Next-Level HEV: Methods to Enhance Hybrid Vehicle Performance

The automotive industry is entering a pivotal phase of transformation. Hybrid electric vehicles (HEVs), once considered a transitional step toward full electrification, have evolved into high-performance stand-alone platforms with distinct market relevance worldwide. Between 2024 and 2032, the HEV category is projected to grow at a CAGR of 20.70%.

Originally designed in response to consumer preference and tightening emissions rules, HEVs find themselves in their own product niche, where automakers are rethinking hybrid electric vehicle architecture from the ground up.

Success in this new era depends on what lies beneath the hood. Powertrain performance is no longer just a concern about engine output; it is an examination of how well the entire system—electric and combustion—is integrated through high-voltage interconnects, distributed power networks and scalable, modular components.

Hybrid electric vehicle architecture integrates an internal combustion engine (ICE) with an electric powertrain to enhance fuel efficiency and reduce emissions. This combination relies on advanced power electronics, control modules and high-voltage energy systems to manage energy flow between mechanical and electric sources.

Early hybrid systems operated primarily on 12V electrical architectures, which supported basic vehicle electronics—lighting, infotainment, power windows and engine control modules. While sufficient for conventional vehicles, the 12V platform lacks the power density to implement meaningful electrification in propulsion and auxiliary systems.

As demand for greater efficiency and functionality increased, HEVs began incorporating high-voltage architectures—ranging from 48V mild hybrids to 400V and higher in full hybrids and EVs. These higher-voltage platforms unlock advanced capabilities, including regenerative braking, electric turbocharging and electric-powered accessories, all while reducing wiring complexity and copper use through thinner-gauge conductors.

Since gaining widespread adoption among some European OEMs in 2018, 48V mild hybrid systems have transitioned from a stepping stone toward full electrification to becoming a long-term solution. These systems deliver an estimated 15–20% fuel savings compared to 12V counterparts, offering a cost-efficient path to electrification without the range limitations of full battery electric vehicles (BEV).

Higher voltage platforms can support mild hybridization across multiple vehicle segments—from compact cars to SUVs and light commercial vehicles—while enabling energy-saving features like stop-start operation and electric boost. 

However, moving up to the next level in voltage is not a drop-in upgrade, nor does it address the specific design challenges across varied models and market segments. HEV engineering requires a full rethinking of the electrical architecture, negotiating the many trade-offs throughout the system. Thinner wires help reduce vehicle weight but introduce thermal and current-handling challenges. The growing number of electronic control units (ECUs), inverters and electric motors adds complexity and increases electromagnetic interference (EMI) risks.

To overcome these challenges, engineers are deploying shielded cable assemblies, aluminum busbars and flexible interconnect systems—components engineered for heat control, EMI protection and reliability in demanding automotive environments.

While the full EV segment continues to chase breakthroughs in solid-state and lithium-sulfur chemistries, HEVs benefit from more incremental but practical advances. At the moment, Lithium-ion batteries remain the foundation of most HEV platforms, with NMC (nickel-manganese-cobalt) and LTO (lithium-titanate) chemistries leading the way. Ongoing research into battery chemistry may rapidly change the direction of energy storage in the years ahead.

NMC offers high energy density for short-duration electric drive modes. LTO is favored for its extreme cycle life, fast charge/discharge capabilities and enhanced thermal stability—especially important in stop-start urban conditions.

While the chemistry of batteries is moving forward, battery architecture is advancing even faster. Distributed battery management systems (BMS) segment control across cell groups, enabling smarter thermal balancing, fault isolation and predictive diagnostics.

One emerging approach employed by BMW and other hybrid makers involves using flexible printed circuit (FPC) technology in battery cell contacting systems, which replaces daisy-chained wiring with lighter, more compact and more consistent connections. This supports simplified assembly, reduced weight and improved signal routing in high-vibration environments.

Reducing vehicle weight is a common design strategy for maximizing fuel efficiency and extending the electric-only range. Aluminum, carbon fiber and advanced composites are replacing traditional steel in key structural and powertrain components.

The integration of these lightweight materials allows smaller, more efficient batteries to achieve the same range, while also improving safety, aerodynamics, acceleration and braking performance.

As system voltages evolve beyond 48V and into the 160V+ range—especially in plug-in hybrid electric vehicles (PHEVs)—safety becomes an even greater design priority. Industry standards play a crucial role in guiding these safety measures, though their implementation can vary across manufacturers and regions. Newer standards such as ISO 6469-3 call for rapid insulation monitoring, arc-fault protection and reinforced isolation barriers. Safety measures once reserved for full EVs are now finding their way into hybrid platforms.

