2008 MERCEDES-BENZ S-Class key battery

713 Practical hints
Replacing SmartKey batteries
3Batteries
4Contact springs
Pull out batteries3.

Using a line-free cloth, insert new bat-
teries 3 under contact springs 4 with
the positive terminal (+) side facing up.

Return battery compartment 2 into
housing until it locks into place.

Slide the mechanical key back into the
SmartKey/SmartKey with
KEYLESS-GO*.

Check the operation of the SmartKey/
SmartKey with KEYLESS-GO*.

731 Practical hints
Batteries
Starter battery (example illustration from
S 550)1Negative terminal
2Positive terminal
Disconnecting starter battery
Secure vehicle in place with electronic
parking brake (
page 422).

Shift the automatic transmission to
park positionP (
page 426).
Do not rub the battery with rags or cloths.
The battery could explode if touched due to
electrostatic charge or due to spark forma-
tion.!
Switch off the engine and switch off the ve-
hicle’s internal electrical functions (
page 732)
before you disconnect or remove the battery’s
terminal clamps. You could otherwise destroy
electronic assemblies such as the generator.
Have the battery checked regularly by an autho-
rized Mercedes-Benz Center. Refer to Mainte-
nance Booklet for maintenance intervals or
contact an authorized Mercedes-Benz Center for
further information.
!
Do not connect any consumers directly to
the starter battery. The starter battery will other-
wise be discharged.
i
Only replace a discharged battery with a bat-
tery recommended by Mercedes-Benz. The con-
sumer battery is installed in the trunk in such a
way that it is safeguarded as much as possible
against mechanical destruction in the event of
an accident.
i
Remove SmartKey from starter switch (vehi-
cles with KEYLESS-GO*: Make sure the vehicle’s
on-board electronics have status 0)
(
page 370) when you turn off the engine and
no longer require any electrical consumers. The
vehicle then uses very little power and the con-
sumer battery is spared.
i
If the consumer battery is discharged, you
must use the mechanical key to unlock the vehi-
cle (page 708). Since the vehicle has a sepa-
rate starter battery, however, you can still start
the vehicle.
!
Always disconnect the starter battery in the
order described below. You could otherwise
damage the vehicle’s electronics.
!
Switch off the vehicle’s internal electrical
functions before disconnecting the starter bat-
tery. If the vehicle is stationary for more than one
hour with the SmartKey removed, you do not
need to switch off the vehicle’s internal electrical
functions.

732 Practical hintsBatteriesSwitching off vehicle’s internal
electrical functions
Turn off all electrical consumers.

Turn SmartKey in starter switch to po-
sition 0.

Turn SmartKey in starter switch to po-
sition 1.

Wait for 30 seconds.
The vehicle’s internal electrical func-
tions are switched off.

Turn SmartKey in starter switch to po-
sition 0.Disconnecting starter battery

Open the hood (
page 573).

Use a 10-mm open-end wrench to dis-
connect the battery negative lead.

Remove cover2 (
page 731) from
the positive terminal.

Disconnect the battery positive lead.
Removing starter battery
Pull out the battery ventilation hose
from the battery (depending on battery
arrangement in your vehicle model, the
ventilation hose is located either on the
left or right side of the battery).

Fold bar on starter battery up.

Take out the starter battery.
Charging battery
i
Vehicles with KEYLESS-GO: remove the
KEYLESS-GO button (
page 371) and use the
SmartKey with KEYLESS-GO like a normal
SmartKey.
!
Do not remove the SmartKey!
i
For your convenience, have the starter bat-
tery removed by a Mercedes-Benz Center.
Warning!
G
Never charge a battery while still installed in
the vehicle unless the accessory battery
charge unit approved by Mercedes-Benz is
being used. Gases may escape during charg-
ing and cause explosions that may result in
paint damage, corrosion or personal injury.
An accessory battery charge unit specially
adapted for Mercedes-Benz vehicles and
tested and approved by Mercedes-Benz is
available, permitting the charging of the bat-
tery in its installed position. Contact an au-
thorized Mercedes-Benz Center for
information and availability. Charge battery
in accordance with the separate instruc-
tions for the accessory battery charger.i
Have the batteries charged by a
Mercedes-Benz Center. If you charge the batter-
ies yourself, follow the operating instructions for
your charging device.

733 Practical hints
Batteries
Starter battery
Connect the switched-off charging de-
vice to the terminals of the starter bat-
tery. Observe the operating
instructions in the manual for the
charging device while doing so.
Reinstalling starter battery
Install starter battery in engine com-
partment.

Swing retaining bar down.
Reconnecting starter battery

Make sure that the consumer battery in
the trunk is correctly installed and con-
nected.

Turn SmartKey in starter switch to po-
sition 0 and remove.

Connect the positive lead and fasten its
cover2 (
page 731).

Connect negative lead1
(page 731).

Attach ventilation tube.

Switch on the ignition (
page 370).

Start the engine (
page 416).

Check vehicle functions.
!
Only use charging devices with a maximum
charging voltage of 14.8 V.
Warning!
G
During the charge procedure, there is a risk
of acid burns due to gases escaping from
the battery. Do not bend over the battery
during the charge procedure.
!
The battery and the battery ventilation hose
must always be securely installed when the vehi-
cle is in operation.
!
Always connect the starter battery in the or-
der described below. Otherwise, the vehicle’s
electronics could be damaged.
Warning!
G
Do not drive without a properly installed and
connected consumer battery.
Have any work on the consumer battery car-
ried out by an authorized Mercedes-Benz
Center.
!
Never invert the terminal connections.
!
Make sure that the battery has a plug where
the ventilation tube is attached to it.

