Anyone who buys 3rd party P2 batteries to save a few bucks is in my opinion flirting with disaster. Unless you plan to cover your Phantom in bubble wrap and fly it over a field of packing peanuts, how do you trust that you won't be hovering at 120m when it loses all power and your Phantom craters. I'll never know what happened to one P2 I was flying over water when some people closer to it than me said it suddenly tilted at a 45 deg angle, then flipped and dropped the 20 feet into the water I was flying over. I just fitted it with the new GoPro Hero 3+. snifff.
It could have been anything from a list of 5 to 10 possibilities.... pilot error being one of them, but not likely, because it was not very windy and I was not doing anything extreme or flying it past it's capabilities. Everything was stock DJI, except the blades, which I stupidly tried a knockoff on both my Phantom Vision and my P2. They looked and seemed to work exactly like the original, so it never crossed my mind, but after I replaced my P2 and got the nerve to fly it without the safety net again... I was flying about 30-45 mins with one battery change. I came down for the second time - landed on the deck of the pier I was flying over and as soon as the skids touched down, one of the blades popped off and spun about 30 feet off the pier onto the sand..... Wait a minute... what!!!!??? Yep, the supposed self tightening blade took off like a boomerang. Sure enough it was a Hong Kong Fooey blade, so I tossed all of them in the garbage and didn't make that mistake again.
Just a little word of warning is all. You're flying $1500 +/- worth of gear - hundreds of feet above ground and possibly peoples heads - to potentially save $75??? Even DJI gets it wrong pretty often lately and well.... they ARE DJI.
I have owned 4 Phantom 2s so far. Other than the unsolved mystery of the P2 that bellyflopped - I have never had catastrophic fails happen in flight. I will NOT be tempting fate with potentially sub par batteries or other flight critical parts.