Inside the Manual Service Disconnect (MSD): Delivering Safe, Custom Solutions for EV Power Systems

Published by Chief Enterprises on May 29th 2025

As electric vehicles become more prevalent in the market, the need for safe, high-voltage assemblies is more critical than ever. Manual Service Disconnects (MSDs) are a key safety feature in EVs, allowing for isolation of the high-voltage battery for ease of service. This blog explores what MSDs are, why they matter in electric vehicles, and how Chief is able to bring precision and customization to every MSD assembly.

What is a Manual Service Disconnect (MSD)?

The Manual Service Disconnect is a mechanical switch device utilized within battery packs or high-voltage distribution that enables safe disconnection of high-voltage circuits. Typically MSDs are designed with a touch-safe design, often located near the battery or power distribution system in a removable enclosure holding a high-voltage fuse. This allows service personnel to work safely on EVs during maintenance by isolating the battery power. These assemblies are commonly rated for systems up to 1000V DC, making them suitable for a wide range of electric vehicle and high-voltage mobility applications.

Why MSDs Are Critical in EVs:

Safety for Service and Emergency Personnel

MSDs prevent accidental energization during vehicle maintenance or collisions. This protects service technicians and first responders working near high-voltage systems.

Compliance with Global EV Safety Standards

Modern electric vehicles must meet stringent safety standards such as ISO 6469 and SAE J2929. MSDs play a critical role in achieving compliance with these regulatory frameworks.

Simplified Maintenance and Repair

By providing an easy and secure method for disconnecting the battery, MSDs enable faster diagnostics, smoother component replacements, and safety system testing.

Chief Enterprises’ MSD Assembly Process:

What Makes Chief’s MSD Assemblies Different

At Chief, every MSD is hand-assembled with precision and backed by engineering expertise. We offer both custom-designed boxes and modified off-the-shelf housings tailored to your specifications. This flexibility allows us to deliver solutions that meet the unique demands of any EV platform.

We also integrate high-performance Amphenol Sine connectors in combination with Amphenol Industrial PCD components to ensure superior reliability and compatibility.

Key Components in the Assembly

Each Chief MSD assembly includes:

MSD Housing and Connector: Configurable with options for venting, heat sinking, and custom mounting brackets.
High-Voltage Cabling: Available in custom lengths and terminations to suit specific design needs.
Protective Features: Includes labeling, heat shrink, sealing, and potting as needed to meet environmental and performance standards.

Quality Control and Testing

Every assembly undergoes rigorous testing and inspection processes:

Electrical continuity and insulation resistance checks
Visual inspections and torque verification
IP67 ingress protection and seal testing
Optional 100% testing available for mission-critical applications

Customization and Flexibility:

Built to Customer Specs

We design to your requirements, offering full enclosure customization and tailored component layouts. Cable lengths, gauges, and colors are adjustable based on your system’s needs, whether you're working with a single unit or complex harness integrations.

Rapid Prototyping Capabilities

Our process supports fast turnaround for development and validation builds, giving you the flexibility to iterate quickly.

Support for Low- to Mid-Volume Production

Chief is an ideal partner for emerging EV startups, specialty vehicle manufacturers, and fleet electrification programs. We scale with you.

Why Partner with Chief Enterprises:

Engineering Support

Our collaborative design process includes Design for Manufacturing (DFM) input and real-time troubleshooting to ensure your product is optimized for both performance and manufacturability.

Reliable Supply Chain

Through strategic partnerships with Amphenol Sine, TE Connectivity, and other industry leaders, we maintain a dependable flow of top-tier components.

U.S.-Based Assembly

All of our MSD assemblies are built and tested in the U.S., providing faster lead times, tighter quality control, and direct communication with our engineering and production teams.