ISO 25981:2020

Overview

ISO 25981:2020 - Road vehicles: Connectors for electronically monitored charging systems (12 V / 24 V) - defines the mechanical, electrical and testing requirements for 7‑pole connectors used between towing and towed vehicles. The standard covers dimensional characteristics, contact allocation, tests and requirements for an electronically monitored charging connection (designed to detect 12 V and 24 V nominal systems and to limit charging current to 50 A). It also specifies a park socket to receive and store the plug when disconnected. This connector is explicitly a charging-only interface (no braking function).

Key topics and technical requirements

• Connector type: 7‑pole plug and mating socket with a park socket; floating contacts aligned to a datum position on engagement.
• Voltage/current: Intended for 12 V and 24 V vehicle systems; electronic monitoring limits current to 50 A.
• Contact allocation: Seven contacts with defined functions (two plus charging pins, multiple minus/feedback/control pins for platform/tailgate signals). Contact designations must be permanently marked on socket cover and terminal faces.
• Terminals and cabling: Terminals accept specified nominal cable cross‑sectional areas for high‑current and control pins (document lists separate capacities for contacts 1–4 and 5–7); connecting cables should conform to the ISO 4141 series.
• Dimensional features: Plug, socket and park socket dimensions and locking lever spaces are specified; socket cover must close automatically when plug is removed.
• Mechanical & electrical tests: Includes mismating prevention (IEC 60512‑13‑5), connection/disconnection force limits, endurance (10 000 cycles), and mounting feature strength (minimum mounting torque specified). Mismating requirement: no pin contact up to a defined force threshold.
• Identification and colours: Minimum colouring requirement - socket cover and plug insert light grey.

Applications and practical value

• Designed for separable truck‑trailer combinations to connect an additional trailer battery pack to the towing vehicle’s generator. Typical uses:
  • Powering tailgate lifts, electric forklifts on trailers
  • Supplying other trailer equipment with high current demand
• Ensures safe charging, prevents damage from wrong system voltage, and supports standardized interchangeability and testing for fleets and manufacturers.

Who should use this standard

• Vehicle manufacturers (truck and trailer OEMs)
• Automotive electrical component designers and connector suppliers
• Fleet operators specifying safe trailer charging interfaces
• Test laboratories and certification bodies ensuring compliance

Related standards

• ISO 4091 (connectors - tests & requirements)
• ISO 4141 (multi‑core connecting cables)
• ISO 12098 (15‑pole connector)
• ISO 7638‑1 / ISO 7638‑2 (braking system connectors)
• IEC 60512‑13‑5 (mismating / mechanical operation tests)

Keywords: ISO 25981:2020, 7‑pole connector, electronically monitored charging system, towing and towed vehicles, trailer battery charging, 12 V, 24 V, park socket, connector tests.