Mercedes-Benz W211 User manual

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W211 Dual Battery System
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
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
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)
Systems Battery (G1)
Location: (G1) installed in trunk

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W211 Systems Battery (G1)
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)
Location of Auxiliary Battery (G1/7)
Auxiliary battery installed below air intake of HVAC

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Location of Auxiliary Battery (G1/7)
Location of Auxiliary Battery (G1/7)
Shown with HVAC air intake / filter removed

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• Auxiliary Battery: 12V, 12Ah, 170 A (DIN)
• Absorbent Glass Mat (AGM) design
• Function - Provides supplemental power if systems battery (G1) voltage is low
Auxiliary Battery (G1/7)
Auxiliary Battery (G1/7)

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AGM / VRLA Battery Properties
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