phone turned off on its own while idle

Attaching the syslog from the device. It starts at 04:19:17 AM, and the last recorded event before the phone turned itself off is at 05:14:00. There are lots of events in between (214226 lines) for a supposedly idle device, I would say.

I grabbed a copy of the contents of /var/log and /home/phablet/.cache/upstart from the phone, I can share selected files on demand if that helps investigate the issue.

A similar thing happened to me last night (I was also on r159 on Aquaris 4.5). I suddenly noticed that the phone had turned off, and I wasn't able to turn it on until plugging it in to the charger. My charge level was about 35%, but it wouldn't turn back on again until it had charged for a while. Attaching syslog.

Similar to bug #1505241 the wakeup source is the MT662x and the phone does not suspend.

It is similar but slightly different. In Oliver's case the system tries to suspend every second, then after almost an hour it suddenly stops.

According to syslog in #1505241, the system tries to suspend 559 times in 3h43min while in the case of this bug it tries to suspend 3273 times in 55min.

I'm wondering if the kernel watchdog could bring the system down if it fails to suspend repeatedly.

What’s quite different from bug #1505241 is that no battery drain happened. The phone turned itself off, but it still had plenty of battery.

Unless this is a symptom of other reports where the reported battery level is incorrect. It acted a lot like it shutdown do to drained battery but no proof there.

The only shutdown triggers I know of are low battery and high temp.

Then the reported battery level would be consistently wrong. I’ve been using the phone quite extensively since 10am this morning (which is when I resurrected it), it was plugged in at times for for short periods of time (when connected to fetch the logs). I’ve actively used the hotspot function for a couple of hours this morning to work from my laptop. If the battery had been empty, the device would have turned itself off long ago.

Attaching a capture of the battery consumption graph, the sudden drop around 10:30am corresponds to when I activated the hotspot while not plugged in to a power source.

Another (probably unrelated) comment: I keep disabling bluetooth, as I never ever use it, and it keeps re-enabling itself. Annoying, and I suppose it has an impact on battery life too.

Actually the description that it could not initially boot until it charged for a while is also consistent with the battery being depleted, or at least the device thinking that was so. What did the charging screen say it was?

My battery reading was from the charging screen. I hadn't used the phone for a while when I picked it up and noticed it was "dead".

Same behavior here. When happened, several times, battery levels range from ~30% to ~45%.
What I've noticed also is that while charging after these sudden power offs, if you turn on to the battery charge animation, wait the screen to turn off, turn on again ... the battery level displayed goes down 1% every turn on until it does it no more. This could be done 10 to 15 times, each time an one percent less than before.