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charge your touchpad without the ac adapter
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Old 12/07/2011, 08:18 PM   #1 (permalink)
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So if you have lost your adapter you you may notice that you are unable to charge via another adapter or the PC. No worries if you have cm7. If your device is completely dead, you will need to keep it on thenon touchpad charge for a little while until it is able to boot. Then let it boot into android. For some reason android supports outside chargers while webos does not. It will charge slower if you use a different charger and even slower if you use the PC, but it will charge. I lost the adapter part of mine a month ago and am still looking for a job so no option to buy a new one. This was the only way I've seen it work. I've tried the same on webos but other then getting it to boot, it doesnt seem to charge at all when plugged into a different adapter or the PC while in webos.
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Old 12/07/2011, 08:29 PM   #2 (permalink)
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You need a charger that puts out 2 Amps and you should be fine

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Old 12/07/2011, 08:32 PM   #3 (permalink)
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you can charge with a regular phone adpt. but its a lot slower
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Old 12/07/2011, 10:02 PM   #4 (permalink)
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Actually webOS does charge while plugged into the computer. It just charges really slow and webOS will not let you know via battery icon. Try it, get the battery to a low level, plug it into the computer and come back a few hours later, you will see that the battery level went up. Make sure you don't enable USB mode though (haven't tested).
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Old 12/07/2011, 10:04 PM   #5 (permalink)
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I just got a new Macbook Pro and was surprised that the two (only two) usb ports put out full 2 amps. So I could use the computer to charge if needed. However, the Touch stone is so much nicer and elegant!
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Old 12/07/2011, 11:31 PM   #6 (permalink)
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Some very good clarifying info here too:

http://forums.precentral.net/hp-touc...ouchpad-5.html
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Old 12/08/2011, 12:29 AM   #7 (permalink)
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just because webOS doesn't show the battery charge icon doesn't mean it isn't charging. the power circuitry will use the power coming in through the USB port, regardless of whether it's booted to webOS or android.

if you connect to a PC or other 500ma charger, which does not have the data pins shorted, the touchpad will charge VERY slowly with the screen off. with the screen on in active use, the battery will drain slowly as the incoming power isn't enough to fully supply the touchpad so the battery will run down slowly.

on a 1 amp charger like those used for Pre phones, where the data lines are shorted (this is part of the USB charging standard), the touchpad will charge slowly but effectively with the screen off. with the screen on in active use, the available current will just keep up with the power draw of the touchpad, maybe a little positive charge (NO, I am not saying the touchpad draws a full amp while in use... in practice it just doesn't draw a full amp of current from a 1 amp charger; i'm guessing it limits the current to what HP considered safe levels).

finally, the real touchpad charger is a 2 amp charger. the touchpad 'knows' it can draw 2 amps due to a pair of resistors that put a voltage around half-way between 0 and 5 volts on the data lines (the exact details are in that car charger thread... I'm not trying to be exact here). I don't think this is part of the USB charging standard, just something reasonable and easy to implement that HP came up with (though I certainly could be wrong). with 2 amps available (10 watts), the touchpad can apply significant positive charge to the battery even with the screen on (i.e. exhibition mode).

edit: also, you have probably seen those dual-plugged USB cables used to provide extra power to an external usb hard drive, and you might wonder if those would let the touchpad charge better from 2 USB ports. these won't provide any extra power to the touchpad UNLESS you open the cable somewhere and short the data lines on the touchpad side and leave them disconnected on the PC side - this cable will now act as a 1 amp charge cable, but of course will no longer act as a USB data cable... you can't have both!

Last edited by johnsonx42; 12/08/2011 at 01:20 AM.
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Old 12/08/2011, 12:48 AM   #8 (permalink)
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Johnsonx42, thank you for confirming what I reported a few posts up. It will charge, but webOS wont tell you it's charging though.
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Old 12/08/2011, 01:12 AM   #9 (permalink)
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further info , based on quick tests performed right now!-

charging from a PC usb port, govnah actually shows me a 'not-too-bad' positive charge current of ~300ma with the screen off. but with a 6600mah battery, it's going to take a good long time to charge a near-dead battery (ie, ~22 hours). is that what we mean by trickle charging?

with the screen on at a mid-range brightness, connected only to usb and otherwise not doing much, I saw a negative battery current of ~100ma. so that tells us the touchpad power circuits are willing to draw ~400ma from a USB port rated for 500ma, a reasonable margin of safety. (edit: oops, left out a line... I meant to say that govnah shows the touchpad draws ~500ma from the battery while not plugged in with the screen on and 100ma while plugged in to usb; that's what yields the ~400ma figure for power draw from a usb port)

moving on to the 1 amp charger scenario, with the screen off I'm seeing ~800ma of positive charge current. pretty decent actually, more than I was surmising in my post above. given that when idle the rest of the touchpad appears to draw in the neighborhood of 100ma, that means the touchpad power circuitry draws ~900ma from a 1 amp charger... again a reasonable margin of safety. this means a 1 amp charger will charge our hypothetical near-dead touchpad battery with the screen off in about 8 hours.

with the screen on at normal brightness but otherwise reasonably idle, the positive charge current on a 1 amp charger is ~330ma, about the same as screen-off on the usb port (500ma) charger.

the 1 amp charger results aren't bad at all really. this despite the "device may not charge" warning from webOS, and the absence of a battery charge indicator. even while playing a 3d game, I think a 1 amp charger could provide power at least equal to the power draw and probably just a little positive charge current (no I didn't test it and am not so inclined) (edit: actually that might not be true. I don't think the touchpad could last 6 hours on battery only playing a 3d game, which given the usuable power of the 6600mah battery implies a current draw of over 1A in that scenario... so even a 1 amp charger couldn't quite keep up in the extreme scenario of continuous 3d game play, but it'd be close!)

I don't happen to have handy a 500ma charger (ie, one that provides 5 volts on the power lines but leaves the data lines open), but I suspect that webOS provides the exact same "device may not charge" warning for it. that warning is quite correct for a 500ma charger.

It would have been nice if HP made the warning for the 1 amp charger "device will charge slowly" and would still show the charge indicator (perhaps a different color to signify the slower charge rate).

I do not believe for a moment that the touchpad will charge any differently running Android. I doubt the OS has any control over these aspects of the charging circuitry, and even if it does webOS is already drawing 80% to 90% of the available current from a USB port or 1 amp charger. you may think android quite wonderful with it's 6-digit app count, but there's no app for changing the laws of physics.

Last edited by johnsonx42; 12/08/2011 at 01:46 AM.
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Old 12/08/2011, 09:22 AM   #10 (permalink)
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tha.ks every.e for clearing that up I have only tested a few times and since It probably charged too slow before i just didnt see it. Especially once already dead. However this is good to know!
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Old 12/09/2011, 03:39 PM   #11 (permalink)
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The charger is under $10 with free shipping on amazon.com right now. I picked up an extra one just in case. Amazon.com: HP North American Power Charger
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