Planning Stage: choosing the donor car

So, I've covered who I am, and what I'm doing, and some of the reasons for it. Let's do a quick recap:

1) Me: Computer Scientist with very little (i.e. none) mechanical experience

2) What I'm doing: Converting a Geo Storm to an electric vehicle

3) Why I'm doing it: My 1994 Honda Accord LX has some age related issues that I just don't want to spend the money on to fix. Also, it feels incredibly wasteful to use a 2,800 lbs. vehicle to drive all 180 lbs. of me 16 miles a day, with three seats and the trunk completey empty. I like the idea of an electric vehicle, not because I have a gas hog or dreams that it is going to save me thousands of dollars (though, as we will see later, it may), but because it's neat. Computer scientist == geek.

That's a pretty good summary. So let's talk about my criteria.

1) I need to get at least 25 miles on a single charge. This is enough for my 16 mile trip, and some left over for possible detours, lunch trips, adverse driving conditions, etc. Most EVs can get this without problem.

2) I need to be able to go at least 45 MPH. The highest speed limit in town is 60 MPH, but I don't go on that road that often, if ever, and I could avoid it. Other than that, 45 is as fast as I'd need to go.

3) I want a two door car. While I realize this does not necessarily make the car smaller, it will feel like it, which is what I wanted. I realize this is not rational in the least, but I feel bad about driving around what seems like a big car. If it doesn't seem like a big car, then I won't feel bad. Rationality has very little to do with this. But in fact, most two doors are significantly smaller and lighter (about a foot or so, and weigh around 300 lbs. less), so while it's a completely superflous decision, it does also serve a purpose, even if on accident.

4) I wanted a sporty car. Not necessarily a sports car, but something sport and fun looking. This ties in to #3 as well. Again, this is just something I wanted, not for any rational reason. But if I'm going to sink a small car's worth of money into this, I want to get something I like.

5) It had to be a manual transmission. This wasn't a preference, but a necessity due to technical issues that I will discuss later.

6) I want to keep the budget under $6000.

So, that gave me some good starting points. The last one was the first considered; I needed a cheap car. That meant used, and used for a while. This lead me to search for 1990-2000 cars. Old enough to have some miles on them and be cheap, not so old that they're just rust-bucket derelict, though I did see plenty of those as well.

I looked on Craigslist.org and found several vehicles that fit my budget in the $500-$1000 range. I didn't want to spend over $1000 because that severly cuts into my already rather optomistic budget.

Next, I elminitated those with more than trivial body damage. Motor is blown? Great! Has a dent in the fender? Eh, not so great. It sounds kind of twisted, but when you're going to gut the engine compartment, what's in there doesn't really matter. On the other hand, spending money fixing superficial issues eats up your budget for no real reason. I didn't cross anything off for a dent or a rust hole, but if it had a fender replaced and was a mistmatched color, or a cracked windscreen, etc. I marked those off.

Between this and my sporty, two door requirement, it didn't leave too many to consider, maybe a dozen cars. Now I started looking at what would make a good EV, and crossed off those that weighed too much. This crossed off more cars than you might think. For example, the 1990 Toyota Supra weighs in at a hefty curb weight of 3,219 lbs.

Let's pause here a moment to talk about why that's important. Weight pretty much determines everything else with the EV. The heavier the car, the larger the motor you will need. The larger the motor, the more voltage you will need to reach decent speeds. That means more batteries, a beefier controller and charge system, all of which adds even more weight. For a typical EV conversion you need to aticipate adding at least 600 lbs. The reason for this is that even though you are removing the heat sheilding, exhaust system, engine, and radiator, along with some other related bits, you're also adding 10-20 batteries at about 70 lbs. each. Quick math, that's 700 to 1,400 lbs. right there on its own. This is mitigated by the weight of those internal combustion bits, but not entirely absorbed.

So if you take a 3,200+ lb. car and add 600 - 1,000 lbs, you now have quite a monster on your hands. The car will handle more like a small truck, especially when you take into account that many EV converters do not hook up power steering (I'll talk more about that in future posts). Also keep in mind that all this added weight on an already heavy car can exceed the gross vehicle weight, either on an individual axle or on a more central component. And you still need to include the weight of you and your passengers/cargo in the gross weight, and take it into account for your power consumption too.

The rule of thumb is that you should shoot for 2,500 lbs. or less. This left me with the following choices in a manual transmission:

1) Toyota Celica - curb weight 2,496 lbs.

2) Eagle Talon - curb weight 2,550 lbs. This is technically over 2,500, but just barely.

3) Geo Storm - curb weight 2,280 lbs.

4) Saturn SC2 - curb weight 2,363 lbs.

You can see that from an objective point of view, the last two are the most favorable. For those of you wondering about the aero-dynamics of these cars, they're all in the .29-.32 drag coefficient, so that won't be a significant consideration.

Now each of these had pros and cons based on the specifics of the cars. The Eagle was perfect except for the motor and the weight, at $600 and was within half an hour's drive. The Celica had minor body damage, only cost $550, but was three hours away. The Saturn was an hour away and $700, but the description was very non-technical. I had concerns there may have been more than just motor problems. They didn't even know the model - I had to look up some pictures and visually identify it.

The Storm had minor engine trouble - it would still crank and run, but appeared to have clogged injectors, as the fuel preasure wasn't there, and some cylinders seemed not to be firing properly. This made it undrivable, but functional enough to know everything else was OK. Keep in mind that even with the conversion, the gear box and transmission still have to be good, or you have to replace them. It was the farthest away at 3 hours and some change, and the most expensive at $1000. I really loved the body style though!

I contacted each of them, and the only one I ever heard back from was the Storm owner. Bingo! I explained to him that $1000 was a bit out of budget (I'm only getting $800 for my Honda) and he agreed to come down to $850. Perfect!

At the lightest, this also gives me more options. With the Talon, I was going to have to get at least an 8' motor and run at 120 volts. There was the same with the Celica. The Saturn and Storm I could both afford to scale back quite a bit, since they're 200-300 lbs. less. I think with either of these, I can use a 96 volt pack and get the performance that meets my criteria. That saves me four six-volt batteries, or 230 lbs. and about $930, depending on the price you get. That's really appealing! The 6' motor is also lighter and less expensive.

In fact, the entire thing is going to be so much lighter than I anticipated, I plan on getting a multi-volt charger, which costs a little more, but start off with only a 72 volt pack. Once I've tried that out, I can easily beef it up to 96 volts if the performance isn't acceptable, but if it is, this saves me another four six-volt batteries. Good for the budget and the handling, and as long as the performance is good enough, it will be fine.

Now, with a 120 volt system, I could probably expect, say 80 miles of range. However, I don't really need 80 miles. Going back to my goals, I only need 25 or so. I think the 72 volt pack will give me the range and speed I need, and I can save up and upgrade later on if I want to take this out onto the highway or visit someone in a neighboring town.

To finish off this post, here's a picture of a Geo Storm. The one I am getting is white, and I'll be picking it up next week. I'm so excited!