Battery Grip BG-E7
By Canon USA

Along with the new LP-E6 battery pack is a totally new optional battery grip for the EOS 7D, called the Battery Grip BG-E7. It's dedicated strictly to the new EOS 7D , and permits one (or two) LP-E6 battery packs to be installed. With two packs, the already-impressive battery life is doubled, compared to using a single LP-E6 pack in-camera. ...