Current TRL: 3 (12/17/21)
“A prototype pack has been fabricated. Simulations have been run of the pack physics to handle necessary stresses.”
Battery Packs and Accumulator Management System
The TSV subsystem delivers high voltage power to the FSAE vehicle in order to power it. Each of the two packs in the vehicle supply about 54V through 16 LiFePO4 battery cells which are each monitored through the accumulator management system (AMS). The AMS consists of a pack manager (PacMan) and 16 cell manager (CellMan) system boards, one per cell. The two packs are wired in series to provide ~108 V to the assembled accumulator system. The subsystem interacts with other car subsystems via data acquisition through CANOpen and via the vehicle’s safety loop.
The scoped problem for this semester is having one fully assembled battery pack that can be used as a prototype. This includes components being designed, manufactured, and/or ordered so the pack can be assembled. Additionally, this semester the firmware for the cell manager boards (Cellman) will be debugged and validated. Also, chargers that can be used in the actual competition will be acquired as well as any other hardware needed to charge the batteries in a rule compliant way.
Motivation for Problem Space
The motivation for this project scope is to create a pack that can be used to develop two additional battery packs that can be used on the current car. Having a prototype that can deliver sufficient power and perform at a high level so that the club can be successful is the driving force behind this design.
Currently we are at a TRL level 3. We are at this state because the pack has not been fully assembled yet. It is almost to a TRL level 4, but until it reaches TRL 8, the pack will not be integrated with the car because a series of tests, including static and load bearing testing as well as Cellman and Carman integration, must happen first. These are our motivation to get to TRL 8.
The proposed solution to achieving the goals of this battery pack problem is to first assemble a full pack like stated above. Since the mechanical parts have been put in the place, the pack will be handed off to electrical engineers to work on integrating the electronic components into the pack in order to complete the prototype and achieve these tests.
The prototype pack will most likely not be handed off to the club due to the danger of live cells once they are placed into the prototype. The mechanical design portion may be handed off for the two additional packs, but the electronic components are too sophisticated for the club to handle alone at any point. It will be a closely guided project for portions handed off to the club.
The FSAE project car for this year consists of many different subsystems. These subsystems all are responsible for uniquely contributing to the overall performance of the car on race day. The battery pack subsystem is responsible for delivering power to the various electrical components of the car, including the motor. Having a safe and efficient battery pack is crucial to having a functional car.
Codes and Standards:
This article for codes and standards addresses the efficiency of a battery pack. The performance of battery packs like the ones on our car should be characterized by including energy inputs, thermal outputs, and electrical outputs. This practice will allow us to calculate the fuel-to-energy conversion efficiency, and it should be determined within 2% uncertainty. This code will allow us to know if our pack will be efficient before we manufacture it, and this design will allow us to effectively run the Carman, motor, and other electrical components of the car.
Metrics and Constraints:
The objective is to produce two 16 cell battery packs, one for either side of the car that can provide adequate voltage supply to the motor controller, car manager, and motor.
The battery pack should have two 12″ handles for ease of picking up.
The battery pack should have an external charger to recharge it.
The battery pack should be chargeable regardless of if it’s in the chassis or not.
The battery pack should be controllable with a screen/interface from the outside. This includes Cellmans and Pacman.
The battery pack must fit into the welded on battery pack holder on the chassis.
The battery pack must be fastened down with (4) 5/16” bolts.
The battery pack must be completely insulated between the cells and structural members. No conductive material may be showing from the circuit of the 16 cells.
The battery pack must have a master kill switch (SMD switch).
The battery pack must be able to withstand a deceleration of 40g in the horizontal plane and 20g in the vertical plane.
Spring 2021 Subsystem Team Poster
Fall 2021 Subsystem Team Poster
Mechanical Test Plans
Full Pack BOM
Mechanical: Complete Battery Parts List
2021-2022 Team, Start Here! Updated 5/19/2021
MechE Battery Pack Errata
Link to the Inventor Files in Google Drive: Updated 12/17/2021 https://drive.google.com/drive/u/1/folders/1woqcmZuH5jgQ1lVCO3KrppOOXsQnlVi2
Where the Mechanical State is as of October 4, 2021:
Pack Assembly Video
Refer here to the high-level drawing section for full mechanical drawings and inventor files located in the CompleteAssembly/2019-2020Complete/TSV/FinalPackAssembly
AMS Board Documentation
|Schematic:||1.0 – PDF||2.2 – PDF|
|1.2 – PDF||—|
|1.3 – PDF||—|
|1.3 – PDF
|PCB Layout:||1.0 – PDF||2.2 – PDF|
|1.2 – PDF||—|
|1.3 – PDF||—|
|BOM:||1.0 – Excel||2.2 – PDF|
|1.2 – Excel||2.2 – CSV|
|1.3 – Excel||—|
|Render:||1.0 – PNG||2.2 – PNG|
|1.2 – PNG||—|
|1.3 – PNG||—|
The firmware for the packs is written in Arduino to reduce the development time and learning curve for new developers. The latest code can always be found at the Lafayette-FSAE Github or by specifically going to the PacMan Firmware Repository.
The Getting Started and further documentation is located on the Github’s README file (which is presented to the visitor when accessing the repo). A copy of the code & binary file from: April 14th, 2020 can be found directly here: PacManFirmware-master
Battery Pack TRL Chart
|TRL||What does this look like?||Expected Completion Date|
|9||Packs have been used in a competition setting.||Race Day|
|8||There is full integration with the car (pack securely attached to chassis, safe and neat wiring/cabling, CellMan-PacMan interface, PacMan-SCADA interface, TSV power).||4/22/22|
|7||There is full integration between CellMan and PacMan and electrical subsystems with SCADA via CANOpen bus along with cabling integration with TSV.||3/2/22|
|6||The frame has been subject to real stresses. CellMan and PacMan integration allows for communication using I2C and charging capabilities have been tested/verified.||12/15/21|
|5||The pack can be lifted without shifting the cells or any internal equipment. CellMan and PacMan boards can operate independently with measurement and display capabilities.||11/17/21|
|4||Assembled frame/walls can hold 16 cells, SMD, electronics, and are equipped with proper holes for wiring.
CellMan and PacMan boards can be programmed and operate independently.
|3||A prototype pack has been fabricated. Simulations have been run of the pack physics to handle necessary stresses.
Fabrication of prototype boards is completed and SPICE simulations or KiCAD simulations have been run as necessary.
|2||Inventor files and KiCAD files have been populated.||Completed|
|1||Preliminary ideas for frame and pack geometry have been cemented, and the stresses the pack must withstand have been defined. Electrical subsystems have been designed (how many boards, hardware hierarchy, communications) as well as the functional contributions of each subsystem.||Completed|
Additional Electrical Documentation
- Display Tutorial: MP4
- Display Design 1.6: PNG
- Object Dictionary: XDD
- I2C Documentation: PDF
- Pre-built RaspberryPi Firmware w/ Arduino IDE & Firmware from 4/5/20: .7z File
- Fuse Calculations: PDF