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

Understanding BMS: Practical vs Theoretical

Introduction to the Session

• The session aims to shift from theoretical concepts learned over the past two weeks to practical applications of Battery Management Systems (BMS).

• The focus will be on observing practical conditions and products, including how BMS, controllers, and MCUs look in real-world scenarios.

Exploring Practical Applications

• Participants are encouraged to choose between continuing with theory or exploring practical applications; the consensus is to proceed with practical demonstrations.

• A detailed examination of a specific BMS will be conducted, focusing on reading data sheets and understanding connections.

Analyzing BMS Specifications

• The first BMS example is identified as a 16S configuration with a maximum current rating of 40 amps for lithium-ion batteries operating at 3.7 volts nominal voltage.

• Participants are prompted to calculate full charge voltage, cutoff voltage, and maximum charging specifications for the observed BMS.

Understanding Temperature Sensors in BMS

• Discussion includes the role of NTC (Negative Temperature Coefficient) sensors as temperature sensors critical for battery operation.

• Explanation of wiring connections where one wire connects to the battery pack while another serves as output from the BMS.

Comparing Different BMS Models

• A second model is introduced: a 14S configuration rated at 48 volts and also capable of handling up to 40 amps.

• Clarification that if only one current value is provided without specification, it should be assumed as discharging current in practical applications.

Calculating Voltage Parameters for Different Configurations

• Participants are tasked with calculating full charge voltage, cutoff voltage, and nominal voltage based on given specifications for both models discussed.

• Emphasis on careful selection when choosing a BMS based on its specified voltages versus actual operational requirements.

Charging a 14S Battery Pack with a 48V Charger: What Happens?

Practical Analysis of Charging Parameters

• The speaker discusses the implications of using a 48V charger on a 14S battery management system (BMS), emphasizing the need for practical analysis beyond theoretical knowledge.

• A scenario is presented where a non-engineer might mistakenly charge a 14S pack labeled as 48V, raising questions about potential outcomes and effects.

• The speaker encourages calculations regarding charging parameters, hinting that there will be no impact in the lower cutoff region when using an incorrect charger.

• It is asserted that the BMS will not experience overcharging or open circuit issues despite the mismatch in voltage.

Understanding Full Charge and Cutoff Voltages

• The discussion shifts to specific BMS data sheets, focusing on parameters such as full charge and cutoff voltages for both 13S and 14S configurations.

• For a 13S BMS, the full charge voltage is identified as 54.6V, while the cutoff voltage is noted at 39V; these values are critical for selecting appropriate chargers.

• The full charge voltage for a 14S BMS is established at 58.8V, highlighting a significant difference from the previous configuration which could lead to undercharging if mismanaged.

Implications of Incorrect Charging Practices

• A major industry challenge arises when users see only the nominal voltage (48V), neglecting to consider whether they are dealing with a true 14S configuration; this can lead to inefficiencies in charging.

• If charged incorrectly, users may experience reduced overall efficiency and range due to undercharging by approximately four volts—equating to about a 20% drop in usable capacity.

Lower Cutoff Voltage Considerations

• The lower cutoff voltage for a typical 14S setup is discussed as being set at around 42V; confusion arises when comparing it with other configurations like the standard cutoff of 39V for a different setup.

• If operating under incorrect assumptions about cutoff voltages, systems may shut down prematurely while still having energy left in reserve—leading to operational faults perceived by users.

Summary of Different Battery Configurations

• The speaker reviews various battery configurations including their respective BMS setups (13S, 14S, and others), emphasizing how each has unique specifications that must be adhered to during operation.

• An example involving an LFP battery pack illustrates how specific designations affect performance expectations and operational guidelines within different applications.

Understanding LFP Battery Packs and BMS

Overview of LFP Battery Characteristics

• The discussion begins with the importance of understanding the full charge voltage for Lithium Iron Phosphate (LFP) batteries, highlighting differences between charging and discharging currents in practical applications.

• A specific example is given regarding a 16S LFP battery pack, prompting questions about its full charge voltage.

• Clarification is provided to avoid confusion between 16S NMC (Nickel Manganese Cobalt) packs and 16S LFP packs, emphasizing that their specifications differ significantly.

Calculating Full Charge Voltage

• The full charge voltage for a 16S LFP battery pack is stated as 57.6 volts, with a cutoff voltage of 44 volts being mentioned.

• The nominal voltage calculation for a 16S configuration is explained as being based on the nominal cell voltage of 3.2 volts, leading to a total nominal voltage of 51.2 volts.

BMS Specifications and Comparisons

• A new BMS (Battery Management System) specification is introduced: a 19S configuration supporting LFP batteries at a nominal voltage of 3.2 volts and rated at 40 amps.

• Questions arise regarding the full charge and cutoff voltages for this new BMS setup, which are calculated as follows: full charge voltage at approximately 68.4 volts and cutoff at around 60.8 volts.

Distinguishing Between Battery Types

• Another BMS example is presented for an NMC battery pack also configured in a series of 16 cells; it has similar nominal voltages but different characteristics compared to the LFP pack discussed earlier.

• Two types of BMS are identified: one providing basic protection without data communication capabilities, and another offering smart features that allow monitoring input/output data from within the battery pack.

Understanding Wiring Configurations in BMS

• The speaker discusses wiring configurations in detail, noting that there are typically multiple wires connected to each BMS unit—21 wires including negative connections for proper functionality.

