\subsection{Battery Benchmark}
The \setting{Battery Benchmark} plugin enables you to test your battery's
performance whilst using your \dap\ normally. Results can be submitted 
to the \wikilink{BatteryRuntime} wiki page.

\subsubsection{How it works}
Once loaded, \setting{Battery Benchmark} runs in the
background recording various information about your battery to memory.
A new point is written to memory every minute.
Every time the disk is accessed for any reason
(such as refilling the audio buffer, opening a directory or entering
USB mode etc.) then the information in memory is written to disk.
Once the memory becomes full (after many hours), then the data
are written to disk anyway. This is done so that the data are not biased by
excessive additional disk accesses. The file is written to the root
directory of your \dap\ and is called \fname{battery\_bench.txt}.
The plugin will continue to log info until:

\begin{itemize}
\item Another plugin is loaded.
\item The \dap\ is shut down.
\item The battery is empty.
\end{itemize}

Benchmarks can be resumed if
you accidentally load a plugin, or turn off your \dap, so long as the log
file \fname{battery\_bench.txt} is not deleted. 

\subsubsection{Information explained}
At the top of the \fname{battery\_bench.txt} file is various
information on how to use the plugin, followed by the data themselves.

\begin{description}
\item[Time] This column reports the total time of operation of the \dap. It is 
not the time that you started the plug-in. If you have your \dap\ on for 5 
minutes and then start the plugin, it will start measuring from 5 minutes.
\item[Seconds] The same as \config{Time}, except measured in seconds.
\item[Level] The percent level of the battery estimated by Rockbox, and not the
actual battery level. The actual battery level can be seen from the
\config{Voltage} column
\item[Time Left] This shows the time remaining until the battery is empty,
again as estimated by Rockbox.
\item[Voltage] The battery voltage in mV at the moment the measurement
was taken.
\item[C] This stands for Charger. An ``A'' in that column shows if the power
adapter was attached to the unit at the time of the measurement.
\item[U] USB powered. Only for targets that support this. A ``U'' will indicate
if the unit was using the USB port for power at the time of the measurement. 
\end{description}

\subsubsection{Usage}
The log file can be used to tell you how long the battery lasted (with some
limitations, see below), but it is most useful for graphing discharge curves
in order to improve Rockbox's estimation of battery level and time remaining.
The battery log (\fname{battery\_bench.txt}) is in CSV format
(comma separated variables) and thus can be easily imported into a spreadsheet
or similar program.

\subsubsection{Limitations}
As \setting{Battery Benchmark} needs to write the data held in memory to
disk in order to save them, it is possible that should Rockbox shut down
due to low battery then there will not be enough power remaining to write the
data to disk. Therefore all measurements since the previous save will be lost.