# EV Chassis Design



## lungley (Nov 23, 2009)

Hi there

I am a masters student at university and am undertaking the task of designing a new chassis for a 4 seat electric passenger vehicle. I am asking for for some assistance on where best to start looking and what i need to consider in the design process. My aim is to model the entire structural frame for the EV, propulsion system, electronics and the body are not to be included initialy. Safety is an important deliverable, i must endevour to produce a safe reliable vehicle. CAD models are to be made and tested to assess crash worthiness. If anyone could provide usefull key information about starting a project such as this or what books or other sources would be of the greatest help it would be much appreciated.

Nick


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## major (Apr 4, 2008)

lungley said:


> what i need to consider in the design process. My aim is to model the entire structural frame for the EV, propulsion system, electronics and the body are not to be included initialy.


Hi Nick,

I think you need to start with the battery. It is the largest, heaviest component in the BEV. Battery placement in the frame is crucial to handling and safety. See how GM did it on the Volt. And they used a similar T pack design on the EV-1. Ref: http://www.diyelectriccar.com/forum...e-new-pictures-38627.html?p=151605#post151605 

This design approach is rarely if ever used by converters or DIYers. Most times they end up sticking batteries all over the place. To do it right, that mass should be centered and low. So, in your project, you'll have to define the battery size and mass to begin with.

My opinions. Good luck.

major


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## Woodsmith (Jun 5, 2008)

I'd second Major.

You could start by considering the size of pack needed for desired the range and speed of the vehicle to determine how many batteries you need and what capacity they will be.

This won't be easy as you have no weight or CDa to work with but you can make some assumptions on a spread sheet and add in these variables to ge a ball park figure.

Then, knowing that you need X number of Y ah cells you can then check with suppliers as to what package size they come in. Then, with some clearance for the terminals and cabling, you can design a box that will take the cells in a format that suits your chassis proposal. This can be a rectangular shape to fit in the floor between the wheels or it can be a long 'spine' that fits down the centre, or a combination of the two.

This will keep the weight low and evenly spread and allow adjustments for the fitting on suspension, motor and transmission components. The occupants will, of course, sit above, or on either side of, the battery pack.

Now, for safety, you will need a crumple zone front and rear and side impact protection. This will encroach on the battery space a bit but you can design around that by including cells in the side impact protection and allowing space between groups of cells in a spine for the battery compartment to crumple. There must also be protection from cells being dislodged in an impact and the terminals shorting out on the frame members or cables being trapped and cut causing an unfused short circuit.


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