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Fall

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2023 Onboard - timeline

To get everyone started on the battery box team, 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 Slack 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

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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 message the #mech-battery-box channel on slack and someone will get back to you!

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https://www.youtube.com/watch?v=8Posj4WMo0o

Battery 101 (Optional but helpful!)

https://www.youtube.com/watch?v=lUZ9l1iAYK8

Start off with reading these: (These are really great!)
Part 1: https://www.electricbike.com/introduction-battery-design-1/

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View file
namePack Building Part 2 _ ELECTRICBIKE.COM.pdf


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

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https://www.youtube.com/watch?v=cX4s-bxn4fs

Step 2

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

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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

Draw a diagram sketch of the cells, how they are connected together, and where the main battery terminals are for the battery configuration calculated for Step 2.cell plate holders (what will hold the batteries in place to make the connections, see below for an example) you would 3D model for your answer, a simple design will work. This will help you on the working session on the 16th when we design cell plate holders together on SOLIDWORKS (smile)

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We will be holding a tutorial session on Sept. 16th @ 1:30PM to work through Steps 2 & 3 but we encourage everyone to try on their own first. You will need to answer question 4 on your own so give it your best shot and don’t be scared to reach out for help!

Step 4

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 XIV):

Car Specs:

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 5

Submit your answer to the Battery Leads (Owen Li , Eric Zhao ) Donna Kim , Shem Kim or Nicole Choe through Slack and then we can discuss some more in detail about your answer. We’ll make sure that you understand what you will be contributing to this term!

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Extra Info

Tip

How does the Solar Work?

The solar panels on the Midnight Sun Vehicles provide power directly into the High Voltage system, which powers the motors - it's another power source for the car and will lighten the load on the batteries.

Extra Resources

https://batteryuniversity.com/articles

And read “Inside 18650 Cells”: https://www.electricbike.com/inside-18650-cell/

Then read these for some more in-depth background for battery packs:

View file
namePack Building ASC 2015-Solar-Car-Conference-Battery-Electrical.pdf

View file
namePack Building ASC 190202_How-to-Build-a-Pack.pdf