Electric Vehicle Crash Safety Expert Overview

Electric vehicles are held to the same crashworthiness standards as conventional vehicles, except for specific requirements surrounding the high voltage systems. This article provides a tutorial for attorneys and insurance professionals to better understand EV crash performance.

For the purposes of this article, we are focusing on electric vehicles (EVs) that can be plugged into charging equipment to charge the battery. We will address how the regulations differ from combustion engine vehicles, how EVs perform in crash tests, and how high voltage systems require a change in approach from first responders.

These are vehicles that have a high voltage (HV) battery (>60VDC) that can be the primary energy source for the vehicle motor(s). There are two main categories: 

• Pure EV (typically battery but fuel cell EVs are also available)
• Plug-in hybrid electric vehicles (PHEV)

Hybrid electric vehicles (HEV) use a battery and motor-generator to improve the gas mileage of the vehicle but the battery (typically 48V) cannot be charged by plugging into charging equipment.

Number of EVs on the Road

Only a small percentage of vehicles on US roads are currently EVs. However, sales continue to accelerate and are expected to reach more than 40% of new car sales in the next twelve years. Consequently, they will make up a larger proportion of the vehicles on our roads and will inevitably be involved in more vehicle crashes.

EV Crash Safety

The National Highway Traffic Safety Administration (NHTSA) does not differentiate between powertrain types when it comes to the main Federal Motor Vehicle Safety Standards (FMVSS) such as 208, which defines the requirements for occupant crash protection. Similarly, the US New Car Assessment Program (NCAP) & the Insurance Institute for Highway Safety (IIHS) perform non-regulatory tests designed to inform consumers of relative vehicle safety using the same tests for EVs.

However, EVs have several safety concerns that are not associated with traditional gasoline powered vehicles. The high voltage battery that all battery electric vehicles (BEVs) use (typically >350VDC) introduces new risks such as electrocution, explosion, and electrolyte spillage. 

To address these risks, NHTSA introduced FMVSS 305 specifically for any type of EV with a GVWR of 10,000lb or less, that uses electrical components with voltages exceeding 60 VDC and which are capable of speeds greater than ~25mph. The standard requires EVs to be tested in frontal, side, and rear impact test modes and contains specific requirements for the performance of the high voltage (HV) battery system: 

• The HV battery must remain anchored to the vehicle, i.e. no separation
• No intrusion of the HV battery or electrolyte leakage into the occupant compartment
• A maximum of ~5.3 quarts of electrolyte spillage from the HV battery (outside of the occupant compartment)
• All HV sources must meet at least one electrical safety requirement (isolation, voltage level or physical barrier protection)

Additionally, the SAE International (formerly Society of Automotive Engineers) has issued multiple standards that define methods for demonstrating the safety of HV batteries during customer usage. The recommended tests include vibration, thermal shock, mechanical impact, and fire resistance.

During an impact event, the vehicle’s contactors will typically disconnect the HV system (based on a signal from the airbag or crash sensors) and/or pyro fuses will be fired to break the HV circuit to isolate the HV battery from the rest of the powertrain. This reduces but does not eliminate the risk of electrocution. There are also fire risks associated with damage to the HV battery pack. Thermal runaway can occur from a single battery cell being damaged or punctured. Finally, chemical hazards can arise when a HV battery pack and associated cells are damaged and releases pollutants and caustic substances such as hydrofluoric acid.

EV Crash Test Performance

Many BEVs have been independently tested by various agencies over the last decade or more (Original Equipment Manufacturers (OEMs) must self-certify for 305, as well as all other FMVSS minimum performance requirements, and so the results are generally not in the public domain). In some cases, these BEVs perform well and achieve the full 5 Star rating for NCAP and Top Safety Pick+ for IIHS tests. Certain OEMs produce vehicles that are available in both BEV and traditional combustion engine form, and for some vehicles where both types have been tested, they have performed comparably well. This highlights that good crash safety performance can be achieved regardless of the powertrain type.

The agencies do not specifically report on the HV battery performance, but in the case of the IIHS, their procedures follow the FMVSS 305 standard and post-test checks include: determining whether the HV battery has disconnected from the drive system, potential fire event, the isolation of the chassis from the HV battery, and general checks for smoke or battery coolant leakage.

EVs - First Responder Considerations

For first responders at an EV crash, manufacturers issue detailed safety instructions on the procedures that need to be followed to ensure responder safety. The typical guide includes warnings about HV component energy states, the time to de-energize the system, correct tools required, and the required Personal Protection Equipment (PPE).

The guide provides details of the HV components including the battery and HV electrical cables. It outlines the location of the “first responder cut loop” and how to safely access and cut this loop (a low voltage harness that can shut down the high voltage system). In some cases, there is an alternative loop in the rear of the vehicle if the front compartment is inaccessible.

Details of safe vehicle lifting points are also provided to prevent unintended damage to the HV systems including the HV battery, which is commonly mounted underneath the center floor. Puncturing or impacting the HV battery pack can lead to a fire event, sometimes days after the battery damage was caused.

Event Data Recorder

As with almost all modern light vehicles, EVs will have an Event Data Recorder (EDR) on board. The basic crash parameters recorded are no different from regular gasoline vehicles. However, in the future, manufacturers are considering adding new data elements specific to EVs. This could include whether or not the HV battery was automatically disconnected during the crash event.

Vehicle Crash Investigations

From complex crash reconstruction to developing demonstrative evidence for court testimony, the transportation experts at Robson Forensic are well equipped to assist in your investigation. The vehicle experts at Robson Forensic are more than just mechanical engineers and reconstructionists, they are automotive engineers with industry experience in the design, development, and manufacturing of gasoline and electric vehicles.

For more information, submit an inquiry or call us at 800.813.6736.

Featured Expert

Christopher D. Roche

Automotive Engineer & Crash Expert

Christopher Roche is an automotive engineer with nearly 30 years of professional experience working for major vehicle manufacturers, specializing in the design of vehicle structures to protect… read more.