Tim Catellier’s 2000 BMW Z3 EV

March 16, 2010 in Featured View Comments

Tim Catellier’s EV conversion stands out as a good example of a personal commuter conversion done with style and to a high standard. 

Name, Age, Location ?

Tim Catellier, 45, Chandler AZ.

What is your primary occupation ?

Computer Systems Administrator.

What got you interested in electric cars ? Just the green aspect or something else ?

The first thing that interested me in electric cars was the cost to operate.  It’s a fraction of the cost associated with an internal combustion engine driven car.  I had my first chance to drive an EV in 1997.  It was an EV1.  It was a great car, quiet, fast and cheap to run.  Sadly, I only had it for a weekend, and even worse I couldn’t afford the rather steep leasing fees.

Shortly after that Toyota announced that it was selling EV Rav4s.  I went to the dealer prepared to negotiate a sale, but was told they only sold them to fleets.  I had to buy 10 or there was no deal.  The salesman proceeded to tell me why I didn’t want an electric car anyway, citing range concerns.  I explained that was why I would have two vehicles; one would be a gas driven car for long trips.  I started explaining all the benefits to him, and before the end of the conversation, he told me HE wanted an EV Rav4.

Is this your first EV ?

This is the first EV I’ve owned.

Why did you choose to convert ?

The only freeway capable EV that I’m aware of for sale everywhere, and more importantly here in Arizona, is the Tesla Roadster.  And while I would absolutely love to buy one, the price is a bit out of my range.  After years of waiting for Detroit and Japan to offer an EV that I could 1 buy, and 2 afford, I gave up and decided to build my own.  I find it ironic that 6 months after I started the conversion virtually every car maker began talking about the EV’s they had on their drawing boards. Still, those are, at best, several months, and at worst, several years away.  I’m driving mine right now!

What donor did you choose and why ?

The choice to convert a BMW Z3 over some other car was one I considered long and carefully.  Several people convert cars with the goal of keeping the cost very low.  That’s fine if it suits them, but to achieve this they often choose a car that is way past its prime.  So, when they are done, they have an electric car in an ugly, beat up 25 year old chassis.  Sure it’s electric, but…  I don’t think that suffering when you drive is a necessary part of going electric.

Some people choose older stylish cars that lack power steering and power brakes to keep things simple.  I certainly see the value in that.

I decide that I wanted a car that had the following qualities.

1.  Modern safety features, i.e. full seat belts, air bags, anti-lock brakes

2.  One that was small, light and aerodynamic

3.  It had to have enough room to hold the batteries and all the components

4.  Finally, when complete, it would be a fun stylish car that I’d want to drive for years and years.

What were your goals for the project, was range your top priority ? how did you balance this with other concerns or aims ?

Engine Pulled - Taken right after the engine was pulled in February of 09.

That’s a very good question because those aspects come into play when designing the car and picking components.  I needed a car that had a range of at least 30 miles.  Ok, that dictated how many kilowatt hours I would need in the battery pack.  My target was 20 kWh’s. Based on the averages that I’d seen for how much energy it took most conversions to drive a mile, that was well within spec.

I needed it to travel some of that distance on the freeway and be able to keep up with the traffic.  That heavily influenced what type of motor I chose.  More than anything, I wanted a car that I could just get in and drive and not have to worry; can I make it to my destination, can I keep up with traffic, will I be able to charge when I’m there and will they have the right kind of plug?

Carefully planning and modeling took a great deal of time, but I think it was worth it in the end.

What do you think the most critical part of the conversion process was ?

Keeping it safe was my primary concern.  Everything is lashed, strapped, or bolted down to the chassis so solidly, that nothing moves or rattles.  It has to be that way because the road is brutal and will exploit any weakness in the design or execution to break or rattle them apart and ruin your day.

But that was only one aspect of safety.  I’m hauling around a 20 kWh battery pack at 160 Volts DC.  Enough to kill you and set you on fire!  There was a great deal of care placed in designing safety into the electrical system.

Who helped you out ?

Often people will consult with professionals who convert cars for a living, which is great if you have access to such a person.  I didn’t, so I had to make do, mostly on my own. A friend of mine helped me to understand electricity.  Before this, I knew very little.  He was extremely patient and helpful.

