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MetroMPG 12-12-2008 10:03 PM

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.


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.


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.

captainslug 12-13-2008 12:49 AM

Doing it cheap would require a great deal of electrical engineering experience. Unless of course you were to make a ridiculously simple electric manual transmission shifter device that controlled the contact setup when you changed the gear setting on the transmission.
Basically turning the shifter nob into a 12V toggle switch. With the pedal being the last bridge on the circuits for stage 2 and stage 3.

MPaulHolmes 12-13-2008 01:48 AM

Or.... You can make a 144v 600amp controller for about $350 in parts ($400 Australian)! Ian of did it! He even shows his progress. In larger quantities (like 50 or so) it can be done for about $250. Ben, remember how you said that in a year, you will be gas free, but you didn't know how yet, but it was as good as done? oh ya! Well, come heck or high water, in a year, there will be a slightly ghetto fully functional 144v (156v?) controller. I'm using 200v components, so I guess as long as it stays under that, it doesn't matter.
If, NAY, when it's usable, I'll do what I can to make it available to people at the cost of parts.

Check out Ian's progress so far! He's an awesome guy with a knack for explaining things. Zero Emission Vehicles Australia

order99 12-13-2008 02:07 AM


My Electronics training goes about as far as 'don't French Kiss the power outlet'-but if Ian's Controller works i'll grab a handy Fire Extinguisher and an insulated rubber suit and give a try!

Be on the lookout for sudden Forest Fires in NC... :D

MPaulHolmes 12-13-2008 02:28 AM

One of his earlier designs burnt up because of an error in his code on his microcontroller. He set the current limiting to 900amp (I think) when it was supposed to be like 450amp (or something). The mosfets had a bit of a problem handling that. Mine will be very safe. His is very safe now too (well it hasn't blown up yet). Don't worry!

order99 12-13-2008 04:36 AM

Well, just because YOU and HE know what you're doing doesn't mean there won't be an earth-shattering KABOOM in NC!

(note to self-pick up Electronics for Dummies tomorrow)

Cd 12-19-2008 08:24 PM

I used to hate the old Hot Rod articles that would shout " 12 seconds for under $500", only to find out that the car was free, the turbo was found 'dirt cheap'on E-bay, the heads were found out in a field, the block was found cheap, and all the engine work was done by the guys brother.

Bad example, but I think you get my point.

Anyone can build a 'dirt cheap' EV if they are lucky enough to find the parts for 'dirt cheap'.

It would be much appreciated if all of you could please give 'real world' costs of the parts and labor, along with any special bargians that you post about.


NachtRitter 12-19-2008 08:50 PM

Ya, agree there... "real world" cheap would be much appreciated.

I've been frustrated because I'd like to go electric but my commute back home is 25+ miles uphill (from about 200ft above sea level to about 2000ft) on a freeway, and is usually in the dark. Finding something affordable that'll maintain in the range of 65mph (speed limit) without stranding me has been challenging... :cool:

MPaulHolmes 12-19-2008 09:32 PM

My conversion was $2200, and the only "lucky find" was a $125 old forklift motor. And that wasn't that lucky! You can find them easily for $300-$500. $12 deep cycle batteries are readily available, but they will only have like half of the range as when they were new. OK, so new real world costs of a 50 mile range freeway speed EV:

8v deep cycle batteries x18: $2300. (first choice on google search)
Used Forklift Motor: $500
144v 500 amp controller: $400 (hehe, once it's done!)
Curtis Pot: $79
Adapter Plate & coupler: $120 (homemade. It's sort of easy with semi-basic tools)
12 12v 10amp Harbor Freight Chargers: $360.
0 gauge copper cable: $150 (EASY to find on ebay)
Angle iron: $50
Gauges: $6 (harbor freight. easy to make ammeter and voltmeter).
Labor: $0. (I have never even changed my oil before doing it, and I payed no one anything! Now I drive all around the town, happy as a clown! But mine is a ghetto 72v system.)

Top speed would likely be 80 mph or more. Range would probably be around 50 miles (if you aren't going 80!).

Notice that if you use used batteries, the price drops A LOT!

Every price I stated is readily available (except controller) to anyone with the worst luck in the world.

MetroMPG 12-20-2008 10:00 PM


Originally Posted by Cd (Post 79459)
Anyone can build a 'dirt cheap' EV if they are lucky enough to find the parts for 'dirt cheap'.

You've seen this, right: It’s a Trend! 3 Dirt Cheap DIY Electric Cars | Hypermiling, Fuel Economy, and EcoModding News -

Three dirt cheap EV's (3, actually, if you count the $800 Yugo that inspired the ForkenSwift) kind of suggests it's not just about luck.

Luck is only part - and I'd argue a smaller part - of finding deals on the parts you need. Patience is far more important. Determination helps too.

The ForkenSwift gross cash outlay was in the neighbourhood of $2k. The net cost was halved by selling left over parts from the forklift, recycling its chassis, and selling left over ICE parts from the cars.

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