Meeting with Your TA

Description

By the Thursday of the third week, you must have a project approved, and should be ready to get working! At this time, you'll need to log into PACE and submit your schedule for the semester. Please be sure to make this as accurate as possible because once it's submitted, it can only be changed manually. Making a block of your schedule red means that you are unavailable during that time.

Once each person on your team has submitted their schedule, your TA will be able to easily check for available times to schedule a weekly meeting. Your TA should contact you, usually by the fourth week, via email, to set up a weekly meeting schedule at mutual convenience. During the first weekly meeting, your TA will assign your team a locker and a lab kit.

Weekly meetings with your TA are required and will be held throughout the entire semester until demonstrations are completed. Your TA is your project manager. The "homework" of the course consists of preparing for the weekly meetings. Your TA will evaluate your lab notebook each week, provide feedback, and recommend improvements. At each meeting you will be expected to present your progress since your last meeting, plans for the coming week, and any technical or administrative questions you need to discuss with your TA. You are expected to arrive on time and prepared to make good use of your time with your TA. Your TA may require that each team member to fill out the Progress Report Template and submit it to them prior to each weekly meeting.

Requirements and Grading

Attendance and participation in weekly meetings is required and will affect Teamwork and Lab Notebook scores. If you can't make it to a particular weekly meeting, it is your responsibility to inform your TA prior to the meeting time and set up an alternate time.

Submission and Deadlines

Your schedule must be submitted by the end of the third week of class and you will receive an email from your TA shortly after. Your first meeting with your TA should be during the fourth week of the semester.

Active Cell Balancing for Solar Vehicle Battery Pack

Tara D'Souza, John Han, Rohan Kamatar

Featured Project

# Problem

Illini Solar Car (ISC) utilizes lithium ion battery packs with 28 series modules of 15 parallel cells each. In order to ensure safe operation, each battery cell must remain in its safe voltage operating range (2.5 - 4.2 V). Currently, all modules charge and discharge simultaneously. If any single module reaches 4.2V while charging, or 2.5V while discharging, the car must stop charging or discharging, respectively. During normal use, it is natural for the modules to become unbalanced. As the pack grows more unbalanced, the capacity of the entire battery pack decreases as it can only charge and discharge to the range of the lowest capacity module. An actively balanced battery box would ensure that we utilize all possible charge during the race, up to 5% more charge based on previous calculations.

# Solution Overview

We will implement active balancing which will redistribute charge in order to fully utilize the capacity of every module. This system will be verified within a test battery box so that it can be incorporated into future solar vehicles.

Solution Components:

- Test Battery Box (Hardware): The test battery box provides an interface to test new battery management circuitry and active balancing.

- Battery Sensors (Hardware): The current battery sensors for ISC do not include hardware necessary for active balancing. The revised PCB will include the active balancing components proposed below while also including voltage and temperature sensing for each cell.

- Active Balancing Circuit (Hardware): The active balancing circuit includes a switching regulator IC, transformers, and the cell voltage monitors.

- BMS Test firmware (Software): The Battery Management System requires new firmware to control and test active balancing.

# Criterion for Success

- Charge can be redistributed from one module to another during discharge and charge, to be demonstrated by collected data of cell voltages over time.

- BMS can control balancing.

- The battery pack should always be kept within safe operating conditions.

- Test battery box provides a safe and usable platform for future tests.