In most cases, to start the engine of a car with a discharged battery, a 12-volt battery from another car is used as an external power source.
Warning! Do not connect to vehicles with a 24 V nominal voltage in the on-board network (usually these are trucks).
Starting the engine from external power sources is performed only if it was not possible to start the engine due to a discharged battery, and there is no possibility or time to charge it. If the battery is dead as a result of repeated attempts to start the engine, then there is no point in making new attempts using an external power source. In this case, it is necessary to find out and eliminate the cause of the engine malfunction, and charge the battery.
To connect a discharged battery to a power source, a set of two wires with a sufficiently large cross-section is required (not less than 16 mm²).
To avoid polarity confusion when connecting, the sheath or handles of the clamps of one of the wires are usually black, and the second is red. It is possible that the insulation of the wires differs only in a strip of a different color. Always connect the red wire to the positive terminals of the battery and an external power source.
Warning. At ambient temperatures below -10°C, the electrolyte of a discharged battery freezes. When "lighting" a battery with frozen electrolyte, an explosion may occur. To avoid this, you must first warm up the discharged battery in a warm room. Avoid mutual contact between the wire clamps and ensure that the wire clamps are red (positive contact) did not come into contact with metal parts of vehicles. This may cause a short circuit and damage the battery.
We carry out the work in the following order:
1. We prepare the car for maintenance and repair.
2. Turn off the ignition and all unused electrical equipment of both vehicles.
3. Open the protective cover of the positive terminal of the battery.
4. Connect one clamp of the red wire to the positive terminal of the external current source...
...and the second clamp to the positive terminal of the discharged battery.
5. Connect one clamp of the black wire to the negative terminal of the external current source...
...and the second clamp is to the vehicle's ground (for example, to the cylinder block or to the engine eye).
Warning. Prevent wires from coming into contact with fans, drive belts and other moving parts.
6. Start the engine of a car with a working battery. After it has been running for 2-3 minutes at idle, we start the engine of the car with a discharged battery.
7. After making sure that the engine is running smoothly, disconnect the wires in reverse order, starting with the black one, connected to the ground of the car with the discharged battery. Lastly, we disconnect the red wire clamp from the positive terminal of the external current source.
Recommendation. It is necessary to take into account that during a short trip the battery will not have time to charge. After arriving at the parking place, you should check the battery charge and charge it if necessary.
(The article was reprinted from the website «CHEVYMAN.RU»)