Project

# Title Team Members TA Documents Sponsor
51 Integrated Robotics Battery/BMS
Adi Nikumbh
Rishav Kumar
Ritvik Kumar
 Shengyan Liu design_document1.pdf
final_paper2.pdf
photo1.jpg
photo2.jpg
presentation1.pdf
proposal1.pdf
video
## Robotics Low Voltage BMS/Battery Pack

Team Members:
rishavk2
ritvik3
nikumbh2
## Problem

One issue with the development of robotics systems for small companies is the issue of battery packs. Manufacturing of a battery pack can be dangerous, and can require the expensive development of a custom BMS system. There are currently few options for completely developed and integrated lightweight battery packs that also contain a high quality BMS system that has capabilities of cutting voltage off in the event of issues. We propose a solution that uses a combination of temperature sensors and voltage sensors to develop a BMS system that can detect when our battery is in danger of thermal runaway and take action to prevent it. This system will be lightweight and inexpensive, making it suitable for use in a wide range of drones, robots and other applications. With the rapidly increasing use of drones and autonomous robots in a wide range of applications, from agriculture to logistics, the need for reliable and safe battery systems is more important than ever. Our solution will help to ensure that these systems are safe and reliable, reducing the risk of development and making robotics safer for everyone.

## Solution
Our solution will be a prototype of a battery pack containing a battery management system (BMS). The system will use temperature sensors to monitor the temperature of the battery, and voltage sensors to monitor the voltage of the battery. These sensors will be hosted on a PCB daughterboard that will directly interface with each cell. The daughterboard will be connected to a mainboard that will be responsible for processing the data from the sensors and taking action to fault the BMS if an improper condition is detected. The fault conditions will include overvoltage, undervoltage, overcurrent, and over temperature or under temperature. If any of these conditions are detected, the BMS will take action to prevent thermal runaway, such as shutting down the battery output through a contactor, or initiating the cooling of our pack through fans. We plan to create a 50V max, 44.4V nominal, 12s1p system that can be used in a wide range of applications, from drones to robotics.
Solution Components

## Battery Pack
This subsystem will be a 12s1p lithium ion battery pack. We will use high capacity pouch cells with a nominal voltage of 3.7V. We have chosen pouch cells due to being able to manufacture our pack without needing to spot weld. The cells will be connected in series to create a 44.4V nominal battery pack, with a capacity of 13 ah. The voltage was chosen to match the 52V system the Tesla Optimus robot runs off of. The battery pack will be housed in a lightweight and durable enclosure, with provisions for mounting the BMS and other components. The cells will be bolted together with low resistance bolts, and the pack will be designed to be easily disassembled for maintenance and repair. The pack will also include provisions for cooling, such as vents or heat sinks, to help prevent thermal runaway.

## Daughterboard
This subsystem will be a PCB that will host the temperature and voltage sensors. The daughterboard will be connected to the mainboard via a two wire isoSPI interface, which will allow for easy communication between the two boards. The daughterboard will be responsible for monitoring the temperature and voltage of each cell in the battery pack, and sending this data to the mainboard for processing. The daughterboard will use Analog Devices LTC chips to monitor the voltage of each cell, and will use thermistors to monitor the temperature of each cell. The daughterboard will also include provisions for connecting to the mainboard, such as headers or connectors.

## Mainboard
The mainboard will be a PCB that will host the microcontroller and other components. The mainboard will be responsible for processing the data from the daughterboard, and taking action to fault the BMS if an improper condition is detected. The mainboard will use a STM32H7 microcontroller to process the data from the daughterboard, and will use relays or MOSFETs to control the battery output. The mainboard will also include provisions for connecting to the daughterboard, such as headers or connectors.

## Software
The software for the BMS will be developed using the STM32 HAL library, and will be responsible for processing the data from the daughterboard and taking action to fault the BMS if an improper condition is detected. The software will use a state machine to monitor the temperature and voltage of each cell, and will take action to prevent thermal runaway if any of the fault conditions are detected. The software will also include provisions for logging data, such as temperature and voltage readings, to help with debugging and troubleshooting. It will communicate with a ground station via a serial interface, such as UART or CAN, to provide real-time data and status updates.

## Criterion For Success
In order to successfully complete this project, we will need to meet the following criteria:
- The BMS must be able to monitor the temperature and voltage of each cell in the battery pack, and take action if any of the fault conditions are detected. This action could include cooling the battery pack, shutting down the battery output, or other actions as necessary.
- The BMS must be able to communicate with a ground station via a serial interface, such as UART or CAN, to provide real-time data and status updates.
- The BMS must be lightweight and inexpensive, making it suitable for use in a wide range of applications.

We also have a number of extensions that we would like to pursue if we have time. Our project will still be - deemed successful without them, but these would allow us to showcase additional technical complexity
- Integration of a shunt resistor or hall effect sensor to measure current and pack power onboard
- Development of a passive or active cell balancing algorithm
- The development of a laptop hosted GUI to view the live status of the cells inside the pack
- Wireless transmission of the pack data for viewing
- (very stretch) integration of an onboard DCDC to output variable voltage and power

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.