2008 MERCEDES-BENZ SL55AMG Battery

391 Practical hints
What to do if …
Left displayRight displayPossible cause/consequencePossible solution
FKey
Not DetectedThe SmartKey with KEYLESS-GO* is
not recognized while the engine is
running because:

The SmartKey with
KEYLESS-GO* is not in the vehi-
cle.

There is strong radio-frequency
interference.
Stop the vehicle in a safe location or as soon
as it is safe to do so.
Search for the SmartKey with KEYLESS-GO*.
Otherwise the vehicle cannot be centrally
locked nor can the engine be started again af-
ter the engine is stopped.
Operate the vehicle with the SmartKey with
KEYLESS-GO* in the starter switch.
Key
Not DetectedThe SmartKey with KEYLESS-GO* is
not recognized when attempting to
start the engine with the
KEYLESS-GO start/stop button* on
the gear selector lever because:

The SmartKey with
KEYLESS-GO* is not in the vehi-
cle.

The battery in the SmartKey
with KEYLESS-GO* is not insert-
ed properly or completely dis-
charged.
Change the position of the SmartKey with
KEYLESS-GO* in the vehicle.
Make sure the batteries in the SmartKey with
KEYLESS-GO* are properly inserted
(
page 407) and are not discharged
(
page 113).
Start the engine with the SmartKey with
KEYLESS-GO* in the starter switch if
necessary.

407 Practical hints
Replacing SmartKey batteries
Replacing SmartKey batteries
If the batteries in the SmartKey or the
SmartKey with KEYLESS-GO* are
discharged, the vehicle can no longer be
locked or unlocked. It is recommended
to have the batteries replaced at an
authorized Mercedes-Benz Center.Batteries contain materials that can harm
the environment if disposed of improperly.
Recycling of batteries is the preferred
method of disposal. Many states require
sellers of batteries to accept old batteries
for recycling.Remove the mechanical key from the
SmartKey or SmartKey with
KEYLESS-GO* (
page 403).
1Mechanical key
2Battery compartment
Insert mechanical key 1 into opening.
Press mechanical key 1 in direction of
arrow.
The battery compartment is unlatched.
Pull battery compartment 2 out of the
housing.
Warning!G
Batteries contain poisonous and corrosive
substances. Therefore keep the batteries
out of reach of children.
If a battery is swallowed, seek medical help
immediately.
Warning!G
SmartKey batteries contain Perchlorate
material, which may require special handling
and regard for the environment. Check with
your local government’s disposal guidelines.
California residents, see
http://www.dtsc.ca.gov/HazardousWaste
/Perchlorate/index.cfm.
iWhen inserting batteries, make sure they
are clean and free of lint.
iWhen replacing batteries, always replace
both batteries.
The required replacement batteries (Lithium,
type CR 2025 or equivalent) are available at any
authorized Mercedes-Benz Center.


408 Practical hints
Replacing SmartKey batteries
3Batteries
4Contact spring
Pull out batteries3.
Using a lint-free cloth, insert new
batteries 3 under contact springs 4
with the positive terminal (+) side
facing up.
Return battery compartment 2 into
housing until it locks into place.
Slide mechanical key 1 back into
SmartKey or SmartKey with
KEYLESS-GO*.
Check the operation of the SmartKey
or SmartKey with KEYLESS-GO* as well
as the KEYLESS-GO* function.


427 Practical hints
Batteries
Batteries
For more information on batteries, see
“Battery” (
page 290).
Your vehicle is equipped with two
batteries:

The starter battery

The battery for electrical consumers
(consumer battery), located in the
trunk
The starter battery is located on the
right-hand side of the engine compart-
ment.
1Positive terminal
2Negative terminal
3Battery ventilationThe consumer battery is located on the
right-hand side of the trunk.
4Positive terminal
5Negative terminal
!The starter battery, its filler caps, and the
ventilation hose must always be securely
installed when the vehicle is in operation.!The consumer battery located in the trunk 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 therefore do not have cell caps
and the battery cover is non-removable. Do not
attempt to open the consumer battery as other-
wise the battery will be damaged.
Even though VRLA batteries do not require top-
ping-up of the electrolyte level and cannot be
opened to check the electrolyte level, the bat-
tery condition must be checked periodically by
performing a battery conductance test. Refer to
Maintenance Booklet for battery condition test-
ing intervals.
As with any other battery, disconnect the con-
sumer battery if you do not intend to operate
your vehicle for an extended period of time to
prevent battery discharge or connect an acces-
sory battery charge unit expressly approved by
Mercedes-Benz for your vehicle model to main-
tain the battery charge. Contact an authorized
Mercedes-Benz Center for further information.

