ISO 10924-4:2025

Overview

ISO 10924-4:2025 - Road vehicles - Circuit breakers - Part 4: Medium circuit breakers with tabs (Blade type), Form CB15 - defines the rated currents, dimensions, test procedures and performance requirements for blade-type medium circuit breakers used in road vehicles. It applies to circuit breakers rated at 14 V, 28 V or 58 V (DC) for use in vehicles with nominal voltages 12 V, 24 V or 48 V (DC), with current ratings up to 40 A and a breaking capacity of 2 000 A. This part is intended to be used alongside ISO 10924-1 and ISO 10924-2.

Key topics and technical requirements

• Form and scope: Blade/tab style circuit breakers, Form CB15; available in electric reset, automatic reset, manual reset and switchable variants.
• Electrical ratings: Rated voltages (14/28/58 V DC), current ≤ 40 A, breaking capacity 2 000 A.
• Test procedures: Comprehensive test sequence plan (see Table 2) covering:
  • Voltage drop (fast and standard versions)
  • Operating time-rating and current steps
  • Absolute breaking capacity and breaking capacity tests
  • Endurance, dielectric strength and strength of terminals
  • Maximum housing temperature, no-current trip and reset temperature
  • Environmental (climatic, chemical, vibration, shock, free-fall) tests
• Test fixtures and conditions: Electrical tests use a Type C fixture per ISO 8820-3 with a connection resistance ≤ 0.8 mΩ. Environmental temperature ranges are guided by ISO 16750-4.
• Marking and colour coding: Standard colour codes for rated currents (e.g., 5 A - tan/light brown, 10 A - red, 20 A - yellow, 40 A - orange) to aid identification.
• Dimensions & categories: Clause 6 defines dimensional categories (A–K) and designation examples to ensure mechanical interchangeability.

Practical applications and users

ISO 10924-4 is essential for:

• Automotive OEMs and ECU/electrical system designers specifying circuit protection
• Tier‑1 suppliers and component manufacturers developing blade-type circuit breakers
• Test laboratories performing compliance and type-testing to ISO requirements
• Procurement and conformity managers verifying component compatibility and safety
• Designers replacing or comparing medium fuse-links (ISO 8820-3) and circuit breakers for accessory, lighting, infotainment and power distribution circuits

Note: while tab dimensions and current ratings can match ISO 8820-3 fuse-links, performance can differ - users should review breaking and endurance characteristics.

Related standards

• ISO 10924-1 - Definitions and general test requirements
• ISO 10924-2 - Guidance for users
• ISO 8820-3 - Fuse-links with tabs (blade type) Type C (medium)
• ISO 16750-4 - Climatic loads for vehicle electrical/electronic equipment
• ISO 6722-1 - Single-core cables (referenced for test cable sizes)

Keywords: ISO 10924-4, circuit breakers, road vehicles, medium circuit breakers, blade type, Form CB15, automotive circuit protection, breaking capacity, test procedures, electrical reset.