The Canon EOS 5D Mark II and Canon 7D digital cameras can really suck up power, especially when shooting HD video. That’s why the Switronix PowerBase 70 Battery Pack is such a valuable accessory. The PowerBase 70 delivers six times more power than the original battery supplied with either of those cameras.
If Captain Kirk were shooting HD video with his Canon EOS 5D Mark II or Canon 7D DSLR and the battery were running low, he could simply shout out, "Scotty, I need more power!" But if the dilithium crystals were spent, Scotty would have no alternative but to pull out the Switronix PowerBase 70.
The PowerBase 70 is a 70 watt-hour, 14.8-volt Lithium-Ion battery pack that mounts under the camera and provides up to six times the power of the original Canon battery. The PowerBase 70 can double as an auxiliary grip or be attached to an HDSLR support via its 1/4"-20 release plate or V-Mt mount.
Wired as a 14.8-volt battery pack, the PowerBase 70 features two PowerTap outputs that can provide extended power for two 12-volt accessories such as lights, monitors and HD converters. The battery pack can also power lower-voltage devices using an optional XP power regulation cable. Additional 1/4"-20 threads on either side of the PowerBase 70 battery pack can 
be used to mount accessories. An indicator gauge consisting of four LEDs can show you the battery pack’s charge status at a glance.
The PowerBase 70 battery pack measures 6.25 inches wide by x 1.8 inches high by 3.3 inches deep and it weighs 1.4 pounds. Because it adds considerable weight to the camera a DSLR video rig or some other kind of support system for the camera will yield more stable video.
The PowerBase 70 battery pack does not come with a charger. Fortunately B&H carries the Switronix PB70C, which is the exact charger you need.