Breadboard Demo

Description

The Breadboard Demo is an informal but mandatory event. Its purpose is to show your instructor and TA a circuit that you have been working on in the lab for your project. It is expected that the circuit will include the microprocessor you will be using in your project (it can be mounted on a development board) and it will be connected to a project subsystem. The microprocessor should have a program downloaded onto it that allows it to communicate with the subsystem, i.e., control the subsystem or receive data from it. It is expected that the power source for the circuit will be a laboratory power supply. The function of the subsystem should be demonstrated. The commands or data should be displayed on a pc or other display means. You should be able to explain how the circuit is used in the project and be able to justify design choices. A Breadboard Checklist will be provided and filled out.). Use the following format:

    See the Breadboard Demo Rubric for specific details.

Grading

Full Credit (20 points) will be given if the circuit works, is of adequate complexity, and a good explanation of its features is given by the team. Point reductions will be given if the circuit fails to work (-2), lacks complexity (-2), or seems inappropriate for your project (-2). The Breadboard Demo is a team activity and results in a team score.

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.