Starter Brushes Supplier

Starter brushes are small components used in brushed starter motors. Although tiny, they play a crucial role in the working of the motors, and therefore, entire starting system. They brushes are also among the most replaced parts due to their rapid rate of wear. Read about starter motor brushes in this guide; their use, material composition, operation parameters, and other information.

What are Starter Brushes?

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.

Starter brushes are usually located on or near the motor’s endplate, housed in brush holders. One end slides freely on the commutator, with tension springs pressing the brush block against the commutator. This serves to ensure constant contact between the two components.

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.

Car starter brushes also come in a wide range of sizes and shapes. One of the most popular shape is the square block, although different designs suit different requirements. Design usually determines a brush’s seating on the commutator and can affect its performance.

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.

What are Starter Brushes Made of?

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.

There are several grades of starter carbon brushes based on material composition. Each grade offers specific advantages and may be preferred for certain applications or conditions. Usually, the grade determines the rate of wear, surface film quality, ability to stand up to vibrations or damage, and more.

As already indicated, the brushes of most starter motors contain copper and carbon. This material grade goes by the name metal carbon. Other major grades are electro graphitic, resin bonded, carbon graphitic, and soft graphite.

A typical copper carbon starter brush is made by mixing natural or synthetic graphite with powdered copper and resin. The mixture produces dense brushes that can operate with high-current circuits. The brushes are also low-friction and low-noise with excellent electrical conductivity.

Starter Motor Brushes Function

What do starter brushes do? To put it simply, the brushes in a starter motor transfer the battery’s current to the segments on the commutator. The commutator, in turn, supplies the current to the armature coils, generating magnetic fields and causing rotation.

Most starters have two or four brushes. When two brushes are used, one connects to the negative lead of the battery. The battery connected brush is also adequately insulated to prevent a leak of electricity. The other brush does not have insulation but makes contact with the motor housing to provide ground and complete the circuit.

With the four starter motor brush set, the same arrangement applies. The only difference is that two brushes connect to the battery’s negative and the other set positive or ground. This allows the brushes to transmit current to the commutator and reverse it as the commutator rotates.

As long as there is a supply of voltage to the starter motor, the brushes continue to convey current to the coils and the armature turns nonstop. But the operating conditions must be favorable for that to happen, as we will see next.

Starter Brushes Operational Requirements

To perform at their optimum, the brushes in starter motor applications require certain conditions. The parameters to explain these conditions can be divided into three categories; mechanical, electrical, and physical. Next is a description of each.

Electrical Requirements

These point to the ability of the starter carbon brushes to conduct electricity, and which can be affected by certain conditions. The electrical parameters for proper starter brush operation include:

Resistivity– This is the ohmic resistance by the brush and its circuit to current flow. Usually, high resistivity improves brush performance by preventing arcing and other problems. Brush design often determines the resistivity and the quality of the film between the commutator and brush surface. The grade, too.

Current distribution- A starter brush transmits current through points on its surface. In the ideal situation, the distribution of these spots is uniform. External factors such as uneven brush pressure, temperature, dust, and even wrong brush grade can disrupt the uniformity. Such occurrences cause brush performance issues.

Voltage drop- The voltage drop should be low enough for the brushes to achieve optimum performance. If too high, overheating occurs. The brush and commutator could also get damaged. Voltage drop is affected by several factors such as brush grade, surface film quality, and operating conditions. Everything should be within limits.

Mechanical Requirements

These refer to conditions when the motor is in rotation. They also involve the commutator since the two components maintain contact throughout. The main ones include:

Surface Condition- When the motor is spinning, a film of copper and humidity forms on the commutator surface. Carbon or graphite dust from the brushes also settles on the commutator. This film helps to reduce friction and heat, protecting the brushes from excessive wear and damage.

But the film must be within limits for the described conditions. If too thick, current transmission drops and friction increases. The same case happens if the film is too thin. To produce the ideal film, the commutator surface must not be too smooth or too rough. The mica undercuts on the commutator must also be right.

More importantly, the brush grade should be the right material. Low quality starter brushes cannot achieve a quality surface film They are often the reason for the rapid wear, chipping, and other forms of damage.

Brush vibrations- It’s inevitable for starter brushes to experience vibrations caused by damaged or worn motor parts such as bearings and gears. That can cause damage or even improper brush operation. With the right design, though, starter motor brushes can be made to withstand vibrations. Fixing broken motor parts also helps to reduce vibrations and damage.

Brush pressure- As we saw earlier, the brushes of a starter motor are always under spring tension. The pressure must not exceed certain limits or reduce too much. It should also be uniform across all brushes to ensure proper seating of the brushes on the commutator. For that, the brush design and size should be right. The springs should also be intact at all times.

Coefficient Friction- The friction caused by the starter brushes should be low enough for different conditions such as speed, commutator surface, and load. This is to avoid overheating and premature damage to both the commutator and brushes. Coefficient friction is usually determined by the brush quality, which is why you should always go for the right material and brush grade.

