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    Default Charging through USB port versus Wall Plug

    I've found that my phone charges much slower when I use a computer USB port to charge with versus the usb port adapter that plugs into the wall. Are all USB ports the same? Is the cable limited in its ability to carry a certain amount of charge? Any tech expertise would be appreciated. When I charge with my USB port at work, the charge can barely keep up with my usage (albeit heavy usage).
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    superm1's Avatar

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    Quote Originally Posted by bluger View Post
    I've found that my phone charges much slower when I use a computer USB port to charge with versus the usb port adapter that plugs into the wall. Are all USB ports the same? Is the cable limited in its ability to carry a certain amount of charge? Any tech expertise would be appreciated. When I charge with my USB port at work, the charge can barely keep up with my usage (albeit heavy usage).
    The wall charger can put out far more current than most computer USB ports. You'll notice the device also heats up more when charging from the wall charger.
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    pwnst_r's Avatar

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    When connected to a USB port instead of a wall charger, it's float charging (as opposed to trickle charging), which is why it's slower.

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    All in all usb charging has NOT been bad for me. It charges pretty fast for me. Yeah when I need an instant pick me up there is nothing better than a wall charger. I thought this was common knowledge.
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    Quote Originally Posted by pwnst_r View Post
    When connected to a USB port instead of a wall charger, it's float charging (as opposed to trickle charging), which is why it's slower.

    That's irrelevant, it float charges no matter what it's attached to.

    The reason your PC's USB port charges more slowly is it is providing the USB specification maximum milliamps of 500ma (or, as low as 100ma, depending on the power situation). Devices CAN ask for more than 500ma, but they cannot expect more. Thus, SOME PCs and USB hubs will end up charging the phone faster, but not all. There's no easy way to tell without testing it yourself.

    The wall charger puts out 1 amp (1000ma), which is double what the maximum spec for a USB port is.
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    @Vincent Law

    As you seem to know your specs, maybe you can clarify this charger related question.

    My SUV has a built in AC plug in the console. IIRC, it's 110 volt and I've read that it's rated 100 watt. Is there any benefit to charging using the wall plug in that outlet versus using a standard car charger?

    I only use the wall charger, so I ask purely out of curiosity.
    Last edited by Blubble; 06-17-2010 at 09:22 AM.
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    Quote Originally Posted by Blubble View Post
    @Vincent Law

    As you seem to know your specs, maybe you can clarify this charger related question.

    My SUV has a built in AC plug in the console. IIRC, it's 110 volt. Is there any benefit to charging using the wall plug in that outlet versus using a standard car charger?

    I only use the wall charger, so I ask purely out of curiosity.
    If the car charger puts out 1amp (1000ma) like the wallcharger does, there is no difference in charging speed. The charger should say on it somewhere how much it puts out (like 1amp @ 5v or similar).

    However, if you care about efficiency, the car charger will be more efficient with your SUV's battery (since it does not need to go from DC to AC to DC again, instead being DC the entire time).
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    Cool. Thanks for the info.
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    I believe there's a charger for the iPad that puts out 2 amps. Would this be any problem for the Evo? Just a faster charge?
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    Quote Originally Posted by tromba View Post
    I believe there's a charger for the iPad that puts out 2 amps. Would this be any problem for the Evo? Just a faster charge?
    Yes there would be a problem.

    The EVO's charging circuits are rated to handle only 1 amp, and this is also likely limited by the battery's ability to charge as well.

    Best case scenario would be as you describe, but in reality any of the following are more likely to happen:

    1. It fries your EVO's charging circuits, and your EVO no longer charges.
    2. It fries your EVO's battery. (The circuits SHOULD stop this, but it's possible if the current is simply too much for them to handle. Think what happens during a lightning strike)
    3. The charging circuits only draw 1amp despite it being a 2amp charger. Everything works fine, although the charger is less efficient.
    4. Nothing happens, it refuses to charge.

    All in all, not a risk you want to take.
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    Quote Originally Posted by tromba View Post
    I believe there's a charger for the iPad that puts out 2 amps. Would this be any problem for the Evo? Just a faster charge?
    I would not try it. It is possible you can overload the EVO and short something. Might not, but why take the chance?
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    Quote Originally Posted by Vincent Law View Post
    Yes there would be a problem.

