Embedded Systems and Design & Development - Feb 19, 2026 | Morning | VisionAstraa EV Academy

Battery Thermal Management System Development

Introduction to the Project

• The session focuses on developing a Battery Thermal Management System (BTMS) for a client project, including system design and functionality verification.

• The team will follow a structured process based on minimal specifications provided by the client to facilitate initial development.

Key Requirements of BTMS

• Temperature Range Maintenance: The primary requirement is to maintain battery cell temperatures between 15°C and 35°C, which is standard for most electric vehicle (EV) batteries. This range ensures optimal performance.

• Active Cooling Strategy: To achieve temperature control, convection methods will be employed, utilizing circulating coolant similar to refrigerator systems for effective heat dissipation.

• Safety Measures: If battery temperature exceeds 80°C, the system will isolate the battery from charging or discharging paths to prevent thermal runaway. This is crucial for safety management.

• Cold Weather Operation: In cold environments where temperatures drop below 5°C, a heater will activate to raise the battery pack temperature back to at least 15°C before vehicle operation begins.

Previous Discussions Recap

• A review of various temperature sensors was conducted in prior discussions, highlighting NTC thermistors as widely used options for accurate temperature measurement in BTMS applications. These sensors should be strategically placed within the battery pack for optimal readings.

• The importance of worst-case scenario design was emphasized; placing sensors centrally allows monitoring of maximum temperatures within the pack during operation. This approach aids in effective thermal management strategies.

Control Logic Implementation

• Temperature data collected from sensors will be processed through an Analog-to-Digital Converter (ADC), converting analog signals into digital values that inform control decisions regarding cooling and heating mechanisms within the BTMS framework.

• The microcontroller plays a pivotal role in executing protective features based on sensor data, ensuring that all operational requirements are met effectively while maintaining safety standards throughout vehicle use.

Battery Management Systems and Thermal Management

Conversion of Analog Voltage to Digital Data

• The analog voltage from the battery is converted into digital data for use in algorithms that make protective and controlled decisions.

• This conversion is essential for processing data collected during the operation of battery management systems (BMS).

Importance of Data Acquisition

• Data acquisition is a critical process in BMS, as it lays the foundation for further data processing and decision-making.

• After collecting data, the next step involves processing this information to take necessary actions regarding battery performance.

Optimal Battery Conditions

• Batteries must be maintained within optimal pressure and temperature ranges to ensure good performance and longevity. Operating outside these ranges can degrade performance and reduce lifespan.

• Preventing thermal runaway is crucial; isolation of the battery may be required under certain conditions to avoid dangerous situations.

Thermal Management System Layout

• A typical layout for a Battery Thermal Management System (BTMS) includes coolant tubes that transport coolant to dissipate heat from the battery pack effectively.

• Control over coolant flow rate is vital, which can be managed through a coolant compressor integrated into the system design.

Goldilocks Zone Concept

• The "Goldilocks zone" refers to an optimal operating range for batteries; temperatures too low can cause lithium plating, while high temperatures risk thermal runaway due to uncontrollable exothermic reactions. Understanding this concept is essential when designing BTMS.

System Structure Overview

• A clear pictorial representation of the BTMS structure helps teams visualize how components interact during discussions about system design. The microcontroller unit plays a central role in controlling operations based on sensor inputs.

Microcontroller Decision-Making Process

• The microcontroller's CPU makes decisions regarding motor speed based on temperature readings from sensors installed in the battery pack, ensuring effective cooling management by adjusting coolant circulation as needed.

Signal Conditioning Network

• Temperature data from sensors undergoes signal conditioning before being processed by an Analog-to-Digital Converter (ADC) within the microcontroller, which converts analog signals into digital format for further analysis and decision-making processes related to motor control speed adjustments based on temperature thresholds.

Cooling System Control and Motor Speed Management

Temperature-Based Coolant Circulation Strategy

• The motor can be kept off without circulating coolant if the temperature is at or below 15°C. If the battery warms up slightly, coolant circulation should increase as temperatures rise to 30-35°C.

