Tech spec of FP2 battery

Hi !

Following this thread :

I would like to verify that my battery is indeed broken. It looks like it is charged as I can measure ~4V. But I guess something is wrong with the inner control circuit: when battery is “cool” (removed for few hours), the phone does wake up and start booting, but after few seconds, everything is switched off. My guess is that the battery (or the phone) decides that something is wrong and stops everything. The best way to verify this would be to use another battery, but that’s not an option as I don’t know anyone with an FP2. The second option would be (I think) to plug the battery to a resistor, measure the current and monitor what happens on the 2 controls pins:

  • is it really possible ?
  • does anyone know how the 2 middle pins should behave ? Are they standard ? Or completely FP2 specific ?
  • would it be possible to use a battery from another phone (brand) and simply check that the phone works correctly ?

I cannot help you with your technical questions, but maybe there is someone in your area with a FP2?

Thanks for the tip… But I already checked and the closest member is a bit far :slight_smile:

I opened the cap on top of battery and did simple multimeter measures, due to my double-battery project, status:suspended. But, for your info: one pin is the thermistor , the other is marked ‘ID’, means producer set a serial 1-wire register, that does nothing else but authentication of itself.

Thanks @anon9505190 !
And do you know what is the behavior of the thermistor pin ? If I want to short it (ie. prevent it from shutting down the phone), what should I do ? IIRC, when I measured the voltage on both middle pins, they were both GND. Would it work if I reworked the thermistor pin to be connected to GND pin ?

And most importantly, which one is the ID and which one is the thermistor ? :slight_smile:

I searched in vain my other topic where I reported the pinout. Sorry , tomorrow I can have a look on my second battery because I don’ t want to open my FP2 for this info only. The thermistor is a simple e.g analog temperature resistor that was not one interests. The other 1- wire was digitally of my interest but a multimeter did not make sense.
Though I have no proof I don’t think that both middle pins cause your shutdown of FP2. The best way to check this would be starting completely without contacting both pins e.g. by only connecting +/- to the FP2 contacts. This is easier as you might think: Either put a tiny piece of paper between contacts. The battery contact get free if you remove the cap slowly from both sides simultaniosly. And then of course you find the pin out lables without me :slight_smile:

@anon9505190 if I simply disconnect the middle pins, phone works correctly… So I’ll stop my experiments on the hw and will wait for fairphone to reply to my support request… Thanks !

Update: just for the sake of being exhaustive, I’ve checked that without the little hack, the phone was still not working. And of course, now it seems to work. Maybe that forcing the battery to work a little “fixed” it somehow ? I really doubt that’s the case, but I’m not able to explain this.

update: that was a false workaround. I guess it was simply the 24h of rest that made the battery boot the phone, not the disconnection of the 2 pins. I’m not able to start the phone again.


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