Embedded Systems and Design & Development - Feb 13, 2026 | Afternoon | VisionAstraa EV Academy

Battery Management Systems Overview

Introduction to Battery Management Systems (BMS)

• The session begins with a reminder about the types of Battery Management Systems (BMS) discussed earlier, specifically focusing on practical combinations like 14S, 13S, 16S, and 20S.

Understanding Voltage Implications

• It is highlighted that for a 14S BMS rated at 48 volts, the battery may not fully charge, leading to underutilization of the battery pack.

Vehicle Setup and Integration

• Discussion shifts to vehicle setup and harness integration. A specific harness was noted as being damaged ("rat bitten"), which could affect performance.

Practical Application: Ola Battery Pack Specifications

• The speaker introduces an Ola battery pack for practical demonstration. Participants are encouraged to read and understand its specifications.

Key Specifications of the Ola Battery Pack

• The Ola battery pack is identified as a 4 kWh unit. Participants are prompted to calculate its series rating based on provided data.

Series Rating Calculation

• The minimum voltage of the battery pack is stated as 35 volts, while the maximum voltage is noted at 58.8 volts with a nominal capacity of 76.8 Ah.

Total Number of Cells Calculation

• Attendees are tasked with calculating the total number of cells in the battery pack using given parameters such as per cell capacity (4 Ah).

NMC Battery Pack Insights

• The discussion confirms that this is an NMC (Nickel Manganese Cobalt) battery pack. Participants are asked again about the total number of cells.

Series Count Determination Process

• An explanation follows regarding how to determine the number of series in this configuration by dividing maximum voltage by full charge voltage (4.2V).

Final Calculations and Considerations

• Emphasis is placed on understanding that maximum voltage indicates full charge status; thus calculations should be based on this figure for accuracy.

Conclusion on Series Configuration

• After determining it’s a 14S configuration from previous calculations, participants are guided through finding out how many parallel connections exist within this setup based on total capacity divided by individual cell capacity.

This structured overview captures key discussions around BMS configurations and practical applications related to electric vehicle batteries while providing timestamps for easy reference back to specific parts of the transcript.

Battery Pack Specifications and Setup Overview

Understanding Battery Limits

• The maximum limit for the battery pack is 35; if it drops below this, the entire battery is considered dead and cannot be recharged. However, in some cases, if the voltage decreases slightly (e.g., to 2.7 or 2.8), there may still be a chance to recharge it.

Calculating Battery Configuration

• The age of the battery is calculated as 76 divided by 4 hours, resulting in approximately 19P (or 19.2P). This indicates a configuration of cells where S (series) multiplied by P (parallel) gives us a total of 266 cells in the setup.

Verifying Power Capacity

• To confirm that the battery pack's capacity is accurate, one must multiply its nominal voltage with its amp-hour rating (AH). In this case, an AH of 76.8 leads to a total energy output of approximately 3.97 kilowatt-hours, which rounds up to about 4 kW.

Output Connections and Communication

• The battery pack has two terminal outputs: negative and positive connections covered with BMS (Battery Management System). Additionally, CAN communication wires are integrated into the harness connecting these outputs to other components like the Vehicle Control Unit (VCU).

Component Integration and Functionality

• Power from the battery pack flows directly to the Motor Control Unit (MCU), which also connects to a charging system via a Type Six socket used in Ola vehicles. Wires from the MCU connect to motors and include Hall sensor wires essential for motor functionality. This integration allows for effective control over vehicle operations such as regenerative braking systems when brakes are applied.

Vehicle Power Transmission and Control System Overview

Starting the Vehicle

• The tail light activates when the vehicle is turned on. The process begins with pressing the brake to start the vehicle.

• Power transmission occurs from the battery pack to the Motor Control Unit (MCU), which responds based on throttle input.

Throttle Response and Motor Speed

• The throttle's resistance affects current flow; maximum resistance results in zero current and speed.

• Decreasing throttle resistance increases current flow, thereby increasing motor speed, demonstrating a direct relationship between throttle input and motor performance.

Regenerative Braking Mechanism

• When braking is applied, it interrupts power to the motor even if the throttle remains engaged, showcasing how braking impacts motor operation.

• Observations confirm that applying brakes stops the motor immediately due to MCU intervention, highlighting safety features in power management.

Instrumentation and Feedback Systems

• A display indicates motor speed based on hall sensor data; this feedback loop is crucial for real-time monitoring of vehicle performance.

• The MCU controls MOSFET switching frequency to regulate motor speed effectively, linking electrical control with mechanical output.

Component Identification

• Key components are identified: battery pack, MCU (Motor Control Unit), mid-drive motor, throttle, VCU (Vehicle Control Unit), display unit, indicators, headlights, horn, and tail lights.

• Tail lights serve as brake lights when brakes are applied; they consist of both brake light functionality and standard tail light features.

Vehicle Component Overview and Integration

Understanding Brake Lights and Indicators

• The brake light activates when the brake is pressed, along with the right and left indicators, collectively referred to as tail lights.

• A charging socket is also mentioned as a crucial component in vehicle systems.

Identifying Key Components

• The final component discussed is challenging to identify; further examples will be provided for clarity.

• Emphasis on the Battery Management System (BMS), which must be integrated within the vehicle or battery pack, not used externally. Without it, battery output cannot be utilized effectively.

Functionality of DCDC Converter

• The device converts input voltage from 48 to 72 volts down to 12 volts, essential for various vehicle functions. This device is known as a DCDC converter or chopper.

• It operates with a three-wire system where positive connects directly to the battery pack while negative serves both 12V and 60V systems. This setup includes a buck converter configuration.

