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How to get Full Power Charge (Mobile battery, car, ...) for HP Touchpad!
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Old 12/13/2012, 05:47 PM   #21 (permalink)
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Thank you for your thorough reply.

With 4 Touchpads (yes, not Touchstones!) I need to supply power at some point. Perhaps 2 could be charging at a time? What's the length of time required to fully charge using one of the smaller devices?

I'm keen on getting this sorted ASAP.

Thanks
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Old 12/13/2012, 07:12 PM   #22 (permalink)
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Originally Posted by Paulscarbs View Post
Thank you for your thorough reply.

With 4 Touchpads (yes, not Touchstones!) I need to supply power at some point. Perhaps 2 could be charging at a time? What's the length of time required to fully charge using one of the smaller devices?

I'm keen on getting this sorted ASAP.

Thanks
Not sure whether your question was directed at me ....

A properly modified 2.1 Amp Charger will charge the TouchPad at the same rate as the TouchPad Barrel Charger so it should take around 3 Hours to recharge a TouchPad.
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Old 12/13/2012, 09:51 PM   #23 (permalink)
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Hi All out there!

The goal within this USB A connector is to implement a bridge between the two data lines and adding 2 additional resistors of 300kOhm between Ground and the data lines and 240kOhm between the data lines and 5V. I did this with cutting a little bit off of the white plastic of the connector part in front of the solder pads and the solder pads itself and two 1206 resistors (green in the pictures). Important is to NOT connect the USB data lines of the USB A connector part again to the white and green cables! ONLY the resistors have to be connected to the white and green cables, NEVER the USB A connector part as this could lead to wrong reading at least of the impedance from the Touchpads charging logic!

1. What I understand from this description is represented in Electrical schematic diagram which is attached herewith. Is this correct?
2. These two resistors together with the bridge between data lines will enable the Touchpad to charge without "device may not charge" warning. Correct or not?

Edit: I think I got the answer. It is here in this post by wheel_nut
http://forums.webosnation.com/hp-tou...ml#post3302975
Attached Images
File Type: jpg TP charging cable connection.jpg (22.7 KB, 46 views) Email Attachment
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Last edited by jmdesai; 12/13/2012 at 10:03 PM. Reason: got annswer
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Old 12/14/2012, 12:03 PM   #24 (permalink)
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Yes, that is the correct one for our lovely Touchpad! :-)
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Old 12/19/2012, 01:09 PM   #25 (permalink)
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what would be my best bet? I have a Samsung Galaxy Note 2 and would like to be able to charge it in my car and get the same charging times as I do with my home 2a charger that it came with.
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Old 12/19/2012, 03:29 PM   #26 (permalink)
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what would be my best bet? I have a Samsung Galaxy Note 2 and would like to be able to charge it in my car and get the same charging times as I do with my home 2a charger that it came with.
This is about the HP TouchPad. For Android devices, please go to Android Central to discuss.
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Old 12/22/2012, 07:35 AM   #27 (permalink)
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Originally Posted by jmdesai View Post
1. What I understand from this description is represented in Electrical schematic diagram which is attached herewith. Is this correct?
2. These two resistors together with the bridge between data lines will enable the Touchpad to charge without "device may not charge" warning. Correct or not?

Edit: I think I got the answer. It is here in this post by wheel_nut
http://forums.webosnation.com/hp-tou...ml#post3302975
I could achieve charge up to 1700mA with 480k and 560k resistors (with screen off)
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Old 12/23/2012, 11:59 AM   #28 (permalink)
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I created a special cable for charging TP from a high powered USB source. This is basically a USB extension cable fitted with resistors. See picture at https://www.box.com/shared/mwiofarqfce4gwb1ae9h

Resistors are soldered to pins of female USB connector (under black tape in photo). I removed some filler material from this place to create a cavity to accomodate 2 small resistors.
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Old 12/23/2012, 12:52 PM   #29 (permalink)
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Hi!

Yes, that's exactly, what I did and linked in my first post of this thread:
https://skydrive.live.com/?cid=9da90...3A%21112&sff=1

What resistors do u use?
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Old 12/23/2012, 01:32 PM   #30 (permalink)
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Hi!

