Most phone batteries will have a connector of some type with 4 contacts. Of course two of those I'd expect to be +- Voltage, but the other two compose some sort of mystery input to the phone (thermistor? signal? I don't know). I was hoping to substitute a primary battery instead of the factory one for my project (I have a 3.6v primary battery), but my device always seems to have a problem with it, presumably due to the battery protection circuit.

I thought I might just leave the protection circuit in place and wire power to both input and output- that way whatever input the phone needs to see is still there, but even that approach seems not to work.

Please help me bypass this system so that I can use a custom battery in this device.

enter image description here

Above is a diagram with some measured resistance/voltage values. If a value between points isn't shown, you can consider it an open circuit (although I didn't measure battery resistance)

  • $\begingroup$ I'm not sure but the two middle terminals are used for battery sensing / control / temperature etc and if the output is not correct to the phone then it will not switch on.... Which means, most likely, that you cannot "trick" it in the way you want... $\endgroup$
    – Solar Mike
    Aug 20, 2017 at 11:22


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy