New EU Regulation Updates Electric Vehicle Power Train Approval Rules

The European Union has published Regulation (EU) 2026/1695 in the Official Journal of the European Union (OJ L, 17 August 2026), consolidating the fifth series of amendments to UN Regulation No. 100 — the global framework governing type-approval of vehicles with electric power trains. The regulation is published under the official reference CELEX 32026R1695 and incorporates all valid text up to the 05 series, whose entry into force date is 26 September 2025.

The regulation sets out uniform provisions for the approval of road vehicles of categories M, N, and O with a maximum design speed exceeding 25 km/h that are equipped with an electric power train. It excludes vehicles permanently connected to the electrical grid. The updated text covers three main pillars: vehicle-level electrical safety requirements, safety standards for Rechargeable Electrical Energy Storage Systems (REESS), and installation requirements for approved battery systems.

Strengthened Electrical Safety for Vehicles

Part I of the regulation establishes detailed safety requirements that vehicles must meet to obtain type-approval. These include protection against direct and indirect contact with high-voltage live parts, minimum isolation resistance thresholds (100 Ω/Volt for DC buses, 500 Ω/Volt for AC buses), and protection against water effects such as driving through standing water or vehicle washing.

The regulation also addresses:

• Protection degrees IPXXB and IPXXD for high-voltage live parts in and outside the passenger compartment
• Orange-coloured cables for high-voltage buses not located within enclosures
• Warning systems for the driver in case of REESS failures, low state of charge, and thermal events
• Prevention of accidental vehicle movement, including an automatic lock preventing propulsion while the vehicle connector is physically connected to the inlet during charging
• Identification labels for vehicles of categories M2/N2 and M3/N3 equipped with high-voltage electric power trains
• Hydrogen emission limits for vehicles with open-type traction batteries: below 125 g during 5 hours of normal charging

Comprehensive Battery Safety Standards

Part II introduces a rigorous testing regime for the REESS, covering a total of 14 distinct safety domains. The REESS must pass tests for vibration, thermal shock and cycling, mechanical impact (including crush forces of at least 100 kN), fire resistance, external short-circuit protection, overcharge, over-discharge, over-temperature, and overcurrent protection. Each test has explicit pass/fail criteria — generally requiring no evidence of electrolyte leakage, rupture, venting, fire, or explosion.

New in the 05 series is the requirement for low-temperature protection, mandating that the REESS manufacturer document the lower boundary temperature for safe operation and the actions taken when that boundary is reached. The regulation also formally defines “alkali metal anodes” — negative electrodes based on lithium, sodium, or potassium — signaling a regulatory framework prepared for next-generation battery chemistries.

Thermal Propagation: The Five-Minute Rule

Perhaps the most consequential update is the new thermal propagation safety requirement (paragraph 6.15). For REESS containing flammable electrolyte or alkali metal anodes, the regulation mandates that vehicle occupants must not be exposed to hazardous conditions — fire, explosion, or smoke in the passenger compartment — within five minutes of a warning signal following a single-cell thermal runaway event. This applies when an internal short circuit is the triggering mechanism.

Verification can follow one of two paths:

• Physical testing using one of four trigger methods: localized fast external heating, localized internal heater, nail penetration (using steel nails 3 to 8 mm in diameter), or laser-based trigger
• Risk management analysis as an alternative when physical testing would compromise the REESS safety design, following a systematic methodology aligned with standards such as ISO 26262, IEC 61508, or SAE J2929

The regulation specifies that if no thermal propagation occurs within 2 hours of triggering, or if thermal runaway itself cannot be triggered, the five-minute warning requirement is deemed satisfied. A reduced pathway exists for REESS charged only by on-board energy sources with capacity not exceeding 2 kWh, which need only perform the risk management analysis.

Transitional Timeline

The transitional provisions lay out a phased implementation:

• From entry into force (26 September 2025): no contracting party may refuse to grant or accept type-approvals under the 05 series
• From 1 September 2027: contracting parties are not obliged to accept type-approvals from preceding series first issued after that date
• Until 1 September 2029: type-approvals issued under preceding series before 1 September 2027 must still be accepted, subject to the transition rules of those preceding series
• From 1 September 2029: contracting parties may refuse all preceding-series approvals
• Until 1 September 2030: approvals under the 03 or 04 series for vehicles unaffected by the 05 series changes may continue to be accepted

The regulation was developed through the United Nations Economic Commission for Europe (UNECE) World Forum for Harmonization of Vehicle Regulations (WP.29), with authentic texts referenced as ECE/TRANS/WP.29/2025/41, ECE/TRANS/WP.29/2025/42, and ECE/TRANS/WP.29/2025/43. Its publication in the Official Journal makes the updated provisions directly applicable across EU member states as part of the 1958 Agreement framework. The 121-page document, with its ten annexes covering detailed test procedures and communication templates, represents the most comprehensive update to electric vehicle battery safety rules since the regulation’s inception — and comes at a critical moment as the European electric car market scales rapidly toward the EU’s 2035 combustion-engine phase-out.

For manufacturers, compliance with the 05 series becomes effectively mandatory from September 2027 for new type-approvals, while the thermal propagation and alkali-metal-anode provisions set a new global benchmark for battery safety certification.

Source: Official Journal of the European Union, L series, 17.8.2026, p. 1/121–121/121 (official reference: CELEX 32026R1695, Regulation (EU) 2026/1695, UN Regulation No. 100, 05 series of amendments).