The Switronix 3-Stud Plate / Battery / and Charger for Blackmagic Camera Kit from B&H -- the battery features a run-time of about 3.5 hours for a camera drawing about 25W of power. In many user forums, the Blackmagic camera has been reported as drawing approximately 20W for common, non-RAW-capture applications. Under such assumption, and if considering a 1/5 difference between 20W and 25W, the battery will power the camera for about 4 hours. Also to be considered in the calculation is whether the internal battery of the camera is fully charged, for if it isn't, it will trickle charge -- charge very little by little -- off of the 3-stud, increasing thus the power draw of the 3-stud and decreasing its run-time. The battery is a 14.4V, 98Wh lithium-ion. The Blackmagic camera accepts batteries from 12-30V. The battery can be legally transported without restrictions under IATA, ICAO, and UN regulations. In addition to a DC port, the battery has two P-Tap ports for accessories to be connected into and to be powered by simultaneously with the camera.
The plate for the battery has two P-Tap ports for accessories to be connected into. Any accessories thus connected would draw power from the attached battery. For connection to the battery, the plate features an integrated 20" cable with a DC connector. The plate can't be attached directly to the Blackmagic camera, as most types of accessories can't since no space is available on the camera for them. The plate would instead need to be mounted on a cheese plate, like Zacuto's Zwiss Plate, and the cheese plate onto a rig along with the camera.
The included charger connects into the battery's P-tap connector and delivers a full charge in 4-5 hours.