shorted USB D+/D- mod needs right V for full current

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By mtucker, Senior Member on 24th May 2012, 04:25 PM
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It looks like just shorting D+ to D- on a USB car charger is not always enough to get the note to charge at 1A. It seems like the voltage on D+/D- has to be in the right range also.

I needed more than 500mA charging current in the car for the Note and its big screen (with GPS going also). I knew that I needed to short the D+ and D- pins of the USB charger or cord to let me pull more than 500mA off a 1A+ car charger. I chose to modify the chargers so I could use any standard cable for charging. I did this to two chargers.
1. Belkin Dual USB Car Charger http://www.amazon.com/Belkin-Dual-US.../dp/B001ILBNGA
2. Griffin PowerJolt Dual Micro Universal Charger http://www.walmart.com/ip/Griffin-Po...142050&veh=cse

I modified the Belkin first. I used an Ohm meter to confirm I was shorting D+ and D- on the “fast charge” port. Once I put it back together, I confirmed I had 5V across the outer pins and the inner pins were tied together. When I plugged my Note into it using a standard cable, I got a MTP message and the USB symbol appeared in the top left corner. It thought I was connecting to a computer. Removing the cable sent the Note into a media scan.


So I took it apart and double checked. I noticed that the shorted data pins on the high current USB port were about 2.5V and the low current USB port data pins were about 2.0V. I also noticed that the 5V pins for both ports were connected together on the PCB (meaning they are fed off the same 5V regulator). I then shorted the data pins together on the low current port and it worked with that port! The Current Widget showed about 1A and no MTP message. This pointed to the data pins needing a specific voltage (or range of voltage) to make the note charge at 1A (2.5V on the data pins didn't work, but 2V did).


Next I moved onto the Griffin PowerJolt dual charger. This is my favorite car charger as it is very low profile. I did the mod to one of the ports and got the same MTP message (along with only 500mA charging). I noticed the data pins were at 2.5V and that two resistors making up a voltage divider for the data pins were right there. I changed the divider ratio (adding a 50K Ohm resistor in parallel with the resistor that went to ground). I re-measured and saw 1.94V on the data pins (very close to the 2V on the working Belkin port). I plugged her in and sure enough it worked (AC charging and about 1A).
Depending on your charger, it seems as though simply shorting D+ to D- may not be enough to get full current. The data pins have to have the correct voltage on them. Around 2V works although it may be a wide range of voltages (maybe 0V up to 2V?).

Later I went back and modified the high current Belkin port so its data pins were about 2V. That port then worked well too.
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24th May 2012, 04:58 PM |#2  
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Check out this video: http://www.youtube.com/watch?v=9LZt4pW97P8
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24th May 2012, 05:17 PM |#3  
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Quote:
Originally Posted by mtucker

It looks like just shorting D+ to D- on a USB car charger is not always enough to get the note to charge at 1A. It seems like the voltage on D+/D- has to be in the right range also.

I needed more than 500mA charging current in the car for the Note and its big screen (with GPS going also). I knew that I needed to short the D+ and D- pins of the USB charger or cord to let me pull more than 500mA off a 1A+ car charger. I chose to modify the chargers so I could use any standard cable for charging. I did this to two chargers.
1. Belkin Dual USB Car Charger http://www.amazon.com/Belkin-Dual-US.../dp/B001ILBNGA
2. Griffin PowerJolt Dual Micro Universal Charger http://www.walmart.com/ip/Griffin-Po...142050&veh=cse

I modified the Belkin first. I used an Ohm meter to confirm I was shorting D+ and D- on the “fast charge” port. Once I put it back together, I confirmed I had 5V across the outer pins and the inner pins were tied together. When I plugged my Note into it using a standard cable, I got a MTP message and the USB symbol appeared in the top left corner. It thought I was connecting to a computer. Removing the cable sent the Note into a media scan.



So I took it apart and double checked. I noticed that the shorted data pins on the high current USB port were about 2.5V and the low current USB port data pins were about 2.0V. I also noticed that the 5V pins for both ports were connected together on the PCB (meaning they are fed off the same 5V regulator). I then shorted the data pins together on the low current port and it worked with that port! The Current Widget showed about 1A and no MTP message. This pointed to the data pins needing a specific voltage (or range of voltage) to make the note charge at 1A (2.5V on the data pins didn't work, but 2V did).


