Embedded Systems and Design & Development - Feb 4, 2026 | Afternoon | VisionAstraa EV Academy

Introduction to Battery Management Systems

Overview of BMS Basics

• The session begins with a confirmation of audio clarity and an introduction to the basics of Battery Management Systems (BMS).

• Discussion on series (S) and parallel (P) combinations in battery configurations, emphasizing their importance in understanding BMS functionality.

• Explanation of key parameters such as nominal voltage, full charge voltage, and cutoff voltage, which are crucial for battery management.

Understanding BMS Functionality

• Clarification that a BMS manages battery operations by closing circuits under certain conditions; errors lead to open circuit scenarios.

• Differentiation between smart BMS and normal BMS: Smart BMS provides detailed data about battery status while normal BMS acts merely as a protective device.

Exploring Examples of Battery Packs

Verification Process

• The speaker emphasizes the need for practical examples to verify the health of battery packs using various criteria.

• Introduction of a second example involving a 16-series NMC battery pack, setting the stage for further analysis.

Criteria for Healthy Battery Packs

• First condition checks if total voltage aligns with expected values; for 16S NMC batteries, full charge is 67.2V and lower cutoff is 48V.

• Confirmation that the first condition is satisfied indicates that the battery is healthy based on its operating voltage range.

Detailed Voltage Analysis

Maximum and Minimum Voltage Checks

• Second condition assesses maximum cell voltage; it should not exceed 4.2V for NMC cells.

• Third condition examines minimum cell voltage requirements; it must be at least 3 volts to avoid triggering an open circuit in the BMS.

Implications of Voltage Conditions

• If minimum voltage falls below acceptable levels (e.g., around 2.4V), the system will enter an open circuit state to protect against damage.

This structured approach captures essential insights from the transcript while providing clear navigation through timestamps for easy reference.

What is the Maximum Acceptable Difference Voltage?

Understanding Voltage Differences and Faults

• The maximum acceptable difference voltage is 0.009, while the observed difference voltage is 0.739, indicating a significant issue with almost 700 millivolts of discrepancy. This can lead to the Battery Management System (BMS) becoming an open circuit.

• Two types of faults are identified: one related to minimum voltage being below required levels and another concerning excessive difference voltage. The BMS will disconnect to protect the battery under these conditions.

Analyzing Cell Voltages

• A review of cell voltages shows most cells at around 3.1 volts, but notable discrepancies exist in the third and tenth series, with values of 2.469 volts and 3.208 volts respectively, leading to BMS intervention for protection.

• To restore functionality after BMS intervention due to low voltage in one series, cell balancing must be performed as a corrective measure for maintaining battery health.

What is Cell Balancing?

Troubleshooting Battery Packs

• Cell balancing addresses issues arising from discharge or physical/chemical problems within cells; troubleshooting methods will be discussed further in relation to battery pack errors and rectification strategies.

• The major error identified involves a specific series having significantly lower voltage compared to others; examples will illustrate how this impacts overall battery performance before moving on to cell balancing techniques.

Identifying Errors in a Battery Pack

• In examining a faulty 14S NMC battery pack, multiple errors are noted: total operating voltage falls below acceptable limits (42V - 58V), with some cells showing zero voltage which constitutes critical failures that need addressing through troubleshooting methods outlined later on.

• Key errors include:

• Total pack voltage being less than rated.

• Minimum individual cell voltages dropping below acceptable thresholds.

• Significant differences between cell voltages exceeding acceptable limits (maximum allowable difference is 0.009).

Examples of Healthy vs Unhealthy Battery Packs

Evaluating Battery Conditions

• Three examples highlight varying states of battery health:

• A healthy pack where BMS remains closed.

• An unhealthy pack with some remaining charge.

• A completely dead series requiring thorough troubleshooting for potential recovery options before proceeding further into repair methodologies for each scenario presented thus far.

Battery Pack Design and Troubleshooting

Identifying Errors in Battery Voltage

• The discussion begins with an example of a battery pack showing zero voltage across the entire series, indicating a significant error.

• A new example is introduced where the minimum voltage drops below 3 volts, and the difference voltage is approximately 0.545 instead of the expected 0.009, highlighting issues that need troubleshooting.

Designing a Battery Pack

• Before troubleshooting, there’s a proposal to design a practical battery pack on the board to understand connections better.

• The initial design discussed is for a smaller battery pack rated at 48 volts and 20 AH (Amp Hours), emphasizing manual involvement in the design process.

