The BG-N5 Battery Grip from Vello is designed specifically for the Nikon D3100 DSLR camera and accepts one or two Nikon EN-EL14 batteries. With two batteries installed, your shooting time is effectively doubled. More so, when one battery is drained, it can be removed and recharged while you continue shooting with the other battery.
The design of a battery grip offers a comfortable and secure way in which to hold your DSLR, especially in the vertical position. And the BG-N5 comes with an alternate shutter release button to facilitate shooting when held vertically. In addition, the BG-N5 is designed with anti-slip rubber grip to further improve handling, a tripod socket to mount your camera directly to a tripod and a wonderful touch: a holder for the camera's battery door so as not to lose it when it has been removed to install the battery grip.