My Battery Powered Car Project for University Please Help!

Science, Engineering, & Tech
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Hi guys,

At the moment i’m studying Mechanical Engineering at University and i’m in my first year, i’m looking to go on and do my doctorate eventually and I want to start working on a project now, this may sound a bit wild and far fetched but I want to design and make my own electric car, now this car I will fit with a Tesla electric charging port, now where i’m stuck is finding material on the Tesla car in terms of its battery cell storage tech and the way all the electronics come together to work in harmony. I’m looking for material to educate me on several things to do with this, I also want to create a touch infotainment system for the car as well which controls most of the cars mechanics and what else comes with an infotainment system. If you guys could recommend any material I could read on these areas which I am lacking at or any guides or anything that can help, Im also going to be recording my journey and I will be publishing it on YouTube on my own channel and I will mention everyone who has helped me in my journey for my masters thesis. Also what coding languages should I learn, what books should I read etc

Thank you in advance to anyone who has helped and it will never be forgotten!!!

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So My understanding is that the Tesla cars are still using 18650 cells in large banks there are more than a few Guides and companies out there that make custom EV or EV conversions a forum like this may be a better place for the mecanical end of things http://www.diyelectriccar.com/

In terms of the Infotainment system you may want to see how or what you can bolt/mod onto a cheap Android car audio system. like an EinCar system or maybe check out the Kodi Car computer option that is out there http://www.ardumotive.com/raspberry-car-pc.html

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I’ve done a lot of research on this actually since it’s a dream project of mine… some day when I have a garage.

  1. You can totally do it with an old car, kit components, tools, and a lot of time. There are plenty of motor + controll + battery components to choose from. http://www.evwest.com/catalog/index.php?cPath=8 Spend some hours doing some googling and you will find TONS of material published by people who have been making their own electric cars for decades now.

  2. As I’m sure your adviser has/will mention that you need to narrow your focus. Do you want to build an electric car or do you want to build the UI with a touch screen? Both are potentially huge projects. If you build the car with kit components that an awesome project, but I don’t see how it’s anything new or paper worthy. If you wanted to make it new and fresh somehow with a custom electronics system then you’re way out of your depth as a mechie… you need an EE. You’ll be dealing with high voltages, dangerous currents, and massive amounts of potential energy stored in the batteries. It can be a very dangerous undertaking without a lot of understanding on how these systems work.

  3. Here are some possible electric car breakdowns that I’ve observed in my many hours of research.

Case 1: Cheapest option.

$2000 - Roller chassis car off craigslist (prolly an 90’s sedan)
$500…$1000 - Fork lift DC motor off ebay… heavy and inefficient
$300 - Speed controller
$10,000 - lots of prev generation lion batteries

With some scrap metal, welder, MANY other tools such as engine lift etc, you can do this yourself in about 6 months of regular work. The car will be able to do about 45mph and go maybe 30 miles on a charge tops. You’ve made a road legal golf cart.

Case 2: Middle of the road.

$ 5000 - Good small car of choice
$ 5000 - AC motor and controller
$ 1500 - Adapter for AC motor to trans
$ 25,000 - Good battery system

This project is also duable for the average handy man with a good shop, lots of tools, and careful engineering. When finished it’ll be able to do 90mph easily with a range of 100mi+. It’ll take 1-2 people a full year of hard steady work to finish but when done will be impressive and a blast to drive.

There are a lot of subsystems that will take up a lot of time to plan, build, test, and debug; Engine water cooling, battery management, car accessory pressure for brakes+steering, weight distribution, battery cooling, etc.

Example: http://www.electricsubaru.com/

Case 3: High end.

$ shit loads… you need to be independently wealthy or have a well motivated sponsor.

Top end garage, cream of the crop parts, no expenses spared. Good relations with a machine shop that can regularly fullfill custom orders. EE, ME, and design experts on hand for careful scrutiny of design. Project is well funded with full time workers…

Example: https://youtu.be/Rt4fGIoVMpM

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I am assuming that by “design”, you also want to build this electric car so my following recommendations assume you are building it as well.

Safety First - Electrical Components

Batteries

When it comes to powering a car with batteries the only viable chemistry is Lithium-Ion cells due to their energy density per volume and energy density per weight. While many precautions are taken by battery manufacturers, there are a few ways that lithium can be dangerous if not handled properly and many involve overheating the cells until they rupture.

  1. Overcurrent
  2. Overvoltage
  3. Overheat
  4. Impact Force

While 4 and parts of 3 are mechanical, 1, 2, and 3 are electrical. If you are interested in designing these from scratch I will go into more detail for how to prevent 1, 2, and 3. If you are using pre-existing battery packs with protection circuits then I will just leave this here as a reference. My recommendation is to buy used Tesla packs from ebay.

Fast Charging Circuits

There are professional electrical engineers that won’t go near the voltages and current output of this stuff. I would recommend using a “slow” laptop-style charger that can output 24V DC 10A

On To Mechanics and Efficiency

Imagine a rear wheel drive gas car. To connect the engine to the rear wheels, an interface needs to be made from:

Motor > Transmission > Drive Shaft > Differential > Rear Axle

There is inefficiency in each connection and just by using a front wheel drive mechanism you can move to:

Motor > Transmission > Front Axle

However, in new electric cars, the front axle and transmission are actually one cohesive piece of machinery! This makes the power train:

Motor > Transmission/Front Axle

There are few losses in this setup and this makes the vehicle quite “torquey”

Motor Selection

I would recommend not going cheap on your electric motor since the mass of a car + person is so high; however, buy used on your first motor in case you burn it out. Large brushed motors are usually cheap.

Aerodynamics

Once you get your vehicle to speed, the main ineffiency you will be fighting is air resistance. I will leave this exercise to the mechanical engineers.

Chassis

The lighter the better. I would buy a used shell with little rust.

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Nope definetly not far fetched … more like super far fetched.
I graduated recently Electrical engineering and had 2 of my coleagues try and make a small racing bolid … 1 month in after they calculated the price expectancy of the project and that they realized no one of them is good with mechanics and programing and also had just 6 months to finish it, they chose to make a scooter.

5k euro it cost them. For a scooter… 2 times change in batteries, 5 electrical motors and 20+ itterations on the controller board. They also changed a few times the structure of the bike because there were differences in the motors and batteries.
I helped them when I was free… it was a lot of work.

And just to point out the end result was not really for the marked. Max speed 30km/h if you are under 70kg. About 40km range. I say about because we tested it on a track and it lasted 43 km so it will be less than that for sure.

Edit:
I don’t mean to discourage you I am just saying to do something like that you will need friends in other fields and if you are able to organize a team of like 5 to 8 students and you have the budget, go for it.
btw who you will need for sure - electrical engineer (at least 1) you and at least 1 more which is studiyng mechanics. Look for someone who has passion for cars and design of cars. And also 3 engineers in automation because they study electronics and programming so you can go without programmer and they can help the electrical engineer.

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A classic CASE 1 that I described above.