Hybrid Electric Vehicle Training Educator

Service Disconnect Switch


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The service disconnect (SD) makes or breaks an internal connection inside the high-voltage battery. When the SD is removed, the internal connection is lost, and the high-voltage battery is isolated from the rest of the vehicle. When the SD is safely removed – following all safety procedures and manufacturer requirements – the battery system is rendered safe. Note to first responders: never cut into the battery assembly. Even if it is rendered safe externally, the battery still has stored charge.

The service disconnect (SD) has a fuse that is part of the device. If current leaving or entering the battery exceeds the fuses' threshold, the fuse will fail opening the circuit. The vehicle will not operate if the SD is removed or the fuse is blown. The internal connection within the high-voltage battery is connected to both sides of the SD. See figure below.

Service Disconnect Switch Diagram

The service plug grip is part of the SD. Notice the internal connection in the above figure.

© 2012 National Alternative Fuels Training Consortium.

Service Disconnect Switch

Service Disconnect Switch