What are the solutions when a car battery is dead and the engine won't start?

[OMatthew]

The solutions when a car battery is dead and the engine won't start are: 1. Jump-start the car; 2. Push-start the car; 3. Replace the battery and then start. Precautions for battery charging include: 1. Charge the battery directly without removing it to avoid data loss; 2. A battery voltage 10% below the rated voltage will cause the battery to drain; 3. Avoid water exposure during charging. The functions of the battery are: 1. When starting the engine, the battery supplies power to the starting system, ignition system, and electronic fuel injection system; 2. When the engine is off or idling at low speed, it powers the car's electrical devices; 3. It assists in powering electrical devices when the generator's output is insufficient; 4. It mitigates voltage surges in the electrical system, protecting the car's electronic devices; 5. It stores excess electricity generated by the alternator.