The case for vehicle 48 V power systems

Moving from 12 to 48 V systems will reduce vehicle weight through thinner, lighter cables. Tradeoffs include more stringent safety requirements.

As vehicles integrate advanced features such as advanced driver-assistance systems (ADAS), vehicle-to-everything (V2X) communications, and electric turbocharging, the limitations of traditional 12 V systems become increasingly evident. To meet these and other power-hungry applications, 48 V power systems are emerging because they promise to provide the scalability, efficiency, and reliability demanded by modern automotive architectures.

Upgrading from 12 V to 48 V improves capabilities by a factor of four, which allows for thinner wiring and lighter connectors while delivering noticeable cost reductions. While thinner wires are not precisely four times less expensive than their 12 V counterparts, the reduction in copper yields measurable savings and simplifies manufacturing. This shift also lowers thermal management challenges since the higher current in 12 V systems produces excess heat, complicating design and lowering performance.

Additionally, 48 V systems optimize regenerative braking, which improves energy recovery and boosts drivetrain efficiency. By solving longstanding power distribution bottlenecks, 48 V systems pave the way for scalable, future-focused platforms ready to meet the electrification era.

Comparing 12 V and 48 V systems

Here’s a compelling argument for what’s ahead in upgrading to 48 V systems (Figure 1). Delivering 1 kW of power requires approximately 83 A in a 12 V system, compared to around 21 A in a 48 V system. Transitioning 12 V to 48 V also allows for thinner, lighter wires, resulting in up to an 85% weight reduction for individual high-current power cables. These savings significantly reduce vehicle weight and improve overall system efficiency, especially in applications where heavy-gauge wiring dominates.

The lower current in 48 V systems also reduces heat generation, simplifying thermal management and improving system efficiency. In contrast, high current in 12 V systems generates more heat, requiring thicker cables and additional cooling solutions. While 12 V systems often rely on heat sinks and forced cooling to manage higher current paths, 48 V systems allow for smaller cooling solutions, such as localized thermal pads, due to reduced heat dissipation needs.

Mild hybrid electric vehicles (MHEVs) highlight the practical benefits of 48 V systems. Stop-start systems powered by 48 V can restart engines faster using alternators as motors, enhancing efficiency and performance. Electric turbochargers eliminate traditional turbo lag, delivering instantaneous acceleration while regenerative braking systems recover energy more effectively, improving vehicle performance.

With their capacity to support high-demand applications, 48 V architectures help engineers be more creative with their applications while future-proofing platforms and addressing critical power constraints.

Zonal Architectures and 48 V systems

The decentralized approach of zonal architectures paired with 48 V systems simplifies wiring complexity and improves vehicle design flexibility (Figure 2). By distributing control to localized zone controllers, zonal configurations significantly cut wiring lengths compared to traditional centralized platforms.

In centralized architectures, parking sensors in the rear bumper might require 3 m of wiring to reach a central controller. With zonal controllers, those same sensors connect to a nearby controller using only 0.5 m of wire, thus reducing vehicle weight. Shorter wires also use less space, which simplifies assembly. Localized power delivery reduces electromagnetic interference (EMI) through shorter wiring runs.

48 V systems complement zonal designs using smaller, lighter cables that deliver sufficient power to localized controllers. While zonal architectures introduce challenges, such as advanced controllers and more complex fault isolation, the benefits of reduced wiring complexity and vehicle weight outweigh these tradeoffs. Table 1 summarizes engineers’ tradeoffs when designing zonal versus centralized architectures, emphasizing wiring complexity, modularity, and EMI management.

Tradeoff comparison: zonal vs. centralized architectures

Aspect	Zonal Architecture	Centralized Architecture
Wiring complexity	Simplified: shorter wiring lengths (e.g., 3 meters to 0.5 meters per connection).	More complex: longer wiring harnesses increase bulk and routing challenges.
Weight	Reduced: lightweight due to shorter, thinner cables.	Heavier: extensive wiring adds weight, impacting fuel efficiency.
Modularity	High: easy to add or upgrade zones for future features.	Low: scaling requires significant redesigns or re-engineering efforts.
Fault    isolation	Complex: it requires advanced controllers and diagnostic tools to localize faults. If poorly managed, faults may propagate across zones.	Easier: fewer zones simplify isolation and troubleshooting.
Cost	Mixed: higher upfront costs for advanced controllers and software, offset by long-term savings from reduced wiring complexity.	Mixed: lower controller costs, but expensive wiring and assembly.
EMI management	Improved: shorter cables inherently reduce EMI risks.	Challenging: long cables are prone to more interference, requiring additional shielding.

