Electric vehicles (EVs) are often defined by their most visible systems, such as the batteries, electric motors, and charging technology. However, electrification affects more than these primary subsystems.
Figure 1. Advanced supporting hardware is essential in modern EVs. Components such as busbars, fuses, contactors, and sensors are essential for reliable power distribution, protection, and system monitoring as vehicles transition to higher-voltage architectures.
A range of supporting hardware responsible for current distribution, protection, switching, and measurement is also essential in determining overall performance, efficiency, and safety.
This article reviews four categories of hardware:
1. Busbars
2. Fuses
3. Contactors
4. Sensors
Each device introduces unique material, thermal, and design challenges, particularly as the industry shifts from 400 to 800-V battery architectures and prepares for even higher-voltage systems. (Figure 1)
Busbars: the backbone of current distribution
Busbars are the primary conductors for high-voltage power distribution in EVs, linking the battery pack with power conversion and control systems. Their design directly affects efficiency, thermal stability, electromagnetic compatibility, and overall safety.
Laminated busbars, constructed from stacked copper or aluminum conductors separated by insulation layers, offer compact, low-inductance pathways for transferring current between the battery, inverter, onboard charger (OBC), and dc-to-dc converter. (Figure 2)
This configuration minimizes parasitic inductance and electromagnetic interference (EMI) during high-frequency switching. Although solid busbars remain common for straightforward high-current links, laminated designs are preferred in inverters and compact battery systems because they spread heat more effectively and deliver predictable electrical performance.
Figure 2. A laminated busbar assembly. Layered copper conductors separated by insulation provide low-inductance current paths. Modern busbars integrate protection and sensing elements to support EV architectures operating at higher voltage. (Image: Rogers Corporation)
Traditionally, high-voltage connections in vehicles were typically made with cable harnesses, which are bundles of insulated wires routed through the chassis. However, harnesses are bulky and challenging to package, generating higher inductance, which limits efficiency in modern, fast-switching power electronics.
Busbars solve these challenges by reducing system volume, improving thermal dissipation, and enabling cleaner electrical behavior, particularly in compact 800-V architectures where space and efficiency margins are tight.
The switch from 400 to 800-V platforms also raises new design requirements. Higher voltages support faster charging and lighter cabling, but they increase the risk of partial discharge and dielectric breakdown. Engineers must specify advanced insulation coatings, maintain precise creepage and clearance distances, and adhere to tight mechanical tolerances to ensure safety under these conditions.
Additionally, material selection is important. Copper maximizes conductivity and thermal performance, while aluminum reduces mass but requires coatings and joining strategies to prevent galvanic corrosion. Aside from conductivity, engineers must account for vibration, thermal cycling, and long-term durability under the stresses of automotive applications.
Modern busbars are also becoming multi-functional. Embedded shunt elements provide precise current measurement for the battery management system (BMS), while integrated high-voltage interlock loop (HVIL) circuits enable real-time safety monitoring. Digitalization is taking this further.
Smart busbars with distributed sensors can generate continuous data on current density, temperature, and insulation health. When combined with advanced analytics or AI-driven diagnostics, this data enables predictive maintenance, early fault detection, and dynamic load optimization, transforming busbars from passive conductors into intelligent nodes within the EV’s electrical architecture.
Fuses: precise protection at high voltage
Every high-voltage EV system depends on fuses as a critical safety barrier, ensuring that short circuits or overloads don’t propagate into catastrophic failures. EV fuses interrupt fault currents in milliseconds to protect battery cells, busbars, and power electronics. Unlike conventional automotive fuses, EV-specific designs must withstand rapid current surges without nuisance trips, maintain stable operation across wide temperature ranges, and operate consistently under repeated thermal and mechanical stress.
The push to 800-V battery architectures magnifies these requirements (Figure 3). Fault currents in higher-voltage packs can reach tens of kiloamps, requiring advanced arc-supressing materials, precision-engineered fuse elements, and reliable housing designs to safely contain fault energy. Thermal derating becomes a critical factor as higher current densities generate localized hotspots within compact module packaging.
Figure 3. High-voltage automotive fuses. Arc-suppressing materials and precision-engineered elements enable rapid fault interruption in EV systems operating at 800 V and higher. (Image: Littelfuse)
Engineers typically rely on multiphysics simulation tools to evaluate fuse behavior under transient loads, ensuring coordination with other protective devices, such as contactors and circuit breakers.
Fuse design is also being reshaped by digitalization. Model-based methods allow engineers to simulate fuse performance under various drive cycles, ambient conditions, and charging scenarios, while real-time pack data can be integrated with thermal models to predict stress on individual fuses.
Additionally, smart fuse concepts are incorporating sensing elements that directly monitor current, voltage, and temperature at the fuse body. When paired with digital twins or AI-based diagnostic platforms, these devices enable predictive maintenance by flagging degradation before failure occurs. Such systems can also dynamically adapt thresholds, optimizing protection strategies as battery and inverter technologies evolve.
For EV engineers, fuse design is no longer a matter of selecting a catalog part. It requires balancing protection speed, endurance under cycling, arc suppression, and digital integration, all within the constraints of higher-voltage, higher-power architectures.
Contactors: switching high currents safely
High-voltage contactors are critical switching devices in EVs, responsible for connecting and disconnecting the battery pack during startup, shutdown, and fault conditions. Their role is to ensure that energy flows only when commanded and that circuits can be isolated instantly in the event of an abnormal condition.
