Can use ipad charger to charge iphone?

Your posts have been repetitively and completely discredited by all objective testing and merely reflects your technical ignorance and/or trolling impulses.

No further time will be wasted responding to your nonsense.

Message was edited by: modular747

Well I charged my wife's phone beside mine last night . Both brightness off and on airplane mode on.. Hers with the provided charger and mine with our iPad 2 charger. Both were at 1% and mine with the iPad charger hit 100% and the wife's phone was at 62% . Proof enough for me. And yes my battery does die really fast but not sure if I plan to do a use age comparison. All I can say is I can't go 5-6 hrs away from a charging cable so I have 4. One at work. One in each car and one at home beside the bed. I took photos of both phones charging and photos every 15 mins to show the time and charge % maybe ill turn it into a video for youtube

Too many variables. The battery condition of both phones may be different, the installed apps different, the state of those apps different, the background processes in different states. And BTW, putting the phone in Airplane mode does not guarantee that nothing is using power; quite the opposite. If there were background apps attempting to update when you switched on Airplane mode the phone will actually use more power in Airplane mode as those apps attempt to complete their update and fail than it would if the connection was permitted to complete.

The only meaningful test would be the same phone charged multiple times with each charger. And even then you would have to assure that exactly the same apps were installed in exactly the same logic state. Or Restore the phone as New and don't install anything before running the tests. I HAVE done tests using the same phone, and the time to charge is about the same with either charger. Did it near the start of this thread, which was THREE YEARS AGO (can you believe?)

The video already posted several times shows that the two chargers provide the same amount of energy when charging an iPhone - 5 watts. 5 watts using an iPhone charger, 5 watts using an iPad charger. If 5 watts goes into the charger no more than 5 watts can come out of the charger. So the most that can go into the phone is 5 watts. So unless you have found a way to violate the First and Second Laws of Thermodynamics the maximum amount of energy entering the phone is the same with either charger.

Now I see... i'm not techincal, i just go with what the crowd says... then what's all the drama around this discussion? lol

The answer has never been clearer! Only one (iPad) charger is needed to charge all iPad, iPad mini, iPhone, iPod... no more fuss about fitting all kind of chargers and cables in my travel bag... Thank you!

Sorry Merlin, much of your post is very good, but you are totally wrong towards the end. A power supply is rated at the maximum it can supply. It does not mean it will force that amount of power through the device. If the power supply is rated to provide less current than the battery will draw when charging, then the battery will charge slower, limited by the output of the charger. If the battery could draw infinite power, it would have to have a resistance of 0 ohms across the terminals.

See the wikipedia page on ohms law (http://en.wikipedia.org/wiki/Ohm's_law) for more details.

Example, a car battery can easily provide in excess of 150A (1.8kW of power at 12V), but connect a small 12V light bulb across the terminals, and will only draw what the bulb needs. Most automotive bulbs pull 5W (0.4A at 12V) or 21W (1.75A at 12V). If the bulb drew the full150W (1.8kW at 12V) from the battery (as my example battery can supply), that would be brighter than 3 or 4 high power floodlights.

Further reading:

http://superuser.com/questions/106792/does-a-power-supply-draw-only-as-much-powe r-as-it-needs

OK, I reran the test I did at very early in this thread. Details:

Airplane Mode: OFF

WiFi: ON

BlueTooth: ON

Notifications: ON

Email: PUSH

No attempt to shut down apps in the Quick Launch ribbon

Day 1:

I ran my iPhone 4S down to 1%, then kept it alive until it shut down. I then charged it with an iPad charger. After 2 hours the battery gauge said 91%. I let it go another hour, and it reached 100%.

Day 2:

I ran the same iPhone 4S with the same settings down to 1%, then kept it alive until it shut down. I then charged it with an iPhone charger. After 2 hours the battery gauge said 92% (the iPhone charger charged it slightly faster, but not statistically significant). I let it go another hour, and it reached 100%.

Conclusion:

An iPad charger DOES NOT charge my iPhone any faster than an iPhone charger does.

I did a more scientific test and used a power meter to measure current draw when charging.

The iPhone limits itself to using only 1 amp (5 watts) regarless if it's connected to a higher capacity adapter like the iPad 10 W or 12 W.

When the iPhone is rapid charging, it will use 0.93 amps with the screen off and 1.03 amps with the screen on (it draws an additional 0.10 amps to power the phone and doesn't reduce the power to charging the battery.) It uses the exact same amount of power when using the iPhone adapter and iPad adapters. Also note that this means the iPhone doesn't seem to charge any faster or slower if you are using it or if the screen is off. Using the phone doesn't reduce the charging rate if .10 A is enough to power the phone.

The iPhone rapdid charges using 0.93 amps below 80%. Above 80% it gradually reduces the power and subsequently charging rate (almost linearly) as it increases to 100%. Once fully charged it stops charging. Also be aware that the display will show 100% at about 97% actual battery charge so it may appear to continue charging for a long time while reading 100% before you see the icon switch to a plug (from a lightning battery.) It's not overcharging, it's just trickle charging the last few percent and it's slow.

I used this power meter I got off of Amazon.com

http://www.amazon.com/Centech-USB-Power-Meter/dp/B00DAR4ITE

I actually also cut open a cable and used an actual digital multimeter until I found this USB meter (and got the same results.)

