W211 Dual Battery System
219 BCM (ACB-ICC) 11-29-02
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These technical training materials are current as of the date noted on the materials, and may be revised or updated without notice. Always
check for revised or updated information.
To help avoid personal injury to you or others, and to avoid damage to the vehicle on which you are working, you must always refer to the
latest Mercedes-Benz Technical Publication and follow all pertinent instructions when testing, diagnosing or making repair.
Illustrations and descriptions in this training reference are based on preliminary information and may not correspond to the final US version
vehicles. Refer to the official introduction manual and WIS when available.
Copyright Mercedes-Benz USA, LLC, 2002
Reproduction by any means or by any information storage and retrieval system or translation in whole or part is not permitted without written
authorization from Mercedes-Benz USA, LLC or its successors.
Published by Mercedes-Benz USA, LLC
Printed in U. S.A.
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Program Highlights
• Power distribution
- pre-fuse diagram
- pre-fuse locations
• Dual battery on-board electrical system components
- systems battery
- auxiliary battery
- battery control module
- auxiliary battery relay
- cut-off relay for interruptible loads
• Dual battery functional description
- normal modes
- failure modes
- charging auxiliary battery
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W211 Dual Battery System Function
An auxiliary battery supplies electrical energy for a
limited time if the systems battery voltage is low.
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Systems Battery (G1)
Location: (G1) installed in trunk
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W211 Systems Battery (G1)
• Systems Battery: 12V, 95 Ah, 520A (DIN)
• Absorbent Glass Mat (AGM) design, also known as Valve Regulated Lead Acid
(VRLA) type
• Function - Primary power source for all vehicle electrical systems
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Location of Auxiliary Battery (G1/7)
Auxiliary battery installed below air intake of HVAC
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Location of Auxiliary Battery (G1/7)
Shown with HVAC air intake / filter removed
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Auxiliary Battery (G1/7)
• Auxiliary Battery: 12V, 12Ah, 170 A (DIN)
• Absorbent Glass Mat (AGM) design
• Function - Provides supplemental power if systems battery (G1) voltage is low
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AGM / VRLA Battery Properties
• Longer service life
• Improved cold starting characteristics
• Improved deep cycle performance
• No liquid acid spills or leaks
• Fast recharge time
• Completely maintenance free
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AGM / VRLA Battery Testing
• Requires the new Midtronics MCR 717 tester and printer
• Tester measures battery conductance by inducing A/C voltage of a given frequency
and amplitude on the battery posts and monitoring the current flow in response to it
• Discard the acid density sheet, and enter test code (recorded by tester) on warranty
claim forms
• Battery replaced under warranty must have a test printout attached to the R.O.
• Detailed information about testing, and using the MCR717 can be found in WIS
SI54.10-P-0003-01
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Front Pre-fuse Box (F32)
71
70
72 73 74 75
76 77
Location: Passenger footwell
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Pre-fuse Box (F33)
3
F3
Location: Front of spare tire well
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Pre-fuse Power Distribution
F32 F33
f78
N10/1 200 A
f77 f79
Res. N10/2 200 A
f76 f80
N22 40 A N10/1 150 A
f75 f81
N10/11 40 A F34 150 A
f74
K67 40 A
f73
A7/3 40 A
f72
A7/3 50 A
f84
N82 5A
f71 f85
M4/7 150 A N112 and A35/11 5A
f70 f86
150 A X58/1 5A
f87
M40/1 40 A
f89
Res.
M1 G2
G1/7 G1
- +
+ -
K57/2 N82
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Legend: Pre-fuse Block Power Distribution
A7/3 Traction system hydraulic unit
A35/11 Voice recognition module (VCS)
F32 Front pre-fuse box
F33 Rear pre-fuse box
F34 Interior fuse box (left of instrument panel)
G1 Systems battery
G1/7 Auxiliary battery
G2 Alternator
K57/2 Auxiliary battery relay
K67 AIRmatic relay
N10/1 Driver signal acquisition and actuation module (SAM-D)
N10/2 Rear signal acquisition and actuation module (SAM-R)
N10/11 Passenger signal acquisition and actuation module (SAM-P)
N22 Air conditioning control module
N82 Battery control module
N112 Communication platform (CP)
M1 Starter motor
M4/7 Electric suction fan with integrated control
M40/1 Pneumatic pump of dynamic seat control
X58/1 Interior socket
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Battery Control Module (N82)
Location: Rear of spare tire well
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Function of N82
1. Monitors the voltages of (G1) and (G1/7)
2. Monitors alternator voltage (terminal 61) via CAN B
3. Controls auxiliary battery relay (K57/2)
4. Controls consumer prioritization function
5. Optimizes charging of auxiliary battery (G1/7)
6. Notes emergency operation and sets fault codes
(CAN communication / DTC’s)
7. Notes emergency operation resulting in IC / MF fault message
displays
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Auxiliary Battery Relay (K57/2)
Location: Below windshield wiper cowl plastic trim
Function:
• Controlled by N82
• De-energized during normal operation (N.O.)