Brush holder height and clearance- Both must be ideal to allow proper brush operation. Insufficient clearance and wrong height can lead to problems such as the starter brush sticking in the holder or brush noise when the motor is spinning.

Physical Requirements

Physical requirements are environmental conditions that affect the operational tendencies of starter brushes. They are mostly caused by external materials. The main ones are:

Corrosive gases- Corrosive vapors can cause damage to the commutator surface, and therefore, the brushes. Examples include sulfur dioxide, ammonia, and other gases. The vapors can affect the essential film that develops on the commutator when the motor is in operation. This leads to excessive friction and overheating, among other problems.

Liquids- These cause brush contamination and reduce performance. They are often responsible for problems such as sticking starter brushes and commutator damage. Main contaminants include oil from leaking bearings and water from condensed air. Keeping the liquids off the brush and commutator assembly would prolong brush life.

Humidity– It forms part of the film that occurs between the commutator and brush to reduce friction and overheating. In its absence, the film mostly comprises abrasive metal oxides. The situation results in rapid brush wear and reduced lifespan. Ensuring proper electrical conductivity and mica undercutting on the commutator can help maintain the film.

Dust- A buildup of dust can harm car starter brushes. Dust increases the wear rate and can even cause grooves to form on the brush surface. This affects the effectiveness of the brush’s to transmit current besides reducing the lifespan. Conductive dust can also cause electrical flashover and surface wear.

The starter brush’s operating parameters explained here are necessary for proper working or the motor. The ideal conditions also help to extend the lifespan of the brushes, reducing maintenance costs. Before concluding this guide, here are answers to questions you might stil have about the components.

Car Starter Brushes FAQs

Automotive starter brushes are often little known, partly because they operate hidden inside the motor. We answered the most popular questions about them.

Q1. What is the average lifespan of car starter brushes

A. It depends on many factors such as the type and grade of material used to make them, their quality, design, and how frequently a car is started. Also, the load and operating conditions. Starter brushes tend to wear quickly than many other components, though. You should expect about 2000 to 5000 hours on average for metal graphite brushes.

Q2. What are starter brushes symptoms that show damage or wear?

A. They are many. Generally, the signs of bad starter brushes include reduced power or torque, excessive sparking or arcing, and total motor failure. Worn starter brushes cannot conduct current properly, while broken ones may not even contact the commutator. When you suspect damage, it’s advisable to have the brushes checked, or do it yourself.

Q3. What causes starter motor brushes to go bad?

A. Many factors can result in the failure of these components. Common reasons include constant heavy sparking, frictional wear, impurities, chipped surfaces or broken brushes, and burned wires. Wear and breakage may result from excessive mica or surface spots, stripped surface film, unequal brush pressure, and electrical problems.

Q4. Can you repair starter brushes?

A. Fixing starter brushes usually involves changing them. You can easily do that using a repair kit. These come with replaceable parts, including the springs and wires. Starter brushes repair kits are inexpensive and usually available in most auto parts stores. You could also take your car to a mechanic to get everything done professionally.

Q5. How can you increase the lifespan of starter brushes?

A. By ensuring conditions that lead to damage such as compromising the commutator film, neglecting worn parts that cause vibrations, or allowing impurities such as oil to get near the brushes. During installation and after, proper seating of the brushes on the commutator and in their housings.

Q6. When should you replace the brushes in a starter motor?

A. Consider changing them when the time is due based on their expected lifespan. The best time is always before symptoms begin to appear. This is when damage has not occurred on the brushes, commutator, or any other part of the motor. If you notice damaged or worn starter brush symptoms, replacement should be immediate.

Q7. Can you replace the starter brushes yourself?

A. Replacing starter brushes should be easy, although it depends on the type of motor. Some manufacturers make the procedure effortless by designing motors whose brushes can be changed without disassembling the starter. Here is a short video showing how to replace starter brushes in a typical motor.

Q8. What does starter motor brushes replacement cost?

A. It’s difficult to quote a specific figure since different motors use different designs and the number of brushes. Still, some motors allow brushes to be changed easily than others. The cost of buying new brushes is usually less than $50. Labor charges too, which brings the total amount to less $100.

Q9. What is the starter brushes price?

A. There are many different starter brushes on sale today, which makes their prices to be different. Prices range from a few to over ten dollars. Many brushes on the market go for between $10 to $50. The cost depends on many factors such as quality and design. The different price tags set by the different starter brushes suppliers also contribute to the variations.

Conclusion

Starter engine brushes are essential parts of a vehicle’s starter motor. Often tucked away in the endplate, the components ensure the supply of current to the motor. Proper care of the brushes means a car that starts at the first attempt. That begins with understanding how the brushes operate, their material composition, and ideal operating conditions. This guide equips you with all that information.