iPhone 4 won't recognize charger, even after replacing dock connector

Over the past two weeks, my Iphone has been having issues not recognizing the charging cable or dock when plugged in. I started to get the "Charging is not supported with this accessory" message when plugged in to the wall, followed shortly thereafter by the phone not charging when plugged in. The phone is dead now. I tried different cables, different wall adapters, car chargers, and docks all with no luck. I did a little research and found out that the dock connector could have gone bad due to moisture or wear and tear from 3rd party docks. I ordered a new dock connector and installed it by following the how-to on ifixit.com. The phone still doesn't recognize chargers or docks.

I'm not sure if it is a battery issue, because I can still hold the power button down and get the screen showing the emtpy battery with the plug + lightning bolt below it. This leads me to believe that there is still enough juice to power up the screen, so it's not completely drained. Battery life before this problem was average for a 2 year old Iphone 4.

I guess my next course of action will be to try to exchange the new dock connector for another new one to verify it wasn't a faulty part. If that doesn't work I am leaning toward replacing the battery, but I'm not sure if there is anything else I could be looking for.

Does anyone have any advice or ideas about what else could be causing the phone to not recognize the charger when plugged in?

Thanks in advance!!