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  1. #21  
    I'm no electrical expert, but this is the way I understand it.

    Look for my charger spec post, then this reply:
    Quote Originally Posted by jaltman View Post
    .3 volts is not a significant difference. Both voltages are within the tolerance allowed of the other.
    This wasn't the point, so I then said:
    Quote Originally Posted by sledge007 View Post
    Pretty much what I was getting at, however notice the amps. Pre charger is 1, TouchPad is 2.
    Quote Originally Posted by brum View Post
    I just needed a couple of extra words to understand why you said 'notice', is that good or bad - why?
    I was simply pointing out the difference in chargers, nothing more, nothing less. Technically, it's possible to charge a TouchPad with a Pre charger, however it will be slow.(because of not enough amps) You can also charge a Pre with a TouchPad charger, as it will only draw what it allows.
    Due to the cancellation of the penny, I no longer give 2 about anything. I may however, give a nickel
  2. #22  
    You can't charge a TP with a Pre Charger, it complains about the current being too low.
  3. #23  
    Yes it does. I just got home, plugged my TouchPad into my Pre charger in the wall. Open Govnah and have 356~mA current. That is still charging.. When you use the proper charger it is around 1241~mA. Your findings may be different depending on what screen brightness is, what you have running in the background, etc.

    If you have a negative number then it's draining. Positive number, charging.

    It also says when you use the wrong charger that "Your device MAY not charge.....yadayadayada"

    Chances are if you have max brightness and are streaming an HD movie at max volume while running extra cards, then you might not charge.
    Last edited by sledge007; 10/07/2011 at 04:53 AM.
    Due to the cancellation of the penny, I no longer give 2 about anything. I may however, give a nickel
  4. jaltman's Avatar
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    #24  
    Quote Originally Posted by sledge007 View Post
    I'm no electrical expert, but this is the way I understand it.

    Look for my charger spec post, then this reply:

    This wasn't the point, so I then said:




    I was simply pointing out the difference in chargers, nothing more, nothing less. Technically, it's possible to charge a TouchPad with a Pre charger, however it will be slow.(because of not enough amps) You can also charge a Pre with a TouchPad charger, as it will only draw what it allows.
    My comment was aimed at the others who said there was a difference in the voltages. Current or Amp rating should be looked at this way. The device has a quantity it wants in order to charge, if you run Govnah you can watch the current decline over time as the battery is charged. The device has a draw governed by the charger regulator.

    The power supply has a capacity, a max. How much of that capacity is drawn is governed by the regulator of the device it is attached to. Right now my Pre3 on its TS is not charging at all, its full, and actually draining at the rate of 60 mA. The TP on which I am typing this has been off its TS all night, just got put on, and is drawing 757 mA, right now.

    If the Pre3 charges faster on the TP charger (and it does) its because the regulator allows it to. The TP is, apparently, smart enough to know that when it wants a full charge current and doesn't get it, don't charge.

    This was probably done to protect the USB port in your laptop from being cooked while in USB or Just Charge mode.
    Jim Altman
    Palm III ->Treos 600->650->750->Pro->Pre Plus->Pre 2->Pre3+TouchPad
  5. #25  
    Has anybody with an opinion either way considered just asking HP?
  6. #26  
    Quote Originally Posted by Double Eagle View Post
    Whether you use the original Pre charger or the TP charger it will not decrease the charging time for your Pre battery. The TP AC charging device is "capable" of delivering a higher current output, but only if the charging device is capable of drawing the current. The battery just accepts what the charging circuity sends to it. The TP charging circuity draws more current (amperage) from the AC charger which the Pre charger cannot deliver.
    Exactly. What matters is the actual voltage supplied by the charger. The TP charger supplies 5.3 V vs. the Pre charger supplies 5 V. The TP charger is capable of supplying up to 2.0 A @ 5.3 V, but the Pre charger can only supply up to 1.0 A. One ampere is insufficient to charge the TP, so that's why you need a charger rated at two amperes. The TP charger supplies a slightly higher voltage at 5.3 V but this difference is not enough to damage your phone, so it's safe to plug your phone to the TP charger. Remember what remains constant is the voltage supplied (5.3 or 5) the current (amperage) varies depeding on whether the TP or Pre is charging or idle. This is also the reason your phone will charge slower when connected to a usb port on a computer since the usb port on a computer will only supply a maximum of 0.5 A, so it would take much longer to charge your phone than if you were using a wall plug supplying up to 1.0 A.
  7. #27  
    Quote Originally Posted by gnulinux View Post
    ... One ampere is insufficient to charge the TP... your phone will charge slower when connected to a usb port on a computer ... maximum of 0.5 A, so it would take much longer to charge your phone than if you were using a wall plug supplying up to 1.0 A.
    You say that phones charge slower because it's receiving 50% less amps when on PC usb compared to wall adapter, but then you say wall adapter can't charge TP because it's providing 50% less amps...

