Hydrogen Internal Combustion Engine (Ice) Vehicles and Fueling Infrastructure Alternative Fuels & Life-Cycle Engineering Program
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Summary
This report documents the development and verification of an alternative electrical isolation test procedure for hydrogen fuel cell vehicles (HFCVs) undergoing crash testing without onboard hydrogen. The research was motivated by safety concerns regarding the use of compressed hydrogen during crash tests, leading manufacturers to propose using inert gas substitutes like helium. This substitution renders the fuel cell inactive, preventing the generation of high voltage and making the existing Federal Motor Vehicle Safety Standard (FMVSS) 305 test procedure inapplicable, as it requires an active propulsion system. Consequently, a new method was needed to verify electrical safety between high-voltage sources and potential human contact points when the fuel cell is inactive. Battelle, contracted by the National Highway Traffic Safety Administration (NHTSA), developed the procedure through a systematic review of existing standards, including ISO 6469-3, IEC TS 60479-1, and SAE J1766. The team established acceptance criteria based on these standards, selecting a minimum insulation resistance of 100 ohms/volt to ensure safety for humans while accommodating instrumentation capabilities. The study identified the QuadTech 1855 megohmmeter as suitable test equipment, which supplies high voltage and measures leakage current to the vehicle chassis. The procedure was refined through technical guidance from General Motors and Ford Motor Company, followed by dry runs at OEM facilities to determine test point locations and sequencing. The final procedure was verified on hydrogen-fueled Ford Focus and Chevrolet Equinox vehicles. Since actual crash tests were not performed, electrical isolation failure was simulated by inserting a resistor between the fuel cell power terminals and the chassis. The verification confirmed that the megohmmeter-based procedure could accurately test electrical isolation on an inactive fuel cell. However, the study identified limitations in the megohmmeter’s ability to measure isolation accurately if the chassis has a conductive connection to earth ground. Additional analysis evaluated the effects of temperature and age on fuel cell coolant conductivity, noting that environmental conditions could alter isolation measurements. The significance of this work lies in filling a regulatory gap for HFCV safety testing. The report provides a verified, standardized method for assessing electrical isolation in HFCVs when hydrogen is absent, ensuring compliance with safety principles outlined in FMVSS 305 and SAE standards. By establishing a reliable testing protocol for inert-gas crash scenarios, the research supports the safe development and regulation of hydrogen fuel cell vehicles, addressing the specific challenges posed by inactive high-voltage systems.
Key finding
A verified electrical isolation test procedure using a megohmmeter was successfully developed and validated for hydrogen fuel cell vehicles with inactive fuel cells, establishing that a minimum insulation resistance of 100 ohms/volt ensures safety for human contact.
Methodology
lab_experiment
Provenance
The full processing record for this entry. Every stage of this paper's journey through the pipeline is logged — what ran, with which tool and model, how many attempts it took, and when it last completed. Discovered via bulk_ingest_rosap on 2026-05-23 (6 acquisition events logged).
| Stage | Outcome | Tool | Model | Prompt | Attempts | Completed |
|---|---|---|---|---|---|---|
| discover | success | rosap | — | — | 2 | 2026-05-23 |
| archive | success | — | — | — | 1 | 2026-05-23 |
| extract | success | cached | — | — | 2 | 2026-06-10 |
| clean | success | — | — | — | 1 | 2026-06-01 |
| chunk | success | — | — | — | 1 | 2026-06-01 |
| embed | success | — | — | — | 1 | 2026-06-02 |
| enrich | success | — | — | — | 1 | 2026-05-23 |
| promote | success | — | — | — | 1 | 2026-05-23 |
| summarize | success | llm | qwen3.6-27b-prismaquant | summ-v5 | 3 | 2026-06-10 |
| tag | success | vector_similarity | — | — | 24 | 2026-06-11 |
| verify | success | — | — | — | 2 | 2026-06-10 |
Summary generated by qwen3.6-27b-prismaquant on 2026-06-10; verification: verified.
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- Applied Guidance: standards test procedures