blog/archive/2015/09/09.rss

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   3         <channel>
   4                 <title>Petter Reinholdtsen - Entries from September 2015</title>
   5                 <description>Entries from September 2015</description>
   6                 <link>http://people.skolelinux.org/pere/blog/</link>
   7
   8
   9         <item>
  10                 <title>The life and death of a laptop battery</title>
  11                 <link>http://people.skolelinux.org/pere/blog/The_life_and_death_of_a_laptop_battery.html</link>
  12                 <guid isPermaLink="true">http://people.skolelinux.org/pere/blog/The_life_and_death_of_a_laptop_battery.html</guid>
  13                 <pubDate>Thu, 24 Sep 2015 16:00:00 +0200</pubDate>
  14                 <description>&lt;p&gt;When I get a new laptop, the battery life time at the start is OK.
  15 But this do not last.  The last few laptops gave me a feeling that
  16 within a year, the life time is just a fraction of what it used to be,
  17 and it slowly become painful to use the laptop without power connected
  18 all the time.  Because of this, when I got a new Thinkpad X230 laptop
  19 about two years ago, I decided to monitor its battery state to have
  20 more hard facts when the battery started to fail.&lt;/p&gt;
  21
  22 &lt;img src=&quot;http://people.skolelinux.org/pere/blog/images/2015-09-24-laptop-battery-graph.png&quot;/&gt;
  23
  24 &lt;p&gt;First I tried to find a sensible Debian package to record the
  25 battery status, assuming that this must be a problem already handled
  26 by someone else.  I found
  27 &lt;a href=&quot;https://tracker.debian.org/pkg/battery-stats&quot;&gt;battery-stats&lt;/a&gt;,
  28 which collects statistics from the battery, but it was completely
  29 broken.  I sent a few suggestions to the maintainer, but decided to
  30 write my own collector as a shell script while I waited for feedback
  31 from him.  Via
  32 &lt;a href=&quot;http://www.ifweassume.com/2013/08/the-de-evolution-of-my-laptop-battery.html&quot;&gt;a
  33 blog post about the battery development on a MacBook Air&lt;/a&gt; I also
  34 discovered
  35 &lt;a href=&quot;https://github.com/jradavenport/batlog.git&quot;&gt;batlog&lt;/a&gt;, not
  36 available in Debian.&lt;/p&gt;
  37
  38 &lt;p&gt;I started my collector 2013-07-15, and it has been collecting
  39 battery stats ever since. Now my
  40 /var/log/hjemmenett-battery-status.log file contain around 115,000
  41 measurements, from the time the battery was working great until now,
  42 when it is unable to charge above 7% of original capasity.  My
  43 colletor shell script is quite simple and look like this:&lt;/p&gt;
  44
  45 &lt;pre&gt;
  46 #!/bin/sh
  47 # Inspired by
  48 # http://www.ifweassume.com/2013/08/the-de-evolution-of-my-laptop-battery.html
  49 # See also
  50 # http://blog.sleeplessbeastie.eu/2013/01/02/debian-how-to-monitor-battery-capacity/
  51 logfile=/var/log/hjemmenett-battery-status.log
  52
  53 files=&quot;manufacturer model_name technology serial_number \
  54     energy_full energy_full_design energy_now cycle_count status&quot;
  55
  56 if [ ! -e &quot;$logfile&quot; ] ; then
  57     (
  58         printf &quot;timestamp,&quot;
  59         for f in $files; do
  60             printf &quot;%s,&quot; $f
  61         done
  62         echo
  63     ) &gt; &quot;$logfile&quot;
  64 fi
  65
  66 log_battery() {
  67     # Print complete message in one echo call, to avoid race condition
  68     # when several log processes run in parallell.
  69     msg=$(printf &quot;%s,&quot; $(date +%s); \
  70         for f in $files; do \
  71             printf &quot;%s,&quot; $(cat $f); \
  72         done)
  73     echo &quot;$msg&quot;
  74 }
  75
  76 cd /sys/class/power_supply
  77
  78 for bat in BAT*; do
  79     (cd $bat &amp;&amp; log_battery &gt;&gt; &quot;$logfile&quot;)
  80 done
  81 &lt;/pre&gt;
  82
  83 &lt;p&gt;The script is called when the power management system detect a
  84 change in the power status (power plug in or out), and when going into
  85 and out of hibernation and suspend.  In addition, it collect a value
  86 every 10 minutes.  This make it possible for me know when the battery
  87 is discharging, charging and how the maximum charge change over time.
  88 The code for the Debian package
  89 &lt;a href=&quot;https://github.com/petterreinholdtsen/battery-status&quot;&gt;is now
  90 available on github&lt;/a&gt;.&lt;/p&gt;
  91
  92 &lt;p&gt;The collected log file look like this:&lt;/p&gt;
  93
  94 &lt;pre&gt;
  95 timestamp,manufacturer,model_name,technology,serial_number,energy_full,energy_full_design,energy_now,cycle_count,status,
  96 1376591133,LGC,45N1025,Li-ion,974,62800000,62160000,39050000,0,Discharging,
  97 [...]
  98 1443090528,LGC,45N1025,Li-ion,974,4900000,62160000,4900000,0,Full,
  99 1443090601,LGC,45N1025,Li-ion,974,4900000,62160000,4900000,0,Full,
 100 &lt;/pre&gt;
 101
 102 &lt;p&gt;I wrote a small script to create a graph of the charge development
 103 over time.  This graph depicted above show the slow death of mylaptop
 104 battery.&lt;/p&gt;
 105
 106 &lt;p&gt;But why is this happening?  Why are my laptop batteries always
 107 dying in a year or two, while the batteries of space probes and
 108 satellites keep working year after year.  If we are to believe
 109 &lt;a href=&quot;http://batteryuniversity.com/learn/article/how_to_prolong_lithium_based_batteries&quot;&gt;Battery
 110 University&lt;/a&gt;, the cause is me charging the battery whenever I have a
 111 chance, and the fix is to not charge the Lithium-ion batteries to 100%
 112 all the time, but to stay below 90% of full charge most of the time.