    I plug my TP into my Pre- wall adapter and it does charge. I still get the warning that it MIGHT not work. However, when I come back a few hours later, the TP is charged. I only do this when I'm away all day, so I have no idea how slow it is compared to the real TP charger.
  8. jaltman's Avatar
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    #28  
    Quote Originally Posted by tony20 View Post
    You say that phones charge slower because it's receiving 50% less amps when on PC usb compared to wall adapter, but then you say wall adapter can't charge TP because it's providing 50% less amps...
    Yes, and he was quite correct. Max Power PC USB= .5 Amp, Max Power pre = 1 Amp, Max Power TP = 2A

    Now the time scale of using the "wrong" charger will not be linear because charging rates vary depending on the condition of the battery. The time improvement of a dead pre battery will be greater on the TP charger than a 90% charged pre battery on the tp charger. The 90% full battery will taper off the charge so that the actual power delivered may be the same for all charger possibilities, i.e. less than .5 amps.

    Another factor has to be the loss occasioned by transferring the power inductively through the touchstone. While my intiution says the loss has to be higher, therefore the charge rate slower, my experience is the opposite. That is, the devices charge faster on the touchstone than when directly connected to the power supply. My observation could be wrong tho, as indicated below.

    The touchstone, however can not operate with DC, it MUST be converted to AC of some frequency, else no current would be induced in the phone. Either the magnetic field has to expand and contract or the phone has to keep moving, since the phone isnt moving it must be the field. Finally, it would also appear more loss occurs in the touchstone as it appears to create more heat than when directly connected.

    Using the govnah we can observe the actual charge current and I have never seen the TP exceed the high 900 mA's implying that losses approach 50% of the 2 Amps available. Similarly, I dont remember the figures for the Pre2, but my 3, while on the TS never exceeds around 500 mA's, also implying about 50% loss. While typing this I put the pre3 on a touchstone and Govnah reported 494 mA, yanking the cord out of the touchstone and plugging it into the phone directly, it rose briefly to about 650 mA but soon fell back to about 570 mA.

    It would also not be unreasonable to assume that there might be two separate regulators for power control, as the USB charge is a DC->DC system and the touchstone is DC->AC->DC system. Guess I'll have to see what Govnah reports when my pre3 is of low battery and I use the TP charger.

    YMMV
    Jim Altman
    Palm III ->Treos 600->650->750->Pro->Pre Plus->Pre 2->Pre3+TouchPad
    sledge007 likes this.
  9. #29  
    I know very little about electrical engineering, but I do know that volts multiplied by amps = watts which is another way to think about this situation. If you have 5 volts multiplied by 1 amp (Pre charger spec) you have 5 watts and if you have 5.3 volts multiplied by 2 amps (Touchstone charger spec) you have 10.6 watts. The wattage that is reaching your device is in some ways the ultimate measure of pure "power".

    Just an aside....and kind of interesting.
    PDA Lineage: Palm Pilot, Palm V, Palm Tungsten, Treo 650 (Cingular), Treo 750 (AT&T), Treo Pro GSM (unlocked), Pre Plus (AT&T), Pre 2 GSM (unlocked), Pre 3 16GB (AT&T Branded) and Touchpad 32 GB
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  10. #30  
    I'm using a TP AC Adapter to power the Touchstone for one of my Pres, I seriously doubt it is making use of the extra current ability. Maybe I should drain both of my phones and set one on each touchstone, one powered by TP and one powered by Pre adapter, and see what happens. Doubt I'll ever get around to that, though.

    When I'm at work, I use a friend's 500mA adapter to power my TouchPad, it barely gives a positive charge while it's in use. But it works, and for that, the TouchPad is a great device. If he connects his Android tablet to his phone's charger, it doesn't even appear to recognize the existence of the charger.

    jaltman,

    Don't forget that when you're looking at a 900mA current on battery on the TouchPad, that your TouchPad is also -using- 600-900mA current.
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  11. #31  
    Quote Originally Posted by brum View Post
    I just needed a couple of extra words to understand why you said 'notice', is that good or bad - why?
    Not an issue. The Pre draws only 1A from the charger, which is capable of delivering 2A max. Its within its range. A 5A (5000mA) charger wont make a difference, neither would a million amp charger. The draw from the device that is being charged is whats important here (since voltage is within tolerance - 5V vs 5.3V).

    Voltage is usually the killer; not amperage. If the latter is too low it'll either trickle charge or not charge at all. Too much voltage, however, and your device will get fried.
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