Embedded Systems and Design & Development - Feb 10, 2026 | Afternoon | VisionAstraa EV Academy

Understanding Battery and Charging Systems

Overview of Battery Pack and Charger Functionality

• The session begins with a recap of the basics regarding how battery packs, motors, controllers, and chargers operate.

• Chargers convert AC (Alternating Current) into pure DC (Direct Current), which is then supplied to the battery pack.

Connectors and Charging Types

• Discussion on various types of connectors used in electric vehicles, including Type 6, Type 7, Chori connectors, Anderson connectors, and DT type connectors.

• Explanation of onboard chargers that convert AC to DC for vehicle charging; direct DC connection bypasses this conversion.

Harnessing Electrical Components

• Introduction to harnesses as bundles of wires that interconnect various electrical components within the vehicle.

• Mention of CCS2 (Combined Charging System 2), highlighting its significance in modern electric vehicles.

Understanding CCS2 Socket Design

• Description of the male and female sockets associated with CCS2; focus on understanding their functionalities.

• Clarification on socket types; identification of a Type 2 socket based on visual characteristics discussed earlier.

Technical Specifications of Connectors

• Breakdown of terminal functions: five terminals for power and two for CAN communication (Control Area Network).

• Detailed explanation about neutral connections and phases in relation to single-phase versus three-phase systems.

Combined Charging System Insights

• Definition and importance of CCS2 as a combined charging system that accommodates both AC and DC charging through one socket.

• Emphasis on mandatory use of CCS2 for all high-voltage electric vehicles in India.

This structured summary encapsulates key discussions from the transcript while providing timestamps for easy reference.

Understanding CCS2 and Data Sheets

Overview of CCS2

• CCS2, or Combined Charging System 2, integrates both AC and DC charging systems into a single framework for electric vehicles.

Discussion on Data Sheets

• The session transitions to discussing the importance of data sheets for battery cells, specifically LFP (Lithium Iron Phosphate) cells.

• Participants are prompted to confirm whether they have accessed the relevant data sheet, indicating engagement in the learning process.

Accessing Data Sheets

• The speaker emphasizes that selecting a reputable brand is crucial when searching for data sheets; examples include Panasonic and LG.

• A specific brand named "High Star" is mentioned as an example for demonstrating how to find a data sheet online.

Analyzing Specifications

• The discussion shifts to examining the specifications within the selected data sheet, starting with maximum charging voltage and nominal charging voltage.

• Rated capacity is highlighted, explaining how it relates to discharge rates (e.g., discharging at 0.5 C).

Calculating Discharge Current

• The rated capacity at different discharge rates is discussed; calculations are provided for understanding current requirements based on battery specifications.

• Rated charge/discharge energy is noted as 300 Wh, aligning with nominal voltage calculations.

Power Ratings and C Rating

• Standard charge/discharge power of 150 W is confirmed through calculations based on rated capacity and nominal voltage.

• Maximum charging power of 300 W prompts questions about determining maximum current input and corresponding C rating from the data sheet.

Practical Calculation Insights

• Participants are encouraged to calculate maximum current based on power ratings using P = V × I formula.

• The speaker reiterates key concepts regarding calculating maximum current input related to specified power ratings.

Understanding Maximum Charging Current and C Rating

Calculating Maximum Charging Current

• The formula for calculating current (I) is derived from power (P) divided by voltage (V). Here, P is 300W, and V is 3.2V.

• The calculated maximum charging current results in approximately 93.75A, which is rounded up to 94A.

Determining the C Rating

• With a maximum charging current of 94A established, the next step involves finding the C rating for a battery pack rated at 100Ah.

• The C rating can be determined using the formula: C = I/AH, where I is the charging current. In this case, it results in a C rating of approximately 0.94C.

Understanding Battery Specifications

• A battery with a capacity of 100Ah can be charged at a rate of 1C (100A). However, since the maximum charging current is only 94A, it suggests that this can be considered as approximately 0.4C for practical purposes.

• Key takeaways include understanding how to apply basic calculations to determine both maximum charging currents and corresponding C ratings effectively.

Essential Parameters for Data Sheet

• Five critical parameters were identified for inclusion in the data sheet:

• Maximum charging current

• Maximum voltage

• Minimum voltage

• Continuous maximum charging capability

• Dimensions

Voltage Specifications from Data Sheet

• The full charge voltage required to fully charge a cell is noted as 3.65V.

• The minimum discharge voltage specified in the data sheet is set at 2.5V, which represents the cutoff point for safe operation according to manufacturer guidelines.

Additional Considerations on Charging Conditions

• It’s important to note that while we have established various parameters such as maximum charge power and continuous charging rates, further investigation into whether continuous operation at these rates is feasible under specific conditions remains necessary.

• The discussion also touches upon max discharge power specifications under certain temperature conditions (25°C), indicating operational limits during high-demand scenarios.

Understanding Discharge C Rating and Current

Introduction to Discharge C Rating

• The speaker introduces the concept of discharge C rating, questioning how to find and calculate it.

• A calculation is proposed to determine the maximum discharge C rating and current for a specific cell.

