Battery Cables - Both

Replace both positive and negative battery cables on the 2007-2013 Mercedes-Benz S65 AMG, ensuring proper electrical connections for the high-current V12 BiTurbo system.

Warnings

Tools required

Parts

• Positive battery cable assembly × 1 — Use OEM specification
• Negative battery cable assembly × 1 — Use OEM specification
• Battery terminal bolts (if corroded) × 2 — M6 battery terminal bolts

Preparation

1. Park vehicle on level surface and ensure engine is completely cool
2. Turn ignition off and remove key from vehicle
3. Open hood and locate battery in right side of engine compartment
4. If using battery memory saver, connect per manufacturer instructions before disconnecting battery
5. Take photos of cable routing and connections for reference during installation
6. Document any electrical accessories or modules connected to battery cables

Procedure

1. 1

   Disconnect negative battery cable
   Using a 10mm socket, loosen the negative (black) battery terminal bolt. Do not fully remove the bolt yet, just loosen it. Use a battery terminal puller if cable is stuck to terminal post. Once loose, carefully lift cable away from battery and secure it away from terminal to prevent accidental contact.
   Torque spec

   Battery Terminal Bolts6 Nm (4 lb-ft)
2. 2

   Disconnect positive battery cable
   Using a 10mm socket, loosen the positive (red) battery terminal bolt. Remove cable from battery post and cover the terminal end with a non-conductive cloth or plastic bag to prevent accidental grounding during service.
   Torque spec

   Battery Terminal Bolts6 Nm (4 lb-ft)
3. 3

   Remove battery hold-down and battery (if needed)
   Remove the battery hold-down bolt using a 13mm socket. Carefully lift battery out of tray to access cable routing underneath and behind battery. Note that battery weighs approximately 60 lbs.
   ⚠Battery is heavy. Use proper lifting technique to avoid injury.
   Torque spec

   Battery Hold-Down Bolt15 Nm (11 lb-ft)
4. 4

   Trace and disconnect positive cable at starter and fuse box
   Follow the positive cable from battery terminal. It connects to the main fuse box (SAM module) and starter motor. Using a 13mm socket, remove the positive cable connection at the starter motor B+ terminal. Remove any retaining clips securing cable to fuse box. Note exact routing path.
   Torque spec

   Module Mounting Bolts8 Nm (6 lb-ft)
5. 5

   Remove positive cable completely
   Trace entire positive cable route and remove any additional mounting clips or ties. The cable may pass through grommets in the firewall area. Carefully extract the complete cable assembly from vehicle, noting routing for new cable installation.
6. 6

   Disconnect negative cable at ground points
   Locate all negative cable ground points. Primary ground is on engine block, secondary grounds are on chassis rail and body. Using a 16mm socket, remove ground cable bolts from engine block. Using appropriate socket (typically 10mm or 13mm), remove ground strap bolts from chassis and body ground points. Document each connection location.
   Torque spec

   Ground Cable Bolt18 Nm (14 lb-ft)

   Ground Strap Bolts12 Nm (9 lb-ft)
7. 7

   Remove negative cable completely
   Remove any cable ties or mounting clips securing the negative cable. Trace the complete cable path and extract from vehicle. The S65 AMG typically has multiple ground straps - ensure all are removed.
8. 8

   Clean all connection points
   Using a wire brush, thoroughly clean battery terminals, starter B+ terminal, all ground connection points on engine block and chassis. Remove all corrosion, oxidation, and debris. Spray with electrical contact cleaner and allow to dry. Ground surfaces must be bare metal for proper electrical contact.
   ℹ️Ground connection quality is critical for V12 engine operation and can cause misfires or starting issues if poor.
9. 9

   Install new positive cable
   Route new positive cable following exact path of original cable. Ensure cable does not contact sharp edges, hot exhaust components, or moving parts. Connect to starter motor B+ terminal first, then route to fuse box. Secure all mounting clips and grommets. Do not connect to battery yet.
   Torque spec

   Module Mounting Bolts8 Nm (6 lb-ft)
10. 10

    Install new negative cable and ground straps
    Route new negative cable to all ground points. Install ground cable to engine block first, ensuring mating surface is completely clean. Install all ground straps to chassis and body points. Ensure each connection has metal-to-metal contact with no paint or corrosion between surfaces. Torque all ground connections in sequence.
    ⚠️Improperly torqued ground connections can cause electrical system damage and fire risk.
    Torque spec

    Ground Cable Bolt18 Nm (14 lb-ft)

    Ground Strap Bolts12 Nm (9 lb-ft)
11. 11

    Reinstall battery
    If battery was removed, reinstall it into battery tray ensuring it is properly seated. Install battery hold-down and torque bolt to specification. Ensure battery cannot move or vibrate.
    Torque spec

    Battery Hold-Down Bolt15 Nm (11 lb-ft)
12. 12

    Connect positive cable to battery
    Clean positive battery terminal post with wire brush. Connect positive (red) cable to positive terminal. Apply small amount of dielectric grease if desired. Install terminal bolt and torque to specification. Ensure connection is tight and cable cannot rotate on post.
    Torque spec

    Battery Terminal Bolts6 Nm (4 lb-ft)
13. 13

    Connect negative cable to battery
    Clean negative battery terminal post with wire brush. Connect negative (black) cable to negative terminal last. Install terminal bolt and torque to specification. Expect a small spark when making final connection - this is normal.
    ℹ️Small spark when connecting negative terminal is normal due to capacitors charging in vehicle modules.
    Torque spec

    Battery Terminal Bolts6 Nm (4 lb-ft)

Reassembly

1. Verify all cable routing matches original configuration with no interference with moving parts
2. Ensure all protective covers and grommets are properly installed
3. Double-check all ground connections are tight and have proper metal-to-metal contact
4. Verify battery hold-down is secure and battery cannot move

Verification

• Turn ignition to position II and verify all dashboard warning lights illuminate normally
• Start engine and verify it cranks normally with no hesitation
• Check that all electrical accessories function properly (windows, lights, HVAC, etc.)
• Verify no warning lights remain illuminated after engine start
• Check battery voltage with engine running - should be 13.8-14.5V indicating proper charging
• Test drive vehicle and verify transmission shifts properly after adaptive relearn
• If available, use Star Diagnostic tool to clear any stored fault codes and verify all systems communicate
• Verify steering functions normally - perform steering angle sensor calibration if warning light appears

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