10W power adapter - faster recharging than standard USB?

Discussion in 'iPad' started by rgbyhkr, Feb 15, 2010.

  1. rgbyhkr macrumors member

    Joined:
    Jul 1, 2007
    #1
    So I got started thinking about power options for the iPad since I know I'll be getting one. I was looking into car charging, external batteries, etc. As an aside, I think that the iPad's ability to charge over USB offers users tremendous flexibility given all the USB power options already out there. So anyway, when breaking down how much extra juice an external battery could offer given the iPad's 25Wh battery, I noticed something.

    The power adapter for the iPad is specifically listed as 10W. Now why would Apple bother making that distinction? Because standard Apple USB power adapters (iPod, iPhone, etc) are only 5W. That being said, you absolutely can still charge the iPad over a standard USB port, which only supplies 2.5W (I think I've seen that the spec calls for 5V at 500mA) according to Apple.

    So, here's my question: Is the likely result then that recharging the iPad on the 10W adapter will yield faster recharge times than on a 5W adapter or standard USB port on a computer?

    Jeff
     
  2. mkrishnan Moderator emeritus

    mkrishnan

    Joined:
    Jan 9, 2004
    Location:
    Grand Rapids, MI, USA
    #2
    Probably... isn't it already faster to charge an iPhone or iPod with a wall charger than with a computer USB port? The last time I did the latter, it seemed to take ages.
     
  3. mkrishnan Moderator emeritus

    mkrishnan

    Joined:
    Jan 9, 2004
    Location:
    Grand Rapids, MI, USA
    #4
    I think it's lower... Wikipedia...

    http://en.wikipedia.org/wiki/Universal_Serial_Bus#Power

    Lists a max load of 500 mA on a USB2 port with a voltage range of 4.4-5.25V, so the typical plan power maximum is more like 2.5W....
     
  4. rgbyhkr thread starter macrumors member

    Joined:
    Jul 1, 2007
    #5
    That makes things interesting. If you needed full capacity recharge in as quick a time as possible, then the wall jack is gonna be your best bet. I'm guessing that most car 12V to USB adapters won't output 10W and likely neither will various portable battery solutions out there. Though, in the case of the latter, if you have a portable battery then recharge speed wouldn't be as critical.

    Here’s something interesting:

    http://www.belkin.com/IWCatProductPage.process?Product_Id=474680

    It's a dual USB port car cigarette lighter adapter and under the features section, it says:

    "- CLA includes 2 USB ports (1-amp, 500Mah) to charge multiple devices at the same time

    - 1-amp USB outlet allows for faster charging on iPhone 3G"

    Ok, so that would seem to confirm what we were talking about above whereby the 1A USB port (5W) charges faster than the 500Mah (2.5W) port. I wonder if we'll see new models that offer a 10W port specifically for the iPad. Here's an off brand available now that does 10W, though it may be only 5W + 5W (has 2 USB ports):

    http://www.alibaba.com/product-gs/246492013/Double_USB_Car_Charger_for_iPhone.html

    Interesting though I have to say, if not for the fact that I am impatiently waiting for the iPad to be released, I never would have dug into this kind of minutia... :D

    Jeff
     
  5. rgbyhkr thread starter macrumors member

    Joined:
    Jul 1, 2007
    #6
    Here are a few more "interesting" thoughts ;):

    There are plenty of external battery solutions out there offering USB outputs. Some are pretty compact and can get you at least one full recharge on the iPad. For example:

    -- http://www.hypershop.com/HyperMac-Mini-7200mAh-Battery-for-iPhone-iPod-iPad-USB-s/165.htm
    -- http://www.Energizerpowerpacks.com/us/products/xp8000/
    -- http://www.imaxpower.com/product-p/imp880.htm
    -- http://www.zagg.com/accessories/zaggsparq.php - Note that a v2 is coming out in March that is supposed to fix the problems that plagued the initial design

    There are certainly others, but theses are ones I've checked out. The iPad's battery is spec'd as 25Wh. All of these batteries are spec'd in mAh, so you have to convert to see how they compare. The conversion is:

    (mAh/1000) * V = Wh

    USB ports offer 5V, so we know that value. So, one example calculaiton would be the HyperMac Mini:

    (7200mAh/1000) * 5V = 36Wh

    There's some lost power in the transfer, so you won't get all of those 36Wh when charging the iPad's 25Wh battery. As a result, it's not a straight calculation of one divided by the other to find out how many recharges you get. That being said, it's safe to assume for this one that you'd get 1 full iPad recharge with some left over.

