How to Correctly Select a Sinofuse EV Fuse for a BMS System

By John Doe, Senior FAEPublished on: August 15, 2025

Selecting the main fuse for a Battery Management System (BMS) in an electric vehicle is one of the most critical safety decisions in the design process. An incorrectly chosen fuse can lead to either nuisance tripping or, far worse, a failure to protect the battery pack during a fault event. This guide will walk you through the key parameters to consider when selecting a fuse from the Sinofuse EV series.

1. The Importance of BMS Protection

The BMS is the brain of the battery pack, but the main fuse is its ultimate failsafe. It's the last line of defense against catastrophic short circuits that could lead to thermal runaway. The fuse must be robust enough to handle normal inrush currents and cycling, yet react instantaneously to dangerous fault currents.

2. Key Parameter Deep Dive

Rated Voltage

The fuse's DC voltage rating must be equal to or greater than the maximum system voltage of the battery pack. For an 800V battery system, you must choose a fuse rated for at least 800VDC, such as a model from the Sinofuse EV318 series.

Rated Current

This is not as simple as matching the fuse to the system's continuous current. You must apply derating factors for ambient temperature. For example, a fuse operating at 85°C may only carry 80% of its nominal rating. Always consult the temperature derating curve in the datasheet for a part like the EV315-M-4Q.

Breaking Capacity

The breaking capacity (or interrupting rating) must be higher than the maximum prospective short-circuit current of the system. A large battery pack can deliver tens of thousands of amps in a fault. A fuse with a 50kA breaking capacity is typically required.

I²t Value (Melting Integral)

This is crucial for coordination. The total clearing I²t of the fuse must be lower than the I²t withstand capability of the components it protects (like battery cells and contactors). This ensures the fuse opens before other components are damaged.

3. A Practical Selection Example

Let's consider an 800V/200A battery pack with a max short-circuit current of 30kA, operating in a 70°C ambient environment...