Senior Design II

Midterm Presentation

September 29, 2009

Team MembersJonathan Chapman

Duties: Recharging Major: Electrical Engineering

Quoc Dang Duties: Recharging Major: Computer Engineering

Quintin Grice

Duties: Power Circuit Major: Electrical Engineering

Richard Teeple

Duties: Communication, System Monitoring Major: Computer Engineering

David Smith

Duties: Fault Protection, System Monitoring

Major: Computer Engineering

Overview:ProblemSolutionConstraints

TechnicalPractical

Progress in Design IIFuture Plans

ProblemWhen dealing with lithium ion battery systems, the

following aspects must be taken into consideration:Safety

Fire and Explosion

Communication CAN-bus

System Life Weakest Link (individual cell)

SolutionA rechargeable battery system that offers the

following:Total output current monitoring Ambient temperature monitoringIndividual cell voltage monitoringCAN-bus communication

Technical ConstraintsName  

Description

Battery Technology

The technology used to output voltage from the REBATEM must be lithium ion cells.

Accuracy Voltage: 0 to 5 volts with an accuracy of ± 0.1 voltsCurrent: 0 to 20 amperes with an accuracy of ± 10 milliampsTemperature: -30 to 200 °F with an accuracy of ± 2 °F

Capacity /Cycle Life

The REBATEM must maintain at least an 80% state of charge for the individual cells and a minimum of a 400-cycle life.

Technical Constraints (cont.)Name  

Description

Fault Protection Disconnect the cells from the system when temperature passes 175 °F or when current passes 20 amps.

Output Output voltage must be within 14 to 16 volts. Current hour rating must be between 1.7 and 1.8 amp hours.

Communication The battery management system must communicate cell voltages, temperatures and current to external devices.

Environmental•Green energy•Contains no toxic metals

• Cadmium• Lead

Safety•Unstable - needs to be monitored

•Sony battery recalls•UL 1642 states that users must be protected from risk of explosion or fire due to any instability of the Li-ion cells [2].

[1]

Summary of Design ISystem Results

Charging Non-operational

Current Sensing Fully Operational

Voltage Sensing Fully Operational

Temperature Sensing Fully Operational

Fault Protection Operational

CAN-bus Communication Operational

Complete System Test N/A

Modifications in Design II4 Lithium Ion Polymer Cells in SeriesAddition of a CAN transceiver IC (MCP2551)Different Charge IC (MAX745)

MAX1758 – Former Charging Chip: Unreliable

Schematic – Main Board

PCB Layout – Main Board

Schematic – Charge Board

PCB Layout – Charge Board

Final Design Test PlanCharging

 Current < 1.9 AFault Protection

 Output current < 20 AOutput

Maximum and minimum current/voltageCommunication

CAN-bus signals

Future PlansCAN transceiver implementation and testingPCB orderedPopulate and test PCBDesign PackagingFinal Testing

Any Questions?

References:[1] [Online] Available: http://www.gadgetreview.com/wp-content/uploads/2006/08/explosion_dcrop1.jpg.

[2] “Lithium Batteries.” [Online]. Available: http://ulstandardsinfonet.ul.com/scopes/scopes.asp?fn=1642.html.