After I learned of the USB dedicated charger protocol last year, I had been wanting perform few simple tests and finally got around to it this afternoon. I tested three chargers with three phones. The phones are a Droid Bionic, a Droid X and a Droid Incredible. The three chargers I tested were:
[FONT="]http://www.scosche.com/consumer-tech/product/1890
powerPLUG - Low-profile USB Car Charger for iPad
High Powered USB Car Charger | Bracketron
The first is rated at 1.0A while the latter two are rated at 2.1A.
First thing I did was test if the data pins were bridged, which is one of the USB specified signals for a dedicated charger. None were. There is another USB spec that I recall reading about, but I didn't understand it upon initially looking at it and didn't study it further to determine what it might actually be doing. The Droid X and the Bionic must recognize that signal as each detected the chargers as dedicated chargers and indicated AC charging. The Incredible did not.
I bought the Bracketron charger primarily for this test as it had a visible screw that led me to believe I might be able to disassemble it without destroying it. I was right. I pulled it apart and bridged the data pins with solder and tested the Incredible and it finally said it was in AC charging mode. It would appear HTC uses a different protocol than Motorola. While I bought the Bracketron charger primarily for testing, I told my girlfriend to use it instead of the others for her Incredible since it should charge faster with it.
Next, I decided to test the actual current being passed to the phone. I picked up a cheap micro usb cable. Tested it to make sure it can charge the phones and pass data normally. It appeared to do so just fine. I cut it in half and exposed the leads. I reconnected all the leads using test clips and tested it on each phone to make sure all the connections seemed solid. Then I disconnected the +5V test clip and put a multimeter in its place to measure the current. With both Scosche chargers, the DX and the Bionic pulled up to 0.75A. Both fluctuated quite a bit down to as low as 0.65A or so. Both seemed to register between 0.6A and 0.7A with the modified Bracketron charger. Though, I didn't get to test the current prior to the modification of the charger as I modified it before I assembled my test rig. The Incredible registered a measly 0.4A with the Scosche chargers since the phone wasn't going into AC charging mode. With the Bracketron charger it was pulling 0.85A.
I was a little disappointed that none of the phones could use the full potential of the chargers. However, I am going to say that these tests were hardly scientific in ruling out other reasons for that. The cable I bought was rather cheap and the wires were quite thin. I also didn't test at different battery levels, with the phone off, or even after a fresh restart and perhaps turning off all radios to try and limit the data to just the charging circuit. I did however, do a quick test using a Griffin Ipad charger (2.1A) and the Incredible's OE charger (1.0A) and there were no remarkable differences except with the Incredible, which pulled 0.75A. I wanted to test an OE 2.1A charger, but my Galaxy Tab 10.1 charger won't charge either of the Motorola phones. I didn't try the Incredible with it. I have a few couple more chargers I can test, but they are currently either behind furniture or permanently attached to my car and I had this all rigged up on my workbench in the garage. Either way, short of the USB cable causing a limitation, it might appear that buying more than the needed amperage in a charger is not necessary.
I did this for my own edification, but I figured others may find it interesting or useful so I figured I'd share what I found. Enjoy.
[/FONT]
[FONT="]http://www.scosche.com/consumer-tech/product/1890
powerPLUG - Low-profile USB Car Charger for iPad
High Powered USB Car Charger | Bracketron
The first is rated at 1.0A while the latter two are rated at 2.1A.
First thing I did was test if the data pins were bridged, which is one of the USB specified signals for a dedicated charger. None were. There is another USB spec that I recall reading about, but I didn't understand it upon initially looking at it and didn't study it further to determine what it might actually be doing. The Droid X and the Bionic must recognize that signal as each detected the chargers as dedicated chargers and indicated AC charging. The Incredible did not.
I bought the Bracketron charger primarily for this test as it had a visible screw that led me to believe I might be able to disassemble it without destroying it. I was right. I pulled it apart and bridged the data pins with solder and tested the Incredible and it finally said it was in AC charging mode. It would appear HTC uses a different protocol than Motorola. While I bought the Bracketron charger primarily for testing, I told my girlfriend to use it instead of the others for her Incredible since it should charge faster with it.
Next, I decided to test the actual current being passed to the phone. I picked up a cheap micro usb cable. Tested it to make sure it can charge the phones and pass data normally. It appeared to do so just fine. I cut it in half and exposed the leads. I reconnected all the leads using test clips and tested it on each phone to make sure all the connections seemed solid. Then I disconnected the +5V test clip and put a multimeter in its place to measure the current. With both Scosche chargers, the DX and the Bionic pulled up to 0.75A. Both fluctuated quite a bit down to as low as 0.65A or so. Both seemed to register between 0.6A and 0.7A with the modified Bracketron charger. Though, I didn't get to test the current prior to the modification of the charger as I modified it before I assembled my test rig. The Incredible registered a measly 0.4A with the Scosche chargers since the phone wasn't going into AC charging mode. With the Bracketron charger it was pulling 0.85A.
I was a little disappointed that none of the phones could use the full potential of the chargers. However, I am going to say that these tests were hardly scientific in ruling out other reasons for that. The cable I bought was rather cheap and the wires were quite thin. I also didn't test at different battery levels, with the phone off, or even after a fresh restart and perhaps turning off all radios to try and limit the data to just the charging circuit. I did however, do a quick test using a Griffin Ipad charger (2.1A) and the Incredible's OE charger (1.0A) and there were no remarkable differences except with the Incredible, which pulled 0.75A. I wanted to test an OE 2.1A charger, but my Galaxy Tab 10.1 charger won't charge either of the Motorola phones. I didn't try the Incredible with it. I have a few couple more chargers I can test, but they are currently either behind furniture or permanently attached to my car and I had this all rigged up on my workbench in the garage. Either way, short of the USB cable causing a limitation, it might appear that buying more than the needed amperage in a charger is not necessary.
I did this for my own edification, but I figured others may find it interesting or useful so I figured I'd share what I found. Enjoy.
[/FONT]