MULTI-CELL LITHIUM-ION BATTERY MANAGEMENT SYSTEM

For Electric VehicleTeam Members• Pramit Tamrakar - EE• Jimmy Skadal - EE• Hao Wang - EE• Matthew Schulte - EE• William Zimmerman - EE

Advisor• Ayman Fayed

Client• Adan Cervantes- Element One Systems

Team-id- SdMay11-04

Problem Statement

To develop an efficient and safe system for charging and monitoring of multi-cell series batteries in Electric Vehicles by using AC to DC converters.

System Specifications

CCCV Charging sequence for

Lithium-Ion Batteries

Charging Goal

18 Series Batteries, 2.3 Ah each 45 minute CCCV charge

Project Goals and System Diagram Design a Lithium Ion Battery Charger that is capable of safely charging 16

parallel packs of 90 cells in series (Large Scale System). Successfully build an 18 cell charger that is capable of monitoring and balancing

the cells. (Small Scale System)

Full Scale System Diagram

Project Plan Acquire boards/parts from TI

Use built in capabilities to daisy chain the boards

Close the feedback loopConnect the boost converter, buck

converter, test board, current sensing resistor, amplifier, and aardvark software to ensure proper charging

Test & Prototype the small scales design Hardware Cost

$2120.00

Project Design

Small Scaled System Diagram

BQ76PL536EVM-3

• Battery management system

• Track the voltage and temp. for all batteries

MSP430 with buck circuit

• Generate All necessary voltages and currents with PWM

• Negative feed-back loop

Aardvark Interface

• To display the status of the charging system

Project Design Issue Daisy-chained EVMs

Proved the ability to hook together multiple EVMs.

System Signal Components

Ordered MOSFET drivers and power resistor to operate our buck converter

Ordered components to amplify small signals produced by the micro-controller

SPI Communication

Programming MSP 430 in order to build SPI communication between micro-controller and EVMs

Buck Circuit Implementation and Testing The buck circuit will take a voltage given by

some supply and decrease the value as needed.

There will be a negative feedback loop in the system so the Buck can accurately output the desired current or voltage.

Inductor 100uH

Capacitor 330uF

Value of components for scaled down buck

circuitTested Buck Circuit with PSpice by changing the input PWM and observing the output.

Buck Testing Variac wall transformer (rectified) to DC Input DC from Variac at 65V Buck output expectations:

32.4V-64.6VMax 3APower Resistor Test Load

Buck Testing Schematic

EVM- Testing Plan TI’s processor bq76PL536EVM-3 and

Aardvark USB-SPI adaptor

Aardvark driver will be installed in a laptop before installing the TI evaluation software

Tested the EVM board with 12-26 VDC Power Supply

Plan to configure the EVM with cells

Use the TI’s WinGUI user interface software to monitor the status of the cell

EVM- Safety The battery connections should be made secure, a loose

connection may result in device destruction.

The ideal connection sequence is from pin P1.1 to pin 3.7 in order to avoid the any connection error

The Absolute Maximum voltage per IC is 36V

Caution must be taken when using the EVM as part of a stack , where lethal voltages may be present

MSP430 Programming

Code Composer Studio v4 Tested modules:

High frequency clockADCTimer/PWMBasic feedbackLow Power Mode

Unfinished:SPI communication

Semester Schedule

Questions ?