Safe to charge 5s with 10w?

Discussion in 'iPhone' started by ronaldcastillo, Nov 22, 2013.

  1. ronaldcastillo macrumors 6502a

    Oct 25, 2009
    Bought a retina iPad mini recently and I've been using the 10w power adapter to charge my 5s. Is it safe to charge my 5s or will it affect the battery over time?
  2. cynics macrumors G4

    Jan 8, 2012
    Safe to charge 5s with 10w?

    What's the output amps on the charger?

    Edit: that's a stupid question. 10watts / 5volt = 2 amps.

    Overheating a battery while charging certainly isn't good for it but I doubt you'll notice much. Does the phone get overly warm when charging?
  3. Gav2k macrumors G3


    Jul 24, 2009
    Op ignore the first reply it is perfectly fine! Check apples store under chargers and you'll see the 12&10 watt chargers are compatible.
  4. kh3khalid macrumors regular

    Dec 2, 2012
    You can control current in a circuit with current sources. I don't think it's as simple as P=I/V. Plus, as the previous post mentions, Apple is saying that these chargers are compatible with the iPhone.
  5. Grahammichaelh macrumors newbie

    Nov 17, 2013

    The iPhone is designed to draw the amount of power it needs just like MacBooks. It will only draw what it needs. Like if you have a 60w MacBook charger and you want to charge a MacBook air that takes 45w the MacBook will only draw 45w. (Just to put it into perspective)
  6. darricksailo macrumors 601


    Dec 18, 2012
    ^thats correct

    You'll charge slightly faster, that's for sure. It will draw around 6 watts if you use an iPad charger
  7. cynics macrumors G4

    Jan 8, 2012
    That's very true. The source will limit it's charge. However have you ever used one? Using my iPad charger on my iPhone makes it very hot. You'll also notice faster charging times with higher amp chargers. Heat is not good for a lithium ion battery.

    I had a 2.5a car charger and it would make phones I charged with it so hot they were uncomfortable to hold. Meanwhile my 750 ma charger keeps the phone at ambient temps but takes a very long time to charge.

    I'm not at all saying it's not compatible I'm just saying it may not be the best thing you can do to a battery. That's why I asked if the phone got hot, if not or just warm I wouldn't worry about it. However if it's not even comfortable to hold I'd avoid it.

    Generally with chargers ohms law works out btw. It does for all mine that I can find anyway granted I'm just looking at what I have laying around. Pretty sure an iPad charger is 2amp.
  8. kh3khalid macrumors regular

    Dec 2, 2012
    Ummmm valid points tbh, can't argue with what you've said. Now I'm afraid of using my iPad charger to charge my new iPhone hahaha :D
  9. iapplelove macrumors 601


    Nov 22, 2011
    East Coast USA
    I have been charging my iPhones with iPad chargers for years.
  10. 158273 macrumors regular

    Aug 29, 2013
    Reminds me of the question on whether "leaving MacBook plugged into the charger all day" was bad for it.

    Realize that there are worse things that you can do to your iPhone than charging it with an iPad charger.

    Every time your iPhone is discharging (aka, you're using it) that wears out the battery in a tiny way.

    Every time you plug-in your iPhone to charge using any charger, that wears out the battery in a tiny way.

    So, just remember, an iPhone is to be used. Not fretted about.

    Using another analogy: clean your touchscreen when it becomes smudged, but otherwise, just use it. Your fingers are meant to touch it and there are natural oils on your fingers, so that's just life.

    Same thing for the battery.
  11. posguy99 macrumors 6502a

    Nov 3, 2004
    Just because the charger can source 2 amps does not mean the phone can sink 2 amps.

    The charging circuit in the phone is designed to sink a certain amount of current. If the phone tries to take too much, the voltage drops, and the phone draws less. If the phone takes less than the maximum current rating, then the regulator is loafing and has no problem maintaining a stable voltage.

    So using a charger less than rated just means it takes longer because the voltage has to stay constant. Using a charger with more than rated current capacity is meaningless because the phone will only sink what it can sink.

    Given that it's going to be designed with some overhead, so if there's more current available, it'll draw that, up to its design maximum.
  12. antiprotest macrumors 65816


    Apr 19, 2010
    Same. It's fine.
  13. cynics macrumors G4

    Jan 8, 2012
    That's what I said in the portion of my post you cut out.

