This is a little known gem of information shared with me by someone-in-the-office (you know who you are), and when retold to others they have all exclaimed ‘Why didn’t I know that before!!’, so I thought it might be worthwhile sharing a bit wider.
If your iPad is taking aaaaages to recharge then check the charger plug. The iPad charger is 10W and and the iPhone charger is 5W. Chances are they have somehow got mixed up, and you are using the 5W charger to recharge your iPad.
Look at the veeeeeery small print on the bottom of the plug to check which one you are using. The 10W plug can charge both iPhone and iPad, the 5W charger will charge the iPhone fine, but the iPad super slowly.
Hope that tip is helpful!