Make use of the high-voltage batteries of electric vehicles to provide 12V voltage more efficiently.

That's right, automotive lead-acid 12V batteries are coming off the market. Europe has decreed that after 2030, all new cars will no longer use lead-acid batteries, which poses a great challenge for Oems to find alternative solutions. While this may seem like a daunting task, it can also present a huge opportunity to not only eliminate environmentally harmful batteries, but also reduce vehicle weight and improve overall efficiency.

The 12V battery and Power Supply Network (PDN) is the global standard and supports hundreds of loads, including some that are closely related to security, so the solution must be both innovative and robust. High-density, high-power, efficient power modules for connecting high voltage, 48V, and 12V PDNS provide a flexible and scalable solution to this emerging challenge.

When considering potential solutions, Oems must consider several important factors: increasing power to support new features with better performance, increasing efficiency to extend driving range and optimize thermal management, reducing carbon dioxide, optimizing cable routing, reducing harness weight, and meeting EMI requirements. These are some of the variables in this complex equation.

There are two main options for solving this equation. Replacing a 12V lead-acid battery with a 12V lithium-ion battery is an option. While it does provide a slight weight reduction, it will also preserve the decades-old tradition of 12V PDN and provide no other benefits. Another option is to support 12V PDN powered by 400V or 800V main batteries in electric vehicles and hybrid/plug-in hybrid vehicles. The latter option has many advantages, but both are worth further exploration.

12V lithium-ion battery is used

Simply replacing a 12V lead-acid battery with a 12V lithium-ion battery does save about 55% in weight, but the cost impact is high. A 12V lithium-ion battery requires a battery management system (BMS) to control charging and keep the battery fully functional throughout the life of the car. That's where Tesla and Hyundai are headed.

In addition, a large DC-DC converter from high voltage to 12V (with voltage and current regulation features) is needed to charge the 12V lithium-ion battery and power the electrical load. But that doesn't add any advantage. It only increases the weight, the complexity of the overall arrangement of the vehicle and the cost of the system, but also reduces the overall reliability of the vehicle. By contrast, eliminating the 12V battery not only reduces the weight of the car by 13kg, but also increases the cargo space by 2.4%.

The traditional 12V PDN is inefficient

Maintaining a 12V physical battery means maintaining an inefficient PDN with unnecessary redundancy. In a typical automotive 12V PDN, all 12V loads connected to a 12V bus have an internal front regulator that converts a wide input voltage range (typically from 6V to 16V) to 5V, 3.3V or lower. From a global system perspective, whether it is an electric vehicle, a hybrid vehicle, or a plug-in hybrid vehicle, there is series regulator redundancy. A high voltage to 12V DC-DC converter provides voltage regulation for the 12V bus (high efficiency), while the front regulator provides the appropriate internal voltage for each load.

This legacy architecture has its roots in the days when cars were equipped with alternators, a sensitive 12V PDN that required voltage regulation to charge the battery, keep the radio working during a startup event, or keep the car's incandescent headlights at the right brightness. Oems have been very creative in getting around the 12V power limit, designing two 12V batteries in recent years, a 24V battery for power steering and several DC-DC converters in between.