CITROEN DS4 Owner's Handbook Manual page 278

12 V battery
Procedure for starting the engine using another
battery or charging a discharged battery.
The presence of this label, in particular
with the Stop & Start system, indicates
the use of a 12 V lead-acid battery with
special technology and specification;
the involvement of a CITROËN dealer
or a qualified workshop is essential
when replacing or disconnecting the
battery.
After refitting the battery, the Stop &
Start system will only be active after a
continuous period of immobilisation of the
vehicle, a period which depends on the
climatic conditions and the state of charge
of the battery (up to about 8 hours).
Access to the battery
The battery is located under the bonnet.
For access to the (+) terminal:
 release the bonnet using the interior lever,
then the exterior safety catch,
 raise the bonnet and secure it with its stay,
 lift the plastic cover for access to the (+)
terminal.
Before doing any work
Immobilise the vehicle: apply the
parking brake, put the gearbox in
neutral, then switch off the ignition.
Check that all electrical equipment is
switched off.