Charge an iPhone with an iPad?

[mrcalabash]

This may seem like a weird question, but I was idly wondering is there a way--cable of some sort--that would charge an iPhone from an iPad. I mean, the iPad has a bigger battery, so it's theoretically possible to use some of that juice for the iPhone.

Maybe this question is only a thought experiment. I googled and found nothing.

 

[darngooddesign]

The problem would be that both devices would try to charge off eachother instead of just the iPhone charging from the iPad.

 

[mertyz]

Unfortunately, it's not possible

 

[Night Spring]

Theoretically, it seems possible, but someone will have to make a special cable that does it, and as darngooddesign pointed out, there would need to be a way to tell the cable which device to charge. And nobody makes such a cable, and if they did, I'm not sure Apple would allow it.

 

[mertyz]

AFAIK, the maximum voltage iPad can output is 3.3V and the maximum current a connected device can request is 20 mA.

Do the calculation

 

[MacBill]

It would be possible, but the cable would have to incorporate a diode to prevent power flow from one direction, then it would have to be pugged in the right direction because both take the same connector.

 

[Dangerous Theory]

No way it can produce a reasonable current.

 

[olesor]

http://www.redmondpie.com/this-gizmo-lets-you-charge-your-iphone-using-ipad-video/

It's there, it seems. But then it's one iPhone-version too late, maybe...