Thanks for the follow-up. I was going to do the same thing when I got a chance. Unfortunately, I doubt that this will convince everyone who KNOWS that a 10 watt charger MUST charge twice as fast as a 5 watt charger.

paulcb wrote:

Using the phone doesn't reduce the charging rate if .10 A is enough to power the phone.

Good info... wasn't aware of that bit of detail.

Well the key word is *IF*. I don't know for a fact that .10 A is. It's possible that the phone for (a purely hypothetical) example .20 A, so that would mean the charge rate would drop to .83 A instead of .93 A and in fact reduce the charging rate but I really don't think that's the case. All I know is that the phone draws .10~.11 A more and the iPad .13~.15 A more when "on" than when just off and rapid charging, so there is at least a significant compensation.

I should charge the phone all the way up to 100% until the battery icon shows without the lightning bolt (charge indicator) then measure the current to determine for sure. I think that would work.

Lawrence Finch wrote:

Thanks for the follow-up. I was going to do the same thing when I got a chance. Unfortunately, I doubt that this will convince everyone who KNOWS that a 10 watt charger MUST charge twice as fast as a 5 watt charger.

I must admit that I thought the iPhone would charge a little faster with a 2 A adapter than the 1 A adapter. I assumed the iPhone charged using 1 A with the 1 A charger, but used something in the range of 1.3 A with a higher capacity charger (2.1 A). Not a full 2 amps, just a little more. I don't know where I got that idea. I was a little surprised (but shouldn't have been) when I did my test and learned that no, the iPhone is what's regulating itself to 1 amp and it uses the EXACT same amount of current no matter what you connect it to (unles of course it's less than 1 amp.)

What I also discovered was that some 99 cent 30-pin cables I ordered in bulk off of an Amazon reseller (you know one with a crazy name like lucky-shop and ships directly from Shenzen) really suck. They only deliver .67 amps so I'd been using those all along wondering why the iPhone didn't charge faster (duh!) I hacked open a cable and found that they are (of course) just really cheaply made with a wire gague that's too thin, especially for a 6ft cable. Lesson learned.

So for best performance, either use genuine Apple or get cables that are "MFI certified" (aka Apple certified) or at least a name brand like Belkin, etc. They can all do well over 1 amp even at 6ft.

I'm sure the phone can require more than 0.1 amp for some functions. For example, sending cellular data in a weak signal area can require up to 600 Mw for the transmitter. Under this condition the phone will get warm. So it's possible that the phone will charge slower with the 5 W charger than with a 10 W charger, because the 5W is being split between charging and powering the phone.

So the observations that a 10 W charger charges faster may be a result of this. However, it's not that the 10 W charger is charging faster; the 5 W charger is charging slower due to the additional drain of the phone.

That sounds right to me except the last part. Even on a 10 watt adapter the iPhone 4S didn't pull more than 1.03 amps. It didn't matter if it was the 5W or 10W, it rapid charges at .93 and pulls a max of 1.03.

I think some people make the mistake that rapid charging only happens below 80%, so maybe they are observing rapid charging on the 10w but noticing slower charging above 80% and not making ann apples to apple a comparison?

I tried to read through the entire post but decided to jump to the end and ask a question that has probably been addressed before. If there is no software load on the battery, clearly the 10w and 5w adapters charge the iPhone the same and the temperature / charge time are also the same. But I would think that there is almost always a background process going on, e.g. if charging at night the iCloud sync/backup is using the wifi circuitry. Now if the 5W is not capable of providing the full current to the battery and the background processes, so that the battery charges at a slower rate than it is designed to, would it not be true that the heat generated is less than the 10W that supplies the battery and the wifi circuit with full current? In that possibly typical situation would not the 10W power supply result in more internal heat, not because of the battery charging process but because of allowing the background activity to run at max?

My total uneducated guess would be that this additional heat would only slightly affect the battery life, because the batteries are designed to be tolerant of extremes. Perhaps a slow steady charge is slightly better for the battery (not because of the wattage but because of the inability of the 5W to provide the full 5W to the battery), but is not a significant issue like with early lithium ion cells. If so, I would think that the users experiencing a problem should use the 5W adapter and/or see if background programs are causing a problem.

My educated guess is that any extra heat will not affect battery life in the slightest. Although I agree that IF the phone is sending gobs of data over Cellular while the phone is charging it will get warmer. The battery does not generate significant heat when charging, however. So if the phone was using gobs of data and sucking up lots of power from the external power source sufficient to make the phone warm the incremental difference in temperature will be small to unmeasurable. And Apple has considered this possibility; if the phone gets hot enough to affect operation (and the battery) the phone will detect this and shut down.

This high power consumption scenario will probably reduce battery life, but for a totally different reason. If apps on the phone use lots of power it will be necessary to charge the battery more often, and the life of the battery is measured in number of full charge cycles. And this reduction in battery life will be the same whether it charges fast or slow. I'm assuming, of course, that apps that use gobs of data will use it whether the phone is connected to its power source or not.

I don't have any technical knowledge in this field, as I'm a nework engineer by proffession.

I've an australian iPhone 5 since a year almost, and Apple supplied the same iPad charger(10w) with all iphone 5's in Austrailia . Unlike the US iphone5 charger.

And I never had any battery problems to this date, it doesn't even gets warm while charging.

I get a battery backup of around 10 hours (on screen time)

Message was edited by: ibnally