Need a way to power your GH3 longer? I showed an example of a GH3 in a video cage using an external power solution. For those who might be interested in the same solution, here's another fairly popular external battery kit originally put together for Panasonic GH2 shooters, but now states it has recently been revised to work with the new Panasonic GH3 camera.
There is also an optional 12 pin Hirose to 12v cable available if you're looking to power 2/3" video lenses (B4, B3) lenses. The GH3 external rechargeable battery kit comes with a charger, properly sized barrel tip cables, and a GH3 DC Coupler a.k.a (kit found here).
Panasonic GH3 External Battery Power Kit
John -- if you haven't read this and are still considering adapting B4/B3s to the GH2/GH3, check out this fantastically thorough article on the subject: https://www.streamingmedia.com/Producer/Articles/Editorial/Featured-Articles/Adapting-Servo-Zoom-Lenses-for-Smooth-Zooming-DSLR-Production-Part-1-80668.aspx
@John Frey - I have not tried one yet for the GH3, been working mostly with the 12-35 and 35-100, or prime lenses.
How well does the Pan 2/3" lens work with the GH3? I come from a background of broadcast cams/lens and would love to get one working on my GH3. Problems/issues? Found one on EBay today for about $450.00.