I ran virtually every design aspect past my dad.  He worked for years as an engineer and is astoundingly mechanically adept.

I had one friend who help me with all the welding.  When I say he helped, what I mean is that he welded and I fetched him refreshing beverages.  I can’t weld at all, and this was no place to learn (though I do want to learn now).

Whenever I needed a spare hand to hold a bolt while I turned the nut, my daughter helped out.

Where did you buy the majority of the parts ?

I got most of the EV parts from http://www.evsource.com.  Ryan Bohm is the owner and a super guy to deal with.

Where did you source your batteries ?

The batteries I got from EV Components http://www.evcomponents.com.  You won’t find LiFePo4 batteries any cheaper.

Mock Ups One of the many cardboard mock ups I made for fitting and sizing purposes.

How did you deal with added weight of the batteries and keep the weight distribution from shifting too much ?

Halfway through the build, the lithium batteries I’m using became affordable, and when you crunch the numbers, a better choice over lead acid.  That nearly cut the battery weight in half, from 871 lbs. for the lead acid batteries I planned on, down to 480.  Of course I went through and removed absolutely everything on the chassis that was there to assist the internal combustion engine.

I had the car weighed today and it came out 386 lbs heavier than stock. The really interesting thing is that I managed to keep the weight distribution the same, 52% front and 48% rear.  If I think it’s necessary, I’ll be putting heavier springs on the front and replacing some of the suspension bushings with urethane instead of the stock rubber.

This is a shot of the engine bay, essentially complete. I ran some additional wiring loom to tidy up all the loose wires, but the car functioned at this point.

Tell me about your pack, controller, motor and drive train, why did you choose this combination ?

The batteries will last well over 130,000 miles if I treat them well, and I intend to treat them well.  The controller is the Zilla HV1K.  The model number signifies that it’s a high voltage version that can handle up to 300 Volts and put out up to 1000 amps.  That is enough to make any car move fast.

The motor is an 11″ series wound DC motor by Netgain Motors, called a WarP 11.  They make smaller motors that arguably would have worked for this conversion.  However, highway speeds need bigger motors, and like I said, I didn’t want to have to worry about the car when I was driving it, so 11″ motor it was!

Each of these components brings something to the party; longer range, good performance and speed associated with regular cars.  That’s why I chose them.

I’m using the original drive train with the clutch.  You can go clutchless, and there are companies that make adapters that let you mount the motor to the transmission and forego the clutch.  The down side to this is slower shift speeds.  I wasn’t willing to make that adjustment.

Attaching the motor directly to the differential and removing the transmission completely is also an option.  But without the gearing in the transmission to reduce your final drive ratio, that means slow starts.  Again I didn’t want that. The advantage is that it drives pretty much like it did stock, except I don’t have to push in the clutch when I come to a stop.

What did you use for replacing the power steering pump ?

The power steering pump was replaced with an electric hydraulic power steering pump that was manufactured by Toyota and used on the MR2.  I’ve attached a proximity switch to the steering column so when you turn the wheel slightly, the pump comes on.  In a straight line, it remains off.  At normal road speeds, I can switch lanes with ease and it won’t come on because I don’t have to move the wheel enough to trigger the switch.

Zilla - Visible at the top left of the frame in the pictures of the full engine bay, you can see an area that is partitioned off from the rest of the engine bay. This is where BMW installed all the electronic components, and they made it water tight. I figured I'd use it for my electronic components. So here we see the zilla resting comfortably on a platform I'd made to support it.

What kind of braking system did you use ?

The original car used vacuum assist brakes, and it had ABS.  I was able to install a vacuum pump and a canister to “hold” the vacuum, to replace the missing vacuum hose from the engine.  That whole apparatus works great.  It draws the vacuum down and then shuts off.  It turns on every third of fourth time I depress the brakes.

The ABS system is still present, but it’s missing one thing.  It used to connect to the engine wiring harness and the car’s ECU.  I left the ECU in place (it controls the speedometer), but obviously the engine’s wiring harness is long gone.  I don’t know how or if the ABS system will work in a panic stop. I haven’t tried it yet.  The brakes, however, do work fine on their own.

What factors for your conversion do you think directly impact its efficiency ?

