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I have an iPhone 4 and an iPad. Since the iPad really charges best off the wall charger I keep it plugged in, but I usually just charge the iPhone off the computer. Although frequently if the iPad is charged I will charge the iPhone with the wall charger.

Now the Apple sales rep said he heard from someone who heard from someone that that would burn out the phone because the iPad charger is 10 watt instead of 5 watt. It is true that it is twice as many watts. I said that I thought it shouldn't burn out the phone because a device should only pull as many watts as it needs, so the watts were irrelevant. He said that made since, but he didn't really know.

So I thought I would ask the experts. Has anyone had their iPad charger fry an iPhone / iPod? Am I correct in my understanding of watts in chargers? Is there an official word about the iPad charger causing trouble with other devices? Have I already voided my warranty?

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8 Answers 8

up vote 18 down vote accepted

Your assumption is correct. Your iPhone has an intelligent charge controller on-board and this controller will only draw as much as it needs.

Sure, the iPad power supply can supply twice as much power as the iPhone needs, but it should not be dangerous by any means.

I don't know if there is an "official" word on this, but I would be genuinely surprised that it voids your warranty. Apple engineers are very smart and know that users will interchange powersupplies if they recognize that the connectors are physically compatible (as is the case here.)

Long story, short: you should be fine.

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however the IPod charger may have a higher running cost then a iPhone charger. –  Ian Ringrose Sep 13 '10 at 9:53

The UK Apple store says the iPad charger is fine with iphones / nano

http://store.apple.com/uk/product/MC359B/A?fnode=MTc0MjU4NjA&mco=MTc3Mzc5MDU

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but only with dock "It also charges iPhone and all iPod models with a dock connector." –  Metal Gear Jul 4 '11 at 5:08
    
By "dock connector" they mean the 30 pin connection. No "dock" required. en.wikipedia.org/wiki/Dock_connector –  XAleXOwnZX Jun 10 at 2:31

I charge my iPad and iPhone with the same cable and notice no difference.

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He meant the wall charger drprusa.com/wp-content/uploads/2014/04/49299031.jpg –  XAleXOwnZX Jun 10 at 2:30

Loads, such as a phone, draw as much current as required for their resistance (see Ohm's Law). Having a power supply that can supply more current than a device can use is not only possible, but basically universal. E.g. A MacBook charger can supply 65W of power max (at a constant voltage, this implies constant max current), but most of the time the MacBook will be drawing FAR less power (and thus less current).

TL;DR: Yes, you can use an iPad charger to charge an iPhone.

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I been using official apple chargers for years on my iPhones and iPads and the only thing I've noticed is that I use the the wrong charger in the iPad it charges much slower. Apple chargers and devices know when to cut off the power once it knows the battery is fully charged. However using non Apple chargers may fry your devices.

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I'm using my ipad charger for all my ios devices for many years wihout any problem

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A devuce draws what it is able. The only problem could occur if the charger supplied less power than the device wants. If the charger supplies 10X the power the device wants then that device will still only take what it can. The charger cannot supply too much power and burn up a device. It is like how hard you are able to suck on a straw. Some suck harder than others but a narrow straw can only provide so much flow. A person can only drink so much so fast and then they are full, no matter how much additional flow the straw can provice. The device pulls power as it can absorb, the charger does not push power.

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I disagree. I actually did this for about a year and recently, the wire attached to the adapter started sizzling and got fried. I tried using a different wire, but the same thing happened. DO NOT DO THIS FOR NO REASON and ruin your iphone (my iphone went black and wouldn't charge; I had to buy a new one). It will save you money and effort if you just buy an iPad charger like you're supposed to.

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I think you had a faulty charger, or a faulty phone. The best information is at source, the current iPad charger (which is rated even higher at 12w than at the time this question was asked) shows compatibility with practically every 30-pin device made in the last 10 years. store.apple.com/uk/product/MD836B/B/… Where devices have intelligent controllers to adjust their power draw, the important thing to remember is that chargers are rated for what they can supply, not what they will supply. –  stuffe Jun 10 at 8:32

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