In developing the Android app we use to collect field data, I recently completed a series of tests. We wanted to determine how worried we should be about the Android “Location” tab’s judgment that Field Day is a “High battery usage” app. We wanted to avoid installing and running any additional apps to do so.
The simple (if slow) protocol we developed to meet those requirements goes something like this. It’s best when run on multiple, comparable devices at the same time.
- Fully charge the device.
- Restart the device.
- Close all applications other than the app you’re testing.
- Disable sleep, screen turn-off – any battery-saving features that apply to your phone but do not fit the use case of Field Day when we actually run it.
- Do any setup tasks – in our case, linking to a remote database and an Arduino sensor platform to collect data for us.
- Run it for hours not minutes. In our case this was convenient because our app and platform can run without much user interference and still produce valid data.
- Close the app.
- Immediately go to the phone settings and find battery info using the built-in Android battery analyzing tools.
- Check “Battery” (possibly a submenu) as well as “Location”.
- Write down the numbers someplace as data.
I did my day of tests using my cheap second-hand Samsung phone and a Nexus tablet. I connected a Bluetooth sensor platform and collected data from it once every five seconds for five hours (this is of course automated in the app). I kept the screens turned on most of the time.
You’ll observe below that different Android versions (including the extra stuff a manufacturer installs) cause apps and services to report battery usage somewhat differently. My phone, for example, doesn’t list Field Day itself, but does list screen and battery usage, which are (nearly) 100% attributable to Field Day because of the constraints we imposed on our device uses in the early steps in the protocol. (The Nexus did list Field Day, conveniently.)
- 64% remaining after 5 hours
- Bluetooth (97%)
- Time on 5h7m35s
- CPU total 19 sec
- Stay awake 1 sec
- Computed power usage 38232 mAh
- Screen (2%)
- Time on 4h 4m 20s
- Computed power usage 1059 may
- (adaptive display, mid-to-low brightness)
- 40% remaining after 5 hours
- Screen 22%
- Time on 5h 5m 0s
- Computed power usage 753 mAh
- (adaptive display, max brightness)
- Field Day 9%
- CPU Total 6m 19s
- CPU Foreground 6m 9s
- Keep awake 3m 25s
- GPS 5h 2m 23s
- WiFi packets received 19
- WiFi packets sent 30
- Computed power use 317 mAh
In both cases, the “Location” menu continues to report Field Day as “high battery usage” as this issue reports. In practice, battery usage appears to be what we might expect: bright screens and Bluetooth make your battery work more (“I’m shocked, shocked…”).
This test wasn’t the only one we’ve run, but it was the most systematic. It also tested a relatively power-greedy case – normally, we do not keep the screen on at all when we collect a data stream.
I’m going to do another round of tests tomorrow, with the screens off to check the more common usage case. However, based on current observations, the app’s battery usage is in line with what I would expect.
There are pieces of this process we should refine – for example, we should have simply controlled for screen brightness rather than let it be such a dominant player in the first place. But after some discussion, we are confident enough to conclude that our battery usage conforms with what should be expected from an app that heavily uses Bluetooth, GPS, cellular, and/or WiFi. We expect and hope that tomorrow’s screen-off test will confirm this.