Mercedes-Benz 2009 M-Class Operator's Manual page 386

Practical hints
Battery
G Warning!
Failure to follow these instructions can
result in severe injury or death.
Never lean over batteries while connecting.
You might get injured.
Battery fluid contains sulfuric acid. Do not
allow this fluid to come in contact with
eyes, skin or clothing. In case it does,
immediately flush affected area with water
and seek medical help if necessary.
A battery will also produce hydrogen gas,
which is flammable and explosive. Keep
flames or sparks away from battery, avoid
improper connection of jumper cables,
smoking etc.
G Warning!
Do not place metal objects on the battery
as this could result in a short circuit.
Use leak-proof batteries only to avoid the
risk of acid burns in the event of an
accident.
! The battery is a Valve-Regulated Lead
Acid (VRLA) battery, also referred to as
"fleece" battery.
Such batteries do not require topping-up of
the electrolyte level. VRLA batteries
384
therefore do not have cell caps and the
battery cover is non-removable. Do not
attempt to open the battery as otherwise
the battery will be damaged.
Even though VRLA batteries do not require
topping-up of the electrolyte level and
cannot be opened to check the electrolyte
level, the battery condition must be
checked periodically by performing a
battery conductance test. Refer to
Maintenance Booklet for battery condition
testing intervals.
The factory-equipped VRLA battery is leak-
proofed. Only use a battery as replacement
that has the same security features and is
of identical size, voltage, and capacity as
the factory-equipped battery.
! As with any other battery, have the
battery disconnect at a qualified workshop
or an authorized Mercedes-Benz Center if
you do not intend to operate your vehicle
for an extended period of time to prevent
battery discharge. You may also connect an
accessory battery charge unit expressly
approved by Mercedes-Benz for your
vehicle model to maintain the battery
charge. Contact an authorized Mercedes-
Benz Center for further information.
The battery, the battery ventilation hose
and the lateral plug must always be
securely installed when the vehicle is in
operation.
! Never loosen or detach battery terminal
clamps while the engine is running or the
SmartKey is in the starter switch or
KEYLESS-GO button is in position 1.
Otherwise the alternator and other
electronic components could be severely
damaged.
Have the battery checked regularly at an
authorized Mercedes-Benz Center.
Refer to Maintenance Booklet for
maintenance intervals or contact an
authorized Mercedes-Benz Center for
further information.
i After battery power was interrupted, do
the following:
Set the clock ( Y page 154).
R
Vehicles with COMAND system with
navigation module: Time and date are set
automatically.
Synchronize the door windows
R
( Y page 120).