Yes, the iPad charger is 10W vs. the iPhone charger being... a lot less. iPad sucks down juice.
Some things I've learned from various places, summarized:
- Both chargers can be plugged into either device. No damage. No problems.
- iPhone charger is tiny. iPad charger is big. (ha...)
- iPhone charger will take FOREVER to charge even iPad 1. Use iPhone charger for iPad 2 or worse, 3... you might as well walk away and forget about using the iPad for a while. (GRIN)
Here's where it gets interesting. I plugged new iPad 3 into iPad 1 charger and cable. Seemed faster than iPhone charger, but slower than it should have been. Did some digging and found...
- There are two types of cable that look almost identical for the USB to iPad connection. USE THE ONE THAT CAME WITH THE SPECIFIC IPAD.
Here's why. Numerous reports of iPad 3 charging SLIGHTLY slower with iPad 1 cable or left-over cable from iPhone... unless it's a recent iPhone 4S.
Now... I can't find any Apple docs that support this, but the new "tougher" cable has a longer strain relief on it, and MIGHT... note I say... MIGHT... have some differences in the little resistors they hide inside to signal to the devices that they can dump more power to the iPad 3.
You can see the difference in the USB cables here:
http://thenextweb.com/apple/2012/03...ck-connector-cable-to-be-tougher-and-thinner/
And you can read and decide if you "believe" the charge speed issues with the new vs. old USB cable, here...
https://discussions.apple.com/thread/3811768?start=30&tstart=0
More objective info is that iPad 3 has a bigger battery to feed the hungry GPU for the nicer screen. It's gonna take a while to charge at 10W. Apparently Apple decided they couldn't go any bigger with the charger. Probably a heat limitation.
Another fairly well confirmed "rumor" is that the iPad 3 will show "100%" charge when it really isn't. This is pretty common with modern Lithium Ion charging control chipsets. It will continue to trickle charge up to a full point which can give an additional 1/2 hour to 1 hour depending on usage and backlight settings (the number one power draw in an iPad) if you leave it on a while after it says "100%".
For even more "confusion" based in reality of charging setups, if you're charging the iPad off of another device... the USB port needs to be able to negotiate and offer 1A of charge current. Apple devices utilize a voltage on the D+ D- pins to negotiate the charging current available. This was done before the USB standards folks caught up to them, and prior to that USB ports could only offer up 500 mA. Later, they could offer up 900 mA if high speed data transfer was going on, and higher if no data being sent.
http://en.wikipedia.org/wiki/Universal_Serial_Bus#Charging_ports_and_accessory_charging_adapters
The very newest spec is apparently (from that article, I haven't seen any yet) allowing up to 5A total draw, and 1.5A per device.
If you're going to charge iPad, say... in the cockpit... from 12VDC, you need to make sure you're using a charging device that can offer up 1A to that USB cable. There are TONS of USB chargers that say "iPad compatible" and they're not really lying... but they'll only feed 500 mA per the old USB spec. Test after you get any cheapie USB chargers for 12VDC after you get it, and send it back to China if it won't charge the iPad in a reasonable amount of time.
I have an HP laptop from work that will not charge at the higher USB 3.0 specified rates unless an OS with USB 3.0 drivers is up, running, and talking to the ports. If you use the laptop as a charger while it's asleep or shut down, it'll drop to the 500 mA rate. Not great for iPad.
Later model iMac, MacBook Pros and what-not in Apple's lineup use that voltage trick on the data lines to allow a higher rate charge, even when the desk/laptop is asleep or whatever... old machines with USB 2.0 ports may not charge iPad at the highest rate available.
But wait... as the barker says... there's more!
Because of the varying standards, things like built in car iPhone plugs may or may not charge iPad (or iPhone) at higher rates. I have an older GM car adapter hard-wired into one of the XM channels in my Yukon. It adds an even stranger flair to this game... it charges at a fairly low rate, but also to protect itself and the car battery from thermal problems and also from getting sucked dry by iDevices... shuts off the charging circuit every 10 minutes. It charges at a high enough rate through the "real" dock connector it utilizes that an old iPhone 3 would almost get a full charge in that amount of time (about 75%) but an iPhone 4 VZ, not even close. An iPad? Fuggetabout it. The only way to charge the iPad off the truck in my setup, is to keep unplugging it and plugging it back in.
Auto manufacturer's built in cables? It's a crap shoot. Hunt Google for the answer from someone with enough time on their hands to time it. LOL.
In general, iPad 3 is a power hog... but it's manageable. And it helps a lot if you use the right chargers and cables so you're not always in a "I'm behind on charging" eight-ball.
I'm seeing similar run times to the iPad 1 doing things like Foreflight, etc... but that's at half or lower on the screen backlight (similar to what I learned from Kent long ago about iPad 1). Go to full brightness, and any iPad will be dead in just a little over two hours, typically.
