Charging from USB battery, phone stops charging, switches on screen, and discharges

[Matthew Exon]

When I was travelling recently I found that if I plugged into a USB battery overnight to charge my phone, when I got up the next morning the phone didn't have any more power than when I started.

Turns out the reason is: when the phone decides the battery is full, it stops drawing current. The battery then decides that charging is over and automatically switches off. The phone then decides that it's been unplugged and turns the screen on. I had set the phone to not automatically switch the screen off, so it just left the screen on all night. The next morning it was as if it had never charged.

So I have the following suggestions:

1) Just don't turn the screen on when the user unplugs the charger
2) If the intention is to let the user know that the charger has been unplugged, pop up a message. Just turning the screen on isn't very useful feedback.
3) If you are turning the screen on automatically it "doesn't count" wrt the user's "automatically turn off screen after..." setting. This should always be just a few seconds.
4) If the user has configured the phone to not automatically switch off the screen, don't automatically turn it on either
5) Give me a few more options for automatically switching off the screen - 1, 2, 3, 4, 5 and 10 is a lot of resolution at the low end. Where is 30mins and 1hour?

P.S. this has nothing to do with webbrowser-app but I still can't figure out how to search launchpad for Ubuntu touch packages.

===============UX comment===================
I will try to address all the points raised in the bug description.

1) is invalid, we should turn on the screen when the user unplugs
the charger and possibly show a message reminding the user to unplug
the charger from the wall socket (if any).

I agree with 2), the system should show a system message as well. This is already specified as one of the usecases of the new notifications system UX (which hasn't been implemented yet).
https://docs.google.com/document/d/1xDSZ_dnAMAlhgFnnyjJEibaITXjVLp1_pnj_tATNm9I (private link)

I agree with 3) and this behaviour is already specified in the Screen blanking policy, that means it is on the plan to implement it (if it's not already)
https://docs.google.com/document/d/1RBoVknCLZ4GQ8E_iVftd3i_KmdxI5d6JrBt7i5EDZO0 (private link)

4) is taken care of by implementing 3)

Point 5) is valid but requires a new bug which should also specify the usecases when those longer values would be needed, so that UX designers can better understand the needs and the reasons behind a UX suggestion :)
Matthew, could you please file that bug? :)

Point 6) (the one presented in comment #1) is valid but requires a new bug, mentioning the usecases, just like 5). I have to say I am not really into that feature, because the screen backlight of devices like the Meizu MX4 probably consumes more power than a USB port provides (which is usually 500mA). So it needs special care and convincing usecases :)
Matthew, could you please file that bug, specifying some usecases when this feature would be really handy? :) I can't promise we will implement it, but we can discuss it ;)

[Matthew Exon (ubuntubugs-mexon)]

Oh, another option:

* Provide a "do not automatically switch off screen when connected to charger" option. That would also avoid the need for me to configure it to never switch off.

[Olivier Tilloy (osomon)]

Thanks for the report Matthew. When in doubt, please file the bug at https://bugs.launchpad.net/canonical-devices-system-image/+filebug.

[Andrea Bernabei (faenil)]

UX fix committed. I will add unity8 package so that the engineers from that team can give more details about what is implemented and what is not (and when it will be).

[Andrea Bernabei (faenil)]

Not sure if this is handled by unity8 or unity-system-compositor or what else. Please change the affected package if needed

[Andrea Bernabei (faenil)]

any update on this Pat?

[Matthew Exon (ubuntubugs-mexon)]

I only just noticed the new description above with the invitation to submit new bugs. I've submitted Bug #1534565 for keeping the screen on while charging, and Bug #1534563 for providing longer blank intervals.

I'd say that neither of these bugs is at all important and in fact I might not even use them anyway. The stuff confirmed as "valid" above are the important things for me. Still, use cases submitted for your viewing pleasure...

[Pat McGowan (pat-mcgowan)]

The case in the description does not happen with simple adapters, I assume the user has some sort of intelligent charger that shuts off? otherwise the phone would not detect being unplugged since it was not.

when the phone decides the battery is full, it stops drawing current.
Correct

The battery then decides that charging is over and automatically switches off.
Not sure what this means. The phone will still be active and will not suspend while something is plugged into the usb port. (which I is a different issue, we wish it would suspend and charge faster when its a charger and not a device thats connected)

The phone then decides that it's been unplugged and turns the screen on.
This does not happen on the standard adapters.

[Michał Sawicz (saviq)]

I'd assume the external battery just drained instead of just switching off? Only way to keep the phone charged to 100% is to keep the voltage up and let the phone operate on it.

[Matthew Exon (ubuntubugs-mexon)]

@pat-mcgowan:

"The battery then decides that charging is over and automatically switches off."

This model of battery pack tries to figure out when the plugged-in device has got to 100% charge, and when it detects that situation it switches itself off and stops supplying power. It then won't supply any more current until I switch it back on by pressing a button on the front. Presumably the idea is to save power by switching off both the battery pack's and the device's charging circuits.

In this case I have a phone at 60% charge and I want to top it up. I plug it into the battery and it starts drawing current. Then I go to sleep. After a couple of hours the phone is at 100% and it stops drawing current from the USB battery. The battery detects this drop in current and switches itself off. But the phone's screen stays on. After a while it would like to top itself up again, but the battery is switched off and won't supply current until I press the button. So the phone just keeps draining itself until I wake up, by which time it's back to 60%.

This is a fairly normal USB power bank, brand name Anker (but likely a fake). I'm pretty sure I've seen this behaviour in other battery packs.

[Pat McGowan (pat-mcgowan)]

Thanks for clarifying

We need to at least fix case 3 per the spec.

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.