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Droid Charging Requirements


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  1. RTAdams89

    RTAdams89 Well-Known Member This Topic's Starter

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    I have several USB-MicroUSB cables (some OEM Motorola, some other brands), several 12 volt-USB converters, several cars, and several devices that accept MicroUSB connection for power. With everything other than my Droid (including a Blackberry and a GPS unit) every combination of cable and 12volt converter works. With the Droid, all of the combinations will turn on the screen (indicating the Droid knows a cable has been connected), but only a few combinations will actually charge the Droid. The only possible explanation I have come up with for this is that the Droid has some sort of minimum current requirement, and that some converter/car/cable combinations are unable to meet this requirement. So, what is the minimum voltage and current that will allow the Droid to charge? And, does anyone have any other ideas about this?
     

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  2. RTAdams89

    RTAdams89 Well-Known Member This Topic's Starter

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    PS: I know that the charger that comes with Droid is 850mA. I also know that the Droid charges form my computer (about 500mA). The car charger I have that works with the Droid is 1000mA, and the one that doesn't is unlabeled. Anyhow, I am just wondering what the very minimum current is that will still allow the Droid to charge (even if it is slow).
     
  3. Szadzik

    Szadzik Well-Known Member

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    The minimum will have to be a tad bit higher than the maximum power consumption of the phone. So that when you connect it to the charger it gives more power than is consumed by the phone.
     
  4. darrenxes

    darrenxes New Member

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    I have been using nokia cable for e71 to link up my dext as well.. No issue
     
  5. RTAdams89

    RTAdams89 Well-Known Member This Topic's Starter

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    Not sure about that, but care to hazard a guess and quantify the value?
     
  6. Szadzik

    Szadzik Well-Known Member

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    If a computer that is capable of outputting a max of 500mA can charge it I think the max usage would be at around 350mA with everything on etc.

    I do not think however you will find a charger with less than 500mA output so I would not worry about it. Just use whatever you have or tell us what you are trying to do.
     
  7. RTAdams89

    RTAdams89 Well-Known Member This Topic's Starter

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    It's interesting: with the default Motorola USB cable the droid charges fine from my computer's USB port, but using another cable (which does "work" as it charges something else) won't charge the Droid.
     
  8. Szadzik

    Szadzik Well-Known Member

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    Different pin connections. There may be manufacturer specific cables that are a bit different from the standard ones and thus not work.
     
  9. RTAdams89

    RTAdams89 Well-Known Member This Topic's Starter

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    The Droid uses a standard MicroUSB conenctor, no?
     
  10. Szadzik

    Szadzik Well-Known Member

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    Yes, but the cable you have my be non-standard.
     
  11. c670809

    c670809 Member

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    I just built a charger so I could use aa's to charge the phone in-case I was in an area without power.

    At first I hooked it up like the 'standard' usb connection should be with + and - pins on the outside. I tried it and it would turn the phone on but would not charge. So, I looked at the AC charger that came with the phone. . . the two center pins are connected. So then I connected mine and it works great.

    I know apple does something tricky like that too.

    Matt
     
  12. RTAdams89

    RTAdams89 Well-Known Member This Topic's Starter

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    As in the two center pins are connected to each other, thereby creating a short between what are normally the data pins? WTF, that seems like a dumb design idea...
     
  13. dmodert66

    dmodert66 Well-Known Member

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    A better place for this may have been in the Droid forum. IIRC there where a few threads about this very issue there in the past. Hope you get it sorted though!
     
  14. c670809

    c670809 Member

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    I know it sounds crazy, but yes, that is exactly what I mean. It's pretty easy to test. Plug in your AC power supply, unplug the USB cable, now with a volt/ohm meter measure it the power supply. The outside pins will be + and - . . . now set your meter to ohms and the two center pins are just connected together.

    Now as a disclaimer . . . this is how mine is but you need to check yours.

    Matt
     
  15. RTAdams89

    RTAdams89 Well-Known Member This Topic's Starter

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    I'll certainly look into this. Is this the "EMU" (aka "enhanced micro usb") connector that Motorola uses? I've heard about it before (and just now researched it more), but I didn't realize it was so sophisticated.

    As a follow up, if this is an EMU setup, then as I Understand it, shorting the two data pins tells the Droid "you are connected to a wall charger, not a computer" and the Droid then attempts to draw more current than the 500ma a USB port can provide. Does anyone know what the maximum current the Droid will draw when it knows it is connected to a computer (500ma, or something less)? How about the maximum when connected to a wall charger?
     
  16. c670809

    c670809 Member

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    I wish I could help more . . . I did all my testing with the original cable and the OEM wall charger.

    I only know that when I plugged the original cable into the 'usb battery' that I made it didn't work. When I measured the OEM charger and then shorted the middle leads on my usb, then everything worked fine. Without the cables shorted it would turn the phone on but it would not charge it.

    I have not tried to see how much the phone will pull but my supply will put out 1.5 amps.

    Hope this helps.
    Matt
     
  17. RTAdams89

    RTAdams89 Well-Known Member This Topic's Starter

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    That is bizarre. So you have a power source that is capable of outputting 1500ma, and when you connect it to the Droid via a USB - MicroUSB cable, it will only charge if the two data pins are shorted? Since the data pins are obviously not shorted on a computer's USB port, how then does the Droid charge when connected to a computer?

    Any ideas where I might find more info about this whole deal?
     
  18. RTAdams89

    RTAdams89 Well-Known Member This Topic's Starter

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    Wikipedia had this to say about the EMU connector:
    Since my Droid seems to charge with some card chargers and from my computer's USB port even before Windows is loaded, I'm not sure how accurate those statements are.
     
  19. KlaymenDK

    KlaymenDK Well-Known Member

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    Hi all,
    I can see you've been doing a fair bit of research -- but you've just missed the true reason! :eek:

    The USB protocol specifies that any ole device should be allowed to draw 100mA; this works fine for charging flashlights and powering other USB-format novelty items. Also, this is juust about what an average smart phone consumes at idle (that is to say I don't know the exact values of the Droid explicitly) -- so this would explain why a charger would be able to sustain, but not charge, a phone plugged into a dumb USB port.

    I say 'dumb' for a reason --this is the point of my post-- because the connected device must communicate with the host in order to obtain more than the minimum allowance (up to between 900 and 1500mA depending on port type).
    The kingpin here is that 'smart' devices err on the side of caution: they refuse to draw more than the minimum allowance unless they can obtain confirmation to draw more. So you need a charger that is 'smart' enough to not only spew 5V, but also to respond to requests from more cautious devices. :cool:

    Sadly, this distinction is rarely made on ebay auctions, so you'd need to buy typically more expensive retail chargers and/or experiment with different models... :(
     

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