Yes, that's exactly, what I did and linked in my first post of this thread:
https://skydrive.live.com/?cid=9da90...3A%21112&sff=1

What resistors do u use?
I missed that post earlier, but saw it after making my cable. I used480k and 560k, because I had these values resistors lying around with me. I also noticed that when you connect TP to charger, voltage drops from 2.7V to less than 1V.
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Old 12/23/2012, 01:37 PM   #31 (permalink)
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Hmmm... That's interesting! I never measured the voltage drop from unconnected to connected. Have to check this. Thanks for keeping an eye on this. But as long as you can achieve ~1800mA current for charging, it should be ok and close enough to the configuration of the original wall charger. :-)

Last edited by BGrosse; 12/23/2012 at 01:55 PM.
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Old 12/23/2012, 01:45 PM   #32 (permalink)
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what would be my best bet? I have a Samsung Galaxy Note 2 and would like to be able to charge it in my car and get the same charging times as I do with my home 2a charger that it came with.
I would suggest you go out and acquire one of those Samsung Galaxy adaptors like this one:
New USB Charger Converter Adapter for Samsung Galaxy P1000 Tab | eBay

Because Samsung uses the same kind of recognition (power adapter sensing) like the Touchpad does - just with other resistor values - this one should work for your Note, too. But of course, don't forget to get a 2A car charger first, otherwise you will not get the same fast charging time like that from your wall charger.
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Old 12/23/2012, 04:50 PM   #33 (permalink)
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Originally Posted by BGrosse View Post
Hmmm... That's interesting! I never measured the voltage drop from unconnected to connected. Have to check this. Thanks for keeping an eye on this. But as long as you can achieve ~1800mA current for charging, it should be ok and close enough to the configuration of the original wall charger. :-)
Beware when measuring LOW Voltages from HIGH Impedance sources.

Most street quality multimeters and Digital Multimeters present a load of between 20,000 Ohms per Volt and 100,000 Ohms per Volt. If you are measuring the voltage of around 2.7V at a point which has a source inpedance of 150K Ohms in the case of the 240K/300K Potential Divider then you can expect to get a LOW reading. This is even more severe in the case of the JMDesai ~ 300K source impedance.

Now, if you are using a VT Votmeter or a FET Voltmeter then the above doesn't apply.

Last edited by Wheel_nut; 12/23/2012 at 07:57 PM.
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Old 12/23/2012, 09:03 PM   #34 (permalink)
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Beware when measuring LOW Voltages from HIGH Impedance sources.

Most street quality multimeters and Digital Multimeters present a load of between 20,000 Ohms per Volt and 100,000 Ohms per Volt. If you are measuring the voltage of around 2.7V at a point which has a source inpedance of 150K Ohms in the case of the 240K/300K Potential Divider then you can expect to get a LOW reading. This is even more severe in the case of the JMDesai ~ 300K source impedance.

Now, if you are using a VT Votmeter or a FET Voltmeter then the above doesn't apply.
Wow... I realize that you are very much right. I used a dirt cheap digital multimeter. But on second thoughts, it should read lower voltage also when TP is not connected?

BTW when I use Pre3 charger (rated 1Amp) with my special cable to charge TP, it draws about 1.2 amps (screen in off state), which is not healthy for charger. Charger gets slightly warm, but it did not go bust even after a few hours. Nevertheless I will avoid fast charging TP with Pre3 charger.

While experimenting fast charging, my 2Amp charger got short-circuited . I regret the loss, may it's soul rest in peace . I ordered a 2amp charger which is called a iPad charger. I am afraid that it may contain low resistance divider resistances as posted by Wheel_nut and BGrosse in earlier posts, and I may have to open the charger case to modify.
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Old 12/23/2012, 09:37 PM   #35 (permalink)
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Originally Posted by jmdesai View Post
BTW when I use Pre3 charger (rated 1Amp) with my special cable to charge TP, it draws about 1.2 amps (screen in off state), which is not healthy for charger. Charger gets slightly warm, but it did not go bust even after a few hours. Nevertheless I will avoid fast charging TP with Pre3 charger.
That is because your Pre Charger is Current Limited to 1.2Amps as would be all good quality Power Supplies. I wouldn't try that with an unbranded charger rated at 1 Amp. it is more likely to overheat and melt the case.
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While experimenting fast charging, my 2Amp charger got short-circuited . I regret the loss, may it's soul rest in peace . I ordered a 2amp charger which is called a iPad charger. I am afraid that it may contain low resistance divider resistances as posted by Wheel_nut and BGrosse in earlier posts, and I may have to open the charger case to modify.
No need to remove the potential divider resistors from the iPad charger as you will not be connecting anything to the data lines of the Charger. However, the safer solution is to open the Charger and remove and replace the Potential divider resistors internally.
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Old 12/24/2012, 02:05 AM   #36 (permalink)
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Hi WheelNut!