    What you quoted I was merely pointing out ohms law isn't just a good idea but the law. But the source will regulate it, ohms law still isn't effected.

    However voltage doesn't vary, current does. A voltage drop wouldn't allow for a full charge ex 4volt can't charge a 5v battery more then 4v. And lithium ion devices cycle the charge (no trickle charge) on/off when the charge is complete.


    Here is a interesting read on charging lithium ion if anyone is interested.

    Neat stuff about the stages of a battery and why when you use a charger that charges faster does it not seem like the battery last as long which is a common question on here.
  14. Max(IT) Suspended


    Dec 8, 2009
    Apple sells 10/12w charger as "iPhone compatible" so I think it's perfectly safe t use that.
    I tried to charge my iPhone 5 with my iPad charger (12w) and it didn't became particularly hot.
  15. scaredpoet macrumors 604


    Apr 6, 2007
    While youj're right that heat can't be good for a LiIon battery, it's been my experience that the phone heating up during charge has a lot less to do with which charger was used, and more to do with what the phone was doing WHILE being charged.

    I've used an iPad 10/12W charger on my iPhones for years, and they have managed to charge rapidly and yet not heat up. At the same time, I've observed iPhones heat up quite a bit while on the standard low-output charger that comes in the box with them. The difference was that the iPhone was actively being used for something (streaming audio, GPS, video, or some other CPU intensive activity) that drew a large amount of power at the same time that the battery was receiving a a charge.

    It is, but that's not its only output level. The Apple chargers have some intelliigence built into them, and will not force a device they're connected to, to take more current than they can handle. This might not be true for other chargers, such as certain cheap car chargers, and those chargers COULD cause problems. But using a genuine iPad charger is perfectly fine, and its use alone will not damage an iPhone or its battery.
  16. rrandyy macrumors 6502

    Jan 14, 2009
    That equation is wrong; it's P=I*V.
  17. kh3khalid macrumors regular

    Dec 2, 2012
    Oh yeah.. How ironic, I'm taking a circuits course this semester :D My instructor would kill me :D
  18. cynics macrumors G4

    Jan 8, 2012
    I feel like everyone I quote we are having an agreeing battle lol.

    I don't believe a charger can force current, typically regulated at the device. Most chargers abide by USB standards and there really isn't much too them. Just an AC/DC converter. Not saying a really cheap or broken charger can't do anything crazy though.

    I have a friend who had Apple replace his iPhone 5 that wouldn't turn on. They told him there was a burn mark on the logic board. He attributed it too his car charger or his iPad charger (last charger he used before it broke) more then likely the car charger or just a defective logic board (loose solder joint).

    I also agree with the what you are doing matters like GPS navigation plus car charging.

    If I get some time this weekend I'll post some pics of my iPhone temp with iPad charger vs iPhone charger vs 750 mA wall charger. I have an IR thermometer. It measures surface temp so it's not TOO scientific but should be able to clearly show a difference. Hard part will be replicating test. I'll think of something. Probably 50% for X minutes with the phone off.
  19. nebo1ss macrumors 68030

    Jun 2, 2010
    Last time I checked Ohms law was V = IR. That would suggest that the current is going to be limited not by what the charger is capable of but by the impedance of the device you are charging.
  20. wxman2003 Suspended

    Apr 12, 2011
    Watt the OP does in his ohm with his iphone, is up to him. Let's not ampere him here by giving him static or any negative responses. I volt that we remain positive and that the OP gets a charge out of our responses.
  21. jr866gooner macrumors 65816


    Aug 24, 2013
    Good one lol :)

    I have a charger that was made by gear 4 and had an iPod adapter.. Used this for my ip4 and might do same as back up for my 5c. Guess it won't hurt!
  22. ABC5S, Nov 23, 2013
    Last edited: Nov 23, 2013

    ABC5S Suspended


    Sep 10, 2013
    Just bought this one, and its on the Apple accessories site for the iPhone 5S as well as on Amazons that is cheaper. 10 Watts. You will be fine with a 10watt power adapter for the home charging

    Attached Files:

  23. darricksailo macrumors 601


    Dec 18, 2012
  24. Col Ronson macrumors 6502a

    Aug 7, 2008
    the iPhone automatically limits how much incoming power it gets. If you charge your phone with the 5W vs the 10W charger, the charge times are the same. the phone won't draw any more power with the iPad charger than it would with a normal iphone charger.

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