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.
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)