I am using the USB cable provided with the iPad 2 and it is plugged directly into a wall socket as it has always been. The problem arose after updating to 5.1.1
It was charging perfectly fine prior to the update and it was plugged in during the update and as soon as the update was done, my iPad 2 displayed 'Not Charging' while still plugged in. I did a a hard reset multiple times, I let it stay plugged up overnight even while it said 'Not Charging' just to see if it would charge or not and it did not charge. Apple and their software updates are killing me and my $700 toy! And $700 is a lot!!
The quickest way (and really the only way) to charge your iPad is with the included 10W USB Power Adapter. iPad will also charge, although more slowly, when attached to a computer with a high-power USB port (many recent Mac computers) or with an iPhone Power Adapter (5W). When attached to a computer via a standard USB port (most PCs or older Mac computers) iPad will charge very slowly (but iPad indicates not charging). Make sure your computer is on while charging iPad via USB. If iPad is connected to a computer that’s turned off or is in sleep or standby mode, the iPad battery will continue to drain.
Apple recommends that once a month you let the iPad fully discharge & then recharge to 100%.
How to Calibrate Your Mac, iPhone, or iPad Battery
At this link http://www.tomshardware.com/reviews/galaxy-tab-android-tablet,3014-11.html , tests show that the iPad 2 battery (25 watt-hours) will charge to 90% in 3 hours 1 minute. It will charge to 100% in 4 hours 2 minutes. The new iPad has a larger capacity battery (42 watt-hours), so using the 10W charger will obviously take longer. If you are using your iPad while charging, it will take even longer. It's best to turn your new iPad OFF and charge over night. Also look at The iPad's charging challenge explained http://www.macworld.com/article/1150356/ipadcharging.html
Also, if you have a 3rd generation iPad, look at
Apple: iPad Battery Nothing to Get Charged Up About
Apple Explains New iPad's Continued Charging Beyond 100% Battery Level
New iPad Takes Much Longer to Charge Than iPad 2
Apple Batteries - iPad http://www.apple.com/batteries/ipad.html
Extend iPad Battery Life (Look at pjl123 comment)
New iPad Slow to Recharge, Barely Charges During Use
Tips About Charging for New iPad 3
Prolong battery lifespan for iPad / iPad 2 / iPad 3: charging tips
In rare instances when using the Camera Connection Kit, you may notice that iPad does not charge after using the Camera Connection Kit. Disconnecting and reconnecting the iPad from the charger will resolve this issue.
An employee at the Apple Store said a lot of people are experiencing this problem after the 5.1.1 update. It's been charging fine and I had it pluged in while updating and as soon as it updating, like as soon as meaning as soon as it came back on after the final step from updating, the ipad said 'Not Charging' I am still going to try some different sords and different ways of charging but either way, it should charge as it's always been. If anything good comes out of it, I will post for sure!