Electric car conversion: Project ForkenSwift

[MetroMPG]

Matt: looks like it's been in the car for about a year and a half (since Oct '08)

It's a commercial converter: Vicor is the brand. Cost about $25 (eBay new old stock).

I have a spare. Haven't had time to investigate further yet, though.

[MetroMPG]

Well, I put the spare DC-DC into the car on the weekend, and confirmed the smoke was let out of the previous one.

And I think I may have discovered another wiring issue that might (?) have contributed to the demise of the first DC-DC.

I have it wired on the input side in a 48v circuit that powers the contactor activated via the ignition key. I haven't confirmed, but it looks like that circuit may not have a "clean" off position. Seemed like there was some residual voltage on a wire that shouldn't have been live with the key off. Have to dig a little further.

[MetroMPG]

Got these questions via e-mail:

I currently own a 94 Metro that I've been planning on turning into an EV, and have been doing research like a mad man to do it. I believe I understand the full process but nevertheless I am a bit 'worried' to start it. I've scouted out different kits, tried to price out pieces, and also took a few glances at forklift projects. I do have a machinist for a neighbor so the trans plate and motor coupler shouldn't be difficult as well as mounting it and the battery rack. I don't have a huge budget either. The car was free and hopefully I can sell the engine and other gas related parts, but right now I have a $2500 MAX budget. I'd like to be able to get highway speeds, and a range of 50 miles. From what I understand the range has more to do with batteries and amp/hours, so I'll cross that bridge when I get there.

Hate to throw cold water on your plans, but for $2500, building a highway capable car with a 50 mile range is a very tall order. Maybe an impossible order with lead acid batteries (you'll be way over the car's GVWR if you fill it with enough lead to go 50 miles at highway speeds).

Have you seen this? http://ecomodder.com/blog/cheap-diy-electric-car/

Also my neighbor has a friend who has done a conversion in the past and is currently getting sponsored batteries, hopefully I can network with him and work something out.

If you can get a battery sponsor, obviously that would help with cost, but you'd still face the weight issue. Look at the types of vehicles in the EV album that have 50 mile range on lead - many are compact pickup trucks.

The alternative is to go with a lithium battery chemistry. (If you get a sponsor for that, would you put in a good word for me too? )

What's a good size/volt/amp motor? If i find a forklift what size motor am I looking for?

Generally people talk about series DC motors for inexpensive conversions. You'd need something in the 7-10 inch diameter size (approx 12-15 inch length) based on the conversions I've seen.

Then what type of controller can I find/want? I found your project metro in the evalbum web page and checked out your total cost and was amazed, most people were spending $5000+, which is too much for me.

Thanks - but realize what performance we got for that price.

The controller is usually the 2nd major cost after batteries. If you want a highway capable car, that implies a pack voltage that puts you in "expensive" controller territory, not the ~$100 used golf cart controller territory the ForkenSwift inhabits.

Although you can make your own high volt / high amp controller for a fraction of the price of a commercially made one. See Paul & Sabrina's controller project here: Open ReVolt: open source DC motor controller - Fuel Economy, Hypermiling, EcoModding News and Forum - EcoModder.com

[Clev]

I would also recommend checking out the EVDL to see what others have managed with this car. Don't look at their conversion cost necessarily, but get an idea of what the parts (controller, battery weight, charger, etc.) can do, and then price them out yourself (check eBay, the various EV resellers, and the EVDL Tradin' Post). That should give you an idea of what you're looking at.

EVAlbum: Search Results

Basically, for a freeway-capable EV, figure $750-1,000 for the motor, $1,000 for a Curtis 1231C 144V and $750 for the charger. That's just the base cost, not including wiring, battery racks, adapter plate, contactors, DC/DC, beefed up springs, etc., and not including batteries. If you are planning a city-only car, then you start with the Forkenswift design and go from there.

[bennelson]

My car fits the freeway capable and on-budget criteria, but not the range.

Ben Nelson's 1996 Geo Metro

In the 144v configuration:
Geo Metro - Free, after selling parts.
Open Revolt controller, built from parts - $300
Used Charger - $200
Forklift motor and new brushes - $100
Used batteries - $144
Machinist work (adapter plate/coupler) $300
Misc - cable lugs, used springs, etc. - about $300

The whole project was under $1500. I typically run the car on a 72V configuration. When I do that, it's not a freeway speed car, but looks very stock. Plenty of room in the trunk for groceries, instead of filling that with batteries.

The achilies heal of the project is that the used batteries DO NOT perform the way new ones would.

The combination of "Freeway Speed AND 50 mile range" is what I hear people ask about most ofter. That's just a tall order for an inexpensive, homebuilt EV.

My current plan is using the EV for ALL SHORT TRIPS, and a diesel/bio-diesel/veggie oil vehicle for longer trips.

[Clev]

I haven't been following the Open Revolt; I had no idea it was so cheap. Bravo.

Would that forklift motor handle 144V at 125 amps for about an hour without overheating? That's about what you'd need for a 50 mile range at freeway speeds (55-65 mph.)

This conversion (Dean Holden's 1994 Geo Metro) seems close to what he's looking for. Add two more batteries to bring up the voltage to 144V and increase the range by another 20% (from 41 miles to 49.2 miles) and it's really close without getting too crazy-heavy. And Trojan 1275s are $145 each, so about $1,740 for a brand new pack.

[Daox]

Originally Posted by Clev

Would that forklift motor handle 144V at 125 amps for about an hour without overheating? That's about what you'd need for a 50 mile range at freeway speeds (55-65 mph.)

I think that estimate is pretty high for a car. 144V @ 125A is roughly 24 hp. You'd need to be driving a large unaerodynamic vehicle to require 24 hp to cruise @ 60 mph. The Metro only requires ~12hp to go 60 mph.

[comptiger5000]

Clev - You could always water cool the motor if needed. Plus, that would give you cabin heat in the winter!

[MetroMPG]

Originally Posted by Clev

This conversion (Dean Holden's 1994 Geo Metro) seems close to what he's looking for.

In terms of performance, yes. But for $2500 max. cost? Nope!

It'd take some crazy resourcefulness to achieve that on a 2500 buck budget.

[Clev]

Originally Posted by MetroMPG

In terms of performance, yes. But for $2500 max. cost? Nope!

It'd take some crazy resourcefulness to achieve that on a 2500 buck budget.

Yeah, I think we both agree that the budget isn't totally realistic. But this should give him some idea of the voltage, amperage and battery weight he'd need to achieve those goals. He could then also start to price out where he could cut that down (getting a used motor, building the Open Revolt and getting a used charger, for instance, instead of paying $4,600 for a "kit", and finding a used vacuum pump instead of paying $300 for a new one.)