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To get everyone started on the battery box team, I’ve thought it would be good to 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 designing a simple pack to understand how to put everything together and then provide a recommendation for a battery pack for a car similar to MSXIV. 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 required knowledge for building battery packs.
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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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
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):
If you think there’s info missing here, message Micah Black on slack and I’ll first make sure I didn’t make a mistake in the info provided, and then help you out to make sure you’re on the right track!
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 4
Submit your answer to the Battery Lead (Micah Black ) through Slack and then we can discuss some more in detail about your answer. I’ll make sure that you understand what you will be contributing to this term!
Extra Info
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 - its another power source for the car and will lighten the load on the batteries.