Hello!
I'd be happy to help explain how e-Tec (mild hybrid) systems work in cars.
In e-Tec mild hybrid systems, the 12V battery is responsible for powering various auxiliary components in the vehicle, such as lights, infotainment system, and other electronics. The main engine starting is indeed done using the 48V battery system, which is typically connected to an electric motor or integrated starter generator (ISG).
If your car's 12V battery is dead or very weak, it can potentially cause some issues with starting the vehicle or powering the electronics. In such cases, the 48V battery system might not be enough to start the engine, as it is primarily designed to assist the engine during acceleration and provide some additional power for efficiency improvements.
As for generating the 12V power in the car, it can be done in a few ways. Some e-Tec systems use a DC-DC converter, similar to Toyota's hybrid technology, which steps down the voltage from the 48V battery to 12V to charge the smaller battery. Others may still use a traditional alternator connected to the internal combustion engine to charge the 12V battery.
In any case, it's essential to ensure the 12V battery is in good condition to avoid any potential starting or electrical issues. Regular maintenance and checking the battery's health can help prevent such problems.
I hope this clarifies how e-Tec (mild hybrid) systems work and how the 12V battery is involved in the process. If you have any more questions or need further information, feel free to ask!