Why not charging when plugged into Mac?

Because your iPad needs more power than your USB port can supply. Read about charging in the User Manual available on iBooks or the Apple support site.

Well, yes, some will charge slowly. Honestly, the best thing for you to is read the user guide section on charging.

If the Ipad doesn't have a build in current sensor that some app could read I wonder how it know it is not charging ?

This is one of the top 10 asked questions and we can hope the next OS update might give more on screen charging information.

Example: Master, if you give me 0.1 amps more I'll change this not charging message to charging.

B0b wrote:
This is one of the top 10 asked questions and we can hope the next OS update might give more on screen charging information.

One of the top 10 asked questions?!? Hmmm.......

There's a useful section in the new "iPad Made Simple" book from Apress (Gary Mazo and Martin Trautschold). It says:

"Will my iPad charge when connected to my computer?

The answer is: "It depends."...
Most Mac computers, some Windows compueters and some powered USB hubs...provide enough power to charge your iPad...but we discovered that with some Windows laptops, the iPad definitely charged fine in sleep mode, even though it said "Not Charging" while it was awake."

So it looks like it depends, as previous posters have said.

You just need to look in the iPad manual from the Apple site on p23 as I've said 3 times now. No need to buy books or speculate.

*From the Guide*: Charge the battery: The best way to charge the iPad battery is to connect iPad to a power outlet using the included Dock Connector to USB Cable and 10W USB power adapter. When you connect iPad to a USB 2.0 port on a Mac with the Dock Connector to USB Cable, iPad may charge slowly while syncing. Important: The iPad battery may drain instead of charge if iPad is connected to a PC, to a computer that’s turned off or is in sleep or standby mode, to a USB hub, or to the USB port on a keyboard.

Lots more useful info in the Guide.

The USB 2 soecification is that a USB port must supply up to 0.5A at 5V (= 2.5W)

The iPad cannot both run and charge the battery from such an 'ordinary' USB port.

With USB now a popular way of powering and charging devices, seems that Apple and maybe other manufacturers are enabling their USB ports to supply more current.

I'd guess that the iPad actually communicates with the Mac/PC/charger using the USB data lines to determine what current can be drawn and defaulting to only draw 0.5A.

The "Not Charging" message is a bit alarming because you see it when you have just taken your lovely new iPad out of the box and are setting it up using iTunes. Makesyou think it's broken if you don't read the manual (and let's face it, who does). I'd suggest that Apple puts something in iTunes so that an explanatory message appears when the iPad is first plugged in.


Some devices like early 3G dongles came with a Y cable to plug in to two USB sockets to obtain 5W power.

A well made USB port is Current limited.

I have a new USB3 card that says it is limited to 0.9 amps but I forgot to plug in the 4 pin Molex external power cable so can't really test.

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Top questions when I got my Ipad on day one was:

1. Where do i plug in the ear buds.
2. Why is it saying not charging when syncing to Itunes via USB.
3. Where am I going to hid the Ipad so my sister doesn't see it and want one too.

How about 3 messages:
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1. Charging
2. Not charging
3. Not discharging as fast.