Since this morning, the battery-stats package in Debian include an extended collector that will collect the complete battery history for later processing and graphing. The original collector store the battery level as percentage of last full level, while the new collector also record battery vendor, model, serial number, design full level, last full level and current battery level. This make it possible to predict the lifetime of the battery as well as visualise the energy flow when the battery is charging or discharging.
The new tools are available in /usr/share/battery-stats/ in the version 0.5.1 package in unstable. Get the new battery level graph and lifetime prediction by running:
Or select the 'Battery Level Graph' from your application menu.
The flow in/out of the battery can be seen by running (no menu entry yet):
I'm not quite happy with the way the data is visualised, at least when there are few data points. The graphs look a bit better with a few years of data.
A while back one important feature I use in the battery stats collector broke in Debian. The scripts in /usr/lib/pm-utils/power.d/ were no longer executed. I suspect it happened when Jessie started using systemd, but I do not know. The issue is reported as bug #818649 against pm-utils. I managed to work around it by adding an udev rule to call the collector script every time the power connector is connected and disconnected. With this fix in place it was finally time to make a new release of the package, and get it into Debian.
If you are interested in how your laptop battery is doing, please check out the battery-stats in Debian unstable, or rebuild it on Jessie to get it working on Debian stable. :) The upstream source is available from github. As always, patches are very welcome.