Safety, EMI, and testing in 48 V Systems

Transitioning to 48 V systems introduces engineering challenges, particularly in safety, EMI, and testing. Arcing becomes a significant risk at higher voltages, requiring strict creepage and clearance standards adherence. These standards prevent current from “creeping” across insulating surfaces or jumping between conductive elements. In contrast, 12 V systems have lower arcing risks but still face challenges in managing high-current applications where improper spacing or insulation can lead to overheating or system failure.

High-performance connectors incorporate enhanced spacing and advanced materials that resist leakage to address arcing risks, helping provide reliability under demanding automotive conditions. For example, compact connector designs in EV battery modules use polyphenylene sulfide (PPS) to maintain creepage and clearance while resisting arcing in high-vibration environments. By comparison, 12 V systems require less stringent insulation and spacing standards due to their lower voltage, simplifying manufacturing but limiting their ability to handle higher power demands.

Isolation and safety are critical in step-down converters interfacing 12 V and 48 V systems. Proper isolation is underscored by the use of safety-rated capacitors, which provide voltage isolation and play a vital role in EMI filtering. For instance, specific 48-V-to-12-V step-down converters incorporate isolation-barrier capacitors to maintain safety and mitigate EMI.

Higher voltages also call for better shielding to protect sensitive components, especially for ADAS and V2X systems prone to interference. In 12 V systems, EMI issues are primarily limited to high-current paths, while 48 V systems require more comprehensive shielding strategies due to increased susceptibility across higher-frequency communication lines. The shorter wiring lengths in zonal designs inherently reduce EMI risks but require careful grounding to avoid signal degradation.

Engineers testing 48 V systems often rely on isolation testers, thermal imaging for detecting hotspots, and mixed-voltage diagnostic tools to quantify system reliability. A common challenge involves validating step-down converters that interface 12 V and 48 V systems, where improper isolation can cause unexpected faults or EMI propagation.

Dynamic simulation software — Ansys, LTspice, Remcom, EMWorks, and others — models EMI behavior in 48 V systems, helping engineers refine shielding designs. These tools address high-power components’ interference challenges, ensuring critical electronic systems’ reliability. These simulation tools often model how mixed-voltage systems behave under different load conditions, helping identify potential design issues early.

Reliability and standardization in 48 V designs

Safety and dependability in 48 V systems rely on adherence to design standards and advanced materials such as Polyphenylene sulfide (PPS) and liquid crystal polymers (LCP), which offer excellent insulation and thermal stability. Creepage and clearance standards (including IEC 60664-1 and USCAR-12) maintain insulation integrity, while advanced materials minimize arcing risks in compact, high-voltage environments.

Standardization across OEMs and suppliers simplifies system integration. Voltage-specific rules for pin sizes, housing designs, and material specifications ensure compatibility. High-performance connectors with keyed designs, distinct housings, and precise color coding (e.g., light blue for mid-voltage systems) prevent assembly errors and improve system reliability across OEMs. These safeguards support reliable operation even in high-vibration environments.

Reliability also depends on robust design. Mechanical keying, arc-resistant materials, and rigorous testing protocols help deliver consistent performance in demanding conditions such as high-current or hot-plugging scenarios. These considerations help engineers design durable 48 V systems that maintain safety and efficiency throughout a vehicle’s life cycle.

Driving the future

The transition to 48 V systems represents a significant shift in automotive design. It provides a scalable framework to address growing power needs and lay the groundwork for future innovations. Engineers moving toward modular designs can seamlessly integrate technologies like autonomous systems and advanced V2X communication, preparing vehicles for the next generation of mobility.

As 48 V adoption accelerates, advances in charging infrastructure, zonal designs, and modular power systems will define the next wave of feature-rich vehicles. Engineers who embrace these architectures today will lead the way in electrification, autonomy, and connectivity, ensuring their designs meet the demands of tomorrow’s automotive landscape.