Warning! If the prescribed connection recommendations are not strictly followed, there is a risk of burns due to spilled electrolyte, which is based on sulfuric acid. In addition, injuries or bruises may occur due to battery explosion, or malfunctions in electrical equipment may occur.
The cross-section of the wire for connecting the starter to the auxiliary battery must be at least 16 sq. mm (diameter about 5 mm) for internal combustion engines with forced spark ignition of the working mixture up to a cylinder volume of 2.5 liters. For engines with a cylinder volume of over 2.5 liters and for diesel engines, the cross-section of this cable must be at least 25 sq. mm. In this case, the determining factor is, of course, a vehicle with a discharged battery. As a rule, the cross-section of the cable is indicated on its packaging. It is recommended to purchase this cable with insulated clamping collets and a cross-section of 25 sq. mm, since it is also suitable for engines with a comparatively lower cylinder displacement.
Both batteries must have a voltage of 12 volts.
A discharged battery can freeze at temperatures as low as -10°C. Before connecting the starter cable to the auxiliary (outside the car) if the battery is frozen, be sure to defrost it.
The discharged battery must be properly connected to the vehicle's electrical system.
Check the fluid level in the discharged battery. If necessary, add distilled water.
Place the cars at such a distance from each other that there is no metal contact between them. Otherwise, current may flow already when the positive pole is connected.
On each of the two vehicles, tighten the handbrake lever. Set the manual transmission to neutral, or the automatic transmission to the park position "P".
Turn off all power consumers.
The auxiliary vehicle engine must be running at idle speed during the starting process of the main vehicle. This eliminates the possibility of damage to the generator due to voltage peaks that occur during starting.
When starting, avoid open flames and burning cigarettes near the battery, as it may emit flammable gases.
Be careful that the starter cables connecting the booster battery cannot be damaged by rotating parts such as the engine cooling fan.
Connect the starter wires to the auxiliary battery as follows:
1. Connect the red wire to the positive terminal of the discharged battery (A).
2. Connect the other end of the red wire to the positive terminal of the battery that supplies current (B).
3. Connect the black wire to the negative terminal of the battery that supplies current.
4. Connect the other end of the black wire to a good point on the chassis (X) of the receiving vehicle. A metal part screwed to the engine block is best suited for this. In unfavorable circumstances: when connecting the wire to the negative pole of a discharged battery, the latter may explode due to sparking and the release of detonating gas.
Caution! The terminals of the wires for connecting the starter to the auxiliary battery must not contact each other when the wires are connected, or the positive terminals must not touch the body (body or frame).
Start and let the engine of the receiving vehicle run (the battery is discharged). When starting, do not press the starter continuously for more than 10 seconds, since the high current consumption heats up the clamping collets of the poles and the wires. Therefore, sometimes maintain a "cooling pause" of at least 1/2 minute.
Original source of information: mercedesman.ru
Do not lean over batteries - there is a risk of injury!
After starting the engine, disconnect the clamps from the terminals in the reverse order: first disconnect the black wire (-) from the terminal on the receiving vehicle, then on the current-supplying vehicle; first disconnect the red wire from the terminal on the current-supplying vehicle, then on the receiving vehicle.