I spoke to Victor at Metric Mind Engineering, they offer high end AC systems for EV conversions. Given that most EV hobbyists use DC systems. I am trying to convince myself that an AC system is what I will use. The benefits of DC are:
- system costs ~3k less than AC systems
- many hobbyists choose DC for its simplicity
- does not require sophisticated controller to provide current to the DC motor and therefore, has higher torque for performance “out-of-the-box”.
The benefits of AC are:
- more efficient (3-4%) due to higher voltage requirements (312-324V vs. 120-144V typical)
- built-in regenerative braking. (10-25% depending on how much braking you do in the driving environment)
- Wider rpm ranges so that shifting maybe avoided.
- Safer than DC in event of failure. With DC, there is a potential that if the controller fails, the entire voltage from the battery pack is applied to the DC motor, resulting in a run-away! Additional safety “kill switches” and fuseboxes need to be incorporated. With AC, when the controller fails, the AC motor simply comes to a stop because it will not be getting any power from the controller.
I’ve decided on using an AC system given these points. I read somewhere that someone had an issue with his porsche AC conversion not having enough torque and thus lacking performance during acceleration. This issue can be overcome by using a proper controller/inverter (~$6-7k) that will provide a higher current to the motor.
The Big Max Ultra Shed was pretty straight forward to assemble with the exception of the roof. I did it by myself mostly with help from my wife only on occasion when I needed someone to hold things in place. It took about 2 hours to assemble everything except for the roof. The roof itself took another 1.5 hours mostly because the roof panels would not lock into the ridge beam easily and there was limited space around the perimeter of the shed to work. Using liquid dish soap to lubricate the pieces and a mallet to bang things into place helps quite a bit.
Note on dimensions of the shed:
I used the outside dimensions of the shed given by the Rubbermaid site here to determine the size of the skid foundation (Outside Dimensions: 7′w x 10′ 6″d x 7′ 11″h) and it was too small!! The final dimensions were 7′ 3/8″ w x 10′ 8 7/8″ d x 7′ 11″h. Because of this, the shed overhangs the skid foundation slightly. I don’t think it will affect the stability of the shed, but I am annoyed at Rubbermaid for not giving the correct outside dimensions on their site, the depth was almost 3 inches off!!! Good thing I had over-sized the depth dimension of the foundation by 2 inches so that the shed is overhanging only by 7/8″.
Here are some pictures of the completed shed.
Time to start working on the car!!
I finished the skid foundation last Sunday. I will buy the shed this weekend and put it together. Almost time to start working on the car!!
I moved my blog today to this web hosting service by startlogic.com. They provide WordPress for blogging and I really like it; certainly makes blogging much much easier. Well, the car has been sitting in the driveway for a while now and not much has been done. Things have just been crazy. Now that I am less busy, I’ve started plans to install a Rubbermaid Big Max Ultra shed to free up much needed space in the garage to start working on the EV conversion. Before I install the shed, I need to build a skid foundation. My nice neighbor David took me to Home Depot in his truck to pick up all the materials needed for the foundation. I spent $160 on the foundation materials. I will build the foundation tomorrow as well as clean up some mess that some friendly pigeons decided to leave under my solar panels. Can’t wait to start actually working on the car. By the way, if you ever find yourself installing solar panels for your home, make sure that the installer put in preventative measures for pigeons nesting underneath the panels. My solar installers didn’t think that through and now I am left with an unpleasant mess to clean up. 
July 6, 2008
I got the car weighed today, although it was sort of an adventure. Since the car has a bad clutch, I had been debating on whether I should drive 10 miles to the closest dump station to weigh my car. Before I go into the story, let me introduce Steve McDonald, a fellow EVer that also lives in Castro Valley and has already converted a Honda Civic Hatchback. Steve has been so enthusiastic about sharing his experience with his conversion. He has been very helpful and getting me started on my own project. Thanks Steve!! Steve was the one that suggested that the dump station may be a good place to get the car weighed. I decided to get the preconversion weight today. I took local roads all the way there… letting people pass me as they got close since my clutch is not catching right away and I can only putt-putt along at about 20 miles an hour. 30minutes later, I made it! I just flat out asked the folks there where I could get my car weighed and the guy was nice enough to tell me that it was 2540 lbs with me in it. Mission accomplished: curb weight = 2365 lbs. On my way back, I could smell stuff burning as I made it up and down through the hills and valleys of Castro Valley. I was so happy when I got near my home and started my ascent up the long 1/2 mile hill… About a tenth of a mile from the top of the hill, my clutch finally gives out completely and my engine is reving but my car is rolling backwards down the hill!!! ARGH!!!!! I pulled the parking brakes and put my hazards on… I needed to get my lovely wife to call AAA for me to tow the thing for the last 1/4 mi back to the house. Thanks for saving me, honey! I was also contemplating on getting it detailed and the internals cleaned out before I start digging into it, but that idea is out the window now..I am just happy it is back in the drive way and I got the thing weighed today.
June 29, 2008
I bought this 1986 MR2 for $730. The clutch needs replacement and there is some body damage because the car is so old. But other than that it is in good shape, therefore, it is a good candidate for a EV donor car because it has a fairly low aerodynamic drag coefficient and is relatively light weight (curb weight: 2300lbs). I will verify the weight soon. Check back often for updates as I intended to update this frequently.
