What Will It Take for 48 V to Replace 12 V in Automotive Power?

The 12-V automotive power system has dominated for decades. However, automakers are taking steps to harness the power of 48-V technology to keep up with all of the power-hungry subsystems under the hood. This new level of power may be key to increasing the energy efficiency in everything from electrical power steering and active suspensions to automated-driving systems. Any one of these can draw peak loads of several thousand watts.

Delivering power at higher voltages comes with many benefits, including higher power capacity and the ability to distribute it more efficiently over thinner, lighter, and lower-cost wiring. Car manufacturers are also pushing to rewire their automotive power architectures for 48 V to reduce the cost and weight of electric vehicles (EVs), which will rely on battery-derived power to drive all accessory functions. The delivery of higher current and voltage is bound to be a boon to regenerative braking, battery pre-conditioning for auxiliary charging, and other functions in EVs.

But it remains in the very early stages of the complex and costly transition to 48-V technology, said Molex, which recently released a status report on the emerging power standard. One of the issues is that everything from the power electronics to the connectors and cables must be overhauled to handle the higher voltages of 48 V. On top of that, engineers must also deal with the difficulties of integrating all of these parts into the existing 12-V power network in a way that maximizes not only performance, but also safety and reliability.

Kirk Ulery, distribution business development manager at Molex and one of the company’s experts on 48 V, talked with Electronic Design about the difficulties of 48 V and what it will take to address them with (watch the video above).

The Steady—Yet Long—Road to 48 V

Tesla is one of the only companies that has fully leveraged the power of 48 V, starting with the CyberTruck, which eliminates the traditional 12-V power network entirely in favor of its all-48-V configuration. While that’s presumably the end goal for other automakers, these companies will want to take more time to replace all 12-V systems in their cars, which have been rigorously tested for reliability and safety. Replacing them with 48-V parts and wiring them into the vehicle requires a vast amount of engineering and testing, and the costs can add up.

As a result, it could take more than a decade for 48 V to replace 12 V as the industry standard for power distribution. As the technological shift plays out, Ulery urged companies to come together to roll out standard designs and modular components that can handle the higher voltage requirements of 48 V. It’s vital to reducing the cost and manufacturing complexity that hampers any new technology in cars. In the short term, most companies will continue to use 12-V power systems in situations where it remains too expensive or complex to replace them.

To bridge the gap between 48 V and 12 V, many companies are zeroing in on zonal architectures that divide the vehicle into several distinct zones, each with a separate power supply. That gives them more flexibility to phase in 48-V components over time while saving 12-V systems where necessary. Local control of power management not only makes a difference in power efficiency, but it also reduces complexity that can risk system reliability. Still, engineers must ensure all of these changes are compatible with the legacy 12-V bus.

The presence of different voltage levels (high voltage for the EV powertrain, 48 V for advanced functions, and 12 V for other auxiliary systems) requires DC-DC converters to control the power flow between the different zones. The tradeoff is that these power electronics can add complexity to the car's internal wiring and become a potential failure point. In EVs, one of these DC-DC converters could also mimic a 48-V battery, converting the 400 V or 800 V from the main battery pack feeding the powertrain to 48 V used by accessory functions.

Overcoming Other Challenges with 48 V

Besides the issue of integrating 48-V power systems under the hood, engineers grapple with other challenges related to the higher voltage levels, which could also cause higher electromagnetic interference (EMI). Another issue is thermal management. For instance, engineers must employ more efficient cooling systems for 48-V components, including batteries and power electronics, to prevent overheating and extend their lifespans.

Ulery said the company is also upgrading its automotive-grade connectors for the 48-V future. The new power standard will likely require innovations in materials for heat-resistant plastics and special metal alloys that can enhance insulation, conductivity, and overall durability.

In addition, the contacts in the connectors are due for a redesign to reduce contact resistance and increase their current-handling capabilities. He said larger contact areas and tighter sealings on locking mechanisms and connector housings may also be required for higher reliability.

One product currently on the market is Molex’s MX150 mid-voltage connector system. It can handle up to 60 V, supporting the use of thinner, lighter wires to reduce weight and cost while delivering the high performance of 48 V.