Can use ipad charger to charge iphone?

Despite your very long and knowledgeable-sounding reply, you are totally wrong. There is no problem charging an iPhone with a charger than can supply MORE current than the device needs.. Current is supplied on demand (unlike voltage). The iPhone charging circuit takes what it needs, not what is supplied. If your claim were true evey device in your house would burn up, because your incoming powerline can supply 150, 200, or even 300 amps. Your hair dryer only requires 10 amps, so why wouldn't it burst into flame?

Yes, I have degrees in electrical engineering, earned long before you were born.

As I biomedical engineer, I can affirm that Mr. Finch's analysis is correct. FWIW, this is a very simple engineering question which doesn't require debate. I'm very impressed that you were part of the team that designed the first electronic landing system for the USS Kitty Hawk. That's really cool!

Also, Merlin has confused mAh and watts in describing the capacity of batteries--watts are a unit of power. One can compare mAh and watt hours.

The essential point that Mr. Finch already explained is that the wall "charger" is just a 5V DC power source, and the iPhone will draw as much current as it is programmed to, and not the maximum output capability of the wall "charger."

Anybody who refers to "forcing too much current" is perhaps not the place to seek explanation.

The point under discussion is whether or not the iPad "charger" is harmful to lesser devices. I believe that Apple employ extremely well qualified people who check the facts before Apple puts the following into every Apple Store on the planet. Look up the iPad charger for yourself, and consider which side of the argument carries more authority.:

Their was another post about this charging issue and I explained it all basic on my educational level with electronics. Their were some people who turned it into and utter and complete joke. 99% had no electronic background but made tons of dumb comments. As the post went on a couple people that were using the iPad charger on their iPhone ruined their iphone battery. Once these people started posting that these people stopped with their stupid replies. the reason volts, watts, and amps are put on chargers are for a reason or else why would they put them on.

I can get really technical with formulas on this but I will go with a very simple one. All Apple chargers are 5 volts. Amps is the amount of current flowing into your device to charge your battery. Watts are easily calculated V x A = W

Example. Charger is 5 volts and is 1 Amp so it has 5 watts (iPhone charger)

Charger is 5 volts and is 2.1 Amp so it is 10 watts (iPad charger)

That one I just rounded up the number like apple did.

Most PC's 5 volts and it is .5 amps so it is 2.5 watts

Slow. Charging your battery is best to get the most out of it but who would want to plug their new iPad into their PC and wait 24 hours for it to charge??? No one, not even me. Despite it saying "not charging" on the screen plug it in your PC overnight and remember what you started off with, turn off the screen, let it go for 4 hours, and YES it will charge at a VERY slow rate. The screen says not charging, but give it a try and you will see that it did charge up but very little.

Has anyone looked up the battery capacity of the new iPad verses the older generations??

iPad 3 11,500 mAh battery 42.5 watts

Pad 2 6,944 mAh battery 25 watts

So with their 5 volt charger 2.1 Amp 10 Watts you are fine because you are not going over the battery specs .Pretty amazing how they achieved that many mAh just by making it slightly thicker. Very technical how it was done but not for this discussion but it is almost double capacity.

Now let's talk iPhone.

IPhone 4S 1,420 mAh battery (1.42 Amps)

5 Volts x 1.42 Amps = 7.1 watts

iPad charger is 5 Volts 2.1 Amps 10 watts. Now you see the problem? Will it work Yes, but you are over charging (forcing to much current) your battery. End result you are decreasing the life of your battery.

Apple says you can use any charger and you can see above a simple formula in simple math. So why would you use a charger that is 2.1 Amps 10 Watts on a battery that is 1.42 Amps = 7.1 watts

Does anyone know what the cost is for Apple to put a new battery in your phone? I am curious on that one and would guess its not cheap.

Their is a formula in simple math. Can you use the ipad charger on your iPhone ? Yes. Will it shorten your battery life using the iPad charger on your iPhone? Yes.

This is the simplest formula broken down into simple math.

Actually, I realize I was a little unfair. Your analysis is correct up to the point where you say "now lets talk iPhone". The problem is you don't understand that current is a measure of the maximum capability of the charger to supply current, not the amount that will be forced on the device.