Calculation of Maximum Discharge Current

• The focus shifts to calculating the maximum discharging current alongside the C rating.

• Key terms required for calculations are identified: maximum discharge current and discharge C rating.

Performing Calculations

• The speaker states that the maximum discharge power is 600 W, leading to a formula where current (I) equals power (P) divided by voltage (V).

• Using nominal voltage of 3.2 V, the calculated maximum discharge current is approximately 187.5 amps.

Understanding Discharge C Rating

• The speaker notes that without detailed calculations, one can estimate a discharge rate of about 1.9C based on previous discussions.

• A comparison is made between charging and discharging rates, highlighting significant differences in their values (0.2C vs. 1.9C).

Importance of Data Sheets in Battery Design

• Different data sheets provide varying specifications; one indicates a maximum discharging current up to 1.9C from a battery rated at 600W.

• Emphasizes that when designing battery packs, understanding these ratings is crucial for safety and efficiency.

Factors Influencing Battery Pack Design

Selecting Battery Specifications

• Discusses how selecting a battery pack involves more than just voltage; it requires consideration of various factors including motor specifications.

Motor Dependency on Battery Selection

• The selection process depends heavily on desired range and vehicle performance metrics such as speed and load requirements.

Load Considerations in Design

• Highlights that if a motor's consumption is known (e.g., 50 amps), designing a battery pack with excessive capacity (e.g., 200 amps max output) may be impractical or unsafe.

Balancing Performance with Safety

• Stresses the importance of matching battery output with motor requirements to avoid system failures like BMS shutdown due to inadequate supply.

Conclusion on Comprehensive Design Approach

• Concludes that all components—motor, controller, charger—must align with selected cells based on their data sheets for effective design outcomes.

Battery Discharge and Charging Parameters

Discharge Cutoff Voltage

• The discharge cutoff voltage for the battery pack is specified as 2.5 volts, which is crucial for ensuring the longevity and safety of the battery.

Operating Temperature Ranges

• The recommended charging temperature range is between 0°C to 45°C, while discharging should occur within -20°C to 60°C. These parameters are vital for optimal battery performance.

• Recommended storage temperatures are between 15°C to 35°C, with room temperatures in India potentially reaching up to 40-50°C.

Battery Pack Weight Considerations

• Approximately 30% of a vehicle's total weight can be attributed to the battery pack, highlighting its significance in design considerations.

• A single cell weighs around 2.25 kg, which must be factored into overall vehicle weight calculations.

Types of Battery Cells

Cell Types Overview

• There are three main types of cells: prismatic cells (solid state), pouch cells (soft layer used in mobile phones), and cylindrical cells.

• Pouch cells are commonly found in mobile devices due to their flexible nature, while prismatic and cylindrical cells offer more structural integrity.

Mechanical Strength Comparison

• Prismatic and cylindrical cells have solid structures making them mechanically stronger compared to pouch cells, which are less robust.

Charging Methods and Internal Resistance

CCCV Charging Method

• The Constant Current Constant Voltage (CCCV) method involves an initial constant current charge at 0.5C until reaching a voltage of approximately 3.66 volts before switching to constant voltage charging.

Importance of Internal Resistance

• Internal resistance plays a critical role in determining how efficiently a battery can charge and discharge; it affects overall performance metrics like cycle life.

Cycle Life and Storage Conditions

Cycle Life Expectations

• Typical cycle life for Lithium Iron Phosphate (LFP) batteries ranges from about 3,500 to 7,000 cycles under ideal conditions but practically averages around 2,000 to 3,000 cycles.

Storage Recommendations

• Proper storage conditions are essential; factors such as temperature control during transport significantly impact battery health over time.

Battery Pack Charging and Discharging Parameters

Overview of Battery Cycle Conditions

• The battery pack is charged to 3.65 volts at 150 watts and then discharged at the same power until it reaches a cutoff voltage of 2.5 volts.

• Key parameters for charging and discharging are outlined, emphasizing constant power during both processes.

• Continuous power is defined as the cell being discharged at a constant rate of 150 watts.

Safety Performance and Data Sheet Insights

• Overcharging, over-discharging, and short-circuiting can affect safety performance; various tests (crush, vibration) are conducted to ensure reliability.

• Understanding data sheets is crucial for determining maximum current, voltage limits, and overall battery performance.

Determining State of Charge (SOC)

Assessing Remaining Charge in Battery Packs

• The remaining charge in a battery pack can be estimated based on its voltage level.

• SOC (State of Charge) terminology is introduced to quantify how much charge remains in the battery.

Life Cycle Assessment of Lithium-Ion Cells

• Lithium-ion cells typically have an average life cycle ranging from 200 to 800 cycles.

• Practical methods for identifying how many cycles have been utilized are discussed, focusing on internal resistance as a key factor.

Impact of Internal Resistance on Battery Life

Understanding Internal Resistance

• Higher internal resistance leads to lower current flow; this relationship affects the overall life cycle of the cell.

• An internal resistance measurement of 0.6 milliohms indicates a fresh cell; aging increases this resistance significantly.

