Caution: If the wiring connections are not strictly followed, there is a risk of burns from battery acid escaping. In addition, there is a risk of injury or damage due to battery explosion and damage to the vehicle's electrical system.
The cross-section of the jumper cable for petrol engines with a displacement of up to approximately 2.5 litres must be at least 18 mm² (diameter approximately 5 mm). For diesel engines and petrol engines with a displacement of over approximately 2.5 litres, the cross-section of the cable must be at least 25 mm². The working volumes are specified for a vehicle engine with a discharged battery. The cross-section of the cable is usually specified on the packaging of the jumper cable. When purchasing a new cable, it is recommended to purchase a jumper cable with insulated clamps and a cross-section of 25 mm², as it is also suitable for engines with a smaller displacement.
Both batteries must be rated for 12V.
A discharged battery can freeze at temperatures as low as -10°C. Before connecting the jumper cable, the frozen battery must be thawed.
The discharged battery must be properly connected to the vehicle's electrical system.
Check the electrolyte level in the discharged battery and top up with distilled water if necessary.
The cars should be placed at a distance that excludes contact with their metal parts. Otherwise, current may flow when the positive pole is connected.
Put both cars on the handbrake. Set the gear selector to neutral, if there is an automatic transmission, set the mode selector lever to position P.
Turn off all power consumers.
During the start-up process, the engine of the vehicle supplying the current must be idling. This helps to avoid possible damage to the generator due to voltage peaks.
During the starting process, do not bring an open flame or a lit cigarette close to the battery, as flammable gases are released from the battery.
Make sure that auxiliary wires are not damaged by rotating parts, such as a fan.
Connect the auxiliary starting wires in the following sequence:
1. Connect the red wire to the positive terminal (+) in the engine compartment of the vehicle with the discharged battery. Remove the protective cap first. If the vehicle receiving the current is not a BMW 5 Series, connect the auxiliary wire to the positive terminal of the battery.
2. Connect the other end of the red wire to the positive connector (+) or, respectively, to the pole of the battery of the vehicle that supplies current.
3. Connect the black wire to the ground connector on the shock absorber strut housing of the vehicle supplying the current. If the vehicle supplying the current is not a BMW 5-Series, connect the black wire to the negative (-) terminal of the battery.
4. Connect the other end of the black wire to the ground connector on the right shock absorber casing of the vehicle receiving the current. If the vehicle receiving the current is not a BMW 5 Series, connect the wire to a reliable ground. A metal part firmly bolted to the engine is best suited for this. Under unfavorable circumstances, when connecting the wire to the negative terminal of a discharged battery, it could explode due to sparking and the formation of detonating gas in it.
Caution: The terminals of the connected auxiliary jumper cable must not contact each other, and the positive terminals must not contact the body parts (body or frame).
Auxiliary wire connection points in a vehicle with a battery in the engine compartment:
1 - positive pole (+) of the current-receiving battery "A";
2 - positive pole (+) of the current-giving battery "B";
3 - negative pole (-) of the current-giving battery "B";
4 - connection point for ground "X" of the vehicle receiving the current.
Current receiving vehicle engine (with a discharged battery) start and let it idle. When starting, do not keep the starter running continuously for more than 10 seconds, as the high starting current will cause the positive terminals and wire to heat up. The pause between two consecutive starting attempts should be at least ½ minute.
Do not lean over the battery - there is a risk of burns from electrolyte acid!
Caution: On BMW vehicles, turn on the ignition, rear window heating and the highest fan speed before disconnecting the auxiliary wires. This will avoid dangerous voltage peaks from the voltage regulator to the consumers.
After starting, disconnect the wires in the reverse order: first disconnect the black wire (-) from the car receiving the current, and then from the car giving the current. First disconnect the red wire from the car giving the current, and then from the receiving one.