Long before I was born? I am 42 and your age is ? Hair dryers? I don't think I ever saw a hair dryer with a lithium ion battery in it. Since we are talking hair dryers why do they sell chargers for cars and ones for motor cycle batteries? Why not just buy one and don't say buy one that does both that has selectable settings. Reason being is if you use a car charger which is 10 amps on a 2 amp motorcycle battery you will cook it and if you ise the motorcyle charger on a car battery it will take forever to charge it So now you see why they sell car chargers, motorcycle chargers, and ones with variable charging rates. Please explain that one why their is not one charger for all car and motorcycle batteries. Please don't use the excuse they are lead acid, AGM, etc. Since we are on AGM batteries tell me about those as well. What charger do you use. What voltage does a car alternator put out?

Since you have such expertise answer these questions too. What voltage reading will you get on a 220 volt 3 phase piece of equipment coming in from testing supply to supply? What reading will you get testing one supply to ground? Do you need a neutral wire to use this 220 bolt 3 phase piece of equipment ? What size light bulbs do they use for an L train that ONLY has a 600 volt power source coming in?

Here's a test I did with help of a couple co-workers.

Just like the last forum post here we go again. I used an old iPhone and obtained 2 other ones and put brand new batteries in them. Altered the charger to put out more than 2.1 amps and did 50 charge/discharge cycles on one. Did the same with te other one at 1 amp, and the other at .5 amps

After that let all 3 devices sit for 3 days all at the same settings and the one that was charged at .5 Amps had the best battery capacity and the one with the altered charger was the worst? Please explain that and answer my 3 phase power question.

I will be anxiously awaiting your answers to ALL these questions.

merlin1128 wrote:

Long before I was born? I am 42 and your age is ?

Yes. Before you were born. Certainly. In the year you were born I was on the team that deployed the first electronic landing system for aircraft carriers on the USS Kittyhawk. I designed the shipboard component, and a co-worker and friend designed the airborne receiver.

Thee's no point in arguing with you, as your mind is made up. What is wrong with all of your analogies is that the "charger" for iPhones and iPads is not a charger at all. It is a 5 volt DC power source. The charger itself is inside the device. The internal charger regulates the charging current to the battery. For car and motorcycle batteries the charger is external. Thus, the external charger must regulate the charging current to prevent damage to the battery.

I think we all agree that overcharging a battery or charging a battery too quickly is not good for its lifespan. However, Mr Finch is correct in many points. Who cares how many degrees you have or how old you are. Your qualifications do not matter if you cannot answer the question correctly.

If you had just broadened your scope of the problem you'd realize that it does not make sense for Apple to design intelligent power adapters. The power regulation comes from the device (iPad, iPhone, etc). The reason why the iPad charges slower when on computer power USB is because the regulation circuit is not getting enough current. However, as Finch said, greater supply current is not a concern.

A better approach to a more valid test is to verify the current being consumed by both the iPhone on the iPhone charger and iPad charger. If the current is the same then we can conclude that the battery regulation is working the same. If it doesn't, then there may be some validity into different regulation circuit designs. We also should check voltages and variation or ripple.

Now I am off to do more fun things than typing on this iPad in this form. Whoops I forgot about voice dictation. Looks like I'm the idiot after all.

Why not just ask someone reliable? I emailed Mr. Schiller from Apple and I got a response.

So what's the verdict? Yes, you can use your iPad charger to charge your iPhone and it will not cause any damage to the battery or iPhone 🙂

In response to JPSSnyder's quesiton 5W and 10W going to be irrelevant because the iPhone will treat both chargers as if they are 5W (or 1 amp at 5V.) That is, the iPhone will pull a max current of about 1.03 amps on a 5W and 10W USB chargind adapter alike. That is according to my tests of 12 different USB adapters that are 5W, 10W, and 15W; and 12 different cables on an iPhone 4S and iPhone 4.

When not at full load, rapid charging pulls .93 amps (.1 amps less) on both 5W and 10W adapters.

As for heat, I can't say with any authory or certainty but we know heat is not good. How warm I don't know. Moderate warmth may be not harmful but very warm or hot may be. Eneloop AA batteries get very very hot when charging and they can do over 2000 cycles. So we know rechargable batteries can handles a good amount of heat without significant damage. Obviously Apple has engineers that have taken this into consideration and probably one reason it doesn't charge faster on 10 watts.

