Is extra voltage of cellphone charger a problem?

Discussion in 'General Electronics Chat' started by tjohnson, Jul 6, 2015.

  1. tjohnson

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    Dec 23, 2014
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  2. MikeML

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    There is no way to know except getting an OEM charger and comparing the voltage (under load) to what your dad bought...
     
  3. tjohnson

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    He called our local Sprint store, and they said the only charger they sell that would work with the phone is a universal charger. So I suppose we should just try the universal charger we got?
     
  4. ian field

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    Most phone chargers that charge a single lithium cell are 5V. You can buy car socket phone chargers with a selection of power jack adaptors - most also include a 5V USB charging connector.

    Personally - I wouldn't trust a vague name-brand charger where lithium is concerned - they can vent with flaming gas if over charged!

    Maybe if you have a room with a bare stone or brick floor that you can leave it charging on till you're sure it isn't going to flame.
     
  5. tjohnson

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    My question was answered in this thread. When someone else mentioned charging a 3.7V cellphone battery with a 5V cellphone charger, Audioguru said:
    So if I understand correctly, although some cellphones have a 3.7V battery, their charging circuit takes a 5V input, meaning that the universal charger we have should work.

    Would it work to plug the cellphone into a computer's USB port, since that's also a 5V DC power source? I wouldn't think it would be wise to do that without a voltage regulator though.
     
  6. MikeML

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    The charging circuit inside the cell phone is likely designed for an external wall-wart that delivers 5V. Therefore it can be charged from a USB port with the appropriate cable.

    If you connect a higher voltage than 5V to it, the internal charger may have to deal with getting rid of more heat than would be produced at 5V. Can it deal with it? I wouldn't bet a $300 phone on it.
     
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  7. ian field

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    Chances are the TS could walk into a shop and buy a USB adaptor for the phone, so the phone could be charged from a computer port or a USB charger wall-wart.

    The charger that has been mentioned has a spread of output voltage as opposed to the tight regulation of a USB device. I'd be hesitant to use that - the charge controller in the phone should take care of it - but can it handle the low load output voltage of that adaptor.

    Its thankfully rare, but fires do sometimes happen with all OEM accessories - using an adaptor that doesn't regulate quite that well seems to be tempting fate.
     
  8. tjohnson

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    The phone charged fine last night with the universal charger my father got on eBay. Since (as I mentioned earlier) our local Sprint store said the only charger they sell that would work with the phone is also a universal one, we figured we might as well just use the one we have.
     
  9. ian field

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    A "universal charger" sold specifically for charging phones will probably have tight regulation that conforms to the USB voltage specification.

    A run of the mill "universal charger" may not.

    Some of the (admittedly few) all OEM phone-charger combinations had been working fine for months - even years, before they flamed.

    If you take one chance with charging lithium - don't take any other chances.

    At least clear the area where you leave it charging of anything that can catch fire.
     
  10. RichardO

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    This is _not_ a joke. Take this advice seriously.
     
  11. tjohnson

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  12. ian field

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  13. ian field

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    It also applies to charging phones with the charger that came in the same box.

    It *IS RARE* - but *DOES* sometimes happen. Most in the news for starting fires lately is the lithium batteries in E-cigarettes.

    Still quite rare - but once is too often!
     
  14. dl324

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    Depends on your opinion of that particular vice...
     
  15. tindel

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    IDK - I think some of you are being a bit conservative. I've worked with many cell phones and chargers and even made a couple of my own for fun.

    USB spec is 5V +/- 0.25V - with a few exceptions based on load current. Almost every phone on the planet that has been made in the last decade uses USB connectors and are required to work with this input voltage to meet USB specification testing. I *would* be a bit cautious if the charger states that the output can be up to 6.5V, but that's probably not much of a concern either as the phone manufactures do design the power inputs for worst case conditions and typically they use switching regulators that won't have much efficiency change with a slightly high (or low) input voltage. The regulators typically limit the charge current to battery too, and not the voltage.

    Could you damage your phone or battery? It's possible I suppose, but not probable.
     
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  16. alfacliff

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    I see no reason that the charge controller isnt in the phone. my ham portable, a Yeasu ft60 takes up to 16 volts in the charging jack and has a 7.2 volt battery.
     
  17. ian field

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    That's like comparing apples with oranges, the TS is talking about a cell phone - they have been known to flame, even with the correct supplied charger.
     
  18. alfacliff

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    not really, the technology is there, and the safety factor would be much better with a charge controller in the phone. portable ham radios have been including the charge circuit for a few years. commercial portable radios too, most can determine the battery type and charge accordingly.
     
  19. tjohnson

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    @ian field: I don't understand how comparing ham radio chargers to cellphone chargers is different from comparing e-cigarette chargers to cellphone chargers.:confused:
     
  20. ian field

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    I Didn't compare E-cig chargers to cell phone chargers - I merely mentioned in passing that accidents have recently been much more frequent with E-cigs.

    Both use lithium batteries, but quality is far better with cell chargers.

    You didn't even bother to mention what battery chemistry you ham rig uses.
     
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