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Measuring Fuel Consumption and Range in Hydrogen Fuel Cell Vehicles: SAE J2572-2024 Overview
The SAE J2572-2024 recommended practice provides uniform chassis dynamometer test procedures for determining fuel consumption and range of fuel cell and hybrid fuel cell vehicles fueled by compressed gaseous hydrogen. Focused on light-duty vehicles, it uses the Urban Dynamometer Driving Schedule (UDDS) and the Highway Fuel Economy Driving Schedule (HFEDS) as mandated by the US Federal Test Procedures. Although this standard has been stabilized and superseded by SAE J1711 for more comprehensive testing, it remains a foundational reference for basic range and efficiency measurements.
Stabilization Note: SAE J2572 has been stabilized and is no longer actively updated. For modern testing that includes five driving cycles, refer to the latest release of SAE J1711.
Key Test Conditions and Procedures
The standard mandates that vehicles undergo a break-in period of 1600 to 9978 km on the EPA Durability Driving Schedule before testing. All tests use a chassis dynamometer to eliminate variability inherent in track testing. Communication between the vehicle manufacturer and testing authority is essential to align on test specifications, including the potential use of an off-board hydrogen source.
Essential definitions are provided for consistent test execution:
| Term | Definition |
|---|---|
| Start-of-Test | The point when the vehicle key switch is first placed in the “on” position. |
| End-of-Test | After test termination criteria are met, the key switch is turned off, and the fuel cell and propulsion battery/capacitor are stabilized per the manufacturer’s automatic shutdown procedure (hydrogen fuel flow stops, energy storage device reaches a stable condition). |
| Total Fuel Capacity | The mass of gaseous hydrogen in the tank when filled to its nominal working pressure at a stabilized temperature of 15 °C. |
| Unusable Fuel Amount | The mass of hydrogen remaining in the tank at point of run-out, where pressure no longer supports stable fuel cell function or the control system halts extraction. |
| Usable Fuel Amount | The difference between total fuel capacity and the unusable fuel amount. |
Engineering Insights and Common Pitfalls 🛠️
The standard simplifies testing by using only two driving cycles, which may not fully replicate real-world conditions. Engineers must carefully condition the vehicle, particularly the fuel cell and energy storage systems, before beginning the test. A frequent mistake is misinterpreting the start-of-test and end-of-test definitions, especially for hybrid vehicles with automatic shutdown functions. In addition, it is critical to measure total fuel capacity at the specified nominal working pressure and 15 °C, and to ensure that off-board hydrogen supplies are properly accounted for.
⚠️ Test Repeatability: Proper conditioning and strict adherence to the defined start- and end-of-test procedures are vital for reproducible results. Ensure the vehicle has accumulated the required mileage before testing.
Frequently Asked Questions
How does SAE J2572 differ from SAE J1711?
SAE J2572 uses only UDDS and HFEDS cycles, while SAE J1711 incorporates all five recognized EPA cycles (UDDS, HFEDS, US06, SC03, and cold FTP) for more comprehensive testing across a broader range of scenarios. J2572 has been stabilized and superseded by J1711.
How is total fuel capacity measured?
Total fuel capacity is calculated as the mass of compressed gaseous hydrogen contained in the tank when it is filled to its nominal working pressure at a stabilized temperature of 15 °C. This value is the baseline for determining usable and unusable fuel amounts.
What defines start-of-test and end-of-test for hybrid fuel cell vehicles?
Start-of-test occurs when the vehicle key switch is first placed in the “on” position. End-of-test is reached after successful completion of the driving schedule, when the key is turned off and the fuel cell and any energy storage system (battery or capacitor) have completed the manufacturer’s automatic shutdown process, with hydrogen flow ceased and the energy storage device stable.
Why is a chassis dynamometer specified instead of track testing?
Chassis dynamometer testing eliminates test-to-test variations inherent in road or track testing, such as wind, grade, and surface conditions. This approach ensures consistent results and aligns with standard industry practice for measuring fuel consumption and range.
By understanding the procedures and definitions in SAE J2572, engineers can obtain reliable baseline data for hydrogen fuel cell and hybrid fuel cell vehicles, while recognizing that SAE J1711 should be used for more extensive testing.
