Using the Website

Project Page

The Project Pages were created in an effort to help promote student projects. The Project Pages provide a showcase where employers, other students, and friends can see what UIUC students are capable of. Many employers, in particular, consider a good Senior Design Project to be just as valuable as internship experience. The Project Pages will develop over time into a valuable library of practical engineering knowledge. Some of the best projects will be identified each semester and placed in the Senior Design "Hall of Fame," while the rest will be accessible by semester and search engine.

Updating Project Information

Once your project has been approved on the discussion board by the Instructor, you should promptly update your project information. In order to do so, find your project on the Project page, and click its title. When a frame expands, click on "Edit." Next, enter your UIUC netid and password. The system will lookup your project and prompt you for information such as your project's title. Please fill in the information that you wish to have appear for your project, and then click on the submit button. The required fields are marked so. You can update this information at any time. We strongly urge you to keep a backup of all of the information, and we would like to caution you of one scenario in particular. If multiple people attempt to edit this information at the same time, the second person to submit the changes will overwrite the first person's changes. Also, be sure to logout when you are done by closing the web browser. It is important that you provide a project desciption. It should be a brief overview of your project and explanation of why it is worth doing. Please provide this information as soon as possible and try to limit the length to about 250 words.

Submit Schedule

After updating your project information, you should proceed to the Submit Schedule page. Here each student should submit his/her schedule so that your TA can schedule a weekly meeting time. We know that there are a lot of boxes to check, but we need this detailed information because of how difficult it is to match schedules. The information is displayed in a convenient way for TAs when it is time for them to schedule meeting times. The system is very intuitive so instructions are not needed. NOTE: Please be sure that the schedule you submit is as accurate as possible, since you won't be able to edit it later!

After submitting your schedule, you should familiarize yourself with the "Upload Files" page.

Uploading Files

This area is used to upload files such as the Proposal, the Final Paper, Images, and additional files. When a file is uploaded, it is renamed and limited to a specified size. Special documents such as Proposals and Final Papers should be uploaded into the appropriate slot and will automatically be added to your Project Page. Images and other files can be uploaded into any other slot such as "file1." To upload a file, simply select which slot to place it in, and then select the file from your computer using the "Browse" button.

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.