Thanks for the fast replies. Just woke up and realized, that you are much quicker. Hehehe...

Of course, your interventions are right. With a normal multimeter it isn't possible to get the right readings. But I have a "real" multimeter here with FET input, so this should not be a problem. I will check it over the holidays now and will report back. :-)

Merry christmas to all of you out there! Have a nice time :-)
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Old 12/24/2012, 02:19 AM   #37 (permalink)
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Originally Posted by jmdesai View Post
Wow... I realize that you are very much right. I used a dirt cheap digital multimeter. But on second thoughts, it should read lower voltage also when TP is not connected?

BTW when I use Pre3 charger (rated 1Amp) with my special cable to charge TP, it draws about 1.2 amps (screen in off state), which is not healthy for charger. Charger gets slightly warm, but it did not go bust even after a few hours. Nevertheless I will avoid fast charging TP with Pre3 charger.

While experimenting fast charging, my 2Amp charger got short-circuited . I regret the loss, may it's soul rest in peace . I ordered a 2amp charger which is called a iPad charger. I am afraid that it may contain low resistance divider resistances as posted by Wheel_nut and BGrosse in earlier posts, and I may have to open the charger case to modify.
STOP!!! STOP! STOP! STOP!
Don't ever use a china made and engineered power supply and overload it!!! NEVER!!! While all modern power supplies should have overload and short circuit protection built in, you never know, if the design engineer has understood, how to implement this protection correctly and if the purchasers had bought the right parts for it. As a electronic design engineer I can only highly recommend to NEVER EVER make use of the protection circuits of chinese power supplies. In theory it should work - yes, but practice is another thing. Please make sure to always use a power supply, that is not overloaded. Load next to full (80-100%) load is ok, especially because switching mode power supplies have their highest efficiency in the range from 50-90%, but never use more than 100%. You never know, if the amperage regulation works as it should, producing a "clear" lower voltage in consequence. Sometimes the output voltage got high ripples on it or the power supply can withstand overload conditions only for a couple of time and then go to hell and fries your lovely Touchpad!

Please don't do that to this wonderful Tablet. If you want to, build your own power supply/charging unit like me or at least buy a quality made one like the original HP charger which is definitively capable of delivering 5,0 - 5,2 volt @ 2A or more.
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Old 07/09/2013, 03:32 PM   #38 (permalink)
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Ah, how I love webOS Nation! According to your instructions I made a cable that charges my touchpad from a simple 3A steupcharger I got on DC 2,6V-5,5V auf USB 5V 3A Stepup Iphone, Ipad alle anderen Smartphones/Tablets | eBay ebay wich is connected to a LiPo which is being charged by a solar panel. Right now my LiPo is tiny (2200maH) therefore all i got is 8% charge on a sunny day but I just ordered 2 5000maH Li/Ion batteries and will report the results. I love the idea of being able to charge my touchpad with the sun (and my Pre2).

BTW: I got this BS 500 - Sound Mobile - Telefunken for 30€ and modded it as the charger. I will provide pictures of the mod if anyone cares enough. I am still a big noob with electronics but it's a fun project wich already gave some encouraging results. Any advice for the novice?
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Old 07/13/2013, 06:24 AM   #39 (permalink)
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Pics Pics Pics...!

What is the solar panel you use? I am not wondering on your little charge because you have much energy loss there. Make the calculation backwards:

Charging the TP needs 5.0 - 5.3 volts @ min. 1A (better 1.5 or 2), that's 5 - 10 watts. Based on a 3.7V LiPo accu cell you need the step-up converter for voltage boost. This has an efficiency of 70 - 90%. Let's assume 80% as a mean value. So you need 10 Watts / 0,8 = 12.5 watts out of your LiPo cell for several hours (until the TP is fully charged).
If you again need a step-down converter on your solar panels' side for charging the LiPo accu cell from the solar panel, you also have power loss on this side additionally. So your solar cell needs to deliver power of 12-20 Watts. And all that under best conditions (light). That's really heavy!

I will follow your activities if you are willing to post them here. Let us know what comes out! :-)
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