735 Practical hints
Jump starting
Jump starting should only be performed on
the starter battery. The starter battery is
located in the engine compartment on the
passenger side (
page 731).

Make sure the two vehicles do not
touch.

Secure vehicle in place with electronic
parking brake (
page 422).

Shift the automatic transmission to
park positionP (
page 426).

Turn off all electrical consumers, ex-
cept hazard warning flashers or work
lights.

Open the hood (
page 573).

Start the engine of the vehicle with the
charged battery and run at idle speed.1Positive terminal of your vehicle’s
battery
2Positive terminal of other vehicle’s
battery
3Negative terminal of other vehicle’s
battery
4Negative clamp
Warning!
G
Keep flames or sparks away from battery.
Do not smoke.
Observe all safety instructions and precau-
tions when handling automotive batteries
(page 729).
i
Vehicles with KEYLESS-GO*: remove the
KEYLESS-GO button (
page 371) and use the
SmartKey with KEYLESS-GO like a normal
SmartKey.


736 Practical hintsJump starting
Remove red cover from positive
terminal 1.

Connect positive terminal2 of the
charged battery with positive
terminal1 of the discharged battery
with the jumper cable. Clamp cable to
charged battery2 first.

Connect negative terminal3 of
charged battery to jumper cables and
attach other end4 to a suitable
ground point on the vehicle.

Get into vehicle and start engine within
30 seconds.
If the starting attempt does not suc-
ceed: 
Turn the SmartKey in starter switch
to position 0.

Take out the SmartKey.

Turn off engine of donor vehicle, re-
start it and let it run at idle speed
for several minutes.

Disconnect the jumper cable during
this time.

Reconnect jumper cable as de-
scribed before.

Restart engine.

While the engine is running, switch off
several electrical consumers such as
the blower.

Disconnect jumper cables first from
ground point4 and negative
terminal3, then from positive
terminals1 and2.

Have the battery checked at the near-
est authorized Mercedes-Benz Center.
!
Never invert the terminal connections.


737 Practical hints
Towing the vehicle
Towing the vehicle
Mercedes-Benz recommends that the
vehicle be transported with all wheels off
the ground using flatbed or appropriate
wheel lift/dolly equipment. This method is
preferable to other types of towing.
When circumstances do not permit the
recommended towing methods, the
vehicle may be towed with all wheels on
the ground or front wheels raised (except
vehicles with 4MATIC) only so far as neces-
sary to have the vehicle moved to a safe
location where the recommended towing
methods can be employed.!
To prevent damage during transport, do not
tie down vehicle by its chassis or suspension
parts.
!
Before towing the vehicle observe the fol-
lowing instructions:


Do not tow-start the vehicle.


Use flatbed or wheel lift/dolly equipment
with the ignition switched off.


Do not tow with sling-type equipment. Tow-
ing with sling-type equipment over bumpy
roads will damage radiator and supports.


Towing of the vehicle should only be done
using the properly installed towing eye bolt.
Never attach a tow cable, tow rope or tow
rod to the vehicle chassis, frame or suspen-
sion parts. For more information see “Install-
ing towing eye bolt” (
page 740).
i
If the battery is disconnected or discharged


the SmartKey will not turn in the starter
switch


the automatic transmission will remain
locked in park positionP.
For more information see “Batteries”
(
page 729) or “Jump starting” (
page 734).

777 Index
B
Backup lamps
Replacing bulbs 715
Bar 606
BAS 69
Batteries, SmartKey
Checking battery condition 366
Replacing 712
Batteries, SmartKey with KEYLESS-GO*
Checking battery condition 366
Replacing 712
Batteries, vehicle 729
Charging 732
Discharged, Jump starting 734
Disconnecting 731
For electrical consumers 729
For starter 729
Message in display 678
Reconnecting 733
Removing 732
Bead 606
Beverage holder see Cupholder
Blind Spot Assist* 495
Messages in display 654
Bluetooth
®
Settings (COMAND) 180Brake assist system (BAS Plus) 70
Brake assist system (BAS) 69
Brake fluid 572, 766, 769
Brake lamp bulbs 715
Brake lamp, high mounted 715
Brake pads
Message in display 666
Brake warning lamp 29
Brakes 560
High-performance brake system
(AMG vehicles only) 561
Warning lamp 29, 629
Break-in period 558
Bulbs, replacing 714
Additional turn signals 715
Brake lamps 715
Fog lamps 715
Front lamps 715
High beam 715
High mounted brake lamp 715
License plate lamps 715
Low beam 715
Parking and standing lamps 715
Rear fog lamp 715
Turn signal lamps 715C
California retail buyers and lessees,
important notice for 15
Can holder see Cupholder
Capacities and recommended
fuel/lubricants 764
Cargo area see Trunk
Cargo tie-down hooks 532
Carpets, Cleaning and care of 624
Catalytic converter 568
CD
Ejecting (COMAND) 122
Loading (COMAND) 120
Menu overview (COMAND) 123
Playback options (COMAND) 128
Selecting a medium (COMAND) 126
Selecting a track (COMAND) 126
CD (COMAND) 116
Central locking
Automatic 368
Locking/unlocking from inside 369
Central locking/unlocking switches 369
Certification label 748
Change of address or ownership 16