# Planning on a 1977 fiat spider conversion



## nucleus (May 18, 2012)

Okay, my thought on this is to build one that is a lot faster than the ICE engine:

Use this motor controller combination:

http://store.evtv.me/proddetail.php?prod=HPEVAC35x2

This will give you 165 HP:











This motor is AC and the regenerative braking is built right in. 

The next big item is the battery pack, and this is where budget, range, and weight collide - something like a 144 V pack composed of 45 CALB CA100 cells. 

This gives you a 14.4 KWh pack that weighs about 340 pounds. The motors and controllers are 210 pounds so depending on the charger and DC-DC converter you choose perhaps 600 pounds overall weight for the electric power train. 

If you can lose 300 pounds in ICE and supporting components then you are looking at a 2650 pound car, which should use 265 watt hours per mile which puts your real world range at about 45 miles.


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## dougingraham (Jul 26, 2011)

Neat car and seems like it would make a fun conversion. Ok, 60-80mph and 40-60 miles in a moderately light weight sports car. This is very similar to all the other sports cars in about that weight range, mine included.

The 60-80 mph is not really anything difficult to obtain. For AC systems an HPEVS AC-50 with the 144V Curtis controller would be what I would recommend. For DC a 9 inch motor like the Netgain WarP 9 or Kostov. I would suggest a Soliton Jr controller for a daily driver. AC systems cost a little more but have a little better efficiency and you get regenerative braking. In theory a little less maint would be required because no brushes but brushes are pretty easy to replace and I would be surprised if you didnt get 100k miles on the latest compound brushes. The DC system would be a little higher performance as well. Switching to a Soliton 1 controller could give you a lot more power than the AC system but at a cost of additional dollars. I would expect it to feel better as an EV than with the original ICE with either setup.

To make your range requirement of 40 miles on a car that weighs 2400 lbs will require an estimated 240wh/mile so you need a minimum pack size of 9.6kwh. Since you want this to last many years you dont want to discharge below about 80% increasing the minimum size to 12kwh and since you still want 40 miles at the end of the life of the pack (when it reaches 80% of new capacity) we need to increase its size a little more to 15kwh.

For the suggested AC system you can use a practical maximum of 46 cells. This means you need 102AH cells which is close enough to 100AH to make it work out. With the DC system on the Soliton your voltage is not the limiting factor. You could use the same 46 cell pack of 100AH cells or you could use 60AH cells which might be easier to fit into the car. With 60AH cells you would need 78 to make your 15kwh pack size.

New cost for the AC system will be in the range of $5500.
New cost for the DC system will be in the range of $4000.

Cost of the batteries will be between $6500 and $7000. Today I would get the CALB CA series cells. You would need a larger AH pack of other brands of prismatic LiFePO4 cells to get the current levels needed. On the flip side other brands cost a little less so you could spend the same amount and get more battery for the same dollars. But that will take more room and weigh more making the car less fun to drive and require more wh/mile.

Also you will need the pieces to connect your motor to your transmission. This will cost around $800 to get off the shelf if available for your car. If you know a machinist you can probably have this done for about that amount of money.

You will need a charger. I would figure spending $2000 at least for that.

I would add an additional $2000 for all the fiddly bits that go into a conversion. Things like cable, cell interconnects, wire ties, contactors, meters, shunts DC-DC converter, water cooling for the controller. Stuff I cant think of off the top of my head.

Since your car is currently operating you are a step ahead. Fix everything that is not related to the ICE before you start the conversion. Brakes, clutch, suspension, steering all electrical stuff needs to be working. Switching to magnetic drive will not make that stuff go away.

With your range requirement the car will weigh about the same after the conversion as it does with ICE. At least with Lithium batteries. If you try to do this with Lead Acid batteries it just is not going to work. Lithium will weigh about 350 lbs and lead will weigh four times that for the same capacity and take up three times the room. So in a practical sense you just cant do Lead Acid.

You can save some money by hunting for used components. I would buy used motors but used electronics I would buy only if I could see that they actually worked. I expect these kinds of conversion to cost between $15000 and $20000 with your range requirement excluding the cost of the roller. 

Best wishes and keep us all apprised of your progress. We love pictures!


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## Duncan (Dec 8, 2008)

Hi Tersta
I agree with the other posters about the batteries
And that gives you a fixed cost - $6,500 - $7,000
As far as the motor is concerned
AC is OK if you have deep pockets

AC is definitely the future but just now it is expensive or wimpy or both

_New cost for the AC system will be in the range of $5500.
New cost for the DC system will be in the range of $4000._

BUT that AC system will be less than half of the oomph of that DC system
You can go cheap on DC
My motor was $100 (forklift motor)
and controller $600 (Paul and Sabrina - OpenRevolt)
That combination will blow away available AC systems costing $8,000+

Going cheap on AC is possible - BUT you need to find somebody who can help you

Going cheap on DC is a lot easier as lots of people have done it and can help you


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## Tersta (Sep 6, 2013)

So what if I didn't need it to go 40-60 miles? How much changes in what I would need? On days that I just go to work and home I drive less than 10 miles.


