P18262: Battery Health Management System
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Customer Handoff & Final Project Documentation

Table of Contents

Team Vision for Final Demo and Handoff

Goals for Team 18262 in this Phase

The teams goal for this phase was to completely integrate the project with EVT's motorcycle. This required to have the system built, validated and coded for the customer hand off. On top of this, the goal was to have all the documentation on EDGE for future EVT teams to use. In the previous stage all the hardware validation has been completed.

Accomplishments for Team 18262 in this Phase

The team was able to successfully hand off the design to EVT. The boards were mounted onto the bike and tested during EVT's test day on April 21st. The driver of the teams motorcycle performed multiple test laps on the bike to test the design. The boards were able to successfully balance the batteries and provide data for the team. This edge page's purpose will be to store all the information that the future members of the team will need to work on the project. The team’s testing approach was to fully test each of the functions of both boards independently to find any design flaws, and then move towards full-system tests. Due to REV2’s scheduled completion day well after the end of MSDII, the final test of the BMS would be on REV1, during an EVT test day. While the hardware configuration is not identical to what will be seen on REV2, it is similar enough to validate the performance of the designs in union with the rest of the tests we have done. This was determined to be the most accurate and effective evaluation of the project by the team, and was approved by our customer.

Test Results Summary

Test Plan Setup

Test Plan Setup

Master Board Test Results and Summary

The master test plans can be found here

The majority of the test plan for the Master boards was completed successfully. Features such as isoSPI and CAN communication interfaces were completely tested with the Slave board and some preexisting EVT hardware. Voltage and current measurement was validated to the extent of our testing equipment. Two minor issues were discovered on Master 4.0: one of the SPI signals was missing a pull-up resistor, and the SOC chip was missing a thermistor input. These issues were resolved on the second revision of the board, Master 4.1. The hardware on the master boards have been fully verified and validated. The second revision of the board was populated and test to ensure it works. The board was mounted on REV1's battery pack in a custom enclosure. More pictures can be seen in the Full Scale Integration and Customer Handoff Results.

Slave Board Test Results and Summary

The slave test plans can be found here

Each of the primary functions of the Slave board were tested individually. Communications via isoSPI was confirmed using the Linduino and LTC6820 development board. The cell voltage and temperature readings were also confirmed. Accuracy of the LTC6811’s ADCs were verified with a multimeter, shown in Table 3. A few small issues were found with the 4.0 design during testing. The power resistors in the discharge array became very hot after a short balance cycle. The isoSPI termination resistor was put on the wrong side of the isolation transformer. It was discovered that the GPIO pins on the LTC6811 could not source current when configured as digital outputs. These design flaws were fixed in concurrent revisions. The slave boards were mounted on to the REV1 battery packs in custom enclosures. More pictures can be seen in the Full Scale Integration and Customer Handoff Results.

Slave Results Showing Balancing

Slave Results Showing Balancing

Firmware Test Results and Summary

The requirements for the firmware team were to create validation software. The firmware validation allows the team to write software to the board, and create the "test software" to give to the customer. This software's purpose is to demonstrate the projects functionality. At this point, the EVT Firmware Team will take over future development of the board.

State of Charge Write-up

The small scale SOC test was done and all of the data was collected. The state of charge readings make sense with what was expected and the voltage readings are similar to normal lithium-ion voltage curves. Continued work on state of charge will be done by the EVT team. The current implementation was deemed enough by the customer.

Example test setup

Example test setup

Voltage curve

Voltage curve

 State of Charge curve

State of Charge curve

State of Charge Test Plans can be found herehere

Full Scale Integration and Customer Handoff Results

Engineering Vs Actual

Engineering Vs Actual

Integration with REV1 was a success, mainly due to the careful communication between the various EVT sub-teams throughout the build process. By sharing 3D CAD models, accurate enclosures for the boards were made by EVT’s mechanical team. Firmware was developed and tested alongside our hardware testing. The BMS voltage measurement functions were tested on REV1, with the results shown in Table XX. The team was pleased with the results, as most of the cell readings were exactly the same as multimeter readings. The last cell in the stack was consistently off by a few millivolts, but were still within our margin of error based on the engineering requirements. The BMS was fully implemented on REV1 during a test day. The only major function not fully validated was the SOC function. All other functions were tested, and satisfy our engineering requirements.

