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

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mtucker

Senior Member
Oct 23, 2011
194
135
Escondido
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-USB-Car-Charger/dp/B001ILBNGA
2. Griffin PowerJolt Dual Micro Universal Charger http://www.walmart.com/ip/Griffin-P...40656&sourceid=1500000000000003142050&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.
SS_500mA_MTP.jpg


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).
SS_1A_no_MTP.jpg


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.
Belkin_charging.jpg
 
Last edited:

i_max2k2

Senior Member
Dec 1, 2007
176
22
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-USB-Car-Charger/dp/B001ILBNGA
2. Griffin PowerJolt Dual Micro Universal Charger http://www.walmart.com/ip/Griffin-P...40656&sourceid=1500000000000003142050&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.
SS_500mA_MTP.jpg


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).
SS_1A_no_MTP.jpg


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.
Belkin_charging.jpg

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?
 

mtucker

Senior Member
Oct 23, 2011
194
135
Escondido
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/details?id=com.manor.currentwidget&feature=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.
 

Phoneguy589

Senior Member
May 1, 2011
1,859
332
S.E. Florida
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.
 

bd11goal

Member
Mar 27, 2010
24
2
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
 

mtucker

Senior Member
Oct 23, 2011
194
135
Escondido
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.
 

kimtyson

Senior Member
Oct 30, 2006
1,989
660
York, Pa
Nice discussion here. I followed the Youtube link in the second discussion and created a short USB cable with the short. Works perfectly.
 

hyukki

Senior Member
Mar 12, 2009
171
22
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?
 
Last edited:

lanwarrior

Senior Member
Mar 5, 2006
2,196
158
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.
 

mtucker

Senior Member
Oct 23, 2011
194
135
Escondido
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-media/permalink/moAZAR6I9DW65J/B0042B9U8Q/ref=cm_ciu_images_pl_link
 

hyukki

Senior Member
Mar 12, 2009
171
22
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-media/permalink/moAZAR6I9DW65J/B0042B9U8Q/ref=cm_ciu_images_pl_link

Well, the inductor in mine is very flimsy and does not have the black cover around it. It literally is being held in place by the two leads of the wire coiled around the ring. I'll probably end up ordering a different plug. Or invest 11 dollars for the one that comes with the iPod cable. Although I'm not really complaining with .7 amps, since at least it doesn't let the battery drain as fast.
 

NeoH4x0r

Member
Oct 9, 2011
27
1
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.
Do you mean 4000 to 9000 ma or 4A - 10A over usb? (this seems a little high for usb most chargers are 500 ma (0.5A) to 2A)
I think it is probably more like 400-1000ma (0.4 to 1A) [which sounds more reasonable for usb]
 

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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-USB-Car-Charger/dp/B001ILBNGA
    2. Griffin PowerJolt Dual Micro Universal Charger http://www.walmart.com/ip/Griffin-P...40656&sourceid=1500000000000003142050&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.
    SS_500mA_MTP.jpg


    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).
    SS_1A_no_MTP.jpg


    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.
    Belkin_charging.jpg