Project

# Title Team Members TA Documents Sponsor
50 "Bar"-O-Meter
 Chen Hu
Tuo Liu
Yiming Song
 Igor Fedorov design_document0.pdf
final_paper0.pdf
presentation0.presentation
proposal0.pdf
Ever had a hard time choosing which bar to go because you don't know whether it's gonna be a fund time or your type of bar? Well, we have come up with A Different Kind of "Bar"-O-Meter to tell you about what's going on at your favorite bars!

We plan on installing weight sensors under the floors at bars to gather our raw data on the total weight at each bar. After data collection, we plan on using simple algorithms to calculate the estimated number of people at the bar. Additionally, the atmosphere (i.e. just chillin' around or busting out my moves) could be determined by taking a look at the fluctuation of the weight data. Ultimately, these data will be transmitted and uploaded to a website so that people can easily see what's the most popular place to go!

Data Collection: we hope to achieve this by installing multiple weight sensors underneath the floors. Our initial thought is to employ a variable resistor controlled by the weight. If this does not provide the level of accuracy we desire, we will modify our approach to accomplish a reasonable result. Additionally, by the time we submit our proposal, we also hope to decide on the way that we power these sensors. To make these devices more economical, we desire to design it in a way that would only require an external battery that needs to be replaced once a year. There are, however, other alternatives to power such system, i.e. wall powered, self-powered, etc.

Data Transmission: to ensure the data quality while lowering the cost, we would use wires to transmit the data. The resistance of the variable resistors would be measured and then the data will be transmitted to a centrally located box to store the data and wirelessly (via bluetooth) upload to a computer.

Data Output: The estimated number of people could be obtained by dividing the total net weight by the average weight of an adult. Also, the weight fluctuation would dictate the type of atmosphere at the bar. The output will be readily available on a social networking site.

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.