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ISO 25981:2020 — Connectors for Electronically Monitored Charging Systems of Towing Vehicles
7-pole connector specifications for 12V/24V auxiliary battery charging in truck-trailer combinations
1. 7-Pole Connector Design Specifications
ISO 25981:2020 specifies dimensional characteristics, contact allocation, tests, and requirements for 7-pole connectors in electronically monitored charging systems for towing combinations. These connectors handle 12V and 24V nominal supply voltages with current capacity up to 50A, connecting trailer auxiliary battery packs to the towing vehicle generator. Key design features include floating self-aligning contacts, a locking lever mechanism, and automatic cover closure upon disconnection. Contact coding ensures correct polarization to prevent mismating with incompatible connector types.
Unlike ISO 12098 15-pole connectors for lighting and signaling, ISO 25981 focuses specifically on high-current charging for tailgate lifts, electric forklifts, and refrigerated units.
| Contacts | Function | Conductor Size | Voltage |
|---|---|---|---|
| 1-4 | Power charging | 6.0 mm² | 12V / 24V |
| 5-7 | Monitoring/signal | 1.0 mm² | 12V / 24V |
2. Electronic Monitoring System Integration
Annex A specifies minimum functionality for the monitoring device, which detects nominal supply voltage and limits current to 50A. This ensures safe auxiliary battery charging without overloading the towing vehicle electrical system. Unlike ISO 7638 braking connectors, ISO 25981 connectors have NO braking capacity. Common applications include refrigerated trailers with cooling units, hydraulic lift gates, and electric material handling equipment on flatbed trailers.
These connectors have NO braking capacity. Never use in safety-critical circuits where failure could cause loss of vehicle control.
3. Testing and Qualification
Clause 6 defines comprehensive test procedures: mismating prevention testing using IEC 60512-13-5 polarizing methods, connection/disconnection force measurement, electrical endurance under load, and mechanical strength of mounting features. The 2020 edition revised socket dimensions and removed ISO 4009 references for improved compatibility with modern vehicle electrical architectures. Endurance testing simulates years of field use under electrical load, while mechanical tests evaluate vibration and shock resistance for bumper and chassis mounting.
The 2020 edition improved dimensional compatibility with modern vehicle architectures through revised socket dimensions and streamlined normative references.
Frequently Asked Questions
Q: Interchangeable between 12V and 24V?
A: Yes. The monitoring system auto-detects voltage and limits current up to 50A. Connector hardware is identical.
A: Yes. The monitoring system auto-detects voltage and limits current up to 50A. Connector hardware is identical.
Q: Difference from ISO 7638 connectors?
A: ISO 7638 is for braking systems with braking capacity. ISO 25981 is for charging. Different pin configurations prevent cross-connection.
A: ISO 7638 is for braking systems with braking capacity. ISO 25981 is for charging. Different pin configurations prevent cross-connection.
Q: What is the park socket?
A: A storage receptacle with automatic-close cover for the plug when disconnected from a trailer, protecting contacts from dirt and moisture.
A: A storage receptacle with automatic-close cover for the plug when disconnected from a trailer, protecting contacts from dirt and moisture.
Q: What changed in the 2020 edition?
A: Revised socket dimensions, removal of ISO 4009 references, and corrections to Figure 2.
A: Revised socket dimensions, removal of ISO 4009 references, and corrections to Figure 2.
