Externally Charging FP5 battery

I am waiting for spare batteries to be sold at the store.
I want to be able to take with me a spare and just swap it during the day when the battery inside FP5 runs out, just like in the old days.
After that I want to slowly charge the spare at the end of the day with an external charger.
The problem is that there are 2 pins for each polarity in FP5 battery compared to 1 in FP4.
What reliable charger should I get?

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I’d measure the voltage on the pins and their combinations. It wouldn’t surprise me if they were just duplicates to distribute the power better when fast-charging. Wasn’t the NFC antenna on the battery, too? That would need some pins, too, I’d assume (but probably not the ones marked with + and -).

For sure one that can hold the very wide battery, that seems to have been an issue with external chargers already. But apart from that I’m not quite sure if the back cover will survive being opened over and over again for too long. For the rare cases when the phone runs out of battery it’s easier to have a power bank or to recharge in advance. For most of us there are sockets around several times per day.


Have you already checked out this thread about external chargers (for FP) in general?

For the rest @Martin_Anderseck pretty much said it all already.
Is there a reason for you not to simply use a power bank? In terms of practical use as well as pricing this is likely the more economical option.


The pins are marked.

The image is from Fairphone 5 Batterie - Ersatzteile | Fairphone

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This image is not correct.
Here is an actual photo of the battery.
I mentioned, 2 pins per polarity.


You could measure the resistance between both - and both + in both directions. That should be nearly zero if there is no difference between it.

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I’d say the truth is somewhere in the middle. The first picture shows that the two contacts which aren’t marked in the second one are the NFC contacts. It’s not printed on the battery but it is in the plastic housing if you zoom in. The one marked with T in the second picture has the label NTC, so it’s for the temperature. And while I was still too lazy to take apart my phone and check the battery myself I’m pretty confident that plus and minus are there twice each.

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Just a graphical summary for our assumption for the pins of the FP5 battery:
⊖ ⊖ O O Ⓣ ⊕ ⊕
M M N1 N2 T + +
Minus, Minus, NFC1, NFC2, Temperature, Plus, Plus


The picture I have sent is a photo I made of my actual FP5 battery with another phone.
Anyway, I emailed support to get a conclusive answer.
I will update this thread with it.

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The first photo is a battery from 3th February 2023 and the second battery is from 6th September 2023.
So it looks like they changed the ‘design’ of the battery.