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Old 12-16-2007, 12:53 PM   #510 (permalink)
MetroMPG
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Location: 1000 Islands, Ontario, Canada
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Blackfly - '98 Geo Metro
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Last 3: 70.09 mpg (US)

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Hi, modul8...

I don't know about that Intrepid. The biggest strikes against it are: (a) its heft, and (b) the automatic transmission. Both are efficiency killers, and the added weight means you need more of everything to compensate: more batteries, bigger motor, more powerful controller... It's a vicious circle.

Quote:
what is the basis for good EV design, in your opinion?
I'm no expert. But I've read some things the real experts say, and on that question they usually answer: since EV's are (usually) about maximizing efficiency, the best donor car to choose is one that was very efficient in its ICE form. That means the smallest, lightest & most aerodynamic vehicle that can hold the amount of batteries (usually lead based) that will permit you to meet your range goals.

Quote:
if you strained your beer budget by 500 bucks somehow, what would be the best way to invest it in the FS?
500 bucks! Woohoo - Christmas comes early!

The car's biggest drawback is that it can't really be driven in "normal" traffic because it won't accelerate at anything you could call a "normal" rate, even flat-out.

The controller is part of the problem, limited to 225A max. But it's also a problem of worn-out batteries: 5+ km off a fresh charge, their voltage sags to dangerous levels when demanding those occasional 200A loads. So the driver has to constantly self-limit the amp draw when accelerating (and going up grades) by watching the volts (or ignore it, and risk ruining batteries).

Since $500 isn't going to get 8 new batteries here's what I'd do:
  • upgrade from the used 48v controller to a used 48-72V controller
  • add 2 more used batteries to the pack (I think that's about the limit before the car would need upgraded springs), for a total of 60v.
Pros: more power, less amperage draw for a given amount of work (= we can get more performance out of the old, tired batteries before they start to sag under heavy loads to damaging levels), more range.

Cons: unfortunately, it would complicate charging, since we don't have a 60v charger (but we do have a 36v + a 24v - of differing amperages though). Also, the added 130+ lbs would reduce overall efficiency a bit more.

So that $500 would have to pay for a used controller, plus a new DC-DC converter (the one we have.. and haven't yet installed... is 48v-12v).
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EcoModder
has launched a forum for the efficient new Mitsubishi Mirage
www.MetroMPG.com - fuel efficiency info for Geo Metro owners
www.ForkenSwift.com - electric car conversion on a beer budget
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