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Old 12-12-2008, 11:03 PM   #1 (permalink)
MetroMPG
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Join Date: Nov 2007
Location: 1000 Islands, Ontario, Canada
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Blackfly - '98 Geo Metro
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Dirt cheap HIGHWAY capable EV?

So in the parting thoughts of the "Three Dirt Cheap DIY EV's" blog series, I basically said that if you want a cheap EV, it's going to be at best a medium speed car, because component costs seem to jump way up once you pass the 72 volt threshold, particularly controllers. Chargers too?

But Ben N and I exchanged PMs after I wrote that and he said, "yeah but once you get up around 100v, you could make your own AC bridge rectified charger" for basically peanuts.

Hmm...

So I'm going to take it back. I think, while harder, you could make a highway capable EV on the cheap. Say, $1500ish.

You'd definitely have to be running on used/surplus batteries to pull that off.

Here's how I think it could be done:

- 96 pack - used, cast off floodies
- beefy Forklift motor
- variac bad boy charger on a timer
- no DC/DC converter

The trick would be the controller. The cheapest NEW 96v capable controller available from EVparts is: Controller, Curtis PMC #1221C-7401, 72-120 VDC, 400 amp. Price: $1397.25. These things probably don't come up on the used market very often, and even if they did, half price is still a killer for a budget EV.

So...

4 strings of 24v and a combo PWM/contactor controller setup:

Speed stage 1: 4 24v strings in parallel, cheap 24/36v PWM controller for variable parking lot stuff, good for maybe 15 mph (?)

Speed stage 2:
contactors connect 2 parallel strings of 48v - good for about 40-45 mph on level ground

Speed stage 3: contactors connect all strings in series for 96v - good for 55+ mph

So, not impossible. The stage 2-3 transition might be too nutty, I don't know.

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Honda mods: Ecomodding my $800 Honda Fit 5-speed beater
Mitsu mods: Oops, I did it again! Bought another cheap, 3-cylinder Mirage. Mods in progress...
Ecodriving test: Manual vs. automatic transmission MPG showdown



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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