Calculating Series and Parallel Configurations

• The configuration involves using NMC cells rated at 5 AH each to achieve the desired specifications of 48 volts and 20 AH.

• Participants suggest configurations of 13S (series) and 14P (parallel), which will be verified through actual design calculations.

Finalizing Design Parameters

• The correct configuration determined is indeed 13S4P, totaling to 52 cells needed for this setup.

• To calculate series connections: textSeries = 48V/3.7V approx 13S . For parallel connections: P = 20AH/5AH = 4P .

Building the Battery Pack

• The total number of cells required is confirmed as 13 times 4 = 52.

• Emphasis on starting with parallel packs first; four cells are connected in parallel to form one unit.

Understanding Parallel Connections

• In parallel configurations, all positive terminals are joined together while maintaining polarity consistency.

• With four cells connected in parallel, the resulting output voltage remains at approximately four volts while maintaining an overall capacity of twenty AH.

Completing Series Connections

• Two separate packs are created by connecting them in such a way that they can later be combined into series configurations for increased voltage output.

Battery Pack Design and Series-Parallel Connections

Understanding Series Connections

• The speaker explains the process of connecting a negative terminal to a positive terminal, emphasizing that this forms a series combination of battery packs.

• A multimeter is used to measure voltage across terminals, resulting in an output of 8 volts while maintaining the same amp-hour (Ah) rating since no cells are added in parallel.

Adding Parallel Packs

• The speaker discusses adding another similar pack and describes how power flows from one battery's positive to another's negative terminal.

• Questions arise about where to connect the new pack—top or bottom—and the importance of maintaining proper flow direction in the circuit.

Voltage and Capacity Calculation

• After connecting additional batteries, the total voltage increases to approximately 12 volts with a capacity of 20 Ah due to series connections.

• The speaker confirms that by combining three parallel packs in series, they achieve a total output of 12 volts.

Circuit Verification

• A verification step checks if the circuit is correct; it confirms that power flows correctly through four parallel packs connected in series.

• The speaker outlines plans for making all necessary parallel connections and emphasizes joining negatives to positives for continuity.

Finalizing Series Count

• The discussion shifts towards counting how many series connections are needed; currently, there are 12 series identified.

• To reach a target configuration, an additional set of parallel packs will be created, leading up to 13 required series connections.

Designing for Specific Voltage and Capacity

• The connection from the last series indicates that they have achieved their desired configuration with sufficient voltage and capacity.

• Confirmation is made regarding cell count (52 cells), establishing a design specification of 13S4P (13 series, 4 parallel), targeting a final output of 48 volts at 20 Ah.

BMS Integration Discussion

• The conversation transitions into integrating Battery Management Systems (BMS), questioning whether further examples or designs should be explored.

BMS Integration in Circuit Design

Overview of BMS Integration

• The discussion begins with the integration of Battery Management System (BMS) into a circuit design, emphasizing its importance for understanding series and parallel combinations.

• A specific example is introduced using NMC (Nickel Manganese Cobalt) batteries, with parameters set at 60 volts and either 18 AH or 20 AH.

Calculating Series and Parallel Configurations

• The nominal voltage of the cells is identified as 3.7 volts, leading to a calculation that determines the required number of series connections (16S).

• The total number of cells needed for the configuration is calculated as 80 cells based on the series (16S) and parallel (5P) arrangement.

Design Types: Series vs. Parallel

• Two design approaches are discussed: starting with a parallel combination or a series combination; it’s suggested that beginning with parallel may be easier.

• The speaker decides to start with the series configuration, laying out how to connect 16 cells in series before adding parallel combinations.

Implementing Connections

• A method for connecting cells in series is described, focusing on maintaining correct polarity throughout the connections.

• The total pack voltage is calculated based on individual cell voltages; an example uses 4 volts per cell resulting in a total voltage of 64 volts.

Verifying Connections

• Discussion shifts to verifying the correctness of parallel connections by measuring voltages across different points using a multimeter.

• It’s noted that due to the nature of parallel configurations, voltage measurements remain consistent regardless of where they are taken within the setup.

Finalizing Design Steps

• Confirmation is made regarding proper connection methods for both positive and negative terminals within the design framework.

• Emphasis on ensuring power flow from positive to negative terminals as part of completing the circuit design process.

Battery Pack Design and Connections

Understanding Series and Parallel Connections

• The discussion begins with the confirmation that two battery packs are connected in series, as indicated by the connection of the negative end of one pack to the positive terminal of another.

• The speaker emphasizes the importance of making proper negative connections, which will be aligned with the positive connections for clarity.