428 Practical hints
Batteries
!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.
The battery, the battery ventilation and the
lateral plug must always be securely installed
when the vehicle is in operation.
Warning!G
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.
!Never loosen or detach battery terminal
clamps while the engine is running or the
SmartKey is in the starter switch. Otherwise the
alternator and other electronic components
could be severely damaged.
Have the starter battery checked regularly by an
authorized Mercedes-Benz Center.
Refer to Maintenance Booklet for maintenance
intervals or contact an authorized
Mercedes-Benz Center for further information.
Warning!G
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 acci-
dent.
Warning!G
The brake system requires electrical power
to operate.
A malfunction in the vehicle’s power supply
or electrical system may impair brake sys-
tem operation and switch it into its emer-
gency operation mode. The same applies if
battery is disconnected. To brake, the driver
must then apply significantly greater brake
pedal pressure and depress the pedal much
further to obtain the expected braking ef-
fect. If necessary, apply full pressure to the
brake pedal. Brakes are only applied to the
front wheels.
Stopping distance is increased! Adjust your
driving style accordingly. For more informa-
tion, see “Electro-hydraulic brake system”
(
page 94).

429 Practical hints
Batteries
Disconnecting the batteries
Apply the parking brake (page 63).
Make sure the gear selector lever is set
to position P (
page 172).
Close the retractable hardtop
(
page 204).
Turn off all electrical consumers.
Turn off the engine (page 64).
Remove the SmartKey from the starter
switch.
Vehicles with KEYLESS-GO*: Open
the driver’s door.
Open the trunk.
Read and observe safety instructions
and precautions (
page 290).
Open the luggage cover in the trunk
(
page 211).
Remove the trunk floor.
The battery for electrical consumers is
located in the right hand area of the
trunk (
page 400).
Use the 10 mm open-end wrench from
the vehicle tool kit to disconnect the
negative lead from negative
terminal5 of the consumer battery
(
page 427).
Warning!G
With a disconnected battery

you will no longer be able to turn the
SmartKey in the starter switch and
pressing the KEYLESS-GO* start/stop
button on the gear selector lever will
have no effect

the gear selector lever will remain
locked in positionP
!Always disconnect the batteries in the order
described below, even if you only want to charge
the starter battery, for example. Otherwise the
vehicle’s electronics can be damaged.


430 Practical hints
Batteries
Open the hood (page 282).
Use the 10 mm open-end wrench from
the vehicle tool kit to disconnect the
negative lead from negative
terminal2 of the starter battery
(
page 427).
Remove the covers from the positive
terminals 1 and 4 (
page 427).
Disconnect the positive lead from pos-
itive terminal 4 of the consumer bat-
tery (
page 427).
Disconnect the positive lead from pos-
itive terminal 1 of the starter battery
(
page 427).
Removing the batteries
Removing the consumer battery
Remove the screws securing the bat-
tery in the trunk.
Remove the battery support and
bracket.
Pull out the battery ventilation hose
from the battery.
Depending on battery arrangement in
your vehicle model, the ventilation tube
is located either on the left or right side
of the battery.
Take out the battery.
Removing the starter battery
Remove the screws securing the start-
er battery in the engine compartment.
Pull battery ventilation 3
(
page 427) out of the battery.
Lift the retaining bracket.
Remove the battery.
Charging and reinstalling batteries
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
battery in its installed position. Contact an
authorized Mercedes-Benz Center for infor-
mation and availability. Charge battery in
accordance with the separate instructions
for the accessory battery charger.


431 Practical hints
Batteries
Charge batteries in accordance with
the instructions of the battery charger
manufacturer.
Reinstall the charged batteries. Follow
the previously described steps in re-
verse order.
Reconnecting the batteries
Turn off all electrical consumers.
Install starter battery in the designated
location in the engine compartment.
Install consumer battery in the desig-
nated location in the trunk.
Attach supports and brackets.
Tighten support and bracket screws.
Connect positive lead 4 (page 427)
of the consumer battery and positive
lead 1 (
page 427) of the starter bat-
tery and fasten covers.
Connect negative lead 2
(
page 427) of the starter battery.
Connect negative lead 5
(
page 427) of the consumer battery.
Reinstall the trunk floor.
Close trunk luggage cover
(
page 211).
!Always connect the batteries in the order
described below. Otherwise the vehicle’s elec-
tronics can be damaged.
!Never invert the terminal connections!
iThe following procedures must be carried
out following any interruption of battery power
(e.g. due to reconnection):

Synchronize the ESP® (page 367).

Synchronize side windows (page 203).