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## Duncan (Dec 8, 2008)

Tersta said:


> So what if I didn't need it to go 40-60 miles? How much changes in what I would need? On days that I just go to work and home I drive less than 10 miles.


You could use a smaller (cheaper) battery

There are three things you need to worry about
Maximum power available
Continuous power available
Range

Range - for 10 miles you will need an absolute minimum of 3 Kilowatt-hours
(240 watt hours/mile x 10 divided by 80%)
This will cost ~ $1,500

If you use CALB cells
Maximum power available = 3Kw x 12 = 36Kw = 48Hp
Continuous power available = 3Kw x 3 = 9Kw = 12Hp

Bit low but possibly OK
Better with 6 Kilowatt-hours

This would give 20 miles range, 96Hp max and 24Hp continuous 

(24Hp continuous does not sound a lot but it is enough to drive that car at about 70mph)

This is a good match to the OpenRevolt controller - 100hp max

Using the OpenRevolt gives a max voltage of 150v

So 44 off 40Ah CALB cells would be a good battery and would cost $2,500 - $3,000

Remember If you use a smaller battery then you will be hitting it harder


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## dougingraham (Jul 26, 2011)

Tersta said:


> So what if I didn't need it to go 40-60 miles? How much changes in what I would need? On days that I just go to work and home I drive less than 10 miles.


Like Duncan says, you can use a lot smaller battery. But there is a minimum size you need in order for it to produce the minimum level of power needed to accelerate reasonably. I kept careful track of my driving for several months and found that my commute if all I did was drive to work and drive home was 8.8 miles. I would average about 12 miles per day and if I drove clear across town and back it would be in the mid 20 mile range. Once you wrap your head around the fact that you dont drive nearly as much as you think you can save quite a lot. I also wanted my project to be fun to drive. If I had built the car to only do around 20 miles I would have spent 1/3 as much on batteries. And I could have made that work. But the car would have seemed a bit gutless in order to protect the batteries from being overloaded.


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## dtbaker (Jan 5, 2008)

Tersta said:


> At this time I live in the city and only work a few miles from home so 40-60 would get me all the way across town and back.
> ...I would like to be able to get 60-80 MPH


The most cost effective DIY solution is DC motor/controller unless you do constant stop/start or have lots of hills. Extending range with higher capacity batteries cost less than regen benefit from AC.

I have found that the efficiency of the DC motor/controllers drops significantly with systems over 120v in normal driving. You can expect a little sports car like yours with 120v DC system to use 200-250watt-hr/mile (or, get about 4 miles per kWhr). Using 38 x 130ah CALB cells would give you 15.8 kWhr on board.... yielding MAX range around 75 miles if you were careful under great conditions, or a pretty safe 60 miles under average conditions not running the batteries down too far. If you wanted to bump the performance up you could add a few cells for 144v or even 156v nominal, but efficiency suffers and you don't get much more range. If you really wanted to be sure you have range to spare, the next common size up would be the 160ah cells, but they'll cost proportionally more, and add weight and space requirements that can be a challenge in a small sports car....

An ADC 8" motor would be 'adequate', but barely, for sustained highway speed.... A Warp9" with Soliton Jr. or Zilla controller would be better, and capable of putting out around twice the torque of the stock Fiat off the line for accelleration.

To do these conversions 'right' is not cheap.... but well worth the investment for a dependable high-performance EV. There are some items you can find at discount that work fine, others you are well advised to pay more for quality like the batteries, motor, and controller. You are going to end up spending $12k-$15k by the time you are done....


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## dragonsgate (May 19, 2012)

dtbaker said:


> The most cost effective DIY solution is DC motor/controller unless you do constant stop/start or have lots of hills. Extending range with higher capacity batteries cost less than regen benefit from AC.
> 
> I have found that the efficiency of the DC motor/controllers drops significantly with systems over 120v in normal driving.


Please explain to Tersta and me why stop and start and hills are bad for DC. Also how efficiency drops after 120 volts.


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## dougingraham (Jul 26, 2011)

dtbaker said:


> I have found that the efficiency of the DC motor/controllers drops significantly with systems over 120v in normal driving.


I agree that DC systems are the most cost effective at this time. I dont agree that efficiency drops at voltages higher than 120V. Motor efficiency is not affected by increasing the battery voltage except that you can see a wider usable RPM band. Controller efficiency is pretty much unchanged. The higher voltage on the input will reduce copper losses on that side of the switcher and on the output side the current is the same. Since the PWM duty cycle is reduced the switching losses will appear as a greater percentage of the losses but overall efficiency improves. The batteries will be happier because the current they see will be reduced which will result in less sag. This is higher efficiency in the batteries. It should be a win/win/win situation.

What makes you think the efficiency goes down?


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## dtbaker (Jan 5, 2008)

dragonsgate said:


> Please explain to Tersta and me why stop and start and hills are bad for DC. Also how efficiency drops after 120 volts.


