Fastest charge?

Discussion in 'iPod touch' started by west.acre, Jan 8, 2009.

  1. west.acre macrumors member

    Joined:
    Aug 26, 2008
    #1
    I have 3 ways of charging my 2G Touch:

    1. USB From MBP - On battery
    2. USB From MBP - On AC power
    3. USB AC Adapter

    Which will charge the fastest, or is there no difference?
     
  2. agargar macrumors member

    Joined:
    May 14, 2008
    #2
    In theory, the one providing the more Amps.
    Check the specs. Usually the AC adapter.
     
  3. west.acre thread starter macrumors member

    Joined:
    Aug 26, 2008
    #3
    Output of the AC adapter is 1A. What would the output of the MBP USB be? Would it change when running on battery?
     
  4. atszyman macrumors 68020

    atszyman

    Joined:
    Sep 16, 2003
    Location:
    The Dallas 'burbs
    #4
    The order from slowest to fastest, if there were any difference would be:

    1. Laptop on battery.
    2. Laptop on AC.
    3. AC adapter.

    The laptop is going to be limited in it's output power by space, heat and other issues that could come into play that would not be present on the AC adapter which can be setup to push as much as the cable and iPt can handle. The laptop on battery power does all sorts of limiting things to conserve the battery like throttling the processor, and video cards, so adjusting peak USB power output does not seem like an unreasonable limitation on battery.

    However it is possible that all three produce the same amount and can charge in the same time period. As a point of reference my 4th gen iPod charges faster from the AC to Firewire adapter than from my laptop using Firewire or USB.
     
  5. west.acre thread starter macrumors member

    Joined:
    Aug 26, 2008
  6. quick5pnt0 macrumors regular

    Joined:
    Sep 14, 2008
    #6
    Ive never timed it but in my experience my AC adapter charges the touch much faster than USB.
     
  7. agargar macrumors member

    Joined:
    May 14, 2008
    #7
    Hi again,

    The USB standard set a maximum of 100mA, that can be increased if the connected device so requires, to a max. of 500 mA. So, the AC, which provides 1A will be faster. I know original apple's wall chargers provide 1A. I won't use a charger providing much more of this. I don't know if the ipod touch is able to manage that and limit the current if needed and the battery could overheat and be "damaged".
     
  8. west.acre thread starter macrumors member

    Joined:
    Aug 26, 2008
  9. jake921660 macrumors regular

    Joined:
    Aug 2, 2008
    Location:
    Australia
    #9
    So if without the iPod overheating, it would in theory charge twice as fast on an AC adapter?
     
  10. agargar macrumors member

    Joined:
    May 14, 2008
    #10
    Let me answer "in theory yes", without much thinking ;)
    If not twice, at least much faster.
     
  11. atszyman macrumors 68020

    atszyman

    Joined:
    Sep 16, 2003
    Location:
    The Dallas 'burbs
    #11
    That all depends on how much current the iPt can dump to the battery. The iPt likely has it's own voltage regulation/protection circuitry in place to handle the 5V input, very little in the digital world runs at 5V anymore and even 3.3 V (the next step down) seems to be on it's way out.

    For portables and battery operated devices the lower the voltage you run at means cooler, more efficient devices. That being said the circuitry in the iPt will have it's own current limits to reduce the risk of damage, along with tolerances put in place to account for slight variances in components used.

    The AC adapter, since it has the potential to deliver the most current, will always yield the fastest charge, but depending on the iPt itself will probably not change charge times linearly with the current provided. Thus a 2x current increase is unlikely to yield a reduction in charge time by a factor of 2. It's entirely possible that no matter where it's plugged in the iPt will charge at the same rate due to it's internal circuitry, however from my own experience on my 4.5 year old iPod and from what others have said in this thread it appears that the wall charger is indeed faster, although by how much remains to be seen.
     
  12. west.acre thread starter macrumors member

    Joined:
    Aug 26, 2008
    #12
    I've seen some really cool battery tests done with a camera on an intervalometer. You can test battery life and charging times by setting the camera up watching over the device overnight, and then just take a look at the pics in the morning. If I hadn't lots my camera I might have done this :).
     

Share This Page