 113 I&#39;ve been told that the Tesla electric cars
 114 &lt;a href=&quot;http://my.teslamotors.com/de_CH/forum/forums/battery-charge-limit&quot;&gt;limit
 115 the charge of their batteries to 80%&lt;/a&gt;, with the option to charge to
 116 100% when preparing for a longer trip (not that I would want a car
 117 like Tesla where rights to privacy is abandoned, but that is another
 118 story), which I guess is the option we should have for laptops on
 119 Linux too.&lt;/p&gt;
 120
 121 &lt;p&gt;Is there a good and generic way with Linux to tell the battery to
 122 stop charging at 80%, unless requested to charge to 100% once in
 123 preparation for a longer trip?  I found
 124 &lt;a href=&quot;http://askubuntu.com/questions/34452/how-can-i-limit-battery-charging-to-80-capacity&quot;&gt;one
 125 recipe on askubuntu for Ubuntu to limit charging on Thinkpad to
 126 80%&lt;/a&gt;, but could not get it to work (kernel module refused to
 127 load).&lt;/p&gt;
 128
 129 &lt;p&gt;I wonder why the battery capacity was reported to be more than 100%
 130 at the start.  I also wonder why the &quot;full capacity&quot; increases some
 131 times, and if it is possible to repeat the process to get the battery
 132 back to design capacity.  And I wonder if the discharge and charge
 133 speed change over time, or if this stay the same.  I did not yet try
 134 to write a tool to calculate the derivative values of the battery
 135 level, but suspect some interesting insights might be learned from
 136 those.&lt;/p&gt;
 137 </description>
 138         </item>
 139
 140         <item>
 141                 <title>Book cover for the Free Culture book finally done</title>
 142                 <link>http://people.skolelinux.org/pere/blog/Book_cover_for_the_Free_Culture_book_finally_done.html</link>
 143                 <guid isPermaLink="true">http://people.skolelinux.org/pere/blog/Book_cover_for_the_Free_Culture_book_finally_done.html</guid>
 144                 <pubDate>Thu, 3 Sep 2015 21:00:00 +0200</pubDate>
 145                 <description>&lt;p&gt;Creating a good looking book cover proved harder than I expected.
 146 I wanted to create a cover looking similar to the original cover of
 147 the
 148 &lt;a href=&quot;https://github.com/petterreinholdtsen/free-culture-lessig&quot;&gt;Free
 149 Culture&lt;/a&gt; book we are translating to Norwegian, and I wanted it in
 150 vector format for high resolution printing.  But my inkscape knowledge
 151 were not nearly good enough to pull that off.
 152
 153 &lt;p&gt;But thanks to the great inkscape community, I was able to wrap up
 154 the cover yesterday evening.  I asked on the
 155 &lt;a href=&quot;irc://irc.freenode.net/%23inkscape&quot;&gt;#inkscape IRC channel&lt;/a&gt;
 156 on Freenode for help and clues, and Marc Jeanmougin (Mc-) volunteered
 157 to try to recreate it based on the PDF of the cover from the HTML
 158 version.  Not only did he create a
 159 &lt;a href=&quot;https://marc.jeanmougin.fr/share/copy1.svg &quot;&gt;SVG document with
 160 the original and his vector version side by side&lt;/a&gt;, he even provided
 161 an &lt;a href=&quot;https://marc.jeanmougin.fr/share/out-1.ogv&quot;&gt;instruction
 162 video&lt;/a&gt; explaining how he did it&lt;/a&gt;.  But the instruction video is
 163 not easy to follow for an untrained inkscape user. The video is a
 164 recording on how he did it, and he is obviously very experienced as
 165 the menu selections are very quick and he mentioned on IRC that he did
 166 use some keyboard shortcuts that can&#39;t be seen on the video, but it
 167 give a good idea about the inkscape operations to use to create the
 168 stripes with the embossed copyright sign in the center.&lt;/p&gt;
 169
 170 &lt;p&gt;I took his SVG file, copied the vector image and re-sized it to fit
 171 on the cover I was drawing.  I am happy with the end result, and the
 172 current english version look like this:&lt;/p&gt;
 173
 174 &lt;img src=&quot;http://people.skolelinux.org/pere/blog/images/2015-09-03-free-culture-cover.png&quot; width=&quot;70%&quot; align=&quot;center&quot;/&gt;
 175
 176 &lt;p&gt;I am not quite sure about the text on the back, but guess it will
 177 do.  I picked three quotes from the official site for the book, and
 178 hope it will work to trigger the interest of potential readers.  The
 179 Norwegian cover will look the same, but with the texts and bar code
 180 replaced with the Norwegian version.&lt;/p&gt;
 181
 182 &lt;p&gt;The book is very close to being ready for publication, and I expect
 183 to upload the final draft to Lulu in the next few days and order a
 184 final proof reading copy to verify that everything look like it should
 185 before allowing everyone to order their own copy of Free Culture, in
 186 English or Norwegian Bokmål.  I&#39;m waiting to give the the productive
 187 proof readers a chance to complete their work.&lt;/p&gt;
 188 </description>
 189         </item>
 190
 191         </channel>
 192 </rss>