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Old 10-13-2008, 01:54 PM   #21 (permalink)
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Originally Posted by Blue Bomber Man View Post
It all depends on your budget really. A 10 kwh pack is around 10 grand for lithium ion batteries, but would only weigh around 140 pounds. The same pack using deep cycle batteries from something like a forklift or golfcart would weigh maybe 550-600 pounds but would cost quite less.

I would suspect a car that weighed around 2000-2200 pounds, with a more typical Cd of around .28-.32 and with low RR tires the range on a 10kw pack would be perhaps 35 city, only 25 high way miles.

It is worth the effort to drive the tires directly without a transmission because you lose some serious energy there.

If you are using an existing car, due everything possible to reduce weight, improve aero etc. Look up car designs that have low Cd and see if you can emulate that exterior.

Steal ideas where ever you can. Look up the Aptera, Probe V, LoReMo.

LoReMo has an interesting idea I plan to put in my car: no side doors, it uses a front hood/windshield door that lifts up. It saves a lot of weight because you can design the side of the car to be much stronger with less weight.

Good luck!
What's the story (especially as regards NYS, since you're a fellow NY'er) with custom vehicles? How far can one go in making a custom car, and what are the legal requirements to getting it on the road?

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Old 10-13-2008, 02:05 PM   #22 (permalink)
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I havent researched that part to thoroughly yet, but it would have to meet criteria of inspection. I am more concerned about getting insurance on it personally. Which is why I really want to get those wheel hub motors. They have some great safety features that would bring my car closer to the standards of manufacturing.

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Old 10-13-2008, 10:09 PM   #23 (permalink)
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Bluebomberman, I hope you understand you are talking a megabucks build...

some other thoughts (since I've let this rattle around in my head a few times...:

1. Microcenter sells huge batches of NiMH AA batteries. Just make a PCB to fit and put several hundred (by buying in batches >50). Before you pull the trigger, make sure you check all the laptop replacement batteries (especially non-name-brand replacements) by Whr/$ I know the homebrew electric bicycle I've seen nearby used laptop batteries (possibly scavenged, I didn't ask), this might be a better deal.

2. You probably want ultracaps. They will take any amount of charging (i.e. regernerative breaking) until full. Expect close enough to perfect efficiency (I'm basing this off of "normal" caps., these are close enough to 100% to ignore the losses in tuning applications, I've hear ultra-caps are chemical based (essentially a hybrid capacitor/battery beast) and might be different)). Note that with lead-acid, pulling any more than half the maximum amount of power out of the battery takes a 50% efficiency hit, if not more. Include the caps.

3. Teh motor: Maxing BSHP at a single RPM seems trivial, but the Chevy Volt PR never seems to mention it. Get a diesel if at all possible (probably not), or a geo metro with custom cams (note that the Atkinson cycle will give you fits...)

4. The body. Ask yourself long and hard why you aren't using either a miata or a Saturn. If you are my size, you don't need to ask (but you might lower the seats in an SC2...). The only way you are going to have modern safety is going the Loremo way (megabucks), but you might accept a little less safety for a lot less weight.

5. Starter engines. Just because they can't power the car doesn't mean they are useless. I suspect a little "e-nitrous" (a lot more power for a very short time) could come in handy (make sure you have the ultracaps charged...).

One final note. Most of these thoughts came from an EE who has never built anything (professionally) with an electric motor. Also most thoughts were generated thinking up ways to soup up my parent's golf-cart (holidays with them are boring, a project would help...).
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Old 10-13-2008, 11:27 PM   #24 (permalink)
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Originally Posted by ncc74656m View Post
So the gist of this is that if I am not using basically a custom or kit car, I shouldn't be able to ever expect more than 50 mi on batts alone, correct?
On a stock vehicle, probably yes. More than that, and you're overweight for the design of most passenger vehicles (with lead acid, that is. You can get a lot further with Lithium Ion.)

However, if you're willing to do the beefing up where necessary, and upgrade springs, axles, brakes, etc., I don't see why you can't do more than 50 miles. In fact, check out the Karmann Ghia conversions on the EVAlbum. There are several that do 50 miles on lead acids, because the aero is good and there's enough trunk space for the batteries. Beef up one of those (maybe even put in a full racing tube frame for strength), upgrade the suspension and brakes with Porsche parts and you can build a mean machine on the fairly cheap. (And registration is cheap and easy.)

As to the hybrid bit, the simplest way is to find a 12-20kW generator head, bolt it up to the same size motor (a Honda Helix 250 motor, for instance, is liquid cooled and around 15kW before any mods), and run the wiring to your on-board charger. You don't necessarily need a lot of watts--just enough to keep up with or slightly surpass freeway cruising draw (10-18kW for most small cars.)

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Old 10-14-2008, 10:52 AM   #25 (permalink)
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If you tune a generator's engine to run at a single set speed, it can run more efficiently then an engine that needs to have low end torque, and still rev up, that is one of the advantages of having a generator that is running at a constant speed, the whole set up can be designed to run at it's peek efficiency.
back in the 1980's a friend of mine started building a car like this, a small bank of batteries, a gas generator, but I believe he had some controller problems and sold his project, but the concept is solid.

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