Losing connectivity when restarted after battery under 10%

Escain

Hi,

I am using a Fairphone 3+, with 2022-W47 4258, but I see this issue since several updates.

When my battery get under 10%, the "low battery" message shows.
I usually react to this either by :

connecting the device to a power source, or
by switching off my device, so I can make a last call in case of urgency.

It happens that if I start my device with still less than 10% of battery, it is not able to connect in any way:

I can enable the wifi, but no wifi is detected
Antena signal shows error, and I can't receive/send calls or SMS.

I usually wait until the battery level is ok, and then restart the device. This fixes the problem (until I start my device under 10% again).

Is this issue known?
Is there any configuration to fix it?
Is this related with Ubuntu-Touch in general or just with my FP3+?

Keneda

@escain
Try to change your battery if not already done.
Fairphone has parts available so that should be easy to find one.
Old batteries make voltage very unreliable, and SOC don't like this.

With mine that is quite close to dying, i loose connectivity lot of time (among other things like loosing vibrator or alarm not firing).
This happens more as it gets low.
Usually i can fix connectivity by activating/unactivating plane mode once or more...

But as i have not the same model than you, maybe issues and workaround will not match.

Escain

My battery seems to work totally fine: I have usually 3+ days of autonomy, and the phone reacts perfectly up to the 0-1%.

I think that UT have a special start-up on low-battery causing the issue. The fact that the phone reacts differently at 9% or 11% is a strong indication that this is software and not hardware.

So I want to highlight that the phone works perfectly until dying at 0%.
The problem only appears when starting the phone below 10%.

Keneda

@escain said in Losing connectivity when restarted after battery under 10%:

I think that UT have a special start-up on low-battery causing the issue.

I'm not aware of anything like that on UT.
I think that this is an issue you have, not a feature.
Also, lot of people have FP3/3+ with UT on it, so if this was present on all of those, we'd already have report of this here.
Best would be to contact porter at first ( @Luksus ), he knows well this device behavior under UT.

You can also check on UBports Git if an issue like that is present.

Did you try as a workaround to turn plane mode on to save battery instead of turning it off ?

By the way, Li-ion batteries (Li-po included) should never be discharged under 15/20%, and full charge is not good either, best is to stop under 90%.

gandalf

@keneda @Escain
https://forums.ubports.com/topic/8125/no-network-is-detected-when-i-boot-the-phone-with-less-than-10-battery
There's another report of this in the fp3 forum. Consensus seem to be it's possibly a battery saving feature :man_shrugging:

Escain

@gandalf

Thanks your. So it's confirmed that this is not solely my battery.

I see no reports of this on Android FP3+, this might be either Linux or UT. Or maybe a mix with the firmware of FP3.

Keneda

@gandalf said in Losing connectivity when restarted after battery under 10%:

Consensus seem to be it's possibly a battery saving feature

A battery saving feature that prevents you to contact anyone in case of emergency ?

gandalf

@keneda

A battery saving feature that prevents you to contact anyone in case of emergency ?

It's still a hypothetical answer and nobody said it was a clever feature

Ian

@escain Just tried this on the Vollphone X running 16.04 OTA 24. With 20% battery wifi and cellular work OK after a restart. Drained the battery further to 10% (received the battery low alert) and did another restart. Wifi and cellular still worked. Tried it yet again at 9% and still OK.

If it is a software feature it does not affect all phones.

Luksus

It is definitely some hardware-specific issue. I would not go as far as calling it a feature.
Maybe because of low power, there is entered some specific bootmode and our halium-stage cannot handle that right or whatever. Though on a quick investigation in the FP3-android-device-source I could not see any obvious passage for this hypothetically case.

Maybe someone could investigate differences in dmesg init logs or journalctl with and without low battery.
I don't see other possibilities to find the root cause for this behavior.

Besides that, that issue is very low priority on my list.
It exists from the very beginning and I know how to avoid it, what makes me not putting too much energy into solving it.