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Galaxy Tab charging issue + solution

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mattcelt
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Thumbs up Galaxy Tab charging issue + solution

Hey guys - I've been dealing with a Tab charging issue for a few days, and finally solved it... but I thought I'd post the problem and solution here in case it can save someone else a load of frustration if they run into the same problem.

From what I've read, we know that the Tab only draws .5A power from a USB socket, but that it draws ~2A from the wall, and that it knows the difference by testing for a short on the TX/RX USB data wires. (Correct me if I'm wrong on the details, but that's the general impression I've gotten.) We also know that the iPhone/iPad/iPod uses a pair of resistors instead (per the USB spec) to determine the current-delivery capability of the source. (I'm no EE, so I'm a little fuzzy on how that works from a technical perspective.)

So to set the stage: I had brought the USB cable for my Tab with me, but had neglected to grab the USB->outlet adapter for the mains. Similarly, a friend who was on vacation with us had forgotten the charging cable for his iPhone. Thinking I was killing two birds with one stone, I bought an aftermarket USB charging cable for the iPhone which had a separate USB->outlet adapter. His iPhone charged swimmingly, and when I charged my Tab overnight (screen off, starting at ~89% charge) using my cable and the aftermarket adapter, it worked flawlessly. No problem, great solution, or so it seemed...

...until I got home. Suddenly, my Tab wouldn't do more than a trickle charge - the same charge it gets when connected to the USB port on my laptop. (I could tell this was the case because of the small red 'x' next to the charging symbol in the battery icon - which I hadn't noticed while on vacation.) A 2.5-hour car trip using Navigator (screen on the whole time), even with the car charger connected, killed the battery completely. No matter what I did - shutting down apps, rebooting the device, resetting every option I could find - I could not get a fast charge to happen. Even leaving the device plugged in overnight resulted in *less* charge than what I started with if I didn't turn the screen off. I called T-mobile, talked to Samsung tech support twice... and all they could offer was to have me send the Tab back for replacement.

I was at a loss. I nearly did a hard reset in frustration, thinking I had screwed something up royally.

Then I saw the resistors in the pictures in this post:
http://forum.xda-developers.com/show...=845844&page=3
and something clicked. I had been assuming that the *cables* were the difference between the iPhone and Tab chargers... but there isn't enough room for resistors in the cables! (Well technically, there is, but regardless...) The resistors must live somewhere else... and, I reasoned, that somewhere must be inside the USB->outlet adapter. So I pulled out the 'proper' Samsung adapter, plugged in the Tab, and voilą... a perfect fast charge.

So this is why the Tab won't charge with an iPod (or Sony-Ericsson, as it turns out) mains USB adapter OR USB-port car charger: the circuitry to let the device know it's capable of a full 2A delivery doesn't live in the Samsung cables; it's only present in the adapter. If that's not there, the device thinks it's connected via USB (and will, in fact, say "USB Connected" every time the charger is plugged in) and won't charge more than a trickle.

So that's my story, and hopefully it can save someone else some pain and frustration. Thanks for giving me the floor.
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rhca50
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Quote:
Originally Posted by mattcelt View Post
Hey guys - I've been dealing with a Tab charging issue for a few days, and finally solved it... but I thought I'd post the problem and solution here in case it can save someone else a load of frustration if they run into the same problem.

From what I've read, we know that the Tab only draws .5A power from a USB socket, but that it draws ~2A from the wall, and that it knows the difference by testing for a short on the TX/RX USB data wires. (Correct me if I'm wrong on the details, but that's the general impression I've gotten.) We also know that the iPhone/iPad/iPod uses a pair of resistors instead (per the USB spec) to determine the current-delivery capability of the source. (I'm no EE, so I'm a little fuzzy on how that works from a technical perspective.)

So to set the stage: I had brought the USB cable for my Tab with me, but had neglected to grab the USB->outlet adapter for the mains. Similarly, a friend who was on vacation with us had forgotten the charging cable for his iPhone. Thinking I was killing two birds with one stone, I bought an aftermarket USB charging cable for the iPhone which had a separate USB->outlet adapter. His iPhone charged swimmingly, and when I charged my Tab overnight (screen off, starting at ~89% charge) using my cable and the aftermarket adapter, it worked flawlessly. No problem, great solution, or so it seemed...

...until I got home. Suddenly, my Tab wouldn't do more than a trickle charge - the same charge it gets when connected to the USB port on my laptop. (I could tell this was the case because of the small red 'x' next to the charging symbol in the battery icon - which I hadn't noticed while on vacation.) A 2.5-hour car trip using Navigator (screen on the whole time), even with the car charger connected, killed the battery completely. No matter what I did - shutting down apps, rebooting the device, resetting every option I could find - I could not get a fast charge to happen. Even leaving the device plugged in overnight resulted in *less* charge than what I started with if I didn't turn the screen off. I called T-mobile, talked to Samsung tech support twice... and all they could offer was to have me send the Tab back for replacement.