A total of 8 fully tested Slaves and 2 Masters were handed off to EVT. While firmware is still being refined at the time this paper was written, final deliverables of this project are complete. Our customer, Alex Young, has expressed his customer satisfaction

We would like to give a special thanks to our customer, Alexander Young, our Faculty Guide, Harold Pascal, and EVT’s Faculty Advisor, Carlos Barrios.

Images of Test Day and Implementation

Integration

Integration

Integration

Integration

Integration

Integration

Integration

Integration

Attaching Boards

Attaching Boards

Test Day Image

Test Day Image

Test Day Image

Test Day Image

Test Day Image

Test Day Image

Test Day Image

Test Day Image

Test Day Image

Test Day Image

Risk and Problem Tracking

Risk Table

Risk Table

Risk Graph

Risk Graph

All risks have been driven to zero. The project has been sucecssfully handed off. All the state of charge hardware is tested and validated on the boards. All that remains is EVT's firmware team to complete coding for it. The customer is fine with this progress.

Final Project Documentation

Link to Paper

Link to Poster

Poster

Poster

Final Documents

Link to Master BOM 4.1

Link to Master Schematic 4.1

Link to Slave BOM 4.1

Link to Slave Schematic 4.1

Recommendations in the Future

We have created gerber filed and Altium Designer files for the team to use to modify and perform any design changes necessary on the project, specifically the state of charge. All work is also documented on the teams wiki page. We will continue to work with the team until the race day in July to help ensure the REV1 project is a success.

Functional Demo Materials

The final presentation can be found here

Testing Standards Used

As part of the Advanced Circuits Sponsorship, the boards were designed based off the standards provided by Advanced Circuits to ensure functionality as well as reduce cost. This is accomplished by following the standards allowing the circuit cards to be produced easier.
 Advanced Circuits Requirements for boards

Advanced Circuits Requirements for boards

public/PDDR/ppihc.PNG

public/PDDR/ppihc.PNG

Pikes Peak International Hill Climb has a number of electrical standards which our team will need to consider when developing our REV2 motorcycle. Of those, two specific standards are extremely relevant to our project. Relevant Competition Standards “All exposed conductors operating at greater than 36V must be properly insulated and marked with ‘High Voltage’ signs”. “A separate fuse (not a circuit breaker) will be placed in series with the main battery and the rating will not exceed 200% of the maximum expected current draw. All low voltage taps from the main battery will be separately fused. All fuses must be placed first in series with the battery starting at the positive connection”. The first can be mitigated with proper enclosure design, in addition to careful labeling in the harness and on the PCB. The second has been considered in the selection of individual fuses on all of the battery management system measurement points. These regulations are important for ensuring the safety of all competitors in the electric vehicle class. A full pdf of the 2017 competition rules can be found here: PDDR/PPIHC_Rulebook.pdf

Plans for Wrap-up

Conclusion of the Project

Since this team are members of the EVT team, we plan on continuing to help the customer with the project. The project itself has been fully tested and implemented on REV1. We will be working on REV1 as a team until the race day in July of 2018. After that, we have provided the team with documentation and brought several members up to speed on the project to allow them to take over after we graduate.

Individual Plans

Steve Titus - 3 Week Plan, Customer Handoff - 3 Week Plan, Final

Ben Stewart - 3 Week Plan, Customer Handoff - 3 Week Plan, Final

Will McCaffrey - 3 Week Plan, Customer Handoff - 3 Week Plan, Final

Murali Prasad - 3 Week Plan, Customer Handoff - 3 Week Plan, Final

Jacob Allison - 3 Week Plan, Customer Handoff - 3 Week Plan, Final

Greg Malanga - 3 Week Plan, Customer Handoff - 3 Week Plan, Final


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