tag:blogger.com,1999:blog-1016709139053396535.post8604022784552432210..comments2024-03-18T17:34:35.079+00:00Comments on A Smackerel of Opinion: Non linear characteristics in a draining battery on the Nexus 7Colin Ian Kinghttp://www.blogger.com/profile/06458723239721015750noreply@blogger.comBlogger5125tag:blogger.com,1999:blog-1016709139053396535.post-78025056632611411292012-12-06T12:08:08.605+00:002012-12-06T12:08:08.605+00:00 It also calculates the standard deviation from th... It also calculates the standard deviation from these samples to give us some idea of the variability of the battery power measurements. free design softwarehttp://www.bestcaddesign.com/noreply@blogger.comtag:blogger.com,1999:blog-1016709139053396535.post-69317984275580771572012-11-17T09:20:05.271+00:002012-11-17T09:20:05.271+00:00Thanks for you insightful comments Philip.Thanks for you insightful comments Philip.Colin Ian Kinghttps://www.blogger.com/profile/06458723239721015750noreply@blogger.comtag:blogger.com,1999:blog-1016709139053396535.post-54549615176515820942012-11-17T09:06:32.509+00:002012-11-17T09:06:32.509+00:00Even if the battery gauge was 100% accurate, it wo...Even if the battery gauge was 100% accurate, it would only be true for that cycle of that battery. Due to manufacturing variations, each battery will have a different characteristic. Also each cycle will change due to ageing effects of the battery. Finally, temperature will have a significant effect, so at the very least these tests need to be done in a controlled environment. stuphihttps://www.blogger.com/profile/14152306993222215939noreply@blogger.comtag:blogger.com,1999:blog-1016709139053396535.post-51414977495199659182012-11-16T22:54:09.920+00:002012-11-16T22:54:09.920+00:00Well, that is something that can be investigated, ...Well, that is something that can be investigated, but we are talking about a small amount of variability in the data. Suppose we could be 100% accurate, the bigger issue is the non-liner discharge characteristic of the battery which produces different readings depending on how full the battery is. So, it really isn't worth pursing. For the kinds of measurements we need to see if wake up reduction or rendering optimisations help, we are looking at minute changes which simple are not accurately measurable from the battery. One argument is that we should charge the battery up and run the software continuously and see how long it takes to discharge and that will show us how much more efficient the code has become. However, as I have already stated, the durations on steady state (idle or all 4 CPUs spinning) are variable and also it can take 7-12 hours to drain the battery. I am really arguing that if we want to get accurate power readings we should use well calibrated measuring equipment and forget using the battery. Colin Ian Kinghttps://www.blogger.com/profile/06458723239721015750noreply@blogger.comtag:blogger.com,1999:blog-1016709139053396535.post-18937394120381389752012-11-16T22:38:48.882+00:002012-11-16T22:38:48.882+00:00In active (normal) mode, the bq27541 samples at on...In active (normal) mode, the bq27541 samples at one-second intervals. powerstat samples at 10sec intervals. Increasing the sample rate in powerstat should reduce sampling error; in practice does that provide cleaner results? Similarly, a 10-second sample rate risks aligning the samples with tasks scheduled at round-number intervals like 60/120sec. Does an 'odd' sample rate like 7 or 9 seconds provide cleaner data by reducing the likelihood of samples being taken during the execution of periodic tasks?Steve Mnoreply@blogger.com