Instructions for Disconnecting and Connecting Battery

12 00 ... - Instructions for disconnecting and connecting battery

Observe safety instructions for handling vehicle battery Service Precautions.
Before disconnecting battery:
Turn off the ignition and other electrical loads/consumers to prevent sparking when reconnecting.

Note:
If the ignition is not turned off when the battery is disconnected, fault memories may be set in some control units.

Important!
- There is a danger of mixing up battery leads: If the battery positive and negative leads are the same colour and you are in doubt, follow the polarity to the battery, then mark and cover the leads.
- On vehicles with radio code: After disconnecting the battery, the radio code must be re-entered. Therefore obtain the radio code card from the customer beforehand. Note stored stations and restore them after connecting the battery.
- Stored settings of the on-board computer and clock will also be lost.
- All available central keys must be recoded for cars with first generation infrared transmitter locking systems.

General notes on disconnecting battery:

- Do not disconnect battery leads and leads from alternator and starter motor while engine is running.
- Cars with IBS on battery negative terminal:
Do not under any circumstances pull/lever off pole shoes by force.
Do not under any circumstances release socket-head cap screw of IBS.
- Detach terminal of battery negative lead from car battery and second battery if fitted. Cover battery negative terminal(s) and secure.
- When work is carried out on the electrical system, faults may be caused in the fault memories of some control units when the battery is connected.
- When installing battery terminal: Tightening torque 61 21 1AZ [1][2]Battery.
After connecting battery:

Important!
The scope of application of some systems may be restricted after a power supply interruption.
Likewise, individual settings may be lost.
Settings or activations must be carried out, depending on the equipment specification.
Example:
- Vehicles with automatic engine start-stop system (MSA):
MSA function is active only after learning period (vehicle must not be woken for a period of approx. 6 hours) > if necessary, notify customer of the situation
- E46 (AWD)/ E53/ E83: Carry out steering angle sensor adjustment Adjustments
- If necessary, carry out adjustment of active front steering
- If necessary, activate sliding sunroof
- If necessary, activate power windows 67 62 ... Notes on Initializing Power Window Unit In Front Door
- If necessary, activate mirror with compass
Please refer to the Progman user documentation for further information on vehicle-specific activation.

Vehicles with a two-battery system
Starter and equipment batteries
A two-battery system has a starter battery circuit and an equipment battery circuit. A supplementary control unit monitors both battery circuits. Depending on the situation, the battery circuits are connected to or isolated from the supplementary control unit via an isolating relay.
Two AGM batteries, whose design and properties are described in AGM batteries Description and Operation, are used as a storage battery.

Important!
These batteries must not under any circumstances be charged with a voltage in excess of 14.8 V. Rapid programs must not be used either.

Receiving/giving starting assistance via jump start terminal

The engine can be jump-started with an external voltage supply via the jump start terminal on the right side of the engine compartment.

Note:
The starter battery is isolated from the alternators when the engine hood/bonnet is open.

Giving starting assistance via the jump start terminal is thus limited by the capacity of the starter battery when the engine hood/bonnet is open.

Charging starter and equipment batteries via jump start terminal
The starter battery is charged as a matter of priority with a charger connected to the jump start terminal. The voltage at the starter battery is the decisive factor in determining whether the equipment battery is also included in the charging operation. The supplementary control unit automatically detects a charging operation at a charging voltage at the starter battery of ≥ 13.5 V. The isolating relay is closed and thus the equipment battery is connected in parallel. Both batteries are now charged.
Prerequisite:
- Terminal 61 inactive
- Terminal 15 inactive
If terminal 15 becomes "active" during the charging operation, the isolating relay is opened immediately and again only the starter battery is charged.

Note:
When the engine hood is open, the isolating relay is also opened in normal operation when the engine is running.
A special mode can be set by means of diagnosis for workshop/garage operation. The isolating relay is closed from terminal R in this operating mode. This mode is automatically reset once a distance of 5 km has been driven.

Trickle charging

The increased closed-circuit current consumption can be compensated for via the jump-start connection point with the aid of the "Acctiva easy" battery trickle charger (Service Information 2 03 05 205).

Important!
The cigarette lighter is isolated from the electrical system after terminal R "OFF" on a timed basis (60 mins.), thereby interrupting charging of the equipment battery via the cigarette lighter. This is prevented if the battery master switch (on the right side of the luggage compartment behind the panel) is turned on and off again twice within 2 seconds. (Cigarette light battery charging function).