• A higher flow rate of coolant is necessary for effective heat dissipation as the temperature increases. Specific motor speeds will be controlled based on these temperature ranges.

• Temperature thresholds are established:

• At 15°C, no coolant circulation is needed (motor off).

• At 20°C, start circulating coolant at a lower flow rate (20% speed).

• At 25°C, increase to 50% speed for more effective cooling.

• At temperatures around 35°C, run the motor at full speed for maximum cooling efficiency.

Power Electronic Converters and PWM Techniques

• To control motor speeds effectively, power electronic converters are required between the motor and microcontroller. These converters modulate power delivery in a controlled manner using Pulse Width Modulation (PWM).

• PWM techniques allow for precise control over the duration of electrical pulses sent to the motor:

• "On time" refers to when voltage is applied.

• "Off time" indicates when there is no voltage.

• Varying these durations adjusts power delivered to the motor.

Duty Cycle and Its Impact on Motor Control

• The duty cycle measures how long electrical pulses remain on versus off; it directly influences power output:

• A duty cycle of 25% means "on time" is one-fourth of total time.

• A duty cycle of 50% indicates equal "on" and "off" times.

• Higher duty cycles result in increased power delivery to the load.

• PWM signals can be generated by microcontrollers like Arduino Uno, which offers six pins for PWM signal output that can control power converters and motors effectively. This setup simplifies understanding DC motor operations within this context.

Battery Thermal Management System Design

Introduction to Battery Thermal Management

• The focus of the class is on designing a battery thermal management system, which aims to maintain battery temperature within permissible limits and address situations when temperatures exceed these levels.

Skills Required for EV Engineers

• EV engineers must be familiar with electrical, programming, and mechanical aspects. The course will progress slowly to align with students' existing syllabi.

Knowledge Transfer Process

• New employees undergo sessions for basic knowledge transfer in companies. This course aims to provide similar foundational knowledge, acknowledging that not all students may have the same background.

Motor Control Circuit Overview

DC Motor Assumption

• The discussion assumes the use of a DC motor for operating the compressor responsible for circulating coolant in the thermal management system.

Understanding MOSFET as a Switch

• A MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor) acts as a semiconductor switch controlled by electrical signals rather than mechanical means.

Switching Mechanism

• Positive voltage turns on the MOSFET (closing the switch), while zero or negative voltage turns it off (opening the switch). This mimics how mechanical switches operate but uses electrical pulses instead.

Circuit Configuration and Safety Measures

Circuit Diagram Explanation

• The circuit diagram includes a supply connected in series with both the motor and semiconductor switch, highlighting how PWM signals control switching actions.

Importance of Freewheeling Diode

• A freewheeling diode is essential for protecting the semiconductor switch from inductive kickback when using DC motors. It safely dissipates energy stored in magnetic fields when the switch is turned off.

Role of PWM Signals

• PWM (Pulse Width Modulation) signals generated by microcontrollers are crucial for controlling motor operation based on input parameters like temperature, ensuring efficient thermal management.

Understanding Coolant Circulation and PWM Control

Coolant Circulation Dynamics

• Minimal or no coolant circulation occurs at lower temperatures, while higher temperatures (around 30°C to 35°C) necessitate increased coolant flow, requiring the motor to operate at maximum speed.

• A 100% duty cycle is achieved by supplying full power to the motor, which is essential for effective PWM signal application in motor control circuits.

Motor Control Circuit Design

• The microcontroller generates a PWM signal that controls an N-channel MOSFET, regulating the power delivered to the motor based on temperature readings.

• Understanding the entire system perspective is crucial as it involves multiple processes: temperature sensing, ADC output processing, and decision-making for motor control.

Tinkercad Implementation Steps

• Transitioning to Tinkercad for circuit design begins with creating a new project and preparing to read temperature sensor values.

