Car Nut

Are you ashamed of the question?

Build Your Own Electric Vehicle: Seth Leitman, Bob Brant ...

• Can You Build Your Own Electric Vehicle? | Earth911.com/‎
• Do-it-yourself: How to build your own electric car, hacker style ...‎
• Build an EV | Electric Vehicle Association of Greater Washington, DC

This is an interesting way to look at it. Cars don't operate that many hours after all! They tend to rust on the spot Thank you for this insight GA!

If you choose to build your own electric car, I would start with an existing car and modify it vs starting from scratch. It will be much easier to register and if you choose a good car, you won't be duplicating the vast engineering work that went into the design (not that you would be able make anything as good and reliable).

Weight, charge and battery life will be your key challenges. Of course the electronics are important and the choice of a/c vs d/c will have to be well researched.

Nissan makes a pretty good EV right now. The Leaf can be bought for around $20K after credits are applied. For a sum this small, it may be better to buy the car vs try to make your own. A plug in hybrid may also make more sense, depending on your usage. Ditto for a car like the Chevy Volt (full electric with gas charging system - similar to current trains).

For kicks, watch the episode of Top Gear (it's on BBC America on UVerse). The guys try to make an electric vehicle, which they fail miserably on their first attempt. The second attempt adds a fuel powered charging system - better power and range, but not well executed.

Good luck and let us know if you actually tackle this - or try to.

GE has made several speed controls for electromotive equipment. One of them the EV-1 model. Saw a lot of use on fork lifts.

If you look here you will find many speed controls used over the years on battery powered equipment to control speed. http://www.fsip.biz/

If you are thinking pure battery electric then here is an extensive blog from someone who restored and converted an old car to 3 phase battery electric. electricvogue.blogspot.com

CarNut,

I have thought about it on/off for about 15 years. For now, ignore the charging system and the topic of hybrid electric/fossil. You are storing your energy in a chemical form in a battery bank or in electrostatic form in a super capacitor (most likely both if a super capacitor is involved). The off-the-shelf VFD has three components--first is the AC/DC input end which is either a diode bridge or a more complicated unit that can feed regenerated energy back to the line. You won't need that portion. The second is the DC storage, which in a VFD is a set of capacitors. Again, you won't need that portion either. Finally is the inverter which converts the DC back to AC (3-phase) at a voltage and frequency as desired to run the motor. That portion you need, and fortunately, manufacturers make them as stand-alone units.

Now look at the motor--you can use off-the-shelf ones that run at 50 or 60 Hz, but these are quite heavy for the power output. If you run the frequency up substantailly, the mass of magnet steel is much lower. First place to look is at aircraft components, which are designed to operate at 400 Hz and weigh MUCH less per unit of power output. The enemy of any motor is heat, so you will need to spend some effort at how to cool it. Liquid cooling is available, and radiators are ubiquitous in the automotive industry. Specialty motors are available that run at even higher frequencies, designed for electric vehicle applications and are liquid cooled.

You may want to talk with the engineering people at the VFD factory, to see how to tweak it to run at a higher frequency (up to 1000Hz should be fairly easy to get). Also, you may want to tweak its safety thresholds for incoming voltage, to allow a greater discharge of the batteries.

Backtracking a little now... Braking is done mostly by regeneration of power back from the motor through the inverter (all you have to do is set its command frequency lower than the driveshaft's resultant speed), so energy formerly lost in brakes is recovered. That is why hybrid cars usually have a higher city MPG than highway and fossil-fueled cars have just the opposite. Fossil-fueled automotive engines have to meet a large number of partially-competing goals such as wide speed range, low-end torque, etc. If the engine is running only at a fixed single speed, then the emissions controls are much simpler to meet, and the optimum conditions can be set for maximum fuel efficiency. In addition, a smaller engine/generator is needed because the average energy output of the engine in real-life is going to be much less than its maximum capability (how much time do you spend idling or at low speeds?).

Have fun--JMM

I belong to a hobbyist group that collectively has built a couple of dozen electric vehicles. They range from converted old trucks to scratch-built cars, from one to six passengers, and even a couple of boats. There is a lot of information available about how to do any of this. As already posted, you may obtain more value from the exercise than from the finished project.

Your GM EV-1 information sounds about right. Its controller is not available (GM made sure of that when they crushed the EV-1s; any EV-1s that escaped were delivered minus their electronics). But similar equipment is available from other sources, some more sophisticated than others.

If you are building a proof-of-concept vehicle then you can be successful by using several different manufacturers' offerings. If you want a practical although limited vehicle then you'll spend at least $20k (for lead-acid batteries / simple DC motor / 25 miles per charge) to $30k or more (for Li-Ion batteries / AC motor / more range). It's hard to beat the Nissan Leaf in price or range, although few dealers will sell a Leaf for base price ($20k) and you may not have government incentives available. If you want to build a car that can replace a gasoline car then you'll be on the cutting edge and will have to spend accordingly.

When designing and building their own electric vehicle, many people forget accessories like lights and heat and entertainment and power assist (brakes and steering). So factor those loads into your range calculations. Also figure that you may end up using currently available equipment which is designed to operate at 12 vdc (requiring a convertor or a system that is charged separately from your main battery bank).

When building our own EVs we keep running into these problems:

· Battery monitors are unreliable (especially for Li-Ion battery packs),

· Battery chargers are unreliable and do not adapt easily to different power sources,

· Battery quality and delivery can be disappointing,

· When re-using an existing chassis, the overall vehicle weight will probably end up higher than that chassis' original vehicle weight, requiring you to beef up the structure and swap in stronger suspension parts, and

· Electrical connections are critical - and need frequent checks and maintenance.

Not trying to discourage you - just forewarning you as you formulate your plans. Best of luck!