• A visual representation is provided to illustrate power flow, showing how both battery packs connect at a junction where series and parallel configurations occur simultaneously.

• The design concept is reiterated: both series and parallel connections are essential in creating an effective battery pack configuration.

Adding Cells and Ensuring Proper Configuration

• The speaker instructs on counting cells to ensure correct assembly, highlighting that practical connections can often lead to confusion if not properly managed.

• An overview of connecting cells in parallel is introduced, emphasizing simplicity for understanding; a screenshot is suggested for reference during calculations.

Creating Busbars for Connection

• The concept of a busbar is explained as a central point where all cell connections converge; this aids in organizing multiple cell connections efficiently.

• Confirmation that all four cells are indeed connected in parallel through their respective busbars is sought from participants to ensure comprehension.

Finalizing Parallel Configurations

• It’s confirmed that with all positives connected to one busbar, the first set of four cells operates under a parallel combination yielding 4 volts total voltage across them.

• Introduction of a second set of four cells follows; their negatives are also connected to maintain continuity within the system.

Combining Packs into One System

• Both sets (first and second packs) have their positives and negatives combined into one busbar point, facilitating both series and parallel combinations effectively at this junction.

• A summary reiterates that all positives are now paralleled while maintaining proper negative configurations across both packs.

Conclusion on Battery Pack Configuration

• The speaker clarifies that both series and parallel combinations occur simultaneously at specific points within the design, ensuring efficient energy distribution throughout the battery pack setup.

• Emphasis on understanding how these configurations work together provides clarity on overall functionality within battery systems.

BMS Integration and Power Flow in Battery Packs

Understanding Series and Parallel Combinations

• The speaker discusses preparing bus power for battery packs, emphasizing the complexity of integrating both series and parallel connections.

• Initial connections are straightforward (e.g., 48 volts), but understanding the combination of series and parallel configurations is crucial for BMS integration.

• A total of 16 series combinations are established, with potential to add more cells in parallel, illustrating the flexibility in design.

BMS Functionality and Data Reading

• The BMS needs to read data from all connected cells; initial connection errors are acknowledged as part of the learning process.

• Clarification on power flow direction is provided, reinforcing that power flows from positive to negative terminals correctly.

• The speaker verifies correct connections before proceeding with BMS integration, ensuring all circuits function properly.

Detailed Steps for BMS Integration

• An overview of the BMS board's layout is given, highlighting key terminals such as R (negative terminal).

• Load connections require careful integration; both positive and negative must be connected appropriately for functionality.

• Each individual series connection will be integrated into the BMS to allow it to read data accurately from each cell.

Voltage Measurement Capabilities

• The BMS can measure voltage across individual cells by utilizing two points per cell connection.

• Verification of second cell readings confirms that the BMS can track multiple series data effectively.

• With 16 series connected, the system allows comprehensive monitoring through the BMS.

Criteria for Effective Monitoring

• The first criteria involve ensuring cell voltages remain within safe limits (between 3V and 4.2V), which is essential for battery health.

• The entire pack voltage can also be monitored by the BMS, allowing it to assess overall performance metrics effectively.

• Additional protective measures include monitoring overcurrent flow and short circuit protection mechanisms built into the system.

BMS Integration and Selection Process

Overview of BMS Functionality

• The MOSFET acts as a switch that opens and closes, safeguarding the entire battery pack through parallel connections.

• The presentation covered key metrics such as total voltage, maximum voltage, minimum voltage, and system status related to BMS integration with the battery pack.

BMS Selection Criteria

• The selection process for a Battery Management System (BMS) begins with determining the number of series connections in the battery configuration.

• Voltage measurement capabilities allow identification of series connections; for example, a 60V setup corresponds to 16 series (16S), while 72V corresponds to 20 series (20S).

• Charger capability must exceed the full charge voltage; for a 60V battery pack, it should be set at 67.2V.

Current Rating Considerations

• Understanding overcurrent conditions is crucial; specific points need to be established where overcurrent protection is necessary during BMS selection.

• Each cell's specifications are vital; for instance, a cell rated at 3.7V and 5AH indicates its capacity and helps determine maximum current output.

Session Conclusion and Key Learnings

• The session concluded with an emphasis on clarifying confusion regarding series-parallel combinations in battery configurations.

• Future sessions will delve deeper into C rating discussions and further explore BMS selection based on identified parameters.

Recap of Learning Points

• Key topics included understanding series-parallel combinations, how they affect overall system design, and detailed insights into integrating BMS with individual cells.