The cost of an EV conversion

[swbluto]

What it would cost to do a basic EV conversion with these specifications?
100 miles range
And a top speed of 60 mph?

Since the bulk of the cost is in the batteries, and the others are pretty fixed, I thought that it'd be pretty straightforward to estimate. I've heard figures of 150wh/mi which would then need a battery with 15,000 wh. With the use of a super-duper-capacitor array that might run about $3000-5000, you can avoid cell degradation that accompanies high C current with accelerations that'd largely run off the capacitor array and then be able to operate with cheaper LiFePO4. I'd guess that "quality LiFePO4" that'd work for this capacitor bank might run $1.50/Wh which is only $22500. Toss in 5 grand for the battery, motor, controller, and BMS(or consider 10-15000 with labor) then it'd only total up to..

22500 - battery
5000 - capacitor bank
5000 - everything else
-----------------------
32500. That seems fairly feasible, doesn't it considering the average consumer spends ~$20-30,000 on a car? If you're to convert from a cheap high-mileage but "classy/sporty/desirable car", then a desirable electric might only cost 42500.

Is there something wrong with my calculations? Can it be done cheaper with something that could probably get at least 7-years/100,000 miles of service with greater than 70% of original range assuming 15,000 miles per year?

 

[Link]

Well, I'm not sure supercaps are to that point yet. Plus, you could get some pretty good lithium for $1.50Wh.

And, to be safe, I'd bet on more like 200-250Wh/mi. The estimate I actually hear is 300Wh/mi, but that's probably based on heavier cars.

 

[pwbset]

The estimate I actually hear is 300Wh/mi

I'm averaging 35-45wh/mi all up weight of 260lbs going up steep hills on my ebike. x10 and that would be 350-450wh/mi for a 2,600lb all up car climbing a 10-15% grade. Heh, heh.. if only conversions were that simple. :wink:

 

[swbluto]

The estimate I actually hear is 300Wh/mi

I'm averaging 35-45wh/mi all up weight of 260lbs going up steep hills on my ebike. x10 and that would be 350-450wh/mi for a 2,600lb all up car climbing a 10-15% grade. Heh, heh.. if only conversions were that simple. :wink:

Assuming the car isn't going up a steep hill at speeds greater than 30 mph, it's not a bad estimate. The amount of energy you expend in propelling your weight up a hill is linearly proportional to the mass with everything else equal. Heck, with the type of car motor used getting higher efficiency than your 4011(?) at the lower end of the speed spectrum(Totally basing this off the Tesla Roadster's efficiency), it might even be less.

That's too bad about the capacitor technology. I thought surely that enough moolah would get the desired capacitance and voltage rating for the high-amp situations. I was kind of hoping 5 grand would've been a healthy estimate but that's definitely due to later analysis. Basically, we need about 1/2*mv^2 energy to accelerate from v_0 to v_f(not accounting for wind and rolling resistance, which is negligible in comparison to kinetic energy.) and the energy stored in a capacitor is 1/2*c*V^2. Assuming you could usefully extract half the energy in a capacitor for motion, you'd need a capacitance of (2mv^2/V^2) farads. 2*1000kg*30(m/s)^2/(60V^2) ~ 50 farads. I don't how feasible such a capacitance is, but 60V doesn't sound impossible.

I just did a quick check. It appears that there are 60V 61mF capacitors for $45. Hook those in parallel, and it'd only take 50,000mF/(61mF/45$) dollars or about $37,000. :lol: Ok, I might have underestimated the cost just a little. Cutting it in half to account for the price I saw was for the "top of the market", then that'd still suggest a minimum cost of $18,500 for a useful capacitor bank. Oh, well, we could limit the speed to accelerate to 2/3 the original amount or about 44 mph. That'd decrease the capacitors cost by 4/9 which nearly halves it. Or limit it to about 1/2 of 67mph, so that'd quarter the cost. So, for about enough energy to accelerate from 0 to 30 mph from capacitors alone, you can get a capacitor bank for about ~$5000 but that would come with reduced acceleration at higher speeds.

 

[Link]

That's too bad about the capacitor technology. I thought surely that enough moolah would get the desired capacitance and voltage rating for the high-amp situations. I was kind of hoping 5 grand would've been a healthy estimate but that's definitely due to later analysis. Basically, we need about 1/2*mv^2 energy to accelerate from v_0 to v_f(not accounting for wind and rolling resistance, which is negligible in comparison to kinetic energy.) and the energy stored in a capacitor is 1/2*c*V^2. Assuming you could usefully extract half the energy in a capacitor for motion, you'd need a capacitance of (2mv^2/V^2) farads. 2*1000kg*30(m/s)^2/(60V^2) ~ 50 farads. I don't how feasible such a capacitance is, but 60V doesn't sound impossible.

It's not that the caps aren't up to it, it's just that it's not cost or space effective. Even supercaps don't compare to a lithium battery yet in terms of energy storage, and lets not forget that you'll only be able to use a small portion of the caps' available energy before they go low enough for the batteries to start doing all the work again. Unless, of course, you have some kind of super huge power converter, but then that will put caps WAY over the cost of equivalent batteries.

There's no reason you couldn't do it, but there's also no reason the batteries shouldn't be capable of it. $1.50Wh is enough to start thinking about using A123s, and, as we all know, they'll have no problem with delivering the power you need. 8)

 

[swbluto]

$1.50Wh is enough to start thinking about using A123s, and, as we all know, they'll have no problem with delivering the power you need. 8)

Oh, yes, you're right. I was under the momentary impression that A123's cost ~$4.00/wh from my mis-recalled memory of http://www.zeva.com.au/tech/LiFePO4.php when they actually list the amount per amp-hour at 4.34. Divide by 3 volts, and that's about $1.44/Wh(Or around there not considering currency conversions and changes in market demand). Doh.

