#BDR Ballast resistors generally

This post/entry is summarised here:

If a ballast resistor is installed in the circuit to the battery instead of the ignition circuit, it is serving a different purpose. To clarify the roles and placements of different types of resistors in automotive electrical systems read on:

### Ballast Resistor in Ignition Circuit:

1. **Purpose**: Manage voltage to the ignition coil.

2. **Placement**: Between the ignition switch and the ignition coil in the ignition circuit.

3. **Function**: Reduces voltage to the ignition coil during normal operation to prevent overheating, and allows full voltage during starting for a stronger spark.

### Resistor in Battery Circuit:

1. **Purpose**: Could serve various functions depending on its specific application within the battery circuit.

2. **Common Uses**:

   - **Voltage Regulation**: To manage and stabilise voltage supplied to various electrical components.

   - **Current Limiting**: To limit the current flow to protect sensitive components from high current spikes.

   - **Load Distribution**: To balance the electrical load across different circuits.

### Potential Different Uses:

1. **Voltage Regulator Circuit**:

   - **Purpose**: To ensure a stable voltage supply to sensitive electronic components.

   - **Placement**: In series with the battery supply to the component needing regulated voltage.

2. **Current Limiting Resistor**:

   - **Purpose**: To limit the amount of current that can flow into a circuit or component.

   - **Placement**: In series with the battery or power supply line to the component.

3. **Load Resistor**:

   - **Purpose**: To simulate a load in the circuit for testing or to ensure proper operation of certain components.

   - **Placement**: Parallel to the component or circuit where the load is required.

### Conclusion:

While a ballast resistor in the ignition circuit specifically manages the voltage to the ignition coil, a resistor installed in the battery circuit could serve a variety of purposes depending on the specific application. These purposes include voltage regulation, current limiting, and load distribution, and their placement would differ based on their intended function.

### Important Points:

- **Ballast Resistor for Ignition**: Always placed in the ignition circuit between the ignition switch and coil. But see in the comments below about the starting circuit NOT going via the ballast resistor, for starting it supplies 12v direct without going via the ballast resistor. 

- **Other Resistors in Battery Circuit**: Serve different roles such as voltage regulation or current limiting, and are placed accordingly in the electrical system, commonly as in my car to stop the alternator hitting the main circuits with excessive charge.

 

#BDR Ballast resistor in the ignition circuit

A ballast resistor is an electrical component used in some ignition systems to help manage the voltage supplied to the ignition coil, thereby optimising the performance of the spark plugs during engine starting and running. Here’s a detailed explanation of how a ballast resistor functions and why it is used:

### Purpose and Function of a Ballast Resistor:

1. **Voltage Management**:

   - **During Normal Operation**: The ballast resistor reduces the voltage that reaches the ignition coil when the engine is running normally. This helps prevent the coil from overheating and extends its lifespan.

   - **During Starting**: When the engine is cranking, the ballast resistor is bypassed, allowing the full battery voltage to reach the ignition coil. This provides a stronger spark to the spark plugs, which is particularly important for starting the engine.

### How It Works:

1. **Normal Running Condition**:

   - When the engine is running, the electrical system typically operates at around 12-14 volts. The ballast resistor is connected in series with the ignition coil, reducing the voltage that the coil receives to around 6-9 volts.

   - This reduced voltage is sufficient to produce a strong enough spark for normal engine operation while protecting the coil from excessive heat and prolonging its life.

2. **Starting Condition**:

   - During engine start-up, the starter motor draws a significant amount of current, which can cause a temporary drop in battery voltage.

   - To ensure a strong spark during this critical time, a bypass circuit is often used. This circuit bypasses the ballast resistor, allowing the full battery voltage (which might be around 10-12 volts during cranking) to be supplied directly to the ignition coil.

   - The higher voltage increases the coil's output, producing a more powerful spark at the spark plugs, which helps to ignite the fuel-air mixture more effectively, making it easier to start the engine.

### Benefits:

1. **Enhanced Starting Performance**:

   - By bypassing the ballast resistor during starting, the ignition system provides a stronger spark, which is especially helpful in cold conditions or with a cold engine, where starting might otherwise be more difficult.

2. **Protection and Longevity**:

   - During normal operation, the ballast resistor reduces the voltage to the ignition coil, preventing overheating and premature failure. This ensures that the coil operates within its optimal voltage range and lasts longer.

### Typical Setup:

- **Ballast Resistor**: A resistor connected in series with the ignition coil.

- **Bypass Circuit**: Often implemented using a relay or an extra terminal on the starter solenoid that temporarily bypasses the ballast resistor during engine start-up.

### Example:

In a typical ignition system with a ballast resistor:

- When the ignition key is turned to the "start" position, a bypass circuit activates, sending full battery voltage to the ignition coil.

- Once the engine starts and the key is released to the "run" position, the ballast resistor comes back into play, reducing the voltage to the coil to its normal operating level.

### Conclusion:

A ballast resistor is a crucial component in some ignition systems that helps balance the need for high voltage during starting with the need to protect the ignition coil during normal operation. By reducing the voltage during normal running conditions, it extends the life of the coil, and by allowing full voltage during starting, it ensures a strong spark for easier engine ignition.

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Personally I am still trying to understand how reducing the voltage gets a stronger spark. See below in the comments where it is explained to me.

Here's a ballast resistor in the main battery cutoff circuit

and here's one included in the sale supply of a new coil designed to be used with a ballast resistor: