Fairphone 2 hardware extensions

For testing this I am still missing the complete pinout of FP2 battery and maybe internal existing PCMs inside FP2 battery.

Do not connect two batteries in parallel: https://www.reddit.com/r/AskElectronics/comments/1p0uiw/asking_for_clarification_on_wiring_cell_phone/

From your link I cite Apathetic_Superhero:
"Infact, without building some extended safety circuitry (it doesn’t have to be very complicated) I wouldn’t do it. We weld cells together ranging from several to hundreds of cells at a time. "

This topic is about possibilities to extend FP2 hardware. Feel free to contribute new ideas for this. I am not sure if prohibitions or contradictory external links will ever extend FP2 hardware.

Fair point, @anon9505190 :slight_smile:

Not sure what you are planning to do.

Most batteries (if you don’t buy them as “soft packs”) come with a PCM. I’ve linked to a few PCMs here in the forum a while ago. If you want to do it, better do it right. Replace the whole battery compartment with your pack that uses two cells (or a bigger one) you know about and how they work and use PCMs configured for them and that give the phone and the charging hardware in the phone correct feedback. Make the standard battery the fallback once your pack is empty, so the user can just swap it back in.

I once asked FP about the specs (Qualcomm charging). No, I never got an useful answer. And I think they are pretty concerned about their “IP” and the “IP” of their ODM. But maybe they are not allowed to talk about it. You can find a few specs online.

Anyway, I wouldn’t start it without FP’s full support as far as they can support you without violating contracts. If they want a hardware community around their phones, this information is critical.

I fear that in the end modules with not be made by users but by licensed partners. But that’s just my speculation. I have nothing to prove it. All I know is that I got no information ever.

Maybe asking during the AMA will help?

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thanks for your answer. You find me really stunned due to your attempts and FPs denial. Even the pin out of the battery was kept secret. Otherwise you already would have received this bare external battery infos (4 pins). Now I don’t have to wait for Kees’ answer on the same question . He is outside FP now and even misses to answer me. Finally I got your point: When no more specs than + and - pin including voltage/power are given of course any other battery pack will do safer. But will it also do better ? This is why FP2 batteries are still an option to me. They fit compartment and they double power.

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You could try the “save” approach that doesn’t need fancy extra knowledge.

Just charging the phone by the other usb port but by using a bigger hunchback battery. Most kids these days look pretty happy with an extra battery pack in their pockets. So all you need is a big hunchback case that fits really well in the old battery compartment and into the bottom usb port. But maybe I just misunderstand your plan? Anyway, good luck and thanks for trying!

can’t help quoting my self from the beginning. Curiously enough when you answered first when I was rather sure you have been first who could have known what I simply want to do. At the end of the day I am sure you misunderstood me . Doubling the battery for doubling power by building a battery pack with 2 cells of original FP2 batteries. This makers task looks obvious after almost everyone somehow complains about too short running time until the next charging cycle is needed. A power bank is an option but is cumbersome and not the same as a bigger battery pack.
Before another warning comes up again and again : I am not too careless because I use protective modules (PCM) for each cell. If they are not tough enough to try I say “Yes I can”.

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Dirkv I saw on your github about using FTDI.

Please reconsider and use a STM32F042 or similar instead.
Those MCU has builtin USB device mode and HID or VCOM drivers.

That means no wierd buggy FTDI drivers needed. And there would be plenty of pin that can be used for cool stuff to connect external sensors/gpio or whatever.

And btw FTDI has buggy driver. Also there is another reason FTDI has bad reputation cause and is not so open and did a huge mistake last year or so… They got plenty of people angry. You can search on youtube “ftdi rant eevblog” and you get a good answer why…

I personally will not support any project with they’r chips.

However I am definitivly interested in your 3D cases if I consider make a STM32 board to FP2… Offtopic I need to get my solary STM32 project ready first :slight_smile:

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Have you used also linux drivers for FTDI ? (I did)

has anyone managed to actually use the back usb vor anything usefull?
I want to have a secondary charging port I can plug in (either wireless or a 2nd µ-connector) when using a power hungry device like a TV receiver…


I don’t know about FTDI exact in this case, but if it depends on USB to Serial Adapters, FTDI is the best one. Much better than the cheaper Prolific PL232 Chipset. I have alot of Adapters and Flashing Equipment with FTDI Chips working very good on Linux.

Fact stand FTDI is bad and should not be supported. The company should be blacklisted in any community IMHO. Also the drivers you said works works is not from FTDI instead it is reverse engineered by the community with no help from FTDI. The real FTDI drivers is closed userlevel driver. If you ask me, and many with me agree, that company is plain evil and p** on the customers. Avoid use.

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Well Mike, companies who p** on the open source and customers are indeed evil. :slight_smile:
After Plextor send the lawyers to one guy, who put online an open source tool which did exact the same like the commercial PlexTools Software - i put Plextor on the top level of my personal shitlist.

Now after Plextor i have also many other companies there:

Whatsapp/Facebook, Microsoft, Apple, RIM/Blackberry, Google, Foxconn, Alcatel
And now FTDI :frowning:

Which USB2Serial Chips you prefer?
Prolific is such a mess…

…I’m still waiting for a µ-usb adapter for the back out… :disappointed:

I use the backport for connecting a Qi wireless charger adapter. works seamlessly


Please! Tell us more! :grinning:


2 posts were split to a new topic: Upgrade FP2 with QI wireless charging through expansion port

um maybe also here just to make sure the information reaches all who might be interested. I made a pcb layout for the expansion port and some prototypes which I currently share for the manufacturing costs (0,55€ per PCB). So if anyone is interested in getting some of those, drop me a line


Since dvl is no longer active let’s continue this here: