cellio | What's confusing my phone?

I have a problem with my (older) Android phone and am not sure how to debug it.

Four times in the last six months, I have used the navigation in Google Maps while in a car (audio, not looking at the screen). Every time the trip has ended the same way: the app informs me that I have reached my destination, I reach for the phone to exit, and the phone crashes. On restarting, it tells me I have 1% battery and crashes again. (Phone was not low at the start of the trip.) Now here's the interesting part: when I plug it in to charge, it reports something in the range of 30-40%. So, something is confusing the phone about its battery state, because no way does my phone charge that quickly (especially on a car charger).

Here's tonight's case: I was at something over 60% when I turned on nav for a 15-minute trip. Crashed on arrival, plugged in (in the car) and turned on, it said 32%, I unplugged, and it crashed again (back to 1%). I left it off while I completed my errand, but plugged it in to charge on the drive home. At home, it was 40% and, this time, did not crash when I unplugged it from the charger.

To determine whether the problem is specific to Google Maps, I installed another navigation app (Waze). When the installation finished I opened the app...and the phone crashed. When I connected it to the charger, it said it was at 31%. I let it charge for a bit (I turned it on while it was connected to the charger), and disconnected it around 50% with no issues.

Here's all that in pictorial form:

Also, the power manager reports no fast-drain apps. iDrive, a backup app, was a fast-drain app and is the singular entry in the history, but I've nerfed it and it hasn't popped up recently. Could its mere presence be a problem?

Now, I'm pretty sure the battery isn't actually being drained to practically nothing, because it wouldn't bounce back that quickly. And apparently it's not just Google Maps or GPS, because Waze didn't even finish opening before that crash. But something, either Android or something in hardware or firmware, sure thinks there's a problem that calls for shutting down.

How do I find it?

I have not had crashes with other apps -- though I also don't stream videos or play games on my phone, so I'm not taxing it. I have noticed the pattern of "steps" you can see in the picture here -- battery will drop noticably, then stay level for a while, then do it again. I don't know what's causing that or if it's related.

The phone is old -- ZTE Axon 7, bought in 2017, running Android 7.1.1 and apparently not eligibile for newer -- but it otherwise works, has the (rare) aspect ratio I crave, and already has all my stuff on it. I'd like to keep using it for a while (and let the 5G world sort itself out in the meantime).

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Unfortunately my first thought is that the battery is flaking out and the only time it gets stressed is when using maps/waze/whatever.

To test this, what might I do to stress the battery? What kinds of apps are hungry but not harmful? (I don't want to install random unvetted apps.)

Possibly not an answer you can use -- but I notice that there are unofficial builds of LineageOs 17.1 for this machine. Installing that would mean wiping the system, but probably give you a useful lifetime until the battery or flash wears out.

https://forum.xda-developers.com/t/rom-10-0-a2017x-unofficial-lineageos-17-1.4107897/

Huh. I had no idea that was possible.

Probably not something I'll do (can't risk not having a working device when I use this for 2FA and other things), and I, um, know most of the words there individually :-). But I'm glad to know that such things exist.

My phone has just randomly started doing something like this lately, too - I will unplug it in the morning, it will suddenly plunge to a few percent and then die, restart itself, show a tiny charge. I plug it in for a minute or two and it's at 99%. (iPhone, so I can't be truly helpful.)

Yeah, it's weird.

I called a few local places that advertise battery replacement. None of them could help me -- don't have the right battery, one half-heartedly offered to try to get one but no promises, others just said no. One of the people I talked with said that based on my description, the problem could be a connection shorting, in which case replacing the battery wouldn't help.

I spent some time today phone-shopping. Interestingly, the answer hasn't appreciably changed since I looked around six months ago; of course there have been new phones since then, but many of them fail some of my requirements. Six months ago I was eyeing the Pixel 4A; that's now been deprecated by the Pixel 5A, which looks like a good fit. (Why not the Pixel 6? Partly size, mostly lack of a headphone jack.)

Monica, due to lithium-ion battery hysteresis, there is no good function from battery voltage to the battery percentage. Various tricks can be used to make this more accurate. It's possible that these tricks are fine-tuned to the battery characteristics, which change as the battery ages, making these tricks less effective.

1. % reported when charging, may not be the % remaining after unplugging
2. Try charging fully, letting the battery run down all the way without charging, then charging fully; for some batteries this is claimed to reset their scoring algorithm.
3. May have to distrust the battery percentage when discharged below some threshold. (50%?)

--Philip V

Just in case anyone is still interested, the same started happening with my phone, but I also noticed it seemed to be getting quite warm. Since lithium-based batteries need to be very carefully managed to avoid the risk of them catching fire (which is almost impossible to extinguish), I suspect that the battery is reporting that it must shut down, but the phone cannot understand any reason except low battery. A bit like how a long time ago DOS programs reported "disk full" when trying to write to read-only network shares because the programmer thought that was the only possible reason for failure.

When using navigation, not only is it continuously using power, but you may have turned up the screen brightness to see it in strong sunlight, and it may be on the dash in the sun.

If it is overheating, it's probably due to the battery struggling to produce high power output due to aging, so a replacement should fix it. But it also could be a defective connection (possibly a poor connection failing under heavy current), in which case replacing tha battery might still fix it if that replaces the defective bit.

-- Charles

Thanks for explaining how a different problem ("must shut down") could manifest as "low battery" in the UI. That makes sense.

I talked with several repair places, none of whom could get the specific battery (too old) and one of whom said "sounds like it could be a connection, though" (so even if they could get it, that might not solve the problem). I ended up getting a new phone -- plenty of clues that trying to maintain this one would be a challenge.

(I actually turn the screen off during navigation if I'm the driver and not the passenger; there's no place I can place or mount the phone such that I'd be able to read it anyway, so I go audio-only. But all the GPS pings and extra computation would still be taxing it more than sitting in my pocket and emitting the occasional ping for new email would.)

What's confusing my phone?

First thought: battery

Re: First thought: battery

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Might be overheating (and age)

Re: Might be overheating (and age)