* Matthias Apitz <[email protected]> wrote: > Yes, exactly like this, with meters in addition.
Although not shown in the picture, I have the phones instrumented with meters along the path for primary power and USB, and use it to check power consumption on each new build. For example, here is a summary of one type of krillin power usage for 50 builds during a time when a relevant bug was introduced: http://toykeeper.net/tmp/phablet/power/krillin-rc-proposed,en-power_usage_display_on-287-336-smooth.png Toward the right side, it spikes for several builds until we had the bug isolated and fixed. The red columns indicate when it thinks there is a new bug, and green is when it thinks something was improved. The blue area is where it expects the result to be based on recent measurements. So, bug found and fixed. If I recall correctly, this particular bug was the reason an OTA release got delayed. Then a few builds later, in r335, it noticed an unusually high variation between individual measurements, and marked that build for inspection. For context, here is a more detailed graph for r334, when everything was behaving: http://toykeeper.net/tmp/phablet/power/krillin.334.display.png The green section is the part of the measurement it "counts" for the test. Red sections mean USB was plugged in so those values aren't relevant. In this case, it's just letting the phone idle with the screen on right after booting. Five measurements, and they're all pretty consistent. Then in the next build it had one measurement which didn't look quite right: http://toykeeper.net/tmp/phablet/power/krillin.335.display.png So it marked that build for inspection, with detailed logs available to help identify what happened. This is how we've been detecting and fixing power consumption bugs, making sure each new OTA is the same or better than the ones before it. But that's mostly for userspace bits. Kernel and firmware issues are trickier. > hat I do not understand is the issue my wife sees from time to > time: her device shows 50% or 60% of remaining capacity, for > longer time (due to nearly no use of the device), and within > minutes the capacity goes to zero and the BQ E4.5 is a brick in > her pocket. I understand what you say, Selene, about > discrepancies in the layers an error in interpreting the > voltage, but I do no see, how can lead this to 50%-to-0% in a > few minutes. Have you found something, which explains this? Yes. Especially when a device spends a lot of time in standby. The daemon which generates that percentage estimate can sometimes go a long time between updates... and when it does update it has a tendency to lag. For example, one day I was testing by manually changing the input voltage and recording how the phone responded. What I found was that the kernel's reported voltage lagged behind the actual voltage when the actual voltage decreased quickly, but it tracked closely when voltage increased. Additionally, it sometimes took a while for the reported percent (and built-in charge graph) to catch up. In this graph comparison, the green line is what the power supply voltage was set to, the blue line is what the kernel reported, and the rainbow graph is a screenshot of what the phone reports to its user. After manually dropping the voltage to "almost empty", it took about 40 minutes for the UI to catch up and it did the thing where it went suddenly from like 60% to 0%. http://toykeeper.net/tmp/phablet/power/battgraphs.png Then a bit later (I let it keep measuring), I noticed some other odd behavior. Although it hadn't noticed earlier that the voltage went back up, when it finally updated again it changed the UI's rainbow graph retroactively: http://toykeeper.net/tmp/phablet/power/battgraphs.2.png After the kernel noticed the increased voltage, the UI took over an hour to update. If it drops suddenly to zero, that usually means the battery itself has been dropping for quite a while and the capacity estimation software simply took a long time to catch up. The kernel's reported voltage level isn't perfect, but it's a lot closer to reality than the percent shown in the UI. Of course, there are other factors which make it a bit awkward... like the way battery voltage sags under load then recovers later. Play an intensive game and the cell voltage might sag to 3.4V... but turn the game and screen off and voltage may recover to 3.8V within a couple minutes. So it can be tricky to convert a measurable trait (voltage) into an un-measurable trait (percent charge remaining). And the effective capacity isn't a simple graph from volts to percent; it changes with the discharge load so it's more of a 3-dimensional graph. And as the cell ages, the 3D mapping from voltage+amperage to percent changes, so it needs recalibration once in a while. -- Selene -- Mailing list: https://launchpad.net/~ubuntu-phone Post to : [email protected] Unsubscribe : https://launchpad.net/~ubuntu-phone More help : https://help.launchpad.net/ListHelp