Next I moved onto the Griffin PowerJolt dual charger. This is my favorite car charger as it is very low profile. I did the mod to one of the ports and got the same MTP message (along with only 500mA charging). I noticed the data pins were at 2.5V and that two resistors making up a voltage divider for the data pins were right there. I changed the divider ratio (adding a 50K Ohm resistor in parallel with the resistor that went to ground). I re-measured and saw 1.94V on the data pins (very close to the 2V on the working Belkin port). I plugged her in and sure enough it worked (AC charging and about 1A).
Depending on your charger, it seems as though simply shorting D+ to D- may not be enough to get full current. The data pins have to have the correct voltage on them. Around 2V works although it may be a wide range of voltages (maybe 0V up to 2V?).

Later I went back and modified the high current Belkin port so its data pins were about 2V. That port then worked well too.

This was informative, my phone discharges as well, when I have gps nav on, along with music and bluetooth connected to my car, yes a lot of things, but I want to use only one device for everything anyway, what widget are you using to check the amperage?
24th May 2012, 07:13 PM |#4  
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Quote:
Originally Posted by i_max2k2

This was informative, my phone discharges as well, when I have gps nav on, along with music and bluetooth connected to my car, yes a lot of things, but I want to use only one device for everything anyway, what widget are you using to check the amperage?

I'm using Current Widget https://play.google.com/store/apps/d...=search_result For Samsung phones, it will display the current *10 until you dig into the menu and use the divide option to tell it to divide by 10.

My GSII would just barely charge with 500mA (screen and GPS on) so I wasn't surprised that the Note can't keep up with 500mA.
25th May 2012, 10:05 PM |#5  
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Shorting the green and white wires (towards the phone) bumped my ma's from mid 4k to about 8-9k. I think the voltage state of the battery affects the charging rate as well. Under 70% I'm in the 9K ma range but above 90% I get around 7K ma's.
25th May 2012, 10:49 PM |#6  
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Quote:
Originally Posted by Phoneguy589

Shorting the green and white wires (towards the phone) bumped my ma's from mid 4k to about 8-9k. I think the voltage state of the battery affects the charging rate as well. Under 70% I'm in the 9K ma range but above 90% I get around 7K ma's.

This makes sense as a lithium ion charging circuit should charge quickly to 80 percent and trickle thereafter. Remember that the chargers ability to supply a large amount of current does not mean the phone will consume it; the charging circuit will only draw what it was designed to draw.

Sent from my SAMSUNG-SGH-I717 using XDA
27th May 2012, 07:25 AM |#7  
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Right. The charging process goes from constant current mode to constant voltage mode (voltage stops near 4.2V and the current drops to keep the voltage the same) somewhere around 80-90% of full charge.
27th May 2012, 04:05 PM |#8  
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Nice discussion here. I followed the Youtube link in the second discussion and created a short USB cable with the short. Works perfectly.
27th May 2012, 09:06 PM |#9  
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I bought the Griffin PowerJolt because of its size as well, however, I think mine is a fake one because the internals look very flimsy and cheapy put together.

Anyways, I can't return it since I already modded it...

I somehow managed it to pull .7 amps using a modded data cable (only if I let the spring contact that touches the inside perimeter of the lighter port touch the metal housing of the USB socket, .5 amps if not touching) but that's all I can do. Voltage is the same between the wall stock wall charger vs car charger @ ~4V.

Is there anything else I can do?
28th May 2012, 04:26 AM |#10  
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Isn't the charger that came with the Samsung official Galaxy Note Car Dock gives out 1A already?

I saw the Car charger output is 1A and the pin should be shorted already, since there is no "sync" capability.
29th May 2012, 06:50 AM |#11  
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Quote:
Originally Posted by hyukki

I bought the Griffin PowerJolt because of its size as well, however, I think mine is a fake one because the internals look very flimsy and cheapy put together............

Some people on Amazon thought they were getting fakes because the Griffin logo looked very light and the packaging was totally generic. Here is a link to a picture someone posted on Amazon showing the insides of the Powerjolt (a authentic version). This is how mine looked too.
http://www.amazon.com/gp/customer-me...images_pl_link
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