since it caches the battery serial number (also after reboot).

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From the FAQ:

Q4. Do I have to return my defective battery?

Answer: No. However, by accepting a replacement battery you are committing to recycling your battery in an approved manner.

Q5. If my battery is recalled, how long will I have to wait for it?

Answer: Orders will typically be processed and shipped within 3 business days. Delivery times will vary based on country.

The FAQ fails to point out the reason for this recall. What's wrong with my T410's battery?