• The first step involves dragging and dropping a microcontroller board into the design workspace.

Temperature Sensor Integration

• A black IC package representing a temperature sensor should be added; this follows a bottom-to-top design hierarchy where overall specifications are broken down into individual tasks.

• Each team member will handle specific subtasks that contribute towards building a complete Battery Thermal Management System (BTMS).

Wiring Connections and Code Development

• Connecting the temperature sensor requires establishing VCC (power), ground connections, and linking analog outputs appropriately for accurate readings.

• The code development phase focuses on reading analog values from the sensor; initial steps include configuring pins as inputs and displaying these values via serial monitor.

ADC Configuration and Testing

Initializing ADC and Reading Values

• The ADC is initialized with zero, although initialization isn't strictly necessary. The setup function configures the ADC pin (pin number three), which can be represented directly or via a variable.

• A function to read analog data is introduced, allowing users to utilize available code from the internet. The read value is assigned to a variable for further processing.

• Data is sent to the serial port using the Serial Print function, requiring initialization of serial communication at a baud rate of 9600, which determines data transmission speed.

Simulation and Value Observation

• During simulation, moving a slider bar representing temperature allows observation of printed values on screen. Case sensitivity in coding must be maintained to avoid errors.

• Initial readings may show garbage values due to potential mismatches in pin configuration; troubleshooting involves checking sample codes online or example sections.

Understanding Temperature Sensor Characteristics

• Important hardware information such as datasheets and command sets should be noted before programming. The temperature sensor's range is -40°C to 125°C, crucial for accurate program development.

• As the slider moves from left (-40°C) to right (125°C), corresponding changes in ADC values are observed, indicating proper functionality of the sensor.

Verification with Multimeter

• A multimeter will be used alongside software readings to verify voltage outputs against expected digital data from the ADC. This ensures that digital outputs correlate proportionally with analog inputs.

• Observations indicate that varying voltages yield different digital readings; this confirms that both hardware and software are functioning correctly during debugging processes.

Motor Control Using PWM Technique

Adding Motor Components

• After testing input sensors, focus shifts towards controlling motor speed using PWM techniques by integrating a DC motor into the design.

• Users are guided through adding components like a DC motor while referencing circuit diagrams for correct connections between motors and microcontrollers.

This structured approach provides clarity on key concepts discussed in the transcript while ensuring easy navigation through timestamps for further exploration of specific topics.

Powering and Controlling a Motor

Selecting the Power Source

• The motor requires a power source, which is selected based on its voltage requirement. A 9V battery is chosen for simulation purposes to check the logic of the circuit.

Initial Motor Connection

• Directly connecting the motor to the 9V battery will cause it to rotate immediately, but speed control is desired. Therefore, controlling the power delivered to the motor is necessary.

Wiring Setup

• The circuit involves connecting the motor in series with a switch and linking it to a microcontroller's PWM pin for speed control. The wiring starts from the control terminal connected to one of six available PWM pins on an UNO microcontroller board, specifically pin number three.

Motor Polarity and Connections

• The positive terminal of the DC motor connects with a red wire; reversing polarity will change its rotation direction. The drain terminal connects to the motor while ensuring that connections are made correctly according to circuit diagrams.

Adding Protective Components

• A diode must be added in an antiparallel configuration for safeguarding against back EMF generated by the motor when switched off. Proper orientation of this diode is crucial for effective protection of components in the circuit.

Testing PWM Logic

• Focus shifts towards testing whether PWM logic can effectively control motor speed after completing wiring connections. Code will be shared later for implementation within Tinkercad simulations, allowing users to copy-paste into their systems for testing functionality.

Code Configuration Details

• The code involves configuring pin number three as a PWM output pin and writing values ranging from 0 (off) to 255 (full speed). This range allows adjustment of duty cycles from 0% to 100%. Users are instructed on how to retrieve this code using an online platform without needing email attachments or additional setups.

