Automotive starter brushes are pieces of contacts that pass battery current to the commutator of a starter motor. They are also called carbon brushes, mainly because they have always contained carbon as the main material.

A car starter motor can have between two and four brushes. These are often divided into two sets, with one set connecting to the battery’s negative terminal and the other ground. Four-brushes is the most common configuration, and what your car could be using.

Brush holders feature different designs, which also affect the working of the brushes. Some come with a swiveling arm, while others are housings that brushes slide into. We will see the impact of these holders later. First, a look at the materials used to make the brushes.

Starter brushes are usually carbon to which ground copper has been added. That is why you hear them called starter motor carbon brushes. The addition of copper enhances electrical conductivity, improving their efficiency. It also decreases the rate of wear and extends the lifespan of the brushes.