Protecting the Battery: How TOPU Optimized Crash Safety for Extended-Range Electric Vehicles

By Huiwen Hu

Case Study: Client Project

Client	Metal Industries Research & Development Centre (MIRDC)
Industry	Automotive / Electric Vehicles
Challenge	Optimize the battery pack and vehicle body structure to improve crash protection for occupants and the high-voltage battery system.
TOPU's Role	Full-vehicle CAE simulation, structural analysis, AI-assisted structural optimization, crashworthiness evaluation, and occupant injury assessment.
Outcome	Achieved enhanced crashworthiness and occupant protection through simulation-driven structural optimization of the vehicle body and battery enclosure.

An Extended-Range Electric Vehicle (EREV) is a battery electric vehicle powered entirely by an electric motor. Unlike conventional hybrid vehicles, its onboard internal combustion engine functions solely as a generator to recharge the battery and does not directly drive the wheels. This series-hybrid architecture effectively eliminates range anxiety while maintaining the smooth driving experience of a pure electric vehicle.

However, the additional mass of the battery system significantly increases the vehicle's kinetic energy during a collision. In particular, severe side impacts may cause excessive deformation of the battery enclosure, potentially leading to battery cell damage, internal short circuits, and thermal runaway.

Leveraging advanced CAE simulation and simulation-driven structural optimization, TOPU collaborated with the Metal Industries Research & Development Centre (MIRDC) to optimize both the battery pack and vehicle body structure, achieving enhanced crash protection for occupants and the high-voltage battery system.

Why Crash Safety Is Different for Extended-Range Electric Vehicles

Fully Electric Drive with Onboard Power Generation

An EREV is propelled entirely by electric motors, while the onboard gasoline engine serves exclusively as a power generator to recharge the battery, extending driving range without directly transmitting power to the wheels.

This architecture provides the driving characteristics of an electric vehicle while introducing additional considerations for vehicle packaging, structural design, and crash safety.

Increased Vehicle Mass Raises Crash Energy

Compared with conventional passenger vehicles, the battery pack substantially increases vehicle mass. During a collision, this results in higher kinetic energy that must be dissipated through carefully controlled structural deformation.

The vehicle structure must therefore absorb crash energy efficiently while maintaining sufficient protection for both occupants and the battery system.

Side-Impact Risks to Battery Systems

For the original vehicle design, severe side impacts could cause excessive deformation of the battery enclosure, increasing the risk of battery cell damage and thermal runaway.

This created a key engineering challenge: how can the vehicle structure absorb impact energy while limiting intrusion into the battery compartment?

Building a Digital Crash Model Before the Physical Test

Crash safety is not determined by a single component. The interaction between the vehicle body, battery pack, chassis, fuel tank, and occupants must all be considered as part of the complete system.

TOPU developed a comprehensive finite element model incorporating the vehicle body, battery pack, chassis, fuel tank, and occupant dummy models to evaluate structural behavior during frontal, rear, and side-impact collisions.

By simulating the complete vehicle system, engineers could evaluate how different components interacted during a crash and identify areas where structural reinforcement could improve overall crashworthiness.

Reinforcing the Battery Where It Matters Most

To improve side-impact resistance, TOPU redesigned and reinforced the battery enclosure crossmembers, significantly enhancing structural integrity.

Using advanced CAE simulation together with optimization algorithms, TOPU evaluated the battery enclosure under frontal, rear, and side-impact loading conditions.

Rather than simply adding material to increase strength, simulation-driven optimization was used to identify an optimal reinforcement strategy that balances structural protection with the need to control vehicle weight.

Controlled Energy Absorption

During a collision, the goal is not simply to make every component as rigid as possible.

The vehicle structure must deform in a controlled manner so that crash energy can be absorbed efficiently while minimizing intrusion into critical areas.

Simulation-driven optimization enabled TOPU to identify an optimal reinforcement strategy that promotes controlled structural deformation, allowing the vehicle body to absorb crash energy efficiently while minimizing intrusion into the battery compartment.

This approach allowed structural performance to be evaluated and refined digitally before physical validation.

Protecting Both the Battery and the Occupants

Vehicle crash safety extends beyond protecting the battery pack. A successful design must also protect occupants and maintain post-crash electrical safety.

TOPU evaluated the vehicle against relevant international EV safety requirements, including UN ECE R100 Rev.3, FMVSS 305, and FMVSS 214.

UN ECE R100 Revision 3

UN ECE R100 Rev.3 establishes requirements for the safety of electrically propelled vehicles, including protection against electric shock following a crash, sufficient insulation resistance, automatic high-voltage isolation, and prevention of battery electrolyte leakage, fire, or explosion.

U.S. FMVSS 305 and FMVSS 214

The vehicle structure was also evaluated in accordance with relevant U.S. Federal Motor Vehicle Safety Standards:

• FMVSS 305: Electric-powered vehicle electrical safety

• FMVSS 214: Side-impact protection

  
  

Together, these requirements address key aspects of battery safety, occupant protection, and crash performance.

Measuring the Impact on Occupants

Protecting the vehicle structure is only part of crash safety. The ultimate goal is to reduce the forces experienced by the people inside the vehicle.

Using validated occupant dummy models, TOPU assessed critical injury metrics including head, neck, chest, lumbar spine, and femur loads throughout the simulated crash events.

The results showed that these critical injury metrics remained below the applicable regulatory limits, supporting the vehicle's overall occupant protection performance.

By combining vehicle-level structural simulation with occupant injury assessment, TOPU was able to evaluate crash safety from both the structural and human perspectives.

From CAE Simulation to AI-Driven Optimization

Traditional crash development can require repeated cycles of physical prototyping, testing, analysis, and structural modification.

CAE simulation changes this process by allowing engineers to evaluate crash behavior digitally before committing to physical prototypes. When combined with optimization algorithms and AI-assisted methods, the design process can go one step further.

Instead of relying solely on manual design iterations, optimization algorithms can evaluate different structural configurations and identify reinforcement strategies that meet multiple performance requirements simultaneously.

For EREVs, this approach is particularly valuable because crash protection must balance several competing objectives: occupant safety, battery protection, structural integrity, energy absorption, and vehicle weight.

The Future of Intelligent Vehicle Engineering

The development of electric and extended-range vehicles is creating new challenges for automotive engineering.

As battery systems become increasingly integrated into vehicle structures, crash safety can no longer be considered separately from battery protection, electrical safety, and occupant protection.

This is where digital engineering becomes increasingly important.

By combining CAE simulation, structural optimization, AI-assisted analysis, and occupant safety assessment, engineers can evaluate complex vehicle interactions earlier in the development process and make more informed design decisions before physical testing.

TOPU's experience in multidisciplinary engineering integration allows these technologies to be brought together into a unified product development workflow—from structural design and simulation to optimization and validation.

The Bottom Line

For an Extended-Range Electric Vehicle, crash safety is about more than protecting the people inside the vehicle.

The battery system must also remain protected from excessive deformation, while the vehicle structure must absorb crash energy in a controlled and predictable way.

Through full-vehicle CAE simulation and AI-assisted structural optimization, TOPU collaborated with MIRDC to address these challenges across the battery enclosure, vehicle structure, and occupant protection system.

The result is an engineering approach that moves crash safety beyond trial-and-error physical testing toward a more predictive, simulation-driven development process.

As electric vehicle architectures continue to evolve, the ability to simulate, optimize, and validate complex interactions before physical testing will become increasingly important.

For TOPU, this is the value of digital engineering: 

Using simulation and intelligent optimization to solve critical engineering problems before they become real-world risks.