    The EVO's charging circuits are rated to handle only 1 amp, and this is also likely limited by the battery's ability to charge as well.

    Best case scenario would be as you describe, but in reality any of the following are more likely to happen:

    1. It fries your EVO's charging circuits, and your EVO no longer charges.
    2. It fries your EVO's battery. (The circuits SHOULD stop this, but it's possible if the current is simply too much for them to handle. Think what happens during a lightning strike)
    3. The charging circuits only draw 1amp despite it being a 2amp charger. Everything works fine, although the charger is less efficient.
    4. Nothing happens, it refuses to charge.

    All in all, not a risk you want to take.
    I'm using am iPad charger and it appears that #3 is in operation.
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    Quote Originally Posted by Vincent Law View Post
    That's irrelevant, it float charges no matter what it's attached to.

    The reason your PC's USB port charges more slowly is it is providing the USB specification maximum milliamps of 500ma (or, as low as 100ma, depending on the power situation). Devices CAN ask for more than 500ma, but they cannot expect more. Thus, SOME PCs and USB hubs will end up charging the phone faster, but not all. There's no easy way to tell without testing it yourself.

    The wall charger puts out 1 amp (1000ma), which is double what the maximum spec for a USB port is.
    my point is that it doesn't trickle charge as people seem to bring up a lot around here.
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    They're probably just using the term incorrectly. In a sense it does trickle, it just has protection from overcharging.
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    right, which makes it a float charger
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    Quote Originally Posted by tromba View Post
    I believe there's a charger for the iPad that puts out 2 amps. Would this be any problem for the Evo? Just a faster charge?
    I disagree with the other posters. The charger is capable of a 2 amp load, but the phone is NOT going to draw that. The charger doesn't "force" 2 amps ... it is a voltage source, not a current source. (Props to any EE majors on the board!)
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    Two things:

    I was using an old Motorola charger for my Evo that was only marked for 500mA (I think), and it worked just fine. The stock charger - and my wife's Hero charger - are both marked at 1A. I wouldn't ever go higher unless somebody else had confirmed it was safe, but theoretically the device will only draw what it needs. Still, electricity isn't something to trifle with. That said, some companies market those high-speed chargers that put out extra current and charge faster - or do they have higher voltages? Either way, I wouldn't screw with it. 5.0V and <1A is safe.

    Second, has anybody noticed the AC plug that came with the Evo making a high-pitched noise when charging? Or maybe only when fully charged?
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    Quote Originally Posted by SilverZero View Post
    Second, has anybody noticed the AC plug that came with the Evo making a high-pitched noise when charging? Or maybe only when fully charged?
    My old phone charger had a faint high-pitched hum, but not the Evo one. Just luck of the draw, unfortunately.
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    http://forum.androidcentral.com/htc-...tml#post135707

    People in this thread have noted 110v versus car charger, etc. As other posters have already noted, that is not relevant to charging a phone.

    The reason why you can plug directly into a computer to charge, versus plugging into a car or wall requires a power adapter (or converter) is noted in the linked thread.
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    Quote Originally Posted by xorbe View Post
    I disagree with the other posters. The charger is capable of a 2 amp load, but the phone is NOT going to draw that. The charger doesn't "force" 2 amps ... it is a voltage source, not a current source. (Props to any EE majors on the board!)
    This is correct. On top of that I will reiterate my empirical experience that I posted earlier -- I am actually using an iPad charger for my Evo (rated at a maximum 2.1A), and it is working just fine.

    Actually, I bought 5 of them because they were priced on Amazon at $0.99 each. I just checked, they are now listed at $3.99 each, so the previous price may have been an error, but $3.99 is still a good deal:

    Amazon.com: Crazyondigital High Capacity Dual USB 2.1A Home Travel…
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    Quote Originally Posted by curthibbs View Post
    I'm using am iPad charger and it appears that #3 is in operation.
    Yeah, that's the correct scenario.

    A device isn't going to draw more current than it's designed for at a given voltage. A situation that is analogous is the average home outlet can provide 120V at 15A. However, short of vacuum cleaners or other heavy duty electric motors, anything you plug in draws far less current.

    The only danger would come in is if you use a charger that delivered a significantly higher voltage as that would throw off the regulatory circuitry and result in an over-current which would undoubtedly damage the device.

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