CITROEN DS3 Handbook page 236

Energy economy mode
System which manages the period of use of certain functions to conserve a sufficient level of charge in the battery.
After the engine has stopped, you can still use functions such as the audio equipment, windscreen wipers, dipped beam headlamps, courtesy lamps,
etc. for a maximum combined period of thirty minutes.
This period may be greatly reduced if
the battery is not fully charged.
Switching to economy mode
Once this period has elapsed, a message
appears on the multifunction screen indicating
that the vehicle has switched to economy mode
and the active functions are put on standby.
If the telephone is being used at the
same time on the eMyWay audio
navigation system, it will be interrupted
after 10 minutes.
Exiting economy mode
These functions are reactivated automatically
the next time the vehicle is driven.
F In order to resume the use of these
functions immediately, start the engine and
let it run for a few minutes.
The time available to you will then be double
the period for which the engine is left running.
However, this period will always be between
five and thirty minutes.
A flat battery prevents the engine from
starting (refer to the corresponding
paragraph).