[Q] [H] Sony Xperia Neo V MT11i & Battery Problems topic

Hello guys, in first place good forum :). Keep up the good work. Now my question. Since 2 weeks ago my cellphone Sony Xperia Neo V MT11i was experiment some problems with the battery. Some days later the battery just dead but this is the weird part: the battery inflated. Well, np I just bought another battery. 5 days ago, the same problem... Now im using a new battery for third time and its working but with problems like "slow interface", "graphics problems", "random disconnections" and I worried about it. Today I checked the battery and it's starting to inflating...

So, guys, please can somebody help me, what is the problem? I read in other forums about the board, but i'm not sure. What you think is the cause and where can I buy that replacement?

Thanks in advance.