MacRumors Forums Using iPad Charger to charge iPhone 4

Apr 7, 2012, 01:54 AM   #26
RegularJoe
macrumors newbie

Join Date: Apr 2012
Quote:
 Originally Posted by sithbrach Ohm's Law: http://en.m.wikipedia.org/wiki/Ohm%27s_Law http://en.m.wikipedia.org/wiki/Volt That tells us what the 5v x 1 or 2A translates to. It would indicate that twice the wattage is coming out of the iPad charger (W=V*A) and twice the current (I=V/R). As I understand it, the block acts as a transformer: http://en.m.wikipedia.org/wiki/Transformer So, it takes the 120V*15A=1800W power from the outlet and converts that power so that it will be transmitted at a much lower rate, giving the device less of that wattage. I'm not sure if the earlier post by someone was trying to say that the iPhone has a particular resistor of it's own and so any different level and rate of power would simply dissipate, but wouldn't that still be stressful on that resistor? I think, in the end, one would be better off spending the couple of bucks for an iPhone charger. If there was absolutely no difference, then why would they make different chargers with different values? There would only be a need for stronger chargers for larger, more powerful devices, but the inverse (using that more powerful charger for a smaller, less powerful device) wouldn't make any sense. Just use the corresponding charger.
In theory, the charger will take in the AC voltage (120V AC) and convert into DC using rectifiers. The DC voltage will then pass through a voltage regulator to maintain the output voltage at 5V (or whatever voltage is desired). The voltage regulator, in basic electrical engineering, it is just a simple circuit involving resistors and zener diode. The zener diode's job is to drain the excess voltage and current to ground. Unlike human, electronics component will just keep working on and on and will not be stressful.

Some devices require higher voltage than other. There are many reasons that could contribute to that differences, which I am not exactly sure. However, some of the reason that might contribute to this are:
(1) the input impedance of the devices might be high or low
(2) poor circuits design that require higher voltage and current but does not use to contribute to the actual need of the equipment
(3) the engineer who design the equipment said "I like it that way"

***hope it helps***
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Apr 7, 2012, 01:59 AM   #27
dukebound85
macrumors P6

Join Date: Jul 2005
Location: 5045 feet above sea level
Quote:
 Originally Posted by aelalfy I don't think charging an iPad using an iPhone/iPod charger is a good idea. The iPad requires more watts than the iPhone. For example my gf tries to charger her macbook with my macbook air charger and the charger really heats up. because my charger is a 45W, hers is 60W or so. I don't think thats a good idea, see above. Thanks AE
It's fine. Apple states it is ok on the box

Edit: dang necro thread. Thanks to whoever bumped it...
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 Apr 18, 2012, 08:38 PM #28 pa1ch macrumors newbie   Join Date: Apr 2012 Power Draw If you plug a light bulb into a light socket it has a power consumption, say 60watts. You can choose a different bulb with a power draw of only 10watts. They both have the same voltage as they are both on your mains supply. The light bulbs draw the power they require. The mains acts like a really powerful 3000watt supply but you can plug in a device of any power as long as voltage is correct, like the pathetic little 10watt light bulb. The iPhone works in the same way, as long as the voltage is correct it will draw the power it needs. 1
 Apr 18, 2012, 11:23 PM #29 daemonite macrumors member   Join Date: Aug 2010 the iPhone regulates itself, if plugged into a 2.1 AMP charger, it will detect that and regulate itself draw it's maximum of 1AMP from the available 2.1 AMPS. 0
Apr 21, 2012, 07:56 AM   #30
Dkorda
macrumors 6502

Join Date: Mar 2012
Quote:
 Originally Posted by RegularJoe I'm reading through too many threads and find too many different response. I am an electrical engineer and would like to offer a simple answer: It is okay to use iPad charger to charge iPhone. Any charger with the same output voltage is also fine. The output current is what you should be less concerned about because it can vary up to max depending on the device being charge (i.e. the load). For example, charging iPad with iPhone charger would take longer because the charger would give out 1amp max. Charging iPhone with iPad charger would take the same amount of time since the iPhone only draw 1amp from the charger even though it is capable of providing 2amp. On a different notes, most electronics is rated about 5% variance in voltage; therefore, a slightly higher or lower voltage of the charger should be okay.
Let's listen to the expert here, RegularJoe says it best, and it makes sense now.

