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I want to buy an iPad charger for in my car. I have one now for my iPhone, but he won't charge my iPad. I know batteries use mAH to denote capacity, so are chargers rated by mAH or some other measure?

What kind of specifications do I need to charge my iPad in my car at a normal speed (equal when connecting to the power network).

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You don't generate mAh, it's a unit for capacity, but you provide an amperage. –  Max Ried Mar 14 '12 at 11:49
    
That's what I figured... So it should be mA instead? –  Michiel Mar 14 '12 at 12:07
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Yes. Either A (= Ampere = 1000 mA) or mA (= Miliampere = 0.001 A) would be appropriate. In the iPad's case 2100mA - 2,1 A. –  Max Ried Mar 14 '12 at 12:12
    
Are you looking for the amount of current needed to have the device say it is charging in conjunction with using the iPad (display on, programs running, etc..) or the bare minimum where it will charge even when off or the device is sleeping with the screen off? –  bmike Mar 14 '12 at 17:32
    
I would like to use Navigon and charge it at the same time... It would be nice to use other programs too while charging... –  Michiel Mar 14 '12 at 18:17
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4 Answers 4

up vote 3 down vote accepted

The original Apple charger has an output limited to 2.1 A at 5.1 V.

I occasionally charge my iPad 2 Wifi with the old charger of my passed Palm Pre. It provides an amperage of 1 A at standard 5 V USB voltage.

I don't know if you can go even lower than 1 A, but the standard USB amperage of .5 A is not enough to charge it. It shouldn't be a problem to get a car charger that is capable of handling 1 A, more is better.
Make sure you buy one, that is capable of charging an iPhone as Apple devices tend to observe the USB standards and try to communicate with the charger. Some dumb China elcheapo chargers may not have USB logic inside and your iDevices could refuse to charge.

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To confuse things, iPhone and iPod touch chargers in the US are rated at 5W and iPad chargers are rated at 10W. I believe it delivers 2 A at 5 V in case that helps you select an auto charger that meets similar amperage and voltage. –  bmike Mar 14 '12 at 17:39
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To make it even more confusing, the 10 W iPad charger is no 10 W charger, but a (2.1 A * 5.1 V =) 10.71 W charger... –  Max Ried Mar 14 '12 at 18:45
    
haha, lol :) Thanks @MaxRied for your answer! –  Michiel Mar 16 '12 at 13:37
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You have the voltage wrong in the first line. –  ughoavgfhw Sep 25 '13 at 17:54
    
Fixed.......... –  Max Ried Sep 26 '13 at 9:45
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A standard USB charge should be enough to charge it, albeit very slowly. It's important to note on a very low charge like this, often it will provide enough to either a) charge when the screen is of, or b) not charge but allow enough to run it without any change in charge levels. In this mode, the charging indicator will always show not charging, as by definition you cannot see it when the display is turned off, but it can happily be charging while you are not using it.

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Apparently 2,1A should suffice to charge an iPad since Apple sells a similar product in his online store.

Did You Notice? Two USB ports with 2.1 amp output allow for the fastest possible simultaneous charging of your iOS devices.

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My Iphone 4 is drawing 288 mA now while it is being charged and has been drawing that amount of current for the last hour. I have it connected to a power supply that displays the current draw. Of course I connected the power supply to a car 12 volt to iphone adapter

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Let's see if we can find an iPhone question or perhaps you could explain how you measured this. It's not really an answer to this question - but could be with some edits. –  bmike Sep 25 '13 at 17:46
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