Ipad2 'Not Charging'. Is it at least being powered by USB?

[Lobsang]

Hopefully some Doper ipad2 owners know the answer to this.

I understand that my PC's usb port is not powerful enough to charge the ipad, so it says 'Not Charging'. I accept that, and am quite happy to use the plug to charge it (I'd do that anyway).

But what I want to know is, does the USB provide enough power to at least power the ipad while it's plugged in? In other words is the battery draining while it's plugged in and syncing (requiring the screen to be on)?

I ask because some sync jobs can take a while, and I worry that a low battery ipad will run out of juice before the sync is complete.

[The Niply Elder]

As an iPad 1 owner I'd say yes, enough juice is provided to power synching jobs.

[Lobsang]

Thanks. Good to know

[jharvey963]

The way I've heard it: The USB doesn't have enough juice to BOTH run the IPad and charge it at the same time. So anytime you turn it on, it says "not charging". But when the IPad is OFF, the USB DOES charge the IPad. I regularly charge my IPad just by leaving it hooked up to the USB overnight.

J.

[Dewey Finn]

BTW, my understanding is that the newest Macs can charge the iPad via the USB port. So what sort of USB ports do they have that allow this? Because I have a nearly new Windows PC and I would think it would have up-to-date USB ports.

[dracoi]

Originally Posted by Dewey Finn

BTW, my understanding is that the newest Macs can charge the iPad via the USB port. So what sort of USB ports do they have that allow this? Because I have a nearly new Windows PC and I would think it would have up-to-date USB ports.

Not all USB ports are powered. Built-in ports probably are, but ports on peripherals might not be. (I'm not sure exactly how the USB specifications define it).

As an example, I have a USB hub that has its own power adapter. When I plug in that adapter, I can charge a device like an iPad from that hub. If I don't plug in the adapter, I can still sync, but not recharge.

[groman]

Originally Posted by Dewey Finn

BTW, my understanding is that the newest Macs can charge the iPad via the USB port. So what sort of USB ports do they have that allow this?

Unfortunately I believe the answer is non-standard.

The USB standard used to provide for two types of host devices with regards to current draw:
1) 100mA unpowered hub
2) 500mA powered host

Then, at some point, a third type of non-host charger device was added (which was indicated using shorted data pins):
3) Up to 1500mA high-speed charger

Then, later, another concept was added
4) 1500mA charging downstream port, which is essentially a combination of 2 and 3.

It seems from my experiments, the iPad nor the newer Macs conform to the USB spec #4 correctly, and use some sort of a proprietary protocol to negotiate higher than 500mA charging current.

[AaronX]

I haven't paid attention, but I don't think I've ever seen my iPad say "not charging", when plugged into my MacBook Pro or iPhone charger. When left overnight, it's full the next day.

[Onomatopoeia]

I just tested this with my iMac.

If I plug my iPad into my iMac's keyboard's USB, I get a Not Charging message in the upper-right of my iPad, but it stays at the same level of power and allows me to continue working even with very minimal battery juice left.

If I plug my iPad into one of the USB ports on the back of my iMac, it charges the device as I'm using it, and I do not get the Not Charging message.