The car has nice wide sticky tires.  Great for cornering and fun handling on a normal Z3, but not so good for a conversion.  Once they wear out, I’ll look into tires with a lower rolling resistance.

I did cover the bottom of the car with aluminium sheets to make it more stream line.  I’d like to think it helped, but I don’t have any empirical data to prove one way or the other.

When I finally got the adaptor plate, I was able to mount the motor to the plate, and then the new lighter flywheel to the new hub mounted on the motor.

What is your Wh/Mile on average ? and what is your typical range ?

I seem to be averaging around 310 Wh/mile, but I have seen results as good as 275. I will only allow myself to use 80% of the energy in the batteries.  This will help to increase the longevity of the pack, which is important to me.  That leaves me enough energy to get roughly 50 miles on normal city streets.

What do you think the advantages and disadvantages of your car being electric are ?

Lets see, it’s cheaper to run and cheaper to maintain.  Accounting for normal maintenance fees on a car and the cost of gas at it’s current $2.75 a gallon, I save roughly $14.00 every 100 miles I drive.  In a normal year with 10,000 miles, that’s $1400.  As gas prices go up I’ll save even more.

Obviously there’s a green advantage.  There’s far less pollution generated to produce the electricity I use per mile than gasoline produces to travel the equivalent distance.

One of the best advantages for me is that I’m helping to reduce our dependency on foreign oil.  I don’t like the idea of sending my money to people that really aren’t too fond of me or my country.

The main disadvantage would be that I can’t take the car up into the mountains and enjoy a top down day driving through the twisty roads of Northern Arizona.  I suppose if I absolutely must do that, I can just rent a car for a day.

In the back of the trunk is the box that occupies some of the area previously occupied by the fuel tank. You can see in the floor of the trunk, I've cut a hole and mounted a box to hold batteries. That box is bolted to the frame of the car and hangs down about 1 inch lower than the spare tire assembly did. I no longer carry a spare tire.

Which are some of your favorite conversions or available new EVs ?

Well, as mentioned above the Tesla is just sublime.  As far as I know, that is the only EV available that you can actually buy and really use as a daily driver.  There are other EVs available by small companies here and there, but the vast majority of them are NEVs, or Neighborhood Electric Vehicles that are limited to 30 MPH. There are more and more EVs available in test markets only, like the Mini EV.  But it’s hard to consider those a real option when they aren’t even available in your state.  Each looks quite good and I’d love to give them all a try.  I’m looking forward to the Nissan Leaf when it becomes available at the end of the year.

What does your wife think of the car ?

My wife thought I was crazy when I started it and was pretty sure it wouldn’t work.  But now that it’s done and she’s driven it, she’s quite fond of it.

Does any of your power come from renewables, either from purchased offsets, directly, or home generation ?

Not yet.  I’ve been looking into solar since the late 80′s.  It’s getting to the point where it’s becoming a viable economic choice. That may be my next project.

What has your conversion experience taught you ?

In real, practical terms, I’ve learned an enormous amount about electricity and electronics.  From a more esoteric point of view, I’ve learned just how good you can be at overcoming seemingly insurmountable problems when you put your mind to it.

What was your conversion cost ?

$21 K, and change.  I knew the conversion would come close to that, and that number seems high to a lot of people.  But I explain “If you went out and bought a new EV, you’d be paying far more.”  While the car isn’t technically new, all the components that make it work are.  So as I see it, I have a “new” car for less than a new car price.  Plus I got to choose the body style!

Also, the running costs are roughly 3 cents a mile in electricity and the occasional set of tires and brakes.

Which EV enthusiast sites do you visit ?

http://www.diyelectriccar.com/

http://jackrickard.blogspot.com/

http://www.wired.com/autopia/

http://green.autoblog.com/

Do you have a favorite story about building or driving your EV ?

Many people just shook their heads when I told them what I was going to do to the car.  Some actually said “What a shame, that’s a nice car.”  I’m sure the ones that didn’t say it were thinking it.  Now that it’s complete, they shake their heads and say “This is amazing.”  I just smile and say “Yes, it is.”

Shortly after the last picture, I mounted the transmission to the adaptor plate and then dropped the whole assembly in the car.

Tim’s car on EVAlbum

Tim’s Blog

Arizona, BMW