Lineageos 18.1 :: Battery charge status when phone is turned off

It feels there’s something off with how my new FP3+ reads its battery status. This is the latest thing I caught it with:

  • I let the phone discharge until it turns off.
  • I connect it to power while it’s turned off. I briefly see the “Fairphone” boot screen and then I see what I assume is the charging status.
  • The charging status always shows as one segment of a circle blinking. The charging seems to work because the phone and the charger are slightly warm.
  • I let it sit like that for 4 hours or so. It’s still one segment of a circle blinking, but the phone and charger are cool to touch, seems they are not charging.
  • I turn the phone on and it shows 100% charge. I turn the phone off and now the status shows as full circle around the “100%”.

Now, I’m wondering whether it’s normal. Do other phones behave the same way? If not, who’s to blame?

  • I’m not sure if the battery or the phone are actually faulty. So far they seem to work fine. Once I caught the phone definitely showing wrong charge level while it was on (it was charging, but the charge level was decreasing over time), but it didn’t reproduce since.
  • I have Lineageos 18.1 and I did not have enough time with the default ROM to see if it behaved differently.
  • The charging cable I bought from Fairphone, just ticked the box when ordering.
  • The charger I used last time is an old iPhone charger (I think it’s 12W, came with iPhone 6 or something like that). I think the behaviour is the same over USB which I assume should always work as soon as the cable is good, right? Do you think I should get the official Fairphone charger?

Welcome to the Fairphone community,

I can see the same behavior on my FP3 too, if I accidentally let it run dead. So I guess that’s a fault in the software, not the battery or charger.

But you should try to charge the battery earlier anyway, as complete cycles wear it out faster than necessary.

P.S.: I have to correct myself. I know this behavior from my FP2. The FP3 with FOS shows a battery symbol, when charged switched off, and that works as expected, including a hint to disconnect the charger from mains, when reaching 100%.
What software is running on your phone?

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Just confirming the above, but I notice you mention Lineageos 18.1 so someone who uses that maybe of help. May be useful, I’m adding to the title, although it is tagged.

Thanks @Incanus and @amoun. Perhaps then the “offline” charging software comes not from the Fairphone, but somehow from Lineageos (or perhaps AOSP, especially if you saw something like that before). To be precise, I have the Micro-G build of Lineageos 18.1, for which I mostly followed the Lineage guide (fastboot flash boot_b ...). Then I locked the bootloader and I assume it should be just vanilla Lineageos without root, TWRP or any tweaks (well, except Micro-G).

I wanted to do this session of charging while powered off since people on the Internet suggest it helps calibrate the battery. So far I’m waiting for my phone to discharge to 0 again and it hasn’t been doing anything suspicious.

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