# mobile phone direct power

I've got a few HTC Desire A8183's in which I would like to power directly off the wall socket.

I've got a 12volt 1amp transformer which I've put through a voltage regulator to bring that down to the required 3.7volts as stated on the back of the phone. WHen I connect the +3.7 to pin 4 of the phone and ground to pin 1 it doesn't boot.

I know there must be something I need to do with the other two pins. Some people say one is for the temperature of the battery and the other is a batter status indicator or something like that which needs a resistor.

I've tried a few different approaches so far. I've linked 1,2,3 to ground and supplied positive 3.7volts to pin4. This resulted in a orange & green flashing light which means it has detected the battery is over heating. I then tried putting a resistor on pin3 to ground of 82KOhms but that didn't help.

How can I run this phone directly off power? I still have a working battery which I can use for testing the voltage supplied.

Update

Phone
3&4 = 1M1
2&4 = 1M3

Battery
1&2 = 4K7
1&3 = 690K
2&3 = 20.3 @200M
3&2 = 1.1 @200M

Battery
Pin 1 & 2 = 0V
Pin 1 & 3 = 0V
Pin 1 & 4 = 3.5V
Pin 2 & 3 = 0V
Pin 3 & 2 = 0V

• Identify ground, use a continuity tester and iterate through each pin with one probe. Keep the other probe on the metal housing of your sim (which is likely to be grounded). Let me know the results once your done :) Feb 20, 2016 at 8:15
• Only pin 1 made a connection with the sim housing.
– map7
Feb 20, 2016 at 8:18
• Sweet, on your battery, keep the ground probe at pin:1, the other probe going through 2,3,4... would you be able to list the values of the voltages on each of those pins Feb 20, 2016 at 8:20
• Holding ground on Pin1 I get voltages: Pin2 = 0volts, Pin3=0volts, Pin4=3.5volts.
– map7
Feb 20, 2016 at 8:23
• Great. So we know pin 1 is ground, pin 4 is your power line (max 4.2V)... Now we need to figure out what pin 2 and 3 are doing... one is likely to be temperature (as you've already mentioned). Since they're both 0V, set your multimeter to measure ohms, and see what values you read at one probe on Pin 1, the other on Pin 2 then Pin 3, careful not to touch Pin 4, You'll short it. Feb 20, 2016 at 8:27

Pin 1: Ground
Pin 2: 4.7K Resistor connecting to ground
Pin 3: NC (If leaving it unconnected doesn't work, add a resistor with a value of about 650K)
Pin 4: 4V (Max: 4.2)

• I've managed to get Pin3 spot on 650K and still no luck
– map7
Feb 20, 2016 at 11:34
• We're in chat if you're around Feb 20, 2016 at 11:49
• Sorry about disappearing in the chat. I've added those extra tests to my original question.
– map7
Feb 22, 2016 at 10:06

I had read someone working on this who seemed very knowledgeable with a samsung phone battery that had 4 contacts and sounded very similar. The 3rd was for the battery temperature thermistor. The 4th was for the NFC that was built into some batteries.

They seemed very knowlegeable and had determined that they could only get the phone to think that it had an acceptable battery was to set the voltage from the regulated PSU to 5.3v dc exactly and connect the voltage through a "dead" battery that they had taken down to 0.0v by using a resistor to drain it and letting it drain for a few days and then sit for a week.

They had not posted any newer progress but had determined that the phone would only fully boot up if they did it through an actual battery that they had "killed" to prevent it from charging or contributing any voltage to the phone in addition to the PSU voltage.

• The post was on the XDA developer forums, i don't recall where.. Mar 21, 2016 at 1:33