My iPhone charges quicker on my iPad charger (2.1amp), my iPad charges slower from my iPhone charger (1.0amp)... But they both still charge.
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Jun 11, 2012, 07:50 AM   #31
chdwil
macrumors regular

Join Date: Jun 2009
Quote:
 Originally Posted by Badfoot You could use a charger rated at 1,000,000 amps, as long as the output voltage is the same. The device will regulate the charging current according to the battery capacity fitted.
yes this is true. I plugged mine into a 1000000 amp cigarette charger and it worked fine.
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 Jun 11, 2012, 09:27 AM #32 greentaloy macrumors member   Join Date: May 2012 I'm also use a iPhone charger for iPod,iPad even they're of different watts, and get a lot from online shop that they always mention that the charger for iPhone/iPod/iPad...the answer will be it's better use them respectively if you show this questions to a professional one,however, who care on this, just forward at your convenience... 0
 Jun 12, 2012, 02:00 AM #33 Ryan658 macrumors newbie   Join Date: Jun 2012 I use a universal solar charger I find that use a universal solar charger for all my iPhone ,iPad, and digital camera is very convenient, solar charger can charge through electricity and solar 0
 Jun 12, 2012, 04:44 AM #34 rgctx macrumors regular   Join Date: Apr 2012 Some people have to much time to ask questions lol. Seriously just charge it with the charger you think works best, to each there own. I have been using my ipad charger for years now on my iphone, had no issues. I dont see the point in taking out a new oem charger out of the iphone box when i already have a ipad charger on the wall. 0
Jun 12, 2012, 08:58 PM   #35
Ryan658
macrumors newbie

Join Date: Jun 2012
Agree

Quote:
 Originally Posted by rgctx Some people have to much time to ask questions lol. Seriously just charge it with the charger you think works best, to each there own. I have been using my ipad charger for years now on my iphone, had no issues. I dont see the point in taking out a new oem charger out of the iphone box when i already have a ipad charger on the wall.

yeah, I totally agree with you, just charge it with the charger you think works best. Convenient will be good!
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 Jun 30, 2012, 08:12 AM #36 Whitegooner macrumors newbie   Join Date: Jun 2012 iPhone charger blows fuses I plugged my iPad into my Iphone charger last night, when I woke this morning my electrics had tripped. after investigating I found my iPhone charger had blown up (black soot) I'm really worried that this could of caused a fire. what is the approximate action I can take as this might in future cause a fire Should I contact apple as they might not be aware 0
 Jul 1, 2012, 09:11 PM #37 Gjwilly macrumors 68000   Join Date: May 2011 Location: SF Bay Area Was it the official charger and did it have the green dot? All early iPhone chargers were recalled and the replacements have the green dot on the back. Of course, even the knockoffs now have the green dot so that's no guarantee. Regarding the original topic though, iPhone and iPad chargers are compatible because Apple is violating USB standards in order to guarantee compatibility. USB is a 4-pin standard -- two pins for DC voltage and two for data. In an ordinary charger you won't see any voltage on the data pins. Apple intentionally puts voltage/resistance on these pins and the iPhone and iPad are looking for it in order to determine how fast they can charge. And the resistance changes according to the charger. A non Apple charger or a computer USB port won't have this voltage so the iPhone will charge at 500mA. If the iPhone sees that it's connected to an iPhone charger it will charge at 1A because it knows the current is there. Same with the iPad. iPad on iPad charger draws full amperage. iPad on iPhone charger and it draws only half amperage. iPad on computer port or non-Apple charger and it shows the not-charging message. The problem can come when non-Apple chargers are created that mimic this data port voltage without actually being built to supply the intended current safely. Last edited by Gjwilly; Sep 24, 2013 at 11:10 AM. 1
 Sep 1, 2012, 05:10 PM #38 nffirster macrumors newbie   Join Date: Sep 2012 Yes it is okay,I use it with all of my iPads,iPhones,and iPods. 0
 Sep 4, 2012, 01:57 PM #39 snapb202 macrumors newbie   Join Date: Apr 2012 Thanks for the all the info 0
 Sep 24, 2013, 09:52 AM #40 satyenshah macrumors newbie   Join Date: Oct 2012 Separate questions There are two questions here. Safety: Is is safe to plug an iPhone 4 into a 12/15 watt iPad charger? Of course it is. The best analogy is that your ordinary bathroom faucet works the same whether it's connected to a 1/2" supply line or a 4" pipe, and you will still only get 1.5 gallons a minute out the aerator as long as the water pressure is the same. To get more water out the tap, you'd need a faucet designed to allow that. Practicality: Did Apple design the iPhone 4 to recognize and take advantage of a 12/15 watt iPad charger to charge itself faster? Sounds like they did though the battery can get warm. You can charge your iPhone faster, at the cost of somewhat higher battery wear. 0
Sep 24, 2013, 11:04 AM   #41
Gjwilly
macrumors 68000

