Multi-Cell Lithium-Ion Battery Management System - Senior Design

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Multi-Cell Lithium-Ion Battery Management System - Senior Design Powered By Docstoc
					          Abstract/Problem Statement                                                                Functional Decomposition
The goal of this project is to develop an efficient, safe and scalable
system for charging and monitoring a multi-cell battery pack for             The system consists of two main components: the battery management
electric vehicles. The system will use a switching mode power supply         hardware and the power supply. Both of these components are controlled by an
and a battery management system. The initial scope of this project           MSP430 microcontroller, and output data for every cell is available with a
was to charge the bank of lithium-ion batteries to 324 VDC supplied          personal computer.
from a 120 VAC wall outlet. In order to focus on battery management
and safe charging, this project was scaling down to developing a
battery management system for 18 series cells that can later be
scaled to 90 series cells.

                   Solution Approach
The first objective of this project is to develop the battery
management system for a small scale battery pack (18 series cells).
Several integrated circuits are offered from Texas Instruments to
provide battery monitoring for battery packs with a large number of
cells. The bq76pl536 is used specifically to monitor the state of
charge and battery status of packs with many series cells. The
information obtained from the bq76pl536 integrated circuits is then
used to control a switching mode power supply that follows the
charging algorithm necessary for safe and efficient lithium ion battery

                 Design Requirements
Functional Requirements
 Li-Ion Battery Management
  • Constant-Current Constant-Voltage
    charging procedure
  • Battery Gauging
  • Temperature Monitoring
                                                                                                         Implementation & Testing
  • Overcharge Protection                                                    Boost Converter                                                             80
                                                                                                                                                                                     SMPS Output Voltage

                                                                              Simulations are run to ensure the boost can                               70

                                                                                                                                    Output Voltage [V]
                                                                             output from 28.8V to 64.8V


                                                                              The maximum current from the boost circuit
Non-Functional Requirements
                                                                                                                                                                                                                                       Output V[23 Ohm]
                                                                             will be 3A at all output voltages                                           20
                                                                                                                                                                                                                                       Output V [50 Ohm]

Usable by our client during the development of the full scale                Average efficiency in operating region is 87%                             10

                                                                              Efficiency ranges from 78%-99%                                                 1   5   10   15   20   25   30   35   40   45   50   55   60   65

                                                                                                                                                                                PWM duty cycle [%]
 Reliable operation, even in the condition of a fault.
 Low price to ensure the product is a competitive market                    Microcontroller
                                                                              The MSP430 is a low power microcontroller used to gather and organize the data from the bq76pl53
                                                                             integrated circuits. MSP430 testing was done by hooking it up to test circuit where known voltage
 Robust and long-lasting.                                                   and current information is present. Then the output PWM signal is observed.
 High efficiency for maximum power usage.
 Protect the user from unsafe conditions.                                   Battery Management System
                                                                              Uses bq76PL536-EVM3 and Aardvark USB-SPI adaptor when displaying on a PC, as well
                                                                             as an MSP430 for control. The EVMs allow SPI communication of the battery information
             Intended Users and Uses                                         and the MSP430. Multiple EVMs can be connected in series to monitor up to 192 series cells
                                                                             (18 shown). EVMs were tested with DC power supplies to model battery voltage information.
Intended Users
The users of the final design will be the vehicle owners, family
members, friends, etc. They could range anywhere between 14 to 100
years old and as long as they can pick up an extension cord and plug
it in, they could use this project. However, since this project is only a
scaled down version of the prototype, the intended user is the client
(Element 1 Systems).

Intended Uses
The intended use of the project is to charge a bank of lithium ion
batteries and manage their charge and discharge cycles. The high
voltage supply is designed to operate as a constant-current constant-                                  Battery Management System                                  bq76PL536-EVM3 battery information display GUI
voltage lithium ion battery supply, and only for the specified A123          Final Testing               (Power Supply not shown)

battery chemistry.                                                           Uncharged batteries are connected to the circuit to ensure they charge correctly

                                                 Summary                                                                                                                                  Budget
With global demand for oil increasing and supplies more difficult to obtain, the price of oil based fuels for                                            Parts                                                               Cost
transportation is expected to rise. The need to find a viable alternative to oil necessitates researching in electric
                                                                                                                                                         bq76PL536EVM-3                                                      $400
alternatives. The long wait time to charge Electric Vehicle batteries makes transitioning from internal
combustion engines to battery electric vehicles inconvenient for a society dependent on traveling large                                                  MSP430                                                              $75

distances. Electric vehicles have to be convenient, safe, and affordable to meet the needs of consumers without                                          Various Discrete components                                         $50
major sacrifices in perceived quality of life. Lithium ion batteries support a high energy density and are the
preferred source of mobile electric power. This project implements a solution for a battery management system
for a large number of lithium ion cells.                                                                                                                 Pramit Tamrakar                                                     $4000

                                                                                                                                                         Matt Schulte                                                        $4000

                                       Team-id- sdmay11-04                                                                                               Jimmy Skadal                                                        $4000

                  Team Members                       Advisor                                                                                             Hao Wang                                                            $4000
                  • Pramit Tamrakar – EE               Ayman Fayed
                  •Jimmy Skadal - EE                 Client                                                                                              William Zimmerman                                                   $4000

                  •Matthew Schulte - EE                Adan Cervantes                                                                                    Total cost                                                          $20,779
                  •Hao Wang - EE
                  •William Zimmerman - EE

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