@sangye thanks- I considered that, I know the stock wiring was backwards from what everyone expects, so I wired it up the standard way when I soldered on a new standard sized plug (+ is now in the center, whereas it used to be negative).

I had tested that before the extended capacity battery arrived with an AC wall wart adapter, and the GH2 powered on and recorded video just fine, so I already knew that was correct.

Meanwhile, I did a quick test the other night, aimed the camera up close at a birdcage (to get some constant movement), hit record and periodically came back to erase the card and hit record again. So far, made it for a solid 5 hours without breaking even 50% on the battery meter. That's more than enough juice for me, I think I could easily go 10+ hours. And unlike the cheap CCTV ones that I originally wanted, this actually tells me how much capacity I have left, so that's a pro as well.

Downside is that it is quite a bit bulkier than I hoped for, so I need to find a convenient place to stick it.

I highly recommend this one: http://www.cinegearpro.com/hdmi-cables/power-batteries/cgpro-gh2-dmw-dcc8-dummy-battery-dc-coupler-for-panasonic-lumix-dmc-gh2-camera.html Basically it's a modified DC coupler with built-in voltage converter. It plugs into an NP-F battery plate and does not require any DIY adjustments. Works great.

@ghill oh yes, thank! That saves me from building this myself into the coupler, its a bit more expensive, but saves time as well.

@Ciclismo , i bought ready made modules, have no schematics for any of them ...

@ghil , thanks for the recommend! their power kit looks exactly what i needed: http://www.cinegearpro.com/cgpro-external-power-kit-for-panasonic-lumix-dmc-gh2.html

@jakef,

Just to clarify: you used this cable (plug tip adapter) - http://www.ebay.co.uk/itm/190671675522?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649

to connect the cable from the Chinese battery to the dc coupler in the gh2?

Did you have to modify the above cable to get it to work?

I'm a bit confused because it doesn't seem to be the right size for the coupler.

I ended up getting the ATC 15000mAh Power Bank from Amazon. It's awesome so far. I tested it out last night, very unscientifically, so take it with a grain of salt.

After charging the battery for the first time and hooking it up to the GH2, the power bank powered the GH2 for about 15 hours. This included about 10 hours of actual recording time (the camera stopped recording a few times when the sd card was full, and when I noticed it stopped, I wiped the card and continued recording).

I simply hooked up the ATC Power Bank to the Panasonic DCC8 Coupler using tip "D" (the power bank comes with lots of tips to choose from) to connect the two. I don't know wtf you guys were talking about when you said you were snipping and soldering parts to test the polarity, but I didn't have to do any of that. I used gaffer tape to tape the power bank to the back of my shoulder rig, so it acts as an additional counter-weight.

Overall, I'm extremely happy. $53 for a battery that lasts all day. I had been using the stock Panasonic battery along with four 3rd party batteries by Opteka. I'll probably never use those batteries again unless I'm just taking photos without using my rig.

Thanks to @dishe for recommending this!

@Roy_Batty, I don't see any polarity markings on the DC-out cable connecting the power bank to the "D" tip connector (which then connects to the DC coupler).

** Edit: Both ends of the cable will fit the "D" tip, but ONLY one end will fit into the DC-out port of the power bank, so there is no need to worry about connecting the wrong end. **

The battery doesn't seem cumbersome because it sits on the back of my rig. It's acting as another counter-weight.

@Roy_Batty, http://ecx.images-amazon.com/images/I/41T9vviFe3L.SS350.jpg <== enter that whole URL, actual link might not be hyperlinked correctly... That's everything that comes with the power bank. The cable I'm referring to does not have prongs. It just has the single cylindrical shaped tip on both ends. It's the one wrapped up on the far left, 2nd from the top (below the very top wrapped up cable), directly left of the various "tip connectors" that are laying just below the actual power bank.

So I bought this power bank: http://www.ebay.co.uk/itm/New-Black-5V-9V-12V-3-in-1-DC-Rechargeable-Li-ion-Battery-For-CCTV-CAM-Camera-ep-/380435831423?pt=UK_ConsumerElectronics_Batteries_SM&hash=item5893be1a7f that finally got in today. The 9v outlet actually outputs 9.39 v. Is this voltage too high for the GH2 or is it ok? Anybody?

@Alfaerik Could you please elaborate more about it? How did it die?

@JohnTollwannabe, I used it on a 3-4 hour shoot recently (at least 2 hours of being turned on) for the first time since my initial tests. The battery meter still said it was almost full or full, I can't remember. It's great so far. One annoying thing is that the DC-out cable that connects to the "D" is not snug, so it can slip out a easier than you would expect. It happened once while shooting. You can just put tape over it to secure it tighter though.

@Mike_C I bought the same one a month ago. Never used it until two days ago. Did a test of 5 hours continuous (stopped camera twice to change sdxc card) shoot before the camera gives error message "cannot use this battery." I then recharged it overnight but the camera still displays the same error message. I thought maybe it didn't recharge correctly or long enough so i recharged it for another 12 hours. I still get the same error message. Then i tested the usb out port to my tablet. it was working fine for 10mins then the red light turned off. i am pretty sure this battery is dead as it can't be recharged. I am testing a second battery right now. Testing to see how long it will record. after that i will recharge and start over. hopefully it won't fail.