Join Date: May 2011
Location: SF Bay Area
Quote:
 Originally Posted by satyenshah There are two questions here. Safety: Is is safe to plug an iPhone 4 into a 12/15 watt iPad charger? Of course it is. The best analogy is that your ordinary bathroom faucet works the same whether it's connected to a 1/2" supply line or a 4" pipe, and you will still only get 1.5 gallons a minute out the aerator as long as the water pressure is the same. To get more water out the tap, you'd need a faucet designed to allow that. Practicality: Did Apple design the iPhone 4 to recognize and take advantage of a 12/15 watt iPad charger to charge itself faster? Sounds like they did though the battery can get warm. You can charge your iPhone faster, at the cost of somewhat higher battery wear.
No, they really truly didn't.
In your faucet analogy, think about a high-flow and a low-flow setting.
The iPhone 4 only has two charge rates and no charger is going to change that.
People have measured and documented it.
The caveat however is that the charge rates are set via firmware so Apple could theoretically change it.
It's pretty unlikely but I don't know if anyone has checked since the release of iOS 7.

Last edited by Gjwilly; Sep 24, 2013 at 11:11 AM.
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 Nov 1, 2013, 03:33 PM #42 edhchoe macrumors regular   Join Date: Oct 2011 Interesting fact. I measured the charging current with my galaxy note 3. Samsung supplied 2.0A charger charged at 1.2A while apple 1.0A charger charged at .450A. USB port on iMac also charged at 450mA. 0
Nov 2, 2013, 09:10 AM   #43
parrot5
macrumors 6502

Join Date: Aug 2010
Quote:
 Originally Posted by edhchoe Interesting fact. I measured the charging current with my galaxy note 3. Samsung supplied 2.0A charger charged at 1.2A while apple 1.0A charger charged at .450A. USB port on iMac also charged at 450mA.
That's because the Note 3 doesn't recognize the Apple charger and the Mac as one of its own Samsung chargers. Which is to be expected. The more surprising element is that it doesn't use the 2.0A of its own Samsung charger. Maybe the phone wasn't discharged enough?
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Nov 3, 2013, 04:00 AM   #44
edhchoe
macrumors regular

Join Date: Oct 2011
Quote:
 Originally Posted by parrot5 That's because the Note 3 doesn't recognize the Apple charger and the Mac as one of its own Samsung chargers. Which is to be expected. The more surprising element is that it doesn't use the 2.0A of its own Samsung charger. Maybe the phone wasn't discharged enough?
That was from 20%-90%. Same readings.
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