How can I diagnose an iPad that seems super slow to recharge? I've had my iPad 1 for almost a year now.  For the past few months it has been charging EXTREMELY slowly.  

Last night I plugged it in with 54% remaining on the battery life.  This morning it is only at 81%.  It charged for 17 hours!  Is this normal?  The battery seems to last just about as long as it used to (once it's finally charged). 

I am using the standard wall charger.  I have also tried using my friend's charger and had the same result.  Any suggestions?
Be sure you are using an iPad charger. If you are using a standard USB charger or an iPhone/iPod charger then it will take a very long time to charge.