I think I used a charger that was too weak for the phone, now I cant power it up

Discussion in 'Motorola Q' started by ciper, Sep 16, 2009.

  1. ciper

    ciper New Member

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    I think I used a charger that was too weak for the phone, now I cant power it up

    Last night my battery was nearly dead so instead of charging the phone from my laptop as I usually do I used the charger from my Motorola headset. I didn't realize it had such a low milliamp rating and I am guessing the phone is now stuck in a catch 22.

    My guess is that the phone was drawing more power than the charger provided and the firmware on the phone has no way of knowing this so It ran the battery down to a point that it cannot even start the low level charging.

    Is there some trick to get the phone to a point that it has enough power to charge this battery? Perhaps there is a pinout for the battery and I can charge it by hand with alligator clips (I used to do this on my nokia)
  2. mike250rs

    mike250rs New Member

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    try a different charger (a/c prefered) with atleast 500 milliamp output. let it charge powered off for a bit
  3. ciper

    ciper New Member

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    Ok I found the quick way to remedy this problem. I gave the battery five volts while a volt meter was connected. It started around 3v and went up by .2 volts every second until it suddenly jumped straight to five. This only took about 20 seconds and it let my phone power up and charge normally.

    If you don't have a volt meter handy Id say just charge it for 30 seconds while monitoring the temperature.

    I have to say that I am not pleased with how Motorola firmware handles charging. The phone should not require a charged battery to be able to star the charging process! It should also not allow you to discharge the battery to a point the phone is not usable, and possibly even notify the user when a charger is too small, maybe on screen or with a sticker in the battery compartment stating to use chargers over 500mah or something
  4. ninjaap

    ninjaap Moderator

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    maybe you need a new alternator? jk... but yeah, a little info would be nice.
  5. ciper

    ciper New Member

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    More info? The "bad" charger was 330mah. The phone has what I believe is a firmware bug that lets it stay powered, even though the battery is below a critical level, on a charger that isnt strong enough. I could see this potentially happening on a cheap USB hub.

    The image below shows the battery has four pins. From the top - one is common, four is positive and 2,3 are used for charging (temperature and to help the phone determine the charge level).
    [​IMG]

    I can't imagine how many people were duped into buying a new battery because the sales drones at the cell phone stores don't have the intelligence to figure out whats wrong.
  6. TreeFrog

    TreeFrog Active Member

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    good info but not sure how your inducing the 5 volts to jump start the battery. and isn't plugging the q into ac power for a while doing it? with a known good moto ac charger of course!
  7. ciper

    ciper New Member

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    I'm not sure I follow the question. I cut a USB cord in half, removed the battery from the phone, held the appropriate stripped wires from the USB cable to the pins on the battery and then connected the USB plug to my laptop.

    A charger (AC or otherwise) is not able to charge the battery properly if the phone is not active in some fashion. Either the low level charging procedure (the screen with a big battery icon) or in the operating system.
  8. TreeFrog

    TreeFrog Active Member

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    ahhh...but that still isn't detailed enough for us noobs as to what wires are what? and also maybe a dumb question but every moto q ive owned and used and had the battery run clear down to dead dead dead...a couple hours on ac would revive it! and i'm not gonna chop a perfectly good charger to quicken the ordeal!! =)

    btw...it doesn't sound like your selling anything at the moment but i see you have a store/shop with wares to sale.
    http://www.ioffer.com/selling/imetroshop
  9. mike250rs

    mike250rs New Member

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    ahhh... you made a redneck cradle charger :)
  10. ciper

    ciper New Member

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    This adventure got me to pour over many of the specifcations for USB and there is a subset of the standard specifically for charging. In the end I have determined that you could make your own super charger for the phone by using a 1.8 amp five volt power supply and a left over usb cord!

    [​IMG]
    If looking at the usb plug pin one is +5v, two and three shorted together (data loopback), four has no connection and five is common. The phones internal charging circuitry will adjust the voltage and draw as much power as needed.

    I wouldnt always trust the color coding of the wires but most often the red is +5 and the black is common. You can use any source of +4 through +5 volts. For example cut the end off an old mouse. I tried leaving the battery connected to a good charging source for a few hours and it didn't help. I verified this by measuring the voltage of the battery at 3volts which was drained to the point that the battery probably suffered damage.

    The real desktop chargers output 4.2V at 250-350ma while a standard USB port is supposed to be 5v at 500ma max and a dedicated USB wall charger has a max of 1800 mA of current! A strange side note - A dedicated USB wall charger is supposed to short the data pins of the USB connection to allow the device to charge at the highest rate and to save money since it doesnt need any type of USB chipset. Think of it like a loopback serial cable.


    I don't sell anything. I just stole that picture for reference sake!

    I prefer MacGyver style cradle charger :dft011:tounge_out
  11. bberryhill0

    bberryhill0 Active Member

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  12. ciper

    ciper New Member

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    I say bridge rectifier - voltage regulator - capacitor - usb cord would work. I am going to guess the Moto Q uses 400-450ma while powered since a 500ma charger will slowly charge it and the 375 adapter I used killed it.

    A bridge rectifier is just a fancy name for four diodes in a single package in a configuration that produces a solid DC stream in one polarity from an AC or DC source. I'd use a voltage regular like this http://www.radioshack.com/product/index.jsp?productId=2062599

    Edit: Here is a diagram if you want to make it from spare parts. I suggest using the female end of a USB extension cord so you can plug whatever you want into it. You'll probably have to short the data pins to make it fully compatible with other devices.
    [​IMG]

    Hmm... Now that I think about it I bet you could just use a car charger connected to the output of the voltage rectifier. Many car chargers are just the second half of this circuit!

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