• It’s clarified that despite having only a specified number of series connections (like "19S"), additional wires may be necessary to read total battery pack voltages effectively.

• The concept of smart versus normal BMS systems is elaborated upon; smart systems can measure entire battery packs using designated positive/negative terminals while ensuring accurate readings across individual series connections.

Understanding Battery Management Systems (BMS)

Identifying Battery Types and Specifications

• The importance of data sheets in identifying battery types like LFP (Lithium Iron Phosphate) and NMC (Nickel Manganese Cobalt) is emphasized, highlighting the need for core knowledge about specifications such as maximum current.

• Different cutoff voltages are discussed, particularly noting that LFP and NMC batteries have distinct voltage requirements, which are crucial for proper charging.

BMS Variations and Features

• The discussion transitions to various BMS configurations, including those suitable for smaller battery packs used in two-wheelers versus larger systems for four-wheelers.

• A distinction is made between BMS types: some can only monitor and protect while others can balance the battery pack. This balancing requires additional wiring in certain designs.

Size and Design Differences in BMS

• Observations on size differences among 14S 40 amps BMS units are noted, despite them having similar ratings; this indicates variations in design or intended use.

• The waterproof nature of one BMS is highlighted, showcasing its IP rating which protects internal components from exposure compared to a less protected model.

Active vs. Passive Balancing

• A key difference between two observed BMS models is their functionality: one supports active balancing while the other only monitors and protects without balancing capabilities.

Smart BMS Capabilities

• Introduction of smart BMS features such as CAN communication ports allows data transfer to monitoring systems, enhancing usability with vehicle control units (VCUs).

• Notable differences in data presentation across various BMS models are discussed; some manufacturers may omit critical information from their datasheets intentionally.

Complexities of Non-standardized Designs

• An example of a complex non-CAN compatible BMS is presented, emphasizing the lack of technical data available for identification purposes.

• Identification challenges arise when no clear specifications are provided; an example given relates to an Ola electric two-wheeler's robust yet costly BMS system.

Understanding Battery Management Systems (BMS)

Cost and Types of BMS

• The entire BMS setup costs around 15,000 rupees, while a two-wheeler BMS setup ranges from 3,000 to 4,000 rupees.

• The speaker mentions that the battery pack used in Ola vehicles is a 14S configuration, which can be paired with compatible BMS systems.

Compatibility and Functionality

• It is possible to use a different battery pack in an Ola vehicle as long as it matches the voltage specifications; however, integration with the vehicle's VCU (Vehicle Control Unit) is crucial for proper functionality.

• The main difference between various BMS units lies in their current output capabilities: one supports up to 200 amps while another only supports up to 40 amps.

Technical Specifications of BMS

• A significant distinction between different types of BMS is their size and current capacity; larger systems are designed for high-performance applications.

• The basic structure of a simpler BMS includes two wires for connecting to the battery pack, whereas more advanced systems have multiple terminals for better control over both positive and negative outputs.

Advanced Features of Smart BMS

• In advanced setups like those used in Ola vehicles, both positive and negative connections are managed through the same unit, enhancing control over battery performance.

• The speaker highlights that smart BMS units include CAN communication features essential for monitoring various parameters such as voltage.

Practical Setup Demonstration

Vehicle Integration Overview

• A practical demonstration will show how the entire electric vehicle setup looks after integrating the battery management system.

Troubleshooting Insights

• An overview of the electric battery pack reveals its internal cell arrangement and troubleshooting aspects during practical demonstrations.

Wiring Harness Condition

• A visual inspection shows that the wiring harness has suffered damage due to rat bites, indicating potential issues with durability in real-world conditions.

Types of Motors Used in Electric Vehicles

Motor Types Explained

• Two types of motors are discussed: mid-drive motors and hub motors. Each type serves different purposes within electric vehicle design.

Hub Motor Details

• The internal structure of hub motors includes hall sensors responsible for detecting magnetic polarity—an essential feature for motor operation.

Understanding Mid Drive and Hub Motors

Overview of Motor Setup

• The mid drive motor operates with the middle part rotating while the outer part remains stationary, contrasting with traditional setups.

• A virtual battery pack is introduced for testing purposes, showcasing various components including sensing wires and input/output connections.

• Key components of the vehicle are identified, emphasizing the importance of understanding each part's function in the overall system.

MCU and VCU Components

• The MCU (Microcontroller Unit) receives inputs from both positive and negative battery terminals along with three output signals indicated by color codes: yellow, green, blue.

• The VCU (Vehicle Control Unit) manages all vehicle operations, connecting multiple components such as the battery and motor through numerous wires.

Practical Demonstration of Motor Functionality

• A demonstration is set to show how the entire setup works when powered on, focusing on how the battery pack functions within this context.

• As the motor starts to rotate, a belt mounted on it drives a rear shaft that visibly rotates during practical demonstrations.

Comparison Between Motor Types

• The hub drive motor is explained as being mounted directly onto a tire shaft for direct wheel rotation.

• Visual comparisons between mid drive motors and hub motors highlight their structural differences and operational mechanics.

Summary of Learning Outcomes

• An overview of different types of Battery Management Systems (BMS), MCUs, and their functionalities will be discussed in future sessions.

• Upcoming sessions will integrate knowledge from previous discussions about batteries, BMS, MCUs, and motors into a comprehensive understanding of vehicle systems.

• Differences between 13S and 14S BMS configurations were noted during practical applications to enhance understanding among participants.