As with all architectures, system components must operate in harsh conditions—temperature swings, road vibration, humidity, dust and chemical exposure—to ensure safety over the product lifespan. Connectors designed for hybrid platforms now often incorporate self-cleaning contacts, aerospace-grade seals and locking mechanisms to maintain long-term performance under the full range of automotive stressors. 

To meet ISO 26262 requirements, connector systems are increasingly built with diagnostic paths that enable fault detection and safe shutdowns in the event of a failure. Rather than measures added after completed designs, safety is now embedded within the electrical architecture from the outset.

Modern vehicle platforms are increasingly designed around modular electrical backbones, giving automakers the flexibility to deploy multiple electrification variants (mild hybrid, full hybrid, plug-in hybrid and BEV) on a single chassis. This scalability reduces development time, simplifies logistics and lowers per-unit cost by allowing OEMs to reuse core components across models and markets.

A modular architecture enables design teams to standardize interfaces for power, signal and data across these vehicle variants. Modularity also reduces complexity in both mechanical integration and software development, since common communication protocols and power paths can be reused rather than redesigned for each platform. It also supports leaner manufacturing, with fewer part numbers to track and faster changeover between builds.

From a systems engineering perspective, modularity accelerates platform evolution. As new powertrain technologies emerge—such as silicon carbide (SiC) inverters or solid-state batteries—they can be integrated into existing vehicle structures with minimal disruption. This adaptability helps automakers respond to shifting regulations and consumer preferences without overhauling their entire design.

Power electronics form the core of HEV energy management, with inverters and converters directing power between the battery, electric motor and internal combustion engine. Inverters convert DC energy from the battery into AC for the motor, while DC-DC converters adjust voltage levels to match the needs of various vehicle subsystems.

The ongoing shift toward wide bandgap semiconductors like silicon carbide (SiC) and gallium nitride (GaN) is enabling greater system efficiency. While more expensive than traditional silicon-based solutions, these materials reduce switching losses, support higher power densities and improve thermal performance—key benefits for compact, high-output hybrid electric vehicle architectures.

HEV systems can generate up to 5 kW of waste heat under peak load—particularly from inverters, converters and battery modules. HEVs employ a mix of active and passive cooling strategies, from liquid-cooled inverters to air-cooled low-power systems. Phase change materials and integrated thermal sensors help regulate temperatures under load.

Thermal management remains an engineering challenge with each new design. Without efficient thermal regulation, component lifespan suffers, leading to performance degradation or even thermal runaway in the case of Lithium-ion batteries. Reducing connector temperature can help automakers meet long-term durability and warranty targets.

In successful HEV architecture, high-speed data delivery is becoming as integral as power distribution. Advanced control algorithms optimize the interaction between combustion and electric systems, managing torque blending, regenerative braking and battery usage. IoT-driven connectivity is also transforming hybrid electric vehicle architectures, adding capabilities such as real-time monitoring, predictive maintenance and over-the-air (OTA) updates. 

As hybrid powertrains evolve, so must their digital infrastructure. Hybrid vehicle platforms require high-speed connectors and cable assemblies capable of supporting CAN and LIN bus communication, Gigabit Ethernet for advanced driver-assistance systems (ADAS) and V2X modules for connected mobility. 

The demands on electrical architecture for hybrids is complex and multi-faceted, requiring a range of advanced hardware specially engineered for automotive use. Molex delivers a broad portfolio of interconnect, power and signal solutions engineered to meet the EMI and integration challenges of refined automotive systems.

By combining proven product platforms with custom engineering support, Molex helps automakers scale performance, accelerate time to market and future-proof hybrid designs for the next wave in electrification.

Hybrid electric vehicles are no longer simply a stepping stone—they are proving grounds for the future of electrified transportation. From 48V starter systems to 400V-and-higher all-electric platforms, current hybrids provide the architectural foundation for the EVs of tomorrow.

Success in this domain depends on more than battery chemistry or motor power. It depends on system-level engineering that includes seamless power integration, real-time control, thermal resilience and scalable architecture.

With a legacy of automotive innovation and a portfolio of high-voltage, EMI-shielded and thermally optimized solutions, Molex is helping drive the hybrid revolution—one connection at a time.

Explore Molex HEV solutions and connect with our automotive engineering teams today.