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Power from USB

Gtatler

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Question. When connected to my PC USB port my iPad states "not charging". My ipodtouch could recharge from the USB port. Anybody know why the difference ?
 

sjleworthy

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Most computers don't deliver enough energy to charge your iPad via the USB cable. Most won't even keep the charge constant, whilst some newer computers deliver enough charge to charge up your iPad very very slowly. This is a known fact and most normal.

The best solution is to use the wall charger. Even this can vary in times depending on what and how many power hungry services or apps you have open in memory at any given time, whether the iPad is off or on even.
 

giradman

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Agree w/ the previous post - this is an oft asked question and a little searching would have provided much information - :)

The iPad charger provides 10W of power (basically 5V x 2Amps); below is a partial quote from a Wiki article on USB (part of the 'power' discussion) - the numbers come no where needed to charge your iPad; a 'twickle' charge may be provided w/ the higher power USB options but you'll still see the no charging indicator; as suggested use the wall adapter or a similarly powered alternative - good luck!

The USB 1.x and 2.0 specifications provide a 5 V supply on a single wire from which connected USB devices may draw power. The specification provides for no more than 5.25 V and no less than 4.75 V (5 V±5%) between the positive and negative bus power lines. For USB 3.0, the voltage supplied by low-powered hub ports is 4.45–5.25 V.[SUP][38][/SUP]
A unit load is defined as 100 mA in USB 2.0, and 150 mA in USB 3.0. A device may draw a maximum of 5 unit loads (500 mA) from a port in USB 2.0; 6 (900 mA) in USB 3.0. There are two types of devices: low-power and high-power. A low-power device draws at most 1 unit load, with minimum operating voltage of 4.4 V in USB 2.0, and 4 V in USB 3.0. A high-power device draws the maximum number of unit loads permitted by the standard. Every device functions initially as low-power but the device may request high-power and will get it if the power is available on the providing bus.[SUP][39][/SUP]
Some devices, such as high-speed external disk drives, require more than 500 mA of current[SUP][40][/SUP] and therefore cannot be powered from one USB 2.0 port. Such devices usually come with Y-shaped cable that has two USB connectors to be plugged into a computer. With such a cable, a device can draw power from two USB ports simultaneously.[SUP][41][/SUP]
 

giradman

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It takes my ipad over 2hrs to charge up to 100% from a wall charger, is this normal?

Well that's a 'loaded' question - :) We need to know at what level of discharge that you plug in your wall adapter? Two hours when the iPad's battery is pretty much discharged is as expected - check this Apple Battery Support Article for more information -good luck!
 

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