• Energized to recharge G1/7
• Energized if engine running and system voltage low
• Connects G1/7 to electrical consumers
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Cut-off Relay for Interruptible Loads (K75)
5 or
K7
5
K7
Location: LF SAM (N10/1)
Function:
• Controlled by N82
• De-energized during normal operation (N.C.)
• Energized during emergency operation
• Opens 30/15R to cigar lighter (R3r1), and 12V socket (X58/1) rear of center
console during emergency operation 19
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Normal Mode
F33 - Battery control module monitors
Kl. 30
voltages and calculates the
CAN-B
condition of both batteries
N82 E
-
G1 - Monitors total current
+
Kl. 31
consumption through common
-
ground
F30 G1/7
+ E
- Consumer prioritization off
F32
30 87 - Relay K57/2 de-energized
K57/2 G2 M1
F30 Polyswitch fuse G1 Battery K57/2 Auxiliary battery relay
F32 Front pre-fuse box G1/7 Auxiliary battery M1 Starter
F33 Rear pre-fuse box G2 Alternator N82 Battery control module
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Multi-Function Display Fault Messages
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Consumer Prioritization
If, for example, the alternator fails:
• Both consumer prioritization stages (1 and 2) are immediately activated
via the CAN
• A red warning info appears in the instrument cluster
• The auxiliary battery is not engaged until G1 voltage is low
If, for example, N82 determines the load capacity of systems battery (G1) is
inadequate:
• Stage 1 consumer prioritization via CAN
• Stage 2 consumer prioritization via CAN
(if deactivating stage 1 consumers was not adequate)
• The auxiliary battery is connected and the red warning then appears
in the instrument cluster
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Emergency Mode
Engine running, systems battery
F33
Kl. 30 low:
CAN-B
- Consumers deactivated in
N82 E 2 stages by CAN messages
-
G1
+
Kl. 31
-
- Fault messages in instrument
G1/7 cluster indicate deactivation of
F30
+ E
consumers
F32
- Auxiliary battery relay (K57/2) is
30 87 energized. Auxiliary battery is
connected for supplying power
K57/2 G2 M1 to electrical consumers
F30 Polyswitch fuse G1 Battery K57/2 Auxiliary battery relay
F32 Front pre-fuse box G1/7 Auxiliary battery M1 Starter
F33 Rear pre-fuse box G2 Alternator N82 Battery control module
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Auxiliary Battery Charging Mode
F33 - Battery control module detects
Kl. 30
CAN-B insufficient voltage at auxiliary
battery
N82 E
G1
- + - Auxiliary battery relay (K57/2) is
Kl. 31
activated for a short period of
-
time if primary system voltage is
F30 G1/7
above 13.5V
+ E
F32
- Auxiliary battery is charged
30 87 by alternator through auxiliary
battery relay (K57/2)
K57/2 G2 M1
- This charging cycle will only
occur once per ignition cycle
F30 Polyswitch fuse G1 Battery K57/2 Auxiliary battery relay
F32 Front prefuse box G1/7 Auxiliary battery M1 Starter
F33 Rear prefuse box G2 Alternator N82 Battery control module
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Dual Battery System Diagram CAN B
N10/1 - circuit 61
N73 - ignition key
inserted
N93 - diagnosis
G1 - systems battery
sensing
N10/2 - trunk switch
G1/7 - auxiliary battery
sensing
A1 - warning messages
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Dual Battery Service Tips
Normalization:
If the systems battery is disconnected or dead, the following systems should be
checked for normal operation. If systems are inoperative or erratic then normalization
will have to be performed.
Potential systems requiring normalizing are:
• ESP • Left front seat
• AAC - automatic air conditioning • Right front seat
• Windows and sunroof • Steering wheel and mirrors
Adding additional electric accessories:
When adding accessories always use a power supply that is fused through the
pre-fuse boxes. This will ensure that the BCM can monitor the current
consumption accurately.
DO NOT CONNECT ACCESSORIES DIRECTLY TO BATTERY TERMINALS
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Appendix
WIS doc.# Topic
AH54.10-P-0002-01A Notes on AGM battery construction, and properties
AR54.10-P-1129-01A Battery test using Midtronics MCR717
OF58.40-P-3000-04A Order form for Midtronics MCR717
GF54.10-P-4201T Auxiliary battery relay, location, and function
GF54.10-P-1001T Two-battery vehicle power supply, function
GF54.21-P-4121-02T Vehicle power supply control module, task
ETM doc #
PE54.15-P-2502DA Pre-fuse F32 wiring diagram
PE54.15-P-2503DA Pre-fuse F33 wiring diagram
PE54.15-P-2501DA Pre-fuse F34 wiring diagram
Internet Sites
www.midtronics.com Total battery management (AGM) charging, testing
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