EV Engineering & Infrastructure

Shifting LEVs to higher voltages: Performance gains and safety challenges

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Many light EV (LEV) manufacturers are shifting from traditional 36 to 48-Volt (V) architectures to higher-voltage powertrains in e-bikes, scooters, mopeds, and neighborhood electric vehicles (NEVs). Operating between 72 and 96 V (and above), these systems address increasing power demands, improve efficiency, and extend range. They also introduce new challenges in safety, thermal management, and regulatory compliance.

This article discusses the technical drivers behind higher-voltage adoption in LEVs, focusing on performance gains in speed, torque, and efficiency. It also addresses evolving safety standards, regulatory thresholds, and the thermal management and integration strategies required for reliable operation.

Higher voltage drives performance benefits

Scaling voltage boosts performance without the added weight and cost penalties of thicker cabling or larger battery traction packs. In many implementations, higher voltage is achieved by connecting more cells in series rather than expanding the battery pack size.

Because speed increases are roughly proportional to voltage, 36 to 48-V systems typically deliver between 25 and 28 mile-per-hour (mph) top speeds with 750 to 1000-W motors, while 72-V systems, as shown in Figure 1, can reach 40+ mph using similar motor configurations.

Figure 1. The WIRED SCOUT 72 V features a 72-V dual battery system and ~180Nm high torque design that delivers 5000-W peak power and 45+ mpg top speed. (Image: Wired Bikes)

The intermediate 52 V step offers 2 to 3 mph gains over 48-V systems and maintains speed more effectively as the battery discharges. This voltage–speed relationship reflects fundamental motor physics: higher voltage drives higher rotational speed for a given magnetic field strength.

Increased voltage boosts torque performance. Standard 36 to 48-V powertrains provide adequate torque for flat terrain and urban or suburban commuting yet struggle with steep grades and heavy loads. At 52 V, torque provides enough improvement to support faster acceleration and more reliable hill-climbing. Powertrains at 72 V and above deliver significant gains, enabling rapid acceleration from a standstill and consistent performance with cargo loads or dual-motor configurations.

Beyond these mechanical performance improvements, efficiency gains represent a key advantage of higher-voltage operation. For a given power output, increasing voltage reduces current proportionally, thereby minimizing copper losses in motors and wiring. These I²R losses fall with the square of the current reduction, producing substantial efficiency improvements. Higher-voltage systems also allow smaller-gauge wiring, reducing both weight and heat generation.

These efficiency improvements enable system-level benefits. Motors operating at higher voltages maintain performance under variable loads, deliver torque at speed, and limit heating during demanding conditions. Additionally, batteries last longer as less stored energy dissipates as waste heat, and overall range improves at sustained high speeds.

Voltage thresholds define safety requirements

These performance advantages incur increasingly stringent safety requirements as systems cross established voltage thresholds. As shown in Figure 2, vehicles operating at 48 V are classified as Safety Extra Low Voltage (SELV) under most international standards, including IEC and ISO frameworks.

Figure 2. The Motrec – MC-480 LITHIUM is a 48-V electric baggage and GSE towing vehicle. (Image: Pilot John)

This classification requires basic insulation and electrical safety protocols but doesn’t stipulate high-voltage isolation, emergency disconnects, or specialized protective equipment. Testing focuses on overcurrent protection, thermal management, and durability rather than arc flash or high-voltage isolation.

The 60 Vdc threshold marks where high-voltage classifications begin, and beyond this point regulatory frameworks increase in oversight. This rating fundamentally alters design considerations and compliance obligations, as higher voltages impose stricter safety requirements.

At 72 V, systems enter high-voltage territory, requiring compliance with UL 2271 for batteries and UL 2272 for complete electrical systems. These standards stipulate warning labels, certified insulation, emergency disconnects, and detailed user documentation. Orange cable color coding above 60 Vdc is mandatory, along with electrical isolation monitoring and fault detection.

At 96 V, vehicles, such as the electric fire truck shown in Figure 3, are subject to full automotive EV regulation, including FMVSS No. 305a in the United States.

Figure 3. Manufactured in China, this electric fire truck is equipped with a 96 V 15-kw ac motor and features a top speed of 30km/H and loading weight of 1800kgs. (Image: GolfCarEN)

These rules require extensive documentation, personal protective equipment protocols for service personnel, robust isolation systems, and reinforced fire and misuse protection. Testing also expands to cover fire resistance, environmental cycling, crash simulation, and emergency response validation.

International standardization efforts through UN R136 and Global Technical Regulation No. 20 synchronize requirements across major markets, though enforcement and documentation vary by region. Together, these frameworks establish clear demarcation points at 48 V, 72 V, and 96 V that impact system design choices and certification costs.

Thermal management strategies adapt to higher voltages

Higher voltages reshape thermal management requirements, though often counterintuitively. For example, reduced resistive losses are the primary thermal benefit of higher-voltage LEVs.

Lower currents at higher voltages decrease I²R heating in motor windings and power cables, often cutting baseline heat generation by 30 to 50% compared to equivalent power delivery at lower voltages. This reduction allows designers to incorporate smaller conductors and more compact motor packages without thermal penalties.

Notably, higher power density and compact packaging shift design challenges from overall heat generation to localized heat concentration. Modern LEV motors deliver more power in smaller housings, driving the need for advanced thermal management systems beyond traditional passive cooling.

Thermally conductive potting compounds improve heat transfer from motor windings to housing surfaces, reducing operating temperatures by 30° to 50° C compared to air-cooled designs. Motor housings with optimized materials and geometries further improve heat spreading and transfer efficiency.

For high-demand applications such as cargo-hauling e-bikes, dual-motor scooters, or fast-charging LEVs, integrated thermal management systems coordinate heat dissipation across motors, inverters, and battery traction packs. These systems use sensor networks and control algorithms to track temperatures in real time, optimizing performance while preventing derating or failure.

Although higher voltage reduces current-related heating, the associated gains in energy density and fast-charging capability add thermal stress. Higher-voltage packs also contain more cells in series, requiring finer balancing, more precise monitoring, and faster fault detection to address risks such as isolation failure or short circuits.

Advanced battery management systems (BMS) incorporate these capabilities and coordinate with motor controllers, providing a foundation for broader system integration.

Integration challenges shape system architecture

Thermal considerations directly impact system integration, with higher-voltage LEVs requiring new motor and inverter strategies. Inverter designs must incorporate optimized fault detection, insulation monitoring, and rapid electronic shutdown capabilities to address electrical hazards.

Power electronics complexity also increases with higher voltages. Inverters need robust isolation systems, advanced switching strategies, and precise protection circuits to rapidly detect and respond to faults. Although these measures add cost and complexity, they ensure reliable operation under varying load conditions.

Zonal architecture concepts, adapted from automotive applications, support more efficient packaging in higher-voltage LEV systems. This approach consolidates power electronics, reduces wiring complexity, and improves thermal management by distributing heat sources more evenly throughout the vehicle structure.

Motor and controller matching is critical at higher voltages. Improper configuration can damage components or offset efficiency gains, requiring meticulous alignment of voltage handling capabilities, thermal characteristics, and control algorithms. To reduce integration risks, some manufacturers provide motor–controller packages designed for coordinated operation.

Summary

Many manufacturers implement higher-voltage LEV architectures to improve performance, efficiency, and overall capability. This approach requires a comprehensive focus on safety standards, thermal management, and system integration. Although higher voltages introduce added complexity and cost, their performance and efficiency advantages will continue to drive adoption across the light EV market.

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