ISO 23274-2:2021

Overview

ISO 23274-2:2021 specifies a chassis dynamometer test procedure for externally chargeable hybrid-electric road vehicles to determine the end of the charge‑depleting (CD) state and the electric energy consumed during CD. The standard focuses on measurement methodology for battery‑equipped HEVs (internally combustion engine + rechargeable energy storage system (RESS)) that can be recharged from an external power source. It does not provide the final determination of exhaust emissions and fuel consumption - rather, it defines the critical step of identifying when a vehicle transitions from CD to charge‑sustaining (CS) operation so that downstream emissions/fuel procedures can apply.

Key topics and technical requirements

• Scope and vehicle types: Applies to passenger cars and light‑duty trucks with batteries as RESS, RESS nominal energy ≥ 2% of total fuel energy consumed over an applicable driving test (ADT). Excludes trolleybuses and solar‑powered vehicles.
• Test environment & charging: Normal charging at (25 ± 5) °C per manufacturer procedure; typical end‑of‑charge criterion corresponds to 12 hours unless the vehicle indicates otherwise. External charge for preconditioning is excluded.
• Chassis dynamometer procedure: Defines sequence - preconditioning, soak, full initial charge, move to test room (no regenerative charging while moving), run ADTs (e.g., WLTC or UDDS), measure RESS energy balance, repeat ADTs until CD end is identified, then fully recharge and measure external AC energy delivered.
• Energy & instrumentation accuracy: Measurement equipment accuracy requirements (examples from Table 1): time ±0.1 s, speed ±1 %, temperature ±1 °C, mass ±0.5 %, current ±0.3 %, electric energy ±0.5 %.
• Determination of end of CD: Clause 6.3 (and informative Annex A) defines procedures (multiple cases) to identify the transition from CD to CS; ADTs run in CS are used only to establish that transition, not for full CS emissions/fuel results.
• Charging measurement: Electric energy delivered from the external source must be measured with metering placed between the external source and vehicle inlet; charging must start within 2 hours after test completion.

Applications and users

• Vehicle manufacturers and component suppliers for validation of hybrid control strategies and battery sizing.
• Emissions and fuel consumption test laboratories performing homologation or type‑approval prep work.
• Regulatory agencies and certification bodies needing repeatable methods to identify CD/CS boundaries.
• R&D teams analyzing real-world electric energy use in plug‑in hybrids and comparing ADT results (WLTC/UDDS).

Related standards

• ISO 23274-1 - Part 1: Non‑externally chargeable vehicles (CS test procedures)
• ISO/TR 8713 - Electrically propelled road vehicles - Vocabulary

Keywords: ISO 23274-2:2021, hybrid-electric road vehicles, charge-depleting, charge-sustaining, chassis dynamometer, RESS, state of charge, electric energy measurement, ADT, WLTC, UDDS.