- not saying hills are bad for DC, only saying that if you have lots of hills you have opportunity for significant braking regen from AC to extend range.

- my comment about a higher voltage pack having lower efficiency is based on my 'real' comparision of my two EVs. The swift has a 120v nominal system, the Miata has 156v nominal. the swifts total battery capacity is 120v x 100ah = 12kWhr and has averaged about 25 miles on 6kWhr = .24kWhr/mile use in regular daily driving. The Miata is pretty close to the same weight, but I do drive it harder with a zilla controller than the swift with a wimpy curtis. The Miata battery pack is 156v x 130ah = 20.3kWhr and I usually get about 30 miles on 10kWhr = .3kWhr/mile

so..... whether this difference is due to voltage, ADC8" versus Warp9" motor, or Curtis1221c controller versus Zilla...or just that I tend to accelerate harder from stops with the Miata, I dunno. My only observation is that the higher voltage pack may not give as good a range as lower voltage with more capacity.


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## Tesseract (Sep 27, 2008)

dtbaker said:


> ...whether this difference is due to voltage, ADC8" versus Warp9" motor, or Curtis1221c controller versus Zilla...or just that I tend to accelerate harder from stops with the Miata, I dunno. My only observation is that the higher voltage pack may not give as good a range as lower voltage with more capacity.


So out of all of the above changes, the one that seems to be the most logical explanation for a reduction in range is "higher pack voltage"?!? Not that you replaced a 400A controller with a 1000A model, or that you've even noticed you have a propensity to use the higher current?


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## dougingraham (Jul 26, 2011)

dtbaker said:


> - my comment about a higher voltage pack having lower efficiency is based on my 'real' comparision of my two EVs. The swift has a 120v nominal system, the Miata has 156v nominal. the swifts total battery capacity is 120v x 100ah = 12kWhr and has averaged about 25 miles on 6kWhr = .24kWhr/mile use in regular daily driving. The Miata is pretty close to the same weight, but I do drive it harder with a zilla controller than the swift with a wimpy curtis. The Miata battery pack is 156v x 130ah = 20.3kWhr and I usually get about 30 miles on 10kWhr = .3kWhr/mile
> 
> so..... whether this difference is due to voltage, ADC8" versus Warp9" motor, or Curtis1221c controller versus Zilla...or just that I tend to accelerate harder from stops with the Miata, I dunno. My only observation is that the higher voltage pack may not give as good a range as lower voltage with more capacity.


I see why you think this. It is more likely due to the differences in the rolling resistance of the cars. I have an ICE powered RX-7 and my EV RX-7 and it does not get as good a wh/mile rating as I expected it to. I found a place where I could do a soap box derby and compare the two cars. The cars are within a 100 lbs of each other but the EV rolls considerably less distance (~1000 ft). The max speed at the bottom of the hill is lower. It is 35mph with the ICE and 32mph with the EV. The tires and wheels are different but common knowledge is that the 205/60 R14 tires should not roll as well as the 185/70 R13's do but the ICE with the larger tires rolls farther. A third data point is that my ICE BMW X5 rolls a 100 feet less than the ICE RX-7 and you would expect it to be the worst of the lot. I expect my issue to be a combination of things but probably alignment will fix most of it.


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## dtbaker (Jan 5, 2008)

Tesseract said:


> So out of all of the above changes, the one that seems to be the most logical explanation for a reduction in range is "higher pack voltage"?!? Not that you replaced a 400A controller with a 1000A model, or that you've even noticed you have a propensity to use the higher current?


ok, ok, ok I dunno what has the larger effect.... a little more weight, higher voltage, little wider tires, lot more available accelleration.... or purely male response to USE more power when its available. I guess I could limit controller output to 120v in the Miata and see.

as pertains to OP however.... given a little sports car and the temptation to use more zap when available, the end result may be more range with lower voltage just because of the alteration in driving style.  Don't get me wrong, I am a believer in higher voltages to reduce average amps comparing apples to apples. All I'm saying is that the Miata doesn't get proportionally more range as I had expected based purely on battery pack capacity.

or, maybe its purely the predictable factors of weight, tires, and more time at higher output with the higher capacity controller.


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## dragonsgate (May 19, 2012)

When I built my car 120volts was what was recommended so that is what I went with. A short time after I got my car on the road I read that the adc fb4001 would take 144 volts. So I added three more batteries. Except for the extra 189 pounds the car was basically the same. I am not an electronic wiz like some of you guys so I do not have all the neat meters and gages but the seat of my pants told me that the car had better acceleration and I pulled the hills a lot easier. While the battery amperage stayed the same I gained an extra mile per charge. That is why I asked the question about efficiency. To direct this post back to Tersta I will say that the dc motor has worked well for the last 14 years of stop and go traffic. It pulls the hills just fine and I occasionally get a chance to hit 70mph or better. I have driven Fiats for the last thirty years and I can tell you while it is not the biggest or badest setup a 9 inch DC motor with a 500 amp controller will give better performance than that 77 Spider ever did with the gas engine.


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