MSD Connector

Exploring MSD Connectors: Versatility Unleashed

What is the MSD connector?

The full English name of MSD: Manual Service Disconnect; the Chinese name: 手动维护开关.

The Manual Service Disconnect is a manual maintenance protection switch with a high voltage interlock function for use in the high voltage or battery box of an electric vehicle. It is a tool-less solution for disconnecting and preventing short-circuiting of the internal high-voltage battery pack.

MSDs are typically located on the exterior of a building and are used by utility crews to disconnect the building’s electrical service during emergencies or scheduled maintenance. The switches are manually operated and designed to be easy to identify and use.


The main function of MSD: to protect the safety of technicians repairing electric vehicles in high-voltage environments or to respond to emergencies. It can quickly separate the connection of high-voltage circuits, making maintenance and other work in a safer state. Such as external short circuit protection, the high voltage needs to be disconnected during maintenance.

MSD needs to meet the functions

Meet fire resistance rating. Except for fuse, the materials of MSD are all plastic. It must be ensured that the material of MSD meets the fire resistance level of UL94 V0.

Meet IP rating. The MSD is generally installed on the box cover. In order to ensure that the Pack meets IP67 or IP6k9k, the MSD itself must meet IP67 and IP6k9k. When selecting MSD, this needs to be considered as a basic parameter, and the supplier is required to provide relevant verification reports.

Meet IP protection. When MSD is connected, it must ensure that IPXXD and meets IPXXB when disconnected.

Can be disconnected manually directly. The design of the MSD must ensure that manual disconnection can be achieved without any tools, and the number of such disconnections must be at least 50 times.

Key features:

  • Allows manual disconnection of power for safety during maintenance
  • Can be manually operated to open, lock, and ground circuits
  • Prevents accidental re-energization while servicing equipment
  • Provides visible disconnection and lockout capability

Why must MSDs be sealed?

A manual disconnect is often referred to as the fourth safety device on a high voltage battery pack. This device is used to disconnect the electrical continuity within the battery pack so that the vehicle can be serviced. The MSD is usually a removable touch-safe enclosure that contains a fuse.

The MSD cannot be removed while current is flowing in the battery pack; the contactor must be opened before the MSD can be removed. Removing the MSD helps to service the vehicle’s high voltage system because the positive and negative battery pack connections are no longer electrically connected.

An important point is that MSDs must be protected from environmental contamination such as water, dust, chemicals, oil ……In this case, there is no better choice than a reliable sealant.


  1. Industrial Machinery and Equipment – Widely used in large-scale industrial machinery and equipment, such as petrochemical equipment, wind power equipment, machine tools, etc., to facilitate the maintenance personnel to carry out safe power failure.
  2. Electrical Switching System – Used on switchgear in power plants, substations, distribution rooms and other power systems to provide safe power isolation for operators.
  3. Medical Electrical Equipment – Used in various types of medical electrical equipment such as medical imaging, surgical equipment, etc. To ensure electrical safety during equipment maintenance.
  4. Industrial Automation Systems – Used in industrial field automation systems, industrial robots and other equipment to provide lockout isolation for maintenance.

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