Vehicle Assembly Insights

• Discussion on integrating components into a chassis reveals how various parts like headlights, VCU (Vehicle Control Unit), harnesses, MCUs (Microcontroller Units), motors, and charging sockets fit together in an assembled vehicle structure.

Mid Drive vs Hub Drive Setup

• Transitioning from mid-drive setups to hub drive setups highlights differences in design: hub drives eliminate additional chains or belts for movement since the motor itself rotates to propel the vehicle forward. This specific example references a TVS IQ model.

Hands-On Learning Experience

• Participants will have hands-on experience disassembling vehicles during offline sessions to understand component integration better and explore different types of MCUs based on current ratings and voltage specifications available in various models including Ola vehicles.

Efficiency Comparisons Between Motor Types

• Mid-drive motors are noted for their efficiency due to additional drive systems enhancing performance compared to hub drives which are easier to install but may lack efficiency benefits found in mid-drives due to their design constraints. Cost considerations also favor mid-drives despite higher initial expenses due to performance advantages over time.

Q&A Session Invitation

• An invitation for questions encourages participants to clarify any doubts regarding topics covered or request repetitions of complex subjects discussed throughout the session.

Why Do Batteries Catch Fire?

Understanding Battery Failures

• The discussion begins with the question of why batteries catch fire, particularly focusing on battery management system (BMS) failures as a primary cause.

• A BMS failure can lead to overcharging or over-discharging, creating an imbalance in the battery pack which increases the risk of fire.

• An example is given of a 14S battery pack where damage to one series can cause energy to convert into heat, potentially leading to an explosion.

Addressing Common Misconceptions

• The speaker addresses concerns about Ola scooters, emphasizing that issues are not unique to them but rather common across many vehicles due to their sales volume and social media attention.

• It is noted that while Ola scooters face scrutiny, similar problems exist in other brands and models, especially those from China.

The Role of ABS in Electric Vehicles

Innovations in EV Technology

• The integration of Anti-lock Braking System (ABS) technology into electric vehicles (EVs) is discussed as a new development.

• The reverse operation for motors is explained; switching polarity allows motors to run in reverse without additional mechanical components.

Understanding Motor Controllers

Basics of Motor Control Units (MCUs)

• The session transitions into discussing different types of controllers used in electric vehicles, specifically focusing on MCUs.

• Technical specifications such as working voltage (DC 60 volts), under-voltage (51.5 volts), and current limitations (35 amps) are highlighted for understanding controller capabilities.

Face Angle and Motor Windings

• The concept of face angle is introduced; it represents how motor windings are configured within a 360° rotation.

• With three windings present, each winding corresponds to a 120° segment of the motor's rotation.

Controller Specifications

Overview of Controller Components

• Details about input/output connections for the controller are provided, including sensor wires for throttle and brake systems.

• This basic controller design serves as an example commonly found in lower-end Chinese electric vehicle models.

Technical Specifications and Controller Comparisons

Overview of Technical Specifications

• The operating voltage for the discussed system is 72 volts, with a maximum rated current of 55 amps. The under-voltage threshold is set at 60 volts, which needs verification.

• Clarification is sought regarding the nominal voltage cutoff for a 72-volt battery pack, emphasizing the importance of confirming that the under-voltage specification is accurate.

Comparison Between Controllers

• A comparison highlights differences between two controllers: one operates at 60 volts while the other at 72 volts; their current ratings differ significantly (55 amps vs. 35 amps).

• Discussion on identifying specifications from a controller lacking detailed technical data; attempts to ascertain its rating through serial numbers are suggested.

Specific Controller Details

• Identification of a controller rated at 72 volts and 80 amps, with color coding provided for wiring connections (blue, green, yellow) along with battery positive and negative terminals.

• Introduction of a Bajaj Chet controller, noting its specific terminal connections and branding as part of the discussion on various controllers available in the market.

Additional Controllers and Their Specifications

• Another controller mentioned has specifications indicating it operates at 72 volts and 35 amps; it includes details about phase winding connections labeled as UVW (yellow-green-blue sequence).

• Reference to an Indian-manufactured controller by Sterling GTech Mobility, highlighting that no technical data is present on this unit without consulting its datasheet for operational details.

Transition to Offline Classes

• Announcement regarding transitioning from online to offline classes; future sessions will focus on hands-on training related to electric vehicle technology design and implementation. Students are encouraged to engage in real-world projects during offline sessions.

• Emphasis on project-based learning where students will work on designing new vehicles and diagnostic setups as part of their practical education experience in electric vehicle technology.

Introduction to Offline and Online Sessions

Overview of Learning Structure

• The session emphasizes the importance of real-world applications, distinguishing between offline and online learning experiences.

• Participants are encouraged to ask questions regarding the basics covered in the sessions.

Safety Measures for Beginners

• Non-working battery packs will be provided to participants to prevent damage during hands-on activities, acknowledging their lack of experience.

Tools and Resources for Learning

Laptop Recommendations

• Initially, laptops are not recommended; however, they become essential later for design tasks.

Internship Diary Guidelines

• Participants should document their learnings about controllers and vehicle integration in an internship diary.

Feedback and Communication

Contacting the Instructor

• Students can reach out via LinkedIn for any doubts or further learning opportunities related to battery technology.

Importance of Feedback

• The instructor seeks feedback on the basic sessions conducted, emphasizing a two-way effort in achieving learning goals.

Closing Remarks

Invitation to Offline Sessions

• Participants are welcomed to upcoming offline sessions at specific locations, encouraging personal interaction and feedback sharing.

Incentives for Feedback Submission

• Genuine feedback on LinkedIn will result in receiving additional resources such as presentations or documents related to the course content.