Nikon has announce a voluntary recall of certain EN-EL 15 rechargeable batteries because they can short circuit and overheat, potentially deforming the battery. This battery model came with Nikon D800, D800e, D7000 and Nikon 1 V1 digital SLR cameras and is also sold separately.
The affected batteries are only models EN-EL15 with a Lot Number containing E or F as the 9th character.
If you purchased one of these spare batteries or a related camera model since March 2012 when they were first distributed, you can exchange the faulty battery for a different one by filling out a form and sending it along with the battery back to Nikon.
For all the details, visit the Nikon web site.