Accessing Shared Code

• Instructions are provided on accessing shared code via qext.in by entering specific retrieval codes, facilitating collaboration among team members working on similar projects or designs involving different analog pins or configurations as needed. Users should ensure they adapt any modifications accordingly in their designs before running simulations successfully.

Final Steps Before Simulation

• After retrieving and pasting code into Tinkercad’s text block, users can start simulations where they should observe expected behavior—namely, that motors begin rotating as intended based on configured settings and inputs provided through PWM signals from microcontrollers used in their designs.

Accessing Shared Content

Retrieving the Code

• A code is provided for accessing shared content: "RQPBg". Users must enter this code in the designated field to retrieve the relevant materials.

• Once the code is entered, users should be able to access and utilize the content within Tinkercad.

Demonstration of Circuit Issues

Current Challenges

• The speaker mentions issues with a motor element in their circuit demo, indicating that voltage generation is not functioning as expected.

• Despite varying duty cycles (from 125 to 255), there are still problems with voltage output, which will be addressed later in the day.

Characterizing Temperature Sensors

Steps for Compatibility

• The next step involves making two sides compatible by controlling motor speed based on temperature sensor values.

• A plot will be created with temperature on one axis and sensor response on another to characterize the temperature sensor effectively.

Plotting Sensor Data

Graphical Representation

• The relationship between temperature (x-axis) and voltage from the temperature sensor (y-axis) needs to be established.

• For a chosen sensor, temperatures range from -40°C to +125°C, correlating with specific voltage outputs: 100 mV at -40°C and 1.75 V at +125°C.

Establishing Linear Relationships

Formulating Equations

• A linear relationship between voltage and temperature will be assumed based on experimental data or datasheet information.

• If datasheet information is unavailable, experiments must be conducted across various temperatures to gather corresponding voltage values for plotting.

Calculating Slope and Offset

Finding Key Parameters

• The equation of a straight line y = mx + c will include an offset value c .

• To find slope m , use dy/dx method over the entire range of temperatures and voltages collected during experiments.

Finalizing Equation Components

Completing Calculations

• With known parameters y_2 , x_2 , and slope m , calculate offset c .

• This finalizes the equation needed for further calculations regarding voltage outputs based on temperature readings.

Understanding ADC and Temperature Measurement

ADC Value and Temperature Calculation

• The temperature can be deduced from the Analog-to-Digital Converter (ADC) output, with a specific equation: y = 0.01x + 5 .

• The ADC provides a 10-bit digital value that represents the temperature, which is crucial for further calculations.

• A relationship must be established between the binary value read from the ADC register and its corresponding voltage range to accurately determine temperature.

Voltage and Digital Value Relationship

• The relationship characterizes the full voltage range of the ADC input (0 to 5 volts) against its digital count values (0 to 1023).

• This relationship results in a conversion factor of approximately 204.6 counts per volt, essential for programming logic related to temperature measurement.

Coding Logic Implementation

• With all necessary relationships defined, coding logic will involve reading temperature sensor values and controlling an LED as part of initial testing.

• After validating basic functionality, this logic will be integrated with motor control systems in future sessions.

Project Management Insights

Project Development Process

• The project development process involves client specifications being relayed through HR to project managers who assign tasks based on high-level parameters.

• Individual teams develop their assigned tasks, which are later integrated into a final system delivery.

Circuit Design Considerations

• Suggestions regarding circuit design are discussed; modifications may be made based on team feedback for optimal performance.

Embedded Controller Design Aspects

Battery Management Systems Overview

• Discussion focuses on embedded controller design aspects relevant to electric vehicles, particularly battery management systems used for charging and discharging control.

Data Collection in Battery Management

• Key parameters monitored include current, voltage, and temperature; various methods for measuring these parameters were explored in previous classes.

Future Discussions on Charging Methods

• Upcoming sessions will cover different charging methods such as constant current/voltage and float voltage control techniques.