Micro USB chargers safe?

Discussion in 'Hardware and Peripherals' started by Rick F., Nov 3, 2010.

  1. Rick F.

    Rick F.

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    I have a Motorola Micro-USB charger that I've used at times to charge my 3yr-old TT-3rd edition. I've used this charger off and on for the past 2 years without problem ? and the 3rd edition's battery still holds a charge. This is the same type charger used to charge Motorola's RAZR phone (pictured below).

    [​IMG]
    But, I wonder if it's safe to use this type charger for two reasons...

    1. The label on the plug says, "from 4.5v to 9.5v 850ma max". I'm pretty sure the TomTom unit has a regulator inside to protect the unit from over voltage as do cell phones.
    2. I noticed that when charging the TomTom with this and turn on the TomTom, it won't find any satellites until I unplug the charger from the wall. It's like the charger generates interference.
    Is this type charger safe to use?

    Thanks.
     
    Rick F., Nov 3, 2010
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  2. Rick F.

    dash8

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    The standard voltage for USB is 5.0 volts. I have no idea why the plug says 4.5 to 9.5 volts. Many devices have a regulator, but I'm not so sure they protect against being over-voltage. Their primary function is to prevent over-charging (i.e. how much current can flow to the battery depending on its pre-charge state). You can find a new charger on Amazon or e-Bay for a few dollars that only outputs 5 volts and nothing else.
     
    dash8, Nov 4, 2010
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  3. Rick F.

    Rick F.

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    Thanks for the reply.

    I know that the TomTom has a 5v battery, and that 5v is the standard for USB ports. When I bought this charger it was listed on the package as having 5 volts output. The small print on the label of the plug is where it says 4.5v to 9.5v DC.

    As I look more closely at the label, it says, "Input AC: 100v to 240v 200ma / Output DC: 4.5v to 9.5v 800ma". I suspect that with 240v input it may yield a 9.5v output, so it's probably alright with 120v household voltage input.

    I'd measure the output with a voltmeter if I could, but the micro USB is too small to get in there with probes without shorting out something.
     
    Rick F., Nov 4, 2010
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  4. Rick F.

    canderson Moderator

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    Not likely that the input voltage is dictating the output voltage, but regardless, I'm not thrilled about using this device with your TomTom. I can imagine two possible scenarios based upon the labeling:

    1) You're right and the output will be lower at 120V, but it's rare that a converter operates this way. "Universal" converters of this sort more typically adjust for input voltage and provide a consistent output voltage.

    2) This unit has a substantial range of output, likely much higher when unloaded, and is very likely a linear supply instead of a switching supply. At full load, it might produce 4.5V, and at light load, 9.5V. As the battery becomes charged and the current demand is decreased as a result, I'm concerned about what the voltage will become.

    Long and short of it - that device is an oddball given the "rating plate". It's also troublesome that the unit cannot be properly operated with this charger connected. With any "normal" charger connected that has sufficient current capacity, I'd expect the unit to operate as usual, including normal satellite capture.
     
    canderson, Nov 4, 2010
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  5. Rick F.

    Rick F.

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    Thanks Canderson,

    Doesn't sound like it's worth risking damaging the unit. Besides, since the new XL-335TM has traffic, I'll be using the cig-lighter cable anyway. :D

    Thanks again guys.
     
    Last edited: Nov 4, 2010
    Rick F., Nov 4, 2010
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  6. Rick F.

    canderson Moderator

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    Considering how inexpensively you can pick up a decent 5V supply with a USB mini-B on the end, I'd have to agree.
     
    canderson, Nov 4, 2010
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  7. Rick F.

    dash8

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    240V is the standard voltage in places such as Europe and Australia. But their USB ports are the same as ours, of course. It's very common for a charger to accept an input voltage of 100-240 Volts AC and output at a fixed DC voltage. Normally, when the output has a wide voltage range like your charger, there's a switch or dial to select the correct one. (These tend to be a bit larger)

    My guess is it's probably a misprint, and you're really getting 5V, but why take a chance?
     
    dash8, Nov 5, 2010
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