I did order a second Anker as the other users didn't report any problems, but having to work for the last 7 days and having heavy rain all the time there was no chance to even use one load of the battery at all, so I can't tell you if this copy works better, but I really hope so.
Here's what Paul Abrahams said in this thread
viewtopic.php?f=2&t=5523&p=42447&hilit=anker#p42447I have the Anker Astro 3 (bought off ebay - Search for: Anker Astro3 External Battery Pack 10000mAh 5V 9V 12V 2A iPad3 iPhone Galaxy Tab) it at least doubles the run time of the camera. The Anker can put out 9v or 12v comes with a charger and the main power cable fits the BMCC socket. The PB70 is rated at 14.5volts the Anker is slightly under that at 12volts, I do also think the PB70 is of higher Amperage too, hence the reason it lasts longer.
A rough guess:
The Anker will at least Double the run time
The PB70 will Quadruple.... so take that into consideration when thinking about price.
So the PB70 is 3/4 times the power.
I have noticed the Anker gets very warm and drains quickly which also shows that it only just copes with powering the BMCC. I was concerned that the power might be weak? Meaning the BMCC loses its power whilst sitting turned off. But I came home today after topping it up with the Anker last night and the BMCC is still showing 100% which is promising. I have noted my BMCC, when turned on, drains down to 50% within half an hour so its a power hungry beast!
In the long term the PB70 seems to be the current best option. Would I get two Ankers? Not sure, I might end up ponying up for the Switronix. But I'm hoping another company comes out with a cheaper alternative who knows maybe NAB might have some goodies in store.
For me the Anker was a cheap, quick solution, for you guys in TAX land it could be throwing money away. At least with the PB70 it will hold its value for resale and will definitely power your BMCC for a shoot.