I bought an iPad3 and have been wondering why the battery takes seemingly forever to charge. Well, like many people I have multiple chargers collected over the years, from the flip-out plug type (the best) to the static plug with the green dot (smallest, but inconvenient).
If you get out a magnifying glass, your problem might be solved by reading the fine print on the charger. Chargers designed for the iPad are 5.1W and output 2.1A — slightly more "pressure" and double the "flow rate" of the 5.0W, 1.0A of my charger labeled iPod. It stands to reason that the newer charger will work a lot faster, and it makes sense that Apple would have to beef up iPod chargers because the batter is so much larger than an iPhone's or iPod's.
Last night, with 13% battery left, I plugged in my iPad3 to the iPod charger. Unused and four hours later itreached 42%. At that rate that's almost a 16-hour charge from zero to full. Unacceptable.
I plugged in the iPad charger (2.1A). It seems to be charging considerably faster. In less than about 15 minutes I've gone from 47% to 50% — and that's while using apps that require internet access. Extrapolating, that's about an 8-hour charge from 0% to full. More acceptable.
Certainly not the most scientific of experiments, but it's good enough for me: Make sure you're using the correct charger with the correct device. Someone suggested using a LabelMaker and putting stickers on them. Good idea.