Continuing your Project

Description

Groups that wish to continue their projects are encouraged to sign up for Undergraduate Independent Study: ECE 396, ECE 397, ECE 497, or ECE 499.

Funds of up to $500 are available in order to defray project expenses. These funds have been generously provided by the ECE Alumni Fund and may be used for materials and supplies, equipment, computer software, etc. Funds may not be used for salaries or wages. Purchases may be made through the ECE Business Office, ECE Stores or reimbursement of personal funds with proper documentation. More information will be provided upon approval.

Please see the Undergraduate Independent Study Funding page for more details.

The Leung Fund provides another avenue for obtaining funding to continue a project conceived of in ECE 445. Prior projects have also continued through various programs in the College of Engineering's Technology Entrepreneur Center programs, including the Cozad New Venture Competition.

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.