Fairphone 2 hardware extensions

Yes, due to the origin of keesj youtube video you may find his and dvl’s github links if you search for yubikey here in this topic.

I want to double original FP2 battery while I already have the fitting 3D-FP2 case available.
I hope my request to @keesJ for full pinout about all 4 battery pins get answered soon .
Maybe this topic also helps me in finding out whether tiny battery protection modules (PCM) are really required. Kees didnot mention them nor did he tell if every FP2 battery maybe even include them. If the other 2 pins are used as a good current monitoring then every FP2 should already include such PCM modules . However Kees sent me advice not to connect battery devices directly. At least I wonder if I am really the first who actually doubles his FP2 batteries ?

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do i understand right, you whant to connect the two batteries parallel to the FP2 Batteries connectors?

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I’m not sure what you are planning to do (2 batteries in parallel?) but PCMs are cheap and small, so it doesn’t matter much. Just use them, won’t hurt. I assume you are you talking about the main battery port, not this.

yes, you got it. Any ideas ?

Thanks for quick answer. But don’t mind about the price of PCMs. Mind about the place and cable issues.(what location inside do you recommend?) It becomes much more easier without 2 aded PCMs including cables cross wise over or under the existing battery. Given the hunchback case there would be only connecters to be created instead of erratic cable bridges.

I don’t think thats a good idea. The doubled capacity load will overheat the chargeing parts and break your phone…
I like the idea but don’t think its possible without a connection over the Back connector and implementing it somehow over USB to switch to charge functionality when its on a source and back when the source is gone and the first battery is low… So thats nothing i can help. But i can help if you need to make pcb or mechanical parts…

your ideas are appreciated. You recommend the safe way by an internal power bank. Looks much more complicated . My battery doesnot show any temp increase alone due to my good charger. Maybe 2 batteries show only little temp increase. Have you tested 2 orignal FP2 batteries this way?

Your approach rather looks to me like a research case before even testing anything.
Why are you that sure that slower charging or controlled start/stop charging stepwise couldnot prevent overheating ?

Im not aware of a possibility to get controll over the charging functionality.
Are you able to controll the charging speed or current?

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…

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