    If you need more than that, there's also the next level of external batteries out there which are intended for use with notebooks. They are usually heavier and physically larger, but offer lots more power. As an example, the HyperMac line is offered in 60/100/150/222 Wh capacities.

    http://www.hypershop.com/HyperMac-External-MacBook-Battery-and-Car-Charger-s/91.htm

    They all have USB ports on them so they can be used to charge the iPad. All the batteries in this larger category which offer USB ports also have a separate power port for notebooks that you connect with a cable that has different tips. The USB ports all seem to be of the 5W variety. I guess they could use the notebook port with a female USB tip to try and give you a 10W USB option, but that's probably more trouble than it's worth if the separate USB port is already there.

    One other thing to consider beyond capacity is recharge cabling. The external notebook batteries all seem to require a specific AC adapter whereas many of the smaller batteries can be recharged over USB. That's one less proprietary cable to have to keep track of, which is nice. I did notice though that the time it takes to recharge the external batteries that draw power from a mini USB port are long - likely because of limited power being supplied over a 2.5W or 5W USB connection. Perhaps that could be cut down though if you used the iPad's own 10W USB power adapter to recharge the external battery.

    Ok, now I'm even starting to bore myself. ;)

    Jeff
     
  6. rgbyhkr thread starter macrumors member

    Joined:
    Jul 1, 2007
    #7
    So, I sent an inquiry to HyperMac asking about the possibility of them developing a cable for use on the 60/100/150/222 Wh units that would offer a 10W output to the iPad. Here's the response:

    "Thank you for your interest in HyperMac battery. Sanho's engineer is working on the battery for IPAD, we might have a new battery for both MacBook and IPAD or just for IPAD only.
    Please check back at www.hypershop.com in April when the IPAD is released."


    No surprise there I guess given the level of interest in the iPad. I for one will hold off and wait to see what they come up with. I think there's the potential for a sweet spot size in between the Mini and the 60Wh version that could offer about 2x recharge with a 10W output for fast charge times. Or, they could just modify some existing models to offer a 10W USB port vs 5W. That would be worthwhile also.

    Jeff
     
  7. elmo151 Guest

    Joined:
    Jul 3, 2007
    Location:
    NYC
    #8
    thanks for those links. the energizer looks very interesting
     
  8. rgbyhkr thread starter macrumors member

    Joined:
    Jul 1, 2007
    #9
    I actually got my hands on one last week when Fry's was running a sale for $50. Once I opened it up and saw the wall charger, I boxed it back up and took it back. This is just my own preference, but for me the thing was just too clunky. It's bigger than the battery and is of the the connecting cable -> power brick -> AC plug design. It's just one more cable to take with me on trips and, in this case, way too big. As far as I can tell from the box and Energizer's site, there's no alternate way of charging the battery.

    Jeff
     
  9. Mactagonist macrumors 65816

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    Feb 5, 2008
    Location:
    NYC - Manhattan
    #10
    Got any links for more information of the Sparq or Hyper Mac battery? Reviews etc... Where did you see that the Sparq was going to be updated?
     
  10. rgbyhkr thread starter macrumors member

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    Jul 1, 2007
  11. Mactagonist macrumors 65816

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    Feb 5, 2008
    Location:
    NYC - Manhattan
    #12
    That is more then I expected! Thanks for sharing the fruit of your research!
     
  12. mwpahr macrumors newbie

    Joined:
    Apr 9, 2010
    #13
    Apple BS

    My IPAD charge is not slower on USB, it does not work at all. I have tried it on 3 separate PC's (A Dell Laptop, an IBM laptop, and a home built PC) all using USB 2.0 and none of them work.. my only option is to use the wall plug. I don't mind so much, but Apple is BS-ing the world... sure you can charge USB if you have a port that puts out 10W... which none do (5W is the best any of them do).

    I am only mad that Apple is not fully explaining its limitations.
     
  13. Mark Booth macrumors 65816

    Mark Booth

    Joined:
    Jan 16, 2008
    #14
    So how do you know those 3 PCs won't charge it? Did you see the little "Not Charging" text on the iPad? Did you know that, with some computers, that text will show up when the iPad is plugged into their USB and the iPad's screen is on. If you shut the screen off (put the iPad to sleep), in many cases the iPad will then charge. Did you try that?

    So far, we've seen reports from Mac Pro, MacBook Pro and MacBook owners that their USB ports charge the iPad just fine. Mac Mini owners aren't having as much luck.

    Finally.... the USB 2.0 spec for a USB port is 5v @ 500 milliamps. That spec WILL charge an iPad, but do it slowly. So, if your computer's USB port won't charge the iPad at all (even with the iPad's screen off), then blame your computer manufacturer not Apple. It's not Apple's fault that your computer manufacturer didn't follow the spec.

    Mark
     
  14. ugp macrumors 65816

    ugp

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    Location:
    Inverness, Florida
    #15
    It charges faster plugged into the wall than plug into my iMac.
     
  15. hmp macrumors member

    Joined:
    Jun 25, 2007
    #16
  16. ugp macrumors 65816

    ugp

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    Jan 7, 2008
    Location:
    Inverness, Florida
    #17
    Specs on the power are starting to increase on the USB. The newer iMacs as well charge with the screen on but is still a lot slower then plugging into the AC Power. Typically with batteries a slower charger is a better quality charge though then a rapid one. This is why I don't use car chargers too much on my phone.
     
  17. NJBlackBerry macrumors member

    Joined:
    Apr 5, 2010
    #18
    USB specs

    Apple simply chose to ignore the USB specifications, and decided that the iPad required different power requirements. This will allow everyone to run out and get new adapters and charging blocks since all of the iStuff we already bought doesn't work anymore. Of course the charging adapter in the box is not available yet (oops) so we need to find third party solutions.

    I bought the Griffin Tecnology mini brick that is sold at the Apple store. It has charged the iPad, iPhone 3g and an old Nano without burning anything out.

    This, above all else, is the most aggravating feature of the iPad.

    Create a new specification but don't bother to tell anyone.

    P.S. - I LOVE the iPad. Replaces a Kindle and iPod Touch that I don't need to carry with me. And so much more...
     
  18. ECUpirate44 macrumors 603

    ECUpirate44

    Joined:
    Mar 22, 2010
    Location:
    NC
    #19
    Sorry i'm reviving this thread, but I have a question and I have no idea what i'm talking about when it comes to electricity. I have an iPhone and iPad that I would like to charge in the car. I have a USB car charger that plugs into the power outlet in the car, and then I use my white sync cable to charge.

    The USB charger I have is listed as:
    Input= 10.5V-18V... 0.65A
    Output= 5V.. 1A


    The iPhone wall charger is listed as:
    Input= 100V-200V 50/60 Hz 0.15A
    Output= 5V.. 1A

    The iPad wall charger is listed as:
    10W
    Input= 100V-200V... 0.45A 50-60Hz
    Output= 5.1V... 2.1A

    Can I use the car charger to charge both devices without causing damage to the batteries?
     
  19. fizzwinkus macrumors 6502a

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    Jan 27, 2008
    #20
    I'm sure it had nothing to do with avoiding 10 hour recharge times...
     
  20. omicron macrumors member

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    Jun 20, 2011
    #21
    Yes. But it will be slower.
     
  21. Krevnik macrumors 68040

    Krevnik

    Joined:
    Sep 8, 2003
    #22
    This is exactly right.

    The iPhone 3GS and 4 can draw more than 2.5W depending on what it's doing at the time. For example, the 3GS draws about 3W when running GPS apps like TomTom with the screen at max (this is why there were issues with power drain while in the car kits). The 4 draws just over 2.5W in the same situation. The iPad draws even more during normal use.

    It's possible to charge with 500mA at 5V (2.5W), but you can't be using the iPad for anything at the time. That means screen off. Apple supports a high-power mode on some machines to put out 1A at 5V (5W) which will charge the iPad more reliably, and it accepts up to 2.1A (10W) for charging through the wall.

    The iPhone accepts up to 1A for faster charging through the wall. More devices are doing similar, providing 1A wall plugs and charging more slowly through a computer. I've got a handful of devices doing this now. It is annoying that it isn't clearer that these wall plugs are providing more than 500mA, but do we need to have multiple plugs on the device to pass power in based on how much current there is? Which is worse, reusing the USB port to pass more power, or having two power cables for the device? Or secret option 3, terrible recharge times where you can't use the device while it is trickle charging?
     

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