That's two areas working against you. Did you try another battery? Why I ask is most are 300 cycle, 18 month affairs and at 2 years, it may be gone.
I've had my S2 for almost 2 years now, I will be eligible for an upgrade in November of this year. My phone got wet about a week or so ago now and well, my battery automatically lost all power. I tried to shut it down and turn it back on but it didn't work. It kept beeping, warning me it was WAY low (as in like 10% low) and wouldn't let me do anything. It wouldn't let me charge it either as I had come to notice water had gotten mostly into my charging port and on my screen (that part was no big deal). I finally managed to get it to charge and left it alone for the night.
The next day the phone seemed to be fine so I went to shut it down and turn it back on. Well, it wouldn't turn back on. It kept flashing the battery symbol. One of them was flashing a battery loading symbol, the other was the battery half full symbol. I immediately took it to AT&T and they informed me I could either get an early upgrade for WAYY to much than I wanted to pay for. They also informed me it was a fried motherboard. They also told me to check with the warranty store itself and see what they could do. Of course my warranty is done, gone, zip, etc.
They were able to get my phone to go into reset mode and then turned on. The guy at the warranty location cleaned out my charging port and set it on the charger. After that day my battery hasn't lasted at all. I took it into a cell phone repair place even and I'm not sure if they even did anything because it didn't seem to be any better. Over the course of the week I noticed my battery didn't hold a charge hardly at all, guessing it lasted maybe 6-7 hours without it going below 30% when before it would last me all day and into the next day without any issue. I also noticed that after it had hit 100%, there was a little icon in the upper left hand corner that wouldn't go away until my battery was considerably lower.
Today I took it in to get a factory reset done. Wiped everything out so I could start over (even though thankfully my pictures and ringtones were still there). Still nothing. At this point I'm ready just to get a refurbished S2 to last me til November when I can upgrade. So we go back up to the warranty location. This time the guy tells my fiance and I to try updating the main program in the phone (IE: Gingerbread to Ice Cream Sandwich). We get home, upload the program and try to do it but my computer doesn't pick up my phone being hooked in with the USB cable. My fiance has the same phone and it hooks up just fine even though the update still doesn't register. I'm thinking we've pretty much narrowed it down to my problem being the charging port itself. We've tried new batteries (the battery I bought at radioshack actually wouldn't charge at all, just shows a flashing battery loading screen over and over again). Hell, my phone won't even shut down anymore unless I take the battery out and after that the battery dies super fast once its put back in.
Again, I'm hoping it is just the charging port and nothing else. I can't afford the early upgrade at all. Anyone else have any sort of problem like this? Could it be the charging port not giving me the charge it needs to last? Or is it something else completely?