Tuesday, April 29, 2003
Battery Life: A Two Year Study
Posted by Jason Dunn in "HARDWARE" @ 02:30 PM
With such a pretensious title, you might expect nicely polished results, but that never quite happened. Here's the story: about two years ago, I started working on some battery tests using some testing methods I had worked up. The Pocket PC OEMs were a little generous in their battery testing estimates, and I wanted to get down to the truth about battery life. I started doing tests with every Pocket PC I could find, and the result was a big spreadsheet with a lot of numbers.
About six months ago, I made a plea to the community to see if anyone had the skills to help me build an engine to host and manipulate the data I had collected. A few people offered, but ultimately none of them followed through on their comittments. I'm working on an application now that will completely re-define how we measure Pocket PC performance and battery life, and once it's realeased my data will quickly become overshadowed by this tool. And no, I can't tell you what it is yet. :wink:
So, rather than sit on this data for any longer, I thought I'd just toss it out to the Pocket PC community. So, for better or worse, here's my data. If someone wants to take this data and create some pretty graphics and charts, I'm happy to attach them to this article (400 pixels wide max) - I just didn't have the time neccesary to analyze this data properly. It would also be cool to see someone do up some Q&A's using this data. ie: "Will leaving a memory card in my device affect battery life"? There's so much to learn from this information, so I hope that someone takes up the task of crunching it.
Battery Life Tests
The battery life on most Pocket PCs is still an area where people are disappointed. While the newest Lithium Polymer batteries are getting better and better with power, they still don't last long enough. If battery life is important to you, these tests I've done should help you gauge how long battery life really lasts. These tests are by no means exhaustive, but by testing a constant activity like listening to music and a passive one like idle runtime, you should get a pretty good idea of how long your Pocket PC will last in most cases.
The standard runtime test was accomplished by using KeepAlive by Scott Seligman. KeepAlive sends phantom taps to the screen, making the Pocket PC think it's being used. The backlight settings were changed to never turn off as long as the Pocket PC was in use, and the runtime was written to a text file on the device. Because the Pocket PC is essentially doing "nothing", this test is only a guideline - even with moderate use, the CPU will chew up power and drive this number down. Actually using the device is where the audio test comes in.
How the Audio Test Worked
With the audio playback test, I wanted to isolate the Pocket PC and truly test it without any complications. I took a 64 kbps WMA file ("Smell the Color 9" by Chris Rice), put it on repeat, and turned off the screen. I plugged in a set of headphones, and placed a computer microphone inside the headphones.
I then started an audio recording stream on the PC using SoundForge, and let it run. When the Pocket PC is low on battery life, it will stop audio playback and make an warning sound (beep). Since I could see this audio spike in the audio stream, it was easy to spot how long the battery would last. Trying to play music beyond that point or even use the device results in repeated warnings about the battery life - you might get another twenty minutes of use if you're lucky, and beyond that you run the risk of losing your data depending on the backup battery technology used in your Pocket PC.
The issue of staggered testing has come up. I've heard people say that if they listen to music, stop for a while, then start again, their battery lasts long. This seemed to make sense, but when I did staggered audio testing on the Casio E-125 with a Microdrive (49 minutes, 43 minutes, and 87 minutes of playback), the end result was approximately 3 hours, the same as the regular test.
And the Winner is...
The data is available in two formats: Adobe PDF and Excel 2002. Feel free to download, distribute, and generally do whatever you want with it. It would be nice of you to reference this site though, because I'd like to see the discussion of the results focused here.
Take a look and tell me what you think!
About six months ago, I made a plea to the community to see if anyone had the skills to help me build an engine to host and manipulate the data I had collected. A few people offered, but ultimately none of them followed through on their comittments. I'm working on an application now that will completely re-define how we measure Pocket PC performance and battery life, and once it's realeased my data will quickly become overshadowed by this tool. And no, I can't tell you what it is yet. :wink:
So, rather than sit on this data for any longer, I thought I'd just toss it out to the Pocket PC community. So, for better or worse, here's my data. If someone wants to take this data and create some pretty graphics and charts, I'm happy to attach them to this article (400 pixels wide max) - I just didn't have the time neccesary to analyze this data properly. It would also be cool to see someone do up some Q&A's using this data. ie: "Will leaving a memory card in my device affect battery life"? There's so much to learn from this information, so I hope that someone takes up the task of crunching it.
Battery Life Tests
The battery life on most Pocket PCs is still an area where people are disappointed. While the newest Lithium Polymer batteries are getting better and better with power, they still don't last long enough. If battery life is important to you, these tests I've done should help you gauge how long battery life really lasts. These tests are by no means exhaustive, but by testing a constant activity like listening to music and a passive one like idle runtime, you should get a pretty good idea of how long your Pocket PC will last in most cases.
The standard runtime test was accomplished by using KeepAlive by Scott Seligman. KeepAlive sends phantom taps to the screen, making the Pocket PC think it's being used. The backlight settings were changed to never turn off as long as the Pocket PC was in use, and the runtime was written to a text file on the device. Because the Pocket PC is essentially doing "nothing", this test is only a guideline - even with moderate use, the CPU will chew up power and drive this number down. Actually using the device is where the audio test comes in.
How the Audio Test Worked
With the audio playback test, I wanted to isolate the Pocket PC and truly test it without any complications. I took a 64 kbps WMA file ("Smell the Color 9" by Chris Rice), put it on repeat, and turned off the screen. I plugged in a set of headphones, and placed a computer microphone inside the headphones.
I then started an audio recording stream on the PC using SoundForge, and let it run. When the Pocket PC is low on battery life, it will stop audio playback and make an warning sound (beep). Since I could see this audio spike in the audio stream, it was easy to spot how long the battery would last. Trying to play music beyond that point or even use the device results in repeated warnings about the battery life - you might get another twenty minutes of use if you're lucky, and beyond that you run the risk of losing your data depending on the backup battery technology used in your Pocket PC.
The issue of staggered testing has come up. I've heard people say that if they listen to music, stop for a while, then start again, their battery lasts long. This seemed to make sense, but when I did staggered audio testing on the Casio E-125 with a Microdrive (49 minutes, 43 minutes, and 87 minutes of playback), the end result was approximately 3 hours, the same as the regular test.
And the Winner is...
The data is available in two formats: Adobe PDF and Excel 2002. Feel free to download, distribute, and generally do whatever you want with it. It would be nice of you to reference this site though, because I'd like to see the discussion of the results focused here.
Take a look and tell me what you think!
