Onboarding - MS16

Fall 2024 Onboard - timeline

To get everyone started on the Battery Structures & Cell subteam, it would be good to go through the basics of designing a simple battery pack. This exercise will help you understand what you are contributing to this term!

You’ll start by reading up on some of the battery pack details and manufacturing methods, and then move to design a simple pack to understand how to put everything together and then provide a recommendation for a battery pack for a car similar to MSXV.

This is the exact same process that we go through when starting to design a new pack for the car (or any battery pack for that matter) - so this is all the required knowledge for building battery packs.

This project can be completed largely offline in your own time, but there will be discussions during check-ins and feel free to ask questions on Discord at other times! There is quite a bit of reading in this intro and you’ll come across a lot of words you might not know. But fear not! As an engineer, you’ll 100% be in this situation basically always. Although difficult, you’ll probably learn the most in these situations too! So, don’t be discouraged, search up words you don’t know, and if all else fails skip sections and you’ll likely come back to it later with the information needed to understand it!

Google is your friend and so is this Confluence, search up what term/system/whatever you are confused about on either one and you will find your answer 99.9% of the time

Onboarding Project

Step 1

Read through these PDFs about designing and building a battery pack. These compile a ton of information - don’t be scared to read them, but be sure to spend the time to understand them. If you have any questions, then leave a comment in your introductory forum post on #bat-onboarding on our Discord and someone will get back to you!

If you have no idea how batteries work, watch this:

How Batteries Work - Battery electricity working principle

If you have no experience with circuits, voltage or current, watch these:

Voltage Explained - What is Voltage? Basic electricity potential difference

What is CURRENT– electric current explained, electricity basics

Battery 101 (Optional but helpful!)

Hardware Week 5 - Batteries Introduction

Start off with reading these: (These are really great!)
Part 1: Introduction to battery pack design and building, Part-1.

Part 2: https://www.electricbike.com/introduction-battery-design-2/

Part 3 (Optional): https://www.electricbike.com/introduction-to-battery-pack-design-and-building-part-3/

Here is a Video explaining basic electrical calculations (Hint: these calculations will be used in the exercise):

Electricity Explained: Volts, Amps, Watts, Fuse Sizing, Wire Gauge, AC/DC, Solar Power and more!

Step 2

We’ll start with a simple pack - here are some of the specs that we want for this project:

Item	Spec	Notes

Item	Spec	Notes
Amount of Energy Stored in pack	100Wh minimum	We also want minimum weight while meeting this criteria. Minimum weight is a hard requirement (must be met).
Cell Nominal Voltage	3.635V
Cell Nominal Capacity	3450mAh
Operating Voltage	6-18V	Must stay in this range for the entire discharge. At any charge state (from fully charged to fully discharged, the pack voltage should be more than 6V and less than 18V).
Single Cell Min, Max Voltage	2.5V, 4.2V	At the full charge and full discharge limits

What do you recommend for the number of cells in series and parallel, and why did you choose those numbers - we’re looking for an answer in the form of XPYS, where X is the number of cells in parallel and Y is the number of cells in series, along with a justification.

Step 3

Now that you should know how to design a battery pack, we’ll get you to run through the process of choosing a battery configuration for a car, given the following parameters (chosen to loosely represent Midnight Sun XV):

Car Specs:

Item	Spec	Notes

Item	Spec	Notes
Race Distance	3000km
Car Average Velocity	60km/h	Assume average velocity for the entire duration of the race, and that the path is flat.
Power Consumed travelling at Average Velocity	1005W	Per Motor
Peak Motor Power	5000W	Max power that the motors will draw (per motor)
Number of Motors	2	Motors on each of the 2 rear wheels
Motor Controller Min, Max Voltage	50V, 165V
Single Cell Min, Max Voltage	2.5V, 4.2V	At the full charge and full discharge limits
Nominal Cell Voltage	3.635V	Average voltage of a cell over the full discharge curve
Single Cell Capacity	3450mAh	Assume all cells are perfectly balanced
Max Discharge Current of Single Cell	10A
Solar Power Input	800W	Assume the sun is always shining for the entire duration of the race

What do you recommend for the number of cells in series and parallel, and why did you choose those numbers - we’re looking for an answer in the form of XPYS, where X is the number of cells in parallel and Y is the number of cells in series, along with a justification.

Step 4

Submit your answer to @Nicole Choe or @Shem Kim through Discord and then we can discuss some more in detail about your answer

Step 5

After you get your answers confirmed with @Nicole Choe or @Shem Kim, use SOLIDWORKS to CAD a very simple cell holder for a 5S1P Battery Pack composed of five 18650 cells. This is meant to be a fun project! Don’t over-think it. We want to see a top cell holder, a bottom cell holder, and five 18650 cells in an assembly. If you are having trouble with getting access to SOLIDWORKS, reach out to us and we’ll help. If you are having trouble with making the CAD, there are a lot of tutorials on YouTube, but you can also reach out to us for help. We highly encourage everyone to try figuring it out by yourself though, self-learning is a very important skill that you will need in the team!

Once you are done, send pictures of your assembly design to @Nicole Choe or @Shem Kim to get it quickly reviewed. Once everything is good, we’ll help you 3D-Print your model and put together your pack!

Example of a Pack Design, Doesn’t Have to Look Like This!

After finishing onboarding, we’ll have a 1-on-1 meeting where we will be going over what your goals are for the team, what you want to work on, so we know what projects to assign to you! Good luck!