I was at a loss. I nearly did a hard reset in frustration, thinking I had screwed something up royally.

Then I saw the resistors in the pictures in this post:
http://forum.xda-developers.com/show...=845844&page=3
and something clicked. I had been assuming that the *cables* were the difference between the iPhone and Tab chargers... but there isn't enough room for resistors in the cables! (Well technically, there is, but regardless...) The resistors must live somewhere else... and, I reasoned, that somewhere must be inside the USB->outlet adapter. So I pulled out the 'proper' Samsung adapter, plugged in the Tab, and voilą... a perfect fast charge.

So this is why the Tab won't charge with an iPod (or Sony-Ericsson, as it turns out) mains USB adapter OR USB-port car charger: the circuitry to let the device know it's capable of a full 2A delivery doesn't live in the Samsung cables; it's only present in the adapter. If that's not there, the device thinks it's connected via USB (and will, in fact, say "USB Connected" every time the charger is plugged in) and won't charge more than a trickle.

So that's my story, and hopefully it can save someone else some pain and frustration. Thanks for giving me the floor.
I've recently seen (somewhere) a usb pigtail cable that shorts the pins to make the tab (or any other usb chargable phone) think it's hooked up to a wall charger, rather than a trickle charging usb port.... I need to find that again and just order a few to have in my various cable bags.
 
mattcelt
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If you do find it again, please post it here. Definitely something I'd like in my bag of tricks as well.
 
Croak
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Just as an FYI, the 2A charger that came with my Nook Color charges the Tab just fine from mains, even indicates charging. Makes sense, since both devices have a 4000mAH battery.

It's also a nicer unit for travel, it's nicely rounded, the prongs fold into the body of the charger, and you can pick it up from Barnes and Nobles stores just about anywhere in the US. Still doesn't solve the Tab cable issue though.
 
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Quote:
Originally Posted by Croak View Post
Still doesn't solve the Tab cable issue though.
I'm planning on hacking apart a spare Tab cable so that it goes to a female microUSB; no more multiple cable types then. The stock Tab cable doesn't appear to have more than 6 pins, of which I'm sure a few are grounds.
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ResonanceZero
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Someone recently posted a link to the first cheap 3rd-party cables:

http://www.dealextreme.com/details.dx/sku.51931

Get those with a 6' USB extension cable and the Nook charger, and that may be a winning combination. I ordered four the the charging cables yesterday, and I'll try to remember to post whether or not they work out well.
 
mattcelt
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Resonance, what are you planning on using for a car charger, if any? I really like the Navigator app, but it's just not practical if I can't keep the Tab charged while using it.

Does anyone know if there are any USB->12v adapters that have the right circuitry for the Samsung? For that matter, do any other devices use the same amperage detection setup the Tab does? It would be good to know what components are cross-compatible.
 
vs2
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Thanks for the info.

How about a list of chargers that work fine on the GTab.

1. Garminfone charger (1amp - works great and I use it as my primary charger)
 
ResonanceZero
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Quote:
Originally Posted by mattcelt View Post
Resonance, what are you planning on using for a car charger, if any? I really like the Navigator app, but it's just not practical if I can't keep the Tab charged while using it.
A 12V inverter, attached to the standard wall charger. :/

I bought the Duragadget 12V->USB charger, since it was advertised specifically as a 2A charger for the Galaxy Tab, but it DOES NOT work as advertised (the Tab treats it like a any other low-current USB port, and even offers to mount mass storage, heh).

Using the inverter and the wall charger worked just fine, though it was a bit clunky and unstable (on mine, the prongs aren't tightly gripped, so it bends out of place easily).

Quote:
Does anyone know if there are any USB->12v adapters that have the right circuitry for the Samsung? For that matter, do any other devices use the same amperage detection setup the Tab does? It would be good to know what components are cross-compatible.
I'd been contemplating giving the Duragadget charger with integrated cable a try, but having been burned once by Duragadget, I'm a bit hesitant to do so.
 
nacron
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Quote:
Originally Posted by ResonanceZero View Post
Someone recently posted a link to the first cheap 3rd-party cables:

http://www.dealextreme.com/details.dx/sku.51931

Get those with a 6' USB extension cable and the Nook charger, and that may be a winning combination. I ordered four the the charging cables yesterday, and I'll try to remember to post whether or not they work out well.
OMG...I bought a charger cable from amazon SOLD BY AMAZON marketed as OEM samsung charger and I got the same one in the deal extreme page. WTF...paid $12 for it too.
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