Age Determination Techniques

• Aging can be assessed through increased internal resistance values; manual calculations without software tools pose challenges in accurately measuring life cycles.

Utilizing Smart BMS for Lifecycle Measurement

Role of Battery Management Systems (BMS)

• A smart BMS tracks charging/discharging currents and helps measure the lifecycle by counting cycles effectively.

• The BMS connects with both positive and negative outputs from the battery pack to monitor performance continuously.

Conclusion on Lifecycle Measurement Capabilities

• Microcontrollers within smart BMS systems facilitate accurate tracking of charging/discharging cycles, providing insights into battery health over time.

Battery Cell Types and Their Characteristics

Overview of Battery Cell Types

• The discussion begins with an overview of three main types of battery cells: cylindrical, prismatic, and pouch cells. Cylindrical cells are highlighted as the major type.

• Participants are prompted to identify the three types of cells discussed: pouch, prismatic, and cylindrical.

Color Coding and Chemical Composition

• Different colorful cells used in assembling battery packs indicate various parameters related to their performance.

• The first type mentioned is INR (Lithium Nickel Manganese Cobalt), which is characterized by its specific chemical composition.

• Other cell types include ICR (Lithium Cobalt Oxide) and IMR (Lithium Magnesium Oxide), each distinguished by their color coding that reflects their operational characteristics.

Data Sheets and Performance Metrics

• The NCR data sheet for LG cells is referenced, noting its composition of nickel, cobalt, and aluminum. This data sheet provides critical information on cell performance.

• The capacity of NCR cells is noted at 3,400 mAh with a common nominal voltage across all cell types except lithium iron phosphate (IFR).

Discharge Capacity Comparisons

• A comparison between different cell types reveals that while IFR has a lower nominal voltage (3.2V), it still falls under the lithium-ion category.

• Discharge capacities vary significantly; NMC exhibits high discharge rates compared to moderate rates for LFP batteries.

Life Cycle vs. Discharge Capability

• Despite LFP batteries having higher life cycles, NMC batteries offer superior discharge capabilities which influence selection based on application needs.

• Discussion includes how C ratings differ among battery types; INR has a higher C rating than LFP batteries.

Application-Based Selection Criteria

• When selecting between LFP or NMC for applications requiring high discharge rates (e.g., motors consuming 10 kW), considerations include both life cycle longevity and discharge capacity.

• Cost factors also play a role in choosing between NCR and INR cells; typically, NCR cells are more expensive than INR due to their commercial viability.

Understanding Battery Cell Selection for Applications

Key Considerations in Product Design

• The cost of designing a product should be minimized while maximizing both discharging capacity and nominal capacity. This balance is crucial based on the required discharge characteristics, whether moderate or high C rating is needed.

NCR Cells and Their Applications

• NCR cells can handle higher charging capabilities, making them suitable for commercial applications where fast charging is essential but high discharge rates are not as critical. For instance, electric vehicles (EVs) benefit from these cells due to their fast charging requirements.

Discharge Current Specifications

• In two-wheeler applications, maximum discharging current can reach between 80 to 100 amps. Higher-end applications also typically have a maximum discharging current of around 100 amps, emphasizing the importance of selecting appropriate cell types based on application needs.

Selecting Between LFP and NMC Cells

• When designing battery packs, the choice between LFP (Lithium Iron Phosphate) and NMC (Nickel Manganese Cobalt) cells depends heavily on application requirements. For EVs, NMC cells are preferred due to their higher discharge rates; however, for inverter batteries where longer life cycles are prioritized over high discharge rates, LFP cells are more suitable.

Transitioning to Embedded Systems in EV Applications

• The upcoming sessions will focus on core embedded systems applied within electric vehicles rather than basic concepts. Participants will explore various components such as battery packs, controllers, motors, and Vehicle Control Units (VCUs), identifying how embedded systems integrate with each component effectively.

Role of Microcontrollers in Battery Management Systems

• Microcontrollers (MCUs) play a vital role in managing battery parameters by controlling outputs based on sensor inputs like hall sensors. They ensure that Battery Management Systems (BMS) operate correctly by opening or closing circuits according to specific conditions monitored through multiple parameters.

Upcoming Offline Sessions and Practical Learning

• Starting February 16th, offline classes will commence where participants will engage hands-on with vehicles and practical applications of what has been learned online regarding design factors and programming of embedded systems in EV contexts. Sessions will cover combined charging systems specifications among other topics relevant to vehicle technology integration.

This structured overview captures the essence of the discussions surrounding battery cell selection for various applications while also highlighting future learning opportunities related to embedded systems in electric vehicles.

Overview of Upcoming Sessions

Introduction to Core Subjects

• The session concludes with a summary of the basics covered, including cell selection, BMS (Battery Management System), and motor controller fundamentals.

• Participants are encouraged to attend the next session, which will focus on hands-on learning experiences.

Hands-On Learning Opportunities

• The upcoming offline sessions will provide practical experience in designing and assembling battery packs.

• Attendees will have the opportunity to open and explore motors, enhancing their understanding through direct engagement with components.

• Emphasis is placed on hands-on activities for those interested in engineering and practical applications, encouraging participants to get involved.