So I suspect that anything othr than extreme heat is going to be "fine" for the iPhone. I wouldn't worry about it.

While rapid charging the battery already gets pretty warm on it's own. I don't think that some background tasks are going to raise the temperature a significant amount that it already is. Just using the phone with the screen on while rapid charging is far warmer than when in standby and charging, even if the phone is doing something.

Will a slower charger be more gentle? It could be? I'm paranoid. I have a 2.5W charger (.5 amp, which is the minimum USB spec) that I use for overnight charging specifically to prevent rapid charging. It's just not necessary overnight so why even risk it? I use normal 5W chargers during the day for mid day and in the car, though. I'm not recommending anyone go out and find a 2.5W charger and do this as well, but if you're worried about it's an option.

In case you're not aware, I'll repeat that the iPhone (and iPad) will rapid charge until the battery reaches about 80%. Above 80% it gradually reduces the charge rate up to 100%. This is to prevent harm to the battery. So it will cool off and slow down as it reaches full charge.

This testing (grahps below) is done with the Apple 10W USB adapter for iPad with genuine apple 30-pin cable. Screen was off, no background tasks running.

Lawrence Finch wrote:

RF9 wrote:

And trickle charing vs. rapid charging is not what this conversation is about. Yes slower charging is always more gentle, but no one is disputing that.

Which is why the iPhone charger IN THE PHONE taper charges after 60% of capacity is reached, and shuts off completely (doesn't even trickle charge) when the battery reaches 100%

Agreed.

My experience is that rapid charging tapers after 80%, not 60%, but I never ran a test from (close to) 0%. Mine always started at around 30% and consistently saw full current until about 80%. I imagine things like increased battery temperature and length of time charing could start the charge rate reduction earlier.

Subsequently Apple also says 80%.

http://www.apple.com/batteries/

Most lithium-ion polymer batteries use a fast charge to charge your device to 80% battery capacity, then switch to trickle charging. That’s about two hours of charge time to power an iPod to 80% capacity, then another two hours to fully charge it, if you are not using the iPod while charging. You can charge all lithium-ion batteries a large but finite number of times, as defined by charge cycle.

I'm not saying it can't happen at 60%. It's very likely that there are cases where charging slows earlier.

The point of the matter is exactly what you said, that the charging slows and eventually stops.

I think the only question is could it be benficial to the battery to never even allow full rapid charging, to say limit the phone to 500mA so the charge rate is slower across the board? Perhaps, but my educated asusmption is that it will not help in a significant way. Apple's engineers designed it this way knowing what they were doing.

Here are my test results graphed.

I can to have a look to answer the same question. One of th later google entries was this http://store.apple.com/uk/product/MC359B/A it talks about the iPad charger charging the iPhone and ups touch as well

Hope this hels

The only thing irrelevant is your post...

Seriously?

The Topic:

Can use ipad charger to charge iphone?

Irrelevant meaning:

Totally unrelated to the matter being considered.

Consider yourself educated.

I wonder...If I cut you in half modular747 - would I find seeds?

Also...

what you say defies all known laws of physics

Chill out dude! It happened - or I wouldn't have posted it... jeeze...

Your ignorant and irrational belief systems have no value to anyone.

I was just posting what happened to my bloody phone man? BELIEFS? You need to relax and get outdoors a bit..

Holy cow, will this thread please die? Have you read this ridiculously, unecessarily long thread that contains the results you asked for? This has been done and mentioned on this thread, here (https://discussions.apple.com/thread/2580579?answerId=20452578022#20452578022) and here (https://discussions.apple.com/thread/2580579?answerId=20524870022#20524870022).

Answer

iPhones SHOULD charge at the same rate, whether you use the iPhone charger or iPad charger. Neither SHOULD do damage to your phone's battery. If you use a PC USB, it will charge slower if its a 0.5 amp port. If you experience different results, it could be due to variances or defects in the charging mechanism of your individual phone.

Are we done?

(The frustration was not directed personally at you rfn_4, its just that this thread needs to be closed).