Yeah, there'd be no reason to not start thinking of a123 at that point besides current lack of availability. But, it seems they're starting to cater to the car market with something like this being a bellwether: http://www.a123systems.com/hymotion/products/N5_range_extender.

Although, that pack's price would suggest $30,000 at 15,000 wh. Perhaps 1.44/wh isn't a good estimate.

 

[mvadventure]

Check out http://www.electric-cars-are-for-girls.com/electric-car-conversion.html for ideas, links and wheels that have already been invented.

Mike

 

[dogman dan]

Also add a few more thou to the everything else part of the equation. 48 volt bug conversions can be pretty cheap, but if you are looking for 60 mph you will spend somewhere between 7 and 10 thou on the everything else. This is assuming you want things like air conditioning power steering and heat. Of course if you weld well, then the battery racks won't cost so much compared to hiring fabrication work.

 

[mvadventure]

Again with the flooded cell batteries and dogman can attest, a battery rack needs a waterproof and acid proof enclosure around the sides and bottom of the batteries. All you have to do is visit any golf course with electric carts and you can see the stains. One set of wet batteries, even from a good rain, and the stain is forever. This doesn't sound like a big deal until you have the stain in your garage or driveway or a friends driveway and all of a sudden your EV is less than welcome.
This I know from experience.
Mike

 

[swbluto]

Well, I'm not sure supercaps are to that point yet. Plus, you could get some pretty good lithium for $1.50Wh.

And, to be safe, I'd bet on more like 200-250Wh/mi. The estimate I actually hear is 300Wh/mi, but that's probably based on heavier cars.

The volt, as described at http://blog.wired.com/cars/2008/09/the-volt-isnt-a.html , has a 16KWH and is supposed to drive on electric alone for 40 miles. Assuming it used 100% of its battery before doing do, that'd come to 400 WH/mile.

But I suspect the gasoline motor is turned on before 100% discharge and probably way before that(for battery-life longevity).

Edit(I read further): It apparently cuts out at 70% DOD and kicks on the generators. So, 16000*.7/40-miles= 280 WH/mile. And, yeah, the Volt is probably a "heavier" car.

 

[andys]

If you convert a small light weight car, the costs go down significantly. weight is a huge obstacle to performance. A fellow in Europe converted a Fiat 500 and is getting 60 MPH and over 60 mile range from a 72V 100AH lithium battery and old DC motor. I know a source for 100AH LIFEPO4 batteries where $5000 gets you a great power source, and $10,000 would buy a battery pack that could power a small car for over 100 miles. I am still thinking about doing a Fiat 850, or a small lightweight kit car.

Curtis just came out with an affordable 120 volt regen fully programmable controller for AC drive motors. There are some small and medium sized affordable and very strong AC motors on the market now as well-the guys at Thunderstruck motors set a world record on their electric drag bike with twin small AC drive motors. A larger version of those same motors is due out anytime now. About $4000 would get you the controller and motor and throttle plus a few other bits needed for the conversion. I think $15,000 would be enough to build a great small EV that would really move and have a good range-better than the Chevy Volt for sure.

 

[dogman dan]

Kicking myself now for selling the Ford Festiva we had years ago. Of course we sold it because it sucked, but as an in town car, that is another story. Trips to california in that car were cheap, but murder on yer butt.

 

[Raphael]

hey andy,

could you please post some additional information about your source for those lithium packs?

thanks!

 

[andys]

Both Thunderstruck motors and Doug at EV tech have 100AH affordable very high quality LIFEPO4 batteries (not Thunderpower) that have been working very well for them. They don't have them listed at their web sites-you have to call them. I priced an 84 volt system 100AH and I think it was about $4400-$4700. The 84 volt battery was about 200 pounds if I remember right. I talked to Thuderstruck this week, and they still haven't gotten in the new Leeson bigger AC drive motor that I want. Gives me more time to save up the needed $. They have been very happy with the Hi-Power brand cells they started getting in last Spring. They told me they haven't had even one bad cell. I think Doug is getting batteries from Korea and he has been amazed at the quality and has built some very high volt packs for projects in Texas.

I think if I end up converting this fun little Fiat 850 Spider, I may go crazy and run it at 120 volts, which the new Curtis Controllers can do. The battery cost will go up about 40%, but then you have a real 12,000 watt battery pack and can do short freeway trips if needed with ease. One fun thing Doug told me, is I could rig up an AC plug on the car and power my entire house if the electricity went out!

 

[pwbset]

One fun thing Doug told me, is I could rig up an AC plug on the car and power my entire house if the electricity went out!

Yeah, that's awesome! I keep thinking about getting a couple hundred AH of lifepo4 and hooking it into a little wind turbine and my house just in case. We have power outages where I live all the frickin time and some can last 12hrs or more. Would be nice to have a backup power source. Last year during a long outage the local bars downtown lit up a bunch of candles and people partied all night long like it was 1899!

 

[lawsonuw]

Trips to california in that car were cheap, but murder on yer butt.

Well the seat is easy to fix. http://www.aircraftspruce.com/ Sells "seat foam" in various thicknesses. I've got 2 inches of this stuff on my Linear 'bent and it's like sitting on a cloud.

Anywho, back on topic, Lots of good info in this thread!

Marty