Dear David,
Was your iPad sleeping while it was on the charger or was it active?
I ran some power tests yesterday. It's important to remember that not only does the new iPad have a battery that is 70% or so larger, it draws substantially more power when running (the reason for the new battery).
Testing with two different Apple AC chargers that I have, it looks like the total charge time for a sleeping iPad should be in the 5-6 hour range (that's going from approximately 0 to 100%). But… trying to charge a wakeful iPad takes more than twice as long as that. Most of the wattage being put out by the charger is going to run the iPad, not to recharging the battery.
You'll see similar effects if you're using the new iPad plugged into a USB port. My iPad2 would hold just about steady plugged into a standard powered USB hub, it would drop maybe 1-2% an hour. The new iPad drops more than 5% an hour. 5 W just isn't enough to sustain it.
Note that these results for wakeful iPads are going to depend very much on the brightness setting for the screen and the processor load. There's no way I'm going to tear my iPad apart and run proper tests on it, but it wouldn't surprise me if at the extremes power consumption ranges from under 5 W to over 10 W.
Not being willing to dig into my precious toy, I have no idea if the internal circuitry can stand much more than 10 W of charging power. If it can, I wouldn't be surprised to see a “fast” 15-20 W charger become available. There are some users who will be vexed by the substantially longer charging time. With the older iPads, you could pop it on the charger over breakfast or lunch and get enough juice to run for the next half day or over dinner to carry you through the evening. That's not going to be the case with the new iPad.
Absent such a “fix” we're just going to have to make some mental adjustments and consider this the price we're paying for a whole slew of major improvements.
pax \ Ctein
[ Please excuse any word-salad. MacSpeech in training! ]
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PS: note to hosts––sorry about the URLs in my sigs in my previous posts. It's just embedded in the macro boilerplate and I don't notice it. I'll try to remember to edit them out by hand. Sorry for putting you guys to the inconvenience.