In most current EVs, electromechanical contactors dominate. These rely on physical contacts that open and close under coil actuation, with arc suppression methods to extinguish the plasma that forms when high current is interrupted. Durable contact materials and precise spring mechanisms allow them to switch hundreds of amps repeatedly.
Figure 4. This contactor offer flexibility. It’s designed for hybrid and electric commercial vehicles, providing reliable switching for battery voltages up to 800 V in trucks and buses. (Image: TE Connectivity)
As with the other devices, the higher 800-V platforms places additional stress on contactor design. At higher voltages, arcs persist longer, increasing erosion of contact surfaces and raising the risk of welded or degraded contacts. Advanced arc management techniques, such as using permanent magnets to extend the arc path or employing gas-filled chambers to dissipate heat, are necessary to maintain reliability.
Solid-state contactors, which use semiconductor devices rather than moving contacts, are emerging as an alternative. They provide faster response times, reduced wear, and lower contact resistance, making them attractive for applications with frequent switching cycles.
Hybrid contactors that combine a mechanical switch with solid-state assistance are also being developed to strike a balance between cost, efficiency, and endurance.
The digital shift is arriving here, too. Smart contactors with embedded sensors can monitor coil current, contact resistance, and temperature rise, streaming data into system-level digital twins. AI tools can then analyze that data to predict wear, anticipate end-of-life, and optimize switching strategies. In safety-critical EV systems, these predictive diagnostics can reduce the risk of in-field failures.
In safety-critical EV systems, predictive diagnostics could help ensure that contactors operate reliably under high duty cycles, minimizing the risk of failure in the field.
For engineers, contactor selection is no longer just a choice between mechanical and solid-state designs. It increasingly involves system-level considerations, including arc suppression, thermal modeling, diagnostic integration, and digital monitoring, to ensure reliable operation under the higher stress of advanced EV architectures.
Sensors: precision data for control systems
Current and voltage sensors provide the real-time data that underpins every primary EV control function. They feed measurements to the battery management system (BMS), inverter, and vehicle control unit (VCU), enabling accurate monitoring of state of charge, power flow, and thermal conditions.
Shunt-based sensors deliver high accuracy but require careful thermal management. In contrast, Hall-effect and magnetoresistive sensors offer galvanic isolation, albeit with different tradeoffs in terms of cost, bandwidth, and precision.
As EVs adopt higher-voltage powertrains, sensor accuracy and reliability become more critical. Faster switching in silicon carbide (SiC) power electronics produces sharper transients, demanding sensors with wide bandwidth and strong immunity to electromagnetic interference. At the same time, space-efficient designs and rising current densities reduce the margin for error. (Figure 5)
Engineers must evaluate baseline accuracy, drift over temperature, and long-term stability to ensure consistent performance.
Figure 5. An overview of EV sensor placement, showcasing systems for battery and thermal management, electric motor control, and brake and tire monitoring. (Image: Sensata Technologies)
Sensors are also becoming smarter. Devices with built-in signal conditioning and self-diagnostics can deliver calibrated data directly over digital protocols, reducing external circuitry. With AI-driven analytics and digital twin models of the powertrain, this data enables predictive control, early fault detection, and adaptive energy management. For example, real-time current profiling can support adaptive thermal management, extending component life while improving range prediction.
For engineers, sensors are no longer simple measurement devices. They’re evolving into intelligent system nodes that support advanced monitoring, diagnostics, and predictive maintenance.
Conclusion
While EV discussions often focus on batteries and traction motors, reliable performance depends on supporting hardware that manages power distribution, protection, switching, and measurement. Busbars, fuses, contactors, and sensors each present their own engineering challenges, ranging from minimizing inductance to containing fault energy and maintaining precise measurements under demanding conditions.
As vehicle platforms transition from 400-V to higher-voltage systems, these components must operate with greater electrical, thermal, and mechanical robustness. At the same time, digitalization is transforming them from passive devices into intelligent subsystems. Embedded sensing, real-time data exchange, and AI-driven diagnostics are enabling predictive maintenance, adaptive protection, and more efficient energy management.
References
- Prashant S. B.T. et al., “Extensive review on laminated bus bar for low and high power applications,” E3S Web of Conferences, 2019. Explains how laminated busbars offer advantages—lower stray inductance, lighter weight, better maintenance—over conventional busbars in EV and power systems. ResearchGate
- M. Xu, N. Wang, Z. Wang, “Optimized design of laminated busbar for large-capacity back-to-back converters,” Energies, vol. 15, no. 3, 2022. Offers design insights and simulation validation of low‑inductance, reliable busbars for high-voltage, high-power converters, including EV relevance. MDPI+1
- Y. Huang, “A novel method for busbar design of electric vehicle…,” MDPI, 2021. Highlights how laminated busbars reduce voltage stress and improve thermal management in EV inverters. MDPI
- C.-E. Sălceanu et al., “Experimental Study on the Behavior of Aluminum Fuse Element Inside 24 kV, 50 kA High‑Voltage Fuses,” Energies, vol. 15, no. 19, 2022. Detailed examination of fuse construction and arc suppression media under extreme conditions. MDPI
- Y. Miyaoka, “Internal State of Fuse Arc Differentiating Interruption…,” IEEE Transactions on Electrical Engineering, 2024. Diagnoses the dynamics of fuse arc during interruption and failure—highly relevant to high-voltage EV protection. Wiley Online Library
- Littelfuse – EV Circuit Protection
- TE Connectivity – High-voltage Contactors
- Infineon: Solid-state Relays and Contactors | Current Sensors
Filed Under: Connectors, FAQs, Safety Systems, Sensors