# Battery sizing in an electric vehicle

• Vibhav
In summary, the conversation discusses the development of an electric vehicle for a final year project. The weight of the vehicle is 800kg and it is designed to reach a maximum velocity of 80 km/h with a range of 100 km. The calculation for the required power led to the use of a 30 kw 3 phase AC induction motor. The conversation also touches on the importance of defining the requirements for the project and considering efficiency in the design process. The comparison to the 2017 Nissan Leaf highlights the scale of the project and the need for a team to complete it. The use of a high voltage battery is discussed and the need for proper sizing of cables is mentioned. The conversation concludes with an interest in updates on the project
Vibhav
Hi..
i am working on a developemnt of electric vehicle as my final year project..i have calculated the max. power required by 800 kg vehicle is 30 kw..
so i am using 30 kw 3 phase AC induction motor..

weight : 800kg
max. velocity : 80 km/h
range : 100 km

The simplest calculation ignores efficiency and use data. Just multiply power times time. 30 kw for one hour means a 30 kwh battery. So how many hours do you need? The hours of use, or the distance range are requirements. One of the first things to learn in your project is that nothing can be designed without first defining the requirements.

What was the requirement that led you to the 30kw number for the motor?

The next step, is to recognize that the vehicle is not driven at maximum power all the time. (Think of a conventional auto. You do not (or should not) drive with the gas pedal all the way to the floor all the time.) So, 30 kw is the maximum power, what is your estimate for the average power? Multiply that by hours to get a better estimate of battery capacity.

Then, make a guess about efficiency. Perhaps 80% is a good number. Divide the battery capacity estimate by 0.8.

These answers are very general. You must provide numbers for averages and efficiency for your own project. Ask your project adviser what proof you need that those numbers are correct.

+1

Governments specify the test conditions/driving profile under which range is assessed. I know its different for Europe and the USA because the range quoted for the Nissan Leaf is quite a bit different in different jurisdictions.

So ideally you need to work out how the weight of the car affects the energy used while driving to one of these standards. Although I'm not sure how easy that is to calculate.

I've never built an electric vehicle, but I've thought about it occasionally, and I've spent some time browsing http://www.diyelectriccar.com/forums/ that I thing is good.

Vibhav said:
weight : 800kg
max. velocity : 80 km/h
range : 100 km

You are making a vehicle that weighs almost 1 ton and you want it to go 50 mph?

in comparison here are the approximate specs for the 2017 nissan leaf...
motor: 80 KW
Weight: 1500 kg
Battery: 30 kWh
range: 160 km
max speed: 150 km/hr

Your car will be about 1/2 the weight, with 38% the motor strength, which is fine. Its just a note of the scale of your project

This is quite the project. I hope you are doing this with a team, because it will be a lot of work.
What are you using for a motor. Do you plan on using a high voltage battery? Low voltage will increase your current and could cause heating problems in cabling and the battery. High voltage will cause a bunch of other problems as well, as well as special considerations in designing it.

To give you perspective if you use a 600V nominal battery pack, you'll expect about 50 Amps of current at peak load. You will need to size your cables for this

What type of controller do you plan on buying/making?

Keep us posted on your progress!

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## 1. How is the battery size determined for an electric vehicle?

The battery size in an electric vehicle is determined by several factors, including the desired range of the vehicle, the weight of the vehicle, and the efficiency of the battery itself. Generally, a larger battery will provide a longer range, but it will also add weight to the vehicle and decrease its efficiency.

## 2. What is the typical battery size for an electric vehicle?

The typical battery size for an electric vehicle varies depending on the make and model, but most EVs have a battery capacity between 40kWh to 100kWh. This translates to a range of about 150 to 400 miles, respectively.

## 3. How does the battery size affect the performance of an electric vehicle?

The battery size has a direct impact on the performance of an electric vehicle. A larger battery will provide a longer range, but it will also increase the weight of the vehicle and potentially decrease its acceleration and handling capabilities. On the other hand, a smaller battery may limit the range but can improve the overall performance of the vehicle.

## 4. Can the battery size in an electric vehicle be upgraded?

In most cases, the battery size in an electric vehicle cannot be easily upgraded. The battery is a fundamental component of the vehicle and cannot be easily replaced or upgraded like a traditional car's fuel tank. However, some manufacturers do offer battery upgrade options for certain models.

## 5. How long does a battery in an electric vehicle typically last?

The lifespan of a battery in an electric vehicle depends on various factors, such as usage, charging habits, and temperature. On average, EV batteries are expected to last between 8 to 10 years or 100,000 to 200,000 miles. However, advancements in battery technology are constantly being made, and the lifespan of EV batteries is expected to improve in the future.

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