Babak

I actually don't like the battery mentioned in the OPs video and others like it, because you will have no idea what the discharge status of the battery is while using it. I bought one of these on ebay for about $60:

http://www.amazon.com/Naztech-PB15000-Universal-Charger-Extended/dp/B007URKIGC/ref=sr_1_cc_3?s=aps&ie=UTF8&qid=1382108393&sr=1-3-catcorr&keywords=15000+mah

Over a year ago, except mine was 18000 instead of 15000mah. And it was a silver version, but otherwise identical unit. I had to record a concert and couldn't swap batteries in the middle of the show, so I wanted to be safe. This thing comes with tons of plugs, and a 5V USB DC-out plug that works independently of the regular DC out. So what I generally do is run the main DC out to the camera at 9v, and the 5v USB goes into my Tascam audio recorder. It powered everything I needed to go on for well over 8 hours. It comes with all the plugs I needed, and it worked so well that I've used it for all-day shoots (8+ hours) and have never had the battery run down on me yet!

 

A couple of things you should know:

The DC-coupler from Panasonic has a weird polarity- the positive and negative parts of the plug are the opposite of what is generally accepted in the electronics world. Some say this was done on purpose to keep parts being proprietary to Panasonic, but who knows. I bought a new standard sized plug from radio shack for less than $1, cut off the plug on the DC Coupler and attached my own with some solder and Sugru (I *love* sugru!). Plug works great, but for a less messy approach, I've seen some adapters for sale that might work too.

 

As far as how the voltage thing works... there's been a ton of research on the GH2 doing this on other forums, but I'll give you the gist of it.  These cameras have a range of voltage. The battery for the GH2/G6 is 7.2v fully charged, and as long as the camera recognizes it as a Panasonic battery (with the ID chip embedded inside), it will happily chug along until it reaches low enough that it is in danger of shutting off (I don't recall where that is, maybe 6.8v?), and will signal the camera to gracefully shut down so you don't lose your footage. 

 

But here's the thing- without an ID chip telling the camera it is a Panasonic battery, the camera WILL NOT ACCEPT an 7.2v power source. It will complain and say you aren't using authentic equipment. But it will accept a 9v one. 

 

Why? Because Panasonic's DC-coupler has no ID chip either. It's just a pass-through that feeds direct current to the battery cavity of the camera. It seems that Panasonic designed the camera to be able to tell if it is running off a battery vs AC adapter by looking at how much voltage is coming in. Is it more than 8.4v of direct current? Must be using that AC adapter, don't bother checking the battery ID. It is less than 8.4v? It must be a battery and we must require a chip ID!

 

Long story short... assuming the G6 uses the same batteries and adapters as the GH2, it is designed to operate at 9v constant power. The problem is, it assumes that the source is consistent and not coming from a battery. That means that unlike using batteries, where it will detect voltage dropping if the battery is dying and gracefully shut off, here if your external battery pack drops too low it will just suddenly shut off without warning. So you really need to watch the voltage on the external battery. This is why I don't recommend the battery in that video above. It will work fine, but it has no battery meter and neither will the camera when using it. The one I linked to has a life meter on the LCD display, which is really wonderful if you need to keep an eye on it.

@dishe thank you for you very useful post on the external battery solution. I have a GH2 and am looking for some reliable external battery and yours seems to be the one! I have a few question and will appreciate your reply: If the camera will shut off when the battery reaches a voltage bellow 8.4v, at which point do I have to switch the camera off manually (in order not to loose the recorder footage)? In other words will the battery's LCD indicator warn me before the selected 9v drops down? And for the correct polarity, what are the adaptors to use if I don't want to replace the plug on the DC-coupler (I am very bad with soldering...)? Thanks for your reply.

@dishe thank you for you very useful post on the external battery solution. I have a GH2 and am looking for some reliable external battery and yours seems to be the one! I have a few question and will appreciate your reply: If the camera will shut off when the battery reaches a voltage bellow 8.4v, at which point do I have to switch the camera off manually (in order not to loose the recorder footage)? In other words will the battery's LCD indicator warn me before the selected 9v drops down? And for the correct polarity, what are the adaptors to use if I don't want to replace the plug on the DC-coupler (I am very bad with soldering...)? Thanks for your reply.