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Senior Design - Group 6

Senior Design - Group 6. CS10 Battery Management System. Group Members: Brad Cox Kevin Burkett Tera Cline Arthur Perkins. Outline. Problem Statement Background Design Requirements Proposed System Design Project Plan Conclusion. Objective Tree. Objectives. Safety:

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Senior Design - Group 6

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  1. Senior Design - Group 6 CS10 Battery Management System Group Members: Brad Cox Kevin Burkett Tera Cline Arthur Perkins

  2. Outline • Problem Statement • Background • Design Requirements • Proposed System Design • Project Plan • Conclusion

  3. Objective Tree

  4. Objectives • Safety: • The system must be designed to protect the batteries, the vehicle owner and the BMS itself. The user and vehicle must be safely isolated from the batteries whenever possible, in-case of battery failures. • Accessibility: • The second priority is accessibility. The owner of the vehicle must be able to easily view the measured data the system collects about the batteries it is monitoring. • Accuracy: • The design must be accurate to ensure the integrity of the batteries. The system must be able to accurately detect when a battery is fully charged or when it reaches and unsafe temperature. • Scalable: • Finally, the device must be scalable to handle a small or a large number of battery cells.

  5. Need For Battery Management System • Save money: • Save the user money by protecting the battery cells from long term charging damage. Instead of broad charging, the system narrows the incoming voltage and current to slow the charge process. • By determining which cells in a battery or which battery’s have failed, the user can bypass affected cells or replace the specific battery. This can save money in the long term by not allowing damaged parts to continue failing or having a technician replace a specific part, as opposed to pay technicians for their time to look for and replace a problem. • Protect the battery: • The system will slow charge battery’s to protect them. • Temperature sensors will monitor overheating and overcharging, and shut down affected battery’s. • Display Data to User via a Windows Based Application.

  6. Battery Technologies

  7. Current Systems • The goal of this project is to use commercially available battery monitoring technologies to design a nickel metal hydride battery management system that will effectively measure the conditions of individual cells in an electric vehicle and report them to the vehicle owner in real time during charging and discharging of the battery packs. • Battery Management Systems are used to do the following • Monitor the state of the battery; voltage, current, temperature. • Collect and report data. • Balance the flow between cells and battery. • Provide reports on State of Charge and State of Health. • Show the maximum and minimum discharge. • Provide an internal switch to remove battery(s) from operation.

  8. Scope of Design • Standalone EV Battery Monitoring Solution • Designed Specifically to work with NiMH Battery Modules • 13.2 Volts • 10 Cells in Series • 90 Ampere Hours • Key Features: • Measure Voltage of Every 3 Cells. • Measure Temperature of Groups of 5 Cells. • Able to Communicate with Smart Chargers. • Bypass 1 Amp of Current Around Fully Charged Cells. • Display Data to User via a Windows Based Application.

  9. Design Assumptions • Vehicle Battery Pack • Total Nominal Voltage is Approximately 333 Volts • Approximately 25 Battery Modules or 250 Cells • Windows Application • The vehicle owner will have a Windows PC running Windows XP or Higher. • Charger • The vehicle owner’s charger will accept two bit input to regulate mode of charger.

  10. Data Flow Diagram • Data Acquisition Chips • Measure voltage and temperature of battery cells • Sends measured data to microcontroller • Microcontroller • Processes measured data from chips and sends it to the user’s computer • User’s Computer/Windows Application • Averages Measured Values • Stores Values in a Database • Displays Values to User

  11. Hardware Overview • Four Main Hardware Components • Bypass Circuit • Data Acquisition Chip (MAX11068) • Digital Isolator • Microcontroller (PIC18F4520) Level 1 Diagram

  12. Bypass Circuit

  13. Data Acquisition Chip • MAXIM 11068 • Measure voltage of up to 12 cells • Measure temperature of battery modules using 2 auxiliary ports • Uses lateral I2C communication • Alarm on overvoltage or over temperature MAX11068

  14. Digital Isolator • Protects the low voltage circuits from the high voltage batteries • Protection rated to 5kV • Must isolate four wires • Data (bidirectional) • Alarm • Clock • Shutdown • System requires 2 ADuM2251 isolators • Designed specifically to work with I2C devices • ADUM2251

  15. Microcontroller • PIC18F4520 • Optimized for C Complier • Large Memory Space • 1536 bytes of SRAM • Enhanced addressable USART module • Supports RS-485 and RS-232 • Master Synchronous Serial Port module • Supporting I2C master and slave modes PIC18F4520

  16. Software Overview • Windows application: • Initialize System • Initializes Cell Measuring • Displays All Measured Data to the User • The Microcontroller • Interface between the Windows application and the MAX11068 chips. • Converts I2C to RS-232/USB and RS-232/USB to I2C • Sends control commands to MAX11068 chips when instructed by the Windows application • Communicates with smart chargers

  17. Windows Application • Coded in C# • Will run on vehicle owner’s PC • Initializes system on User’s Command • Alerts from microcontroller will be displayed to the user • A bar graph will display voltage of every 3 cells in the battery pack • User can select bars of bar graph to create a second graph of voltage and temperature versus time

  18. Microprocessor Functions • Sends commands to MAX11068 chips • Initialize • Measure Cells • Bypass Cell • Collects data from MAX11068 chips and sends it to Windows application • Monitors MAX11068 chips for alarms • Sends alerts to Windows application • Sends commands to charger

  19. Project Challenges • Printed Circuit Boards • Time Constraints • Board Layout Design • Cost • Windows Application • Limited Experience • Soldering • Surface Mount Parts • Mounting System • Difficult to mount to battery modules

  20. Expected Outcomes • Prototype • Built for 3 battery modules • 3 Data Acquisition Chips (Max 11068) • 10 Bypass Circuits • Master Control Board • Completed Windows Application • User Friendly • Demonstrate Scalability of System Design

  21. Project Plan • Purchase Parts • Build and Test Circuits • Breadboard Design • Design printed circuit boards • Program and Test Microcontroller • Program and Test Windows Application • Finalize Documentation • Present at Design Fair

  22. Component Procurement

  23. Conclusion • Much larger project than initially expected • Difficult to meet all of the stakeholder’s requirements • Building and testing the prototype will pose many challenges • Once completed, easily converted to a full scale model

  24. Questions?

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