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Discussion Starter #1
Hi;

I've been lurking for awhile and would appreciate some different opinions on my project before I start buying expensive pieces. :)

I have a F2000 car that I am converting to an electric setup. My plan is to use a Soliton controller coupled with a Warp9 engine, direct drive to the limited slip rear differential. Coupling will likely be chain drive although I am looking at shaft-drive options. I was in the process of a motorcycle conversion for this car when I noticed electric again.

Car being converted: http://xdesignlabs.com/pictures/reynard-done.jpg

Range wise, a typical race is about 20km. Distance calculations are tricky. I am willing to accept being short on range as this is experimental. My hard limit is weight; more than 200 or 250kg of batteries (upper limit) will stress the chassis beyond safe design limits. I'm wanting to see what I can do with those constraints; the controller and motor should be OK for the future, I hope.

My questions I'd like feedback on:

- Battery voltage vs. current - Am I better to aim for maximum voltage vs. current? My current plan is to attempt to max out the voltage rating of the Warp9 engine and then size the cell amp/hour rating to my maximum weight.

- Battery configurations for range and performance - rules of thumb?

- Battery chemistry: I am pretty much sold on Lithium Iron Phosphate but I am open to consider other technologies. My peak current draw is likely to be limited by this choice, but the energy density, packaging, and cost make them very attactive.

- Performance - The ICE in this car makes about 160hp in good trim from ~2000cc. Will the Warp9 engine offer similar capabilities, properly fed? (this goes to my questions regarding battery pack selection).

- Direct drive - the total design car weight is about 600kg, with driver and batteries, at the top end. It will likely be closer to 500kg; removal of the ICE bits, tank, electronics etc doesn't leave much there. Will this be a good match in this type of car, or am I better off to design back in a transmission? I am hoping to hold similar acceleration characteristics to the ICE or better.

Either way it will be a fun project and I am hoping to get some good performance, even if only for a short time.

I am a EE but I am very new to this and I appreciate any input.
 

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Hi Xtal
- Battery voltage vs. current - Am I better to aim for maximum voltage vs. current? My current plan is to attempt to max out the voltage rating of the Warp9 engine and then size the cell amp/hour rating to my maximum weight.

You need to understand that the controller is power in - power out device
It effectively reduces the voltage and increases the current to the motor
From that you should use the highest voltage the controller can take and use it to drop the voltage to the motor
300 volts??

Range/weight a race-car should be as light as possible, with TS cells I think 100Kg = 80km (road) - the latest batteries have about double the energy to weight
I would design with 100Kg and keep the other 100kg - just in case

Gearbox - you need to do some rough calcs
Weight - 500 Kg - 60% on rear = 300Kg
Race tires coefficient of friction ~ 1.5 (guess)
Therefore 300Kg x 10 (to become Newtons)N x 1.5 = maximum force you can put down
Times radius of rear tires divided by diff ratio = max useful motor torque

300 x 10 x 1.5 = 4500N = 990 lbsforce at about 1 ft radius = 990 ftlbs = diff ratio ~ 4:1??
= 250 ftlbs

I think a Warp9 with a Soliton tickling it can beat that number so a gearbox is not required (or useful)

Batteries - read the battery thread, I think you are looking at Headways or these new Tungisty?? RC batteries

I think that if you keep it light you should be able to produce something that will give the IC guys a fright

Good luck!
 

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Having owned and raced a F1600 and F2000 in my past life, I can offer some thoughts.

I would use the Hewland gearbox that came with the car if you still have it. It leaves you with a proven clutchless shift dog transmission and retains the all important rear suspension geometry to make you go fast. You also have unlimited gear combos to tune the ratios.

It would be an easy adaptor to mate the warp motor to the trans. I would go with an 11 inch motor. You could pack a lot of batteries under the existing cowling over the motor and in the side pods sense you won't need the two rads anymore. You could get a few in front of your toes in the nose too.

You are going to want max voltage to get the speed you desire. I used to hit 140+ in my car on the longest straight. Of course wing settings affect this and I tended to run mine with fairly low downforce.

Good luck with it and please post pictures.
 

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Discussion Starter #4
Advice noted on transmission. I have considered it, but the problem is the transmission, while proven, requires frequent and very expensive maintenance that I am not set up to do. I've run the mk8 and mk9 setups for a few years now. (f1600/2000 as well).

The transmission is also quite heavy. Getting rid of it if at all possible is a major objective of the project, and I am prepared to spend more on the differential, controller and battery bank to accomplish this end.

I am not prepared to be slow and if the transmission is required so be it. From all the other threads, this seems to be a topic of a lot of debate. My thought was I could adjust my top end speed via the differential gearing and then compensate for slower acceleration with brute force from the controller.

The replacement subframe is being engineered to retain the geometry. Not worried too much about that.

Batteries - I am correct with my thinking that the highest input voltage to the controller within weight limits is the correct design objective.

Range is still my big concern. 20km is a long time to go as almost all of the time you are at WOT or under braking. The brakes on these cars are very powerful so you spend a lot of time on the throttle.

Battery manufacturer and chemistry type I am not sure of yet.

Going to scratch my head on some of the calculations - still worried about direct drive and top speed vs. acceleration. Have to start ordering things soon.
 

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My thought was I could adjust my top end speed via the differential gearing and then compensate for slower acceleration with brute force from the controller.
With the right motor and controller you might be able to but at the cost of heat and reduced efficiency. You may need to increase the pack size to compensate.
 

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Laymans thoughts: I recall reading that the ProEV blokes tended to use 4 times as much energy racing as they would in regular driving, so a '200km' pack would only be 50km. And that was in a low-downforce car. With that in mind you're probably looking at 16kWh+ pack (200wh/km*4*20km race), probably more like 20, then add reserve capacity on top of that. That's edging up on your upper weight limits. Professionals may not care about the lifetime, aiming for lowest weight, but it's a consideration for those who have to watch the budget.
Since you'll be on the picks a lot, a regen-capable motor/controller may be the go (or a second motor/controller setup somewhere that only generates when you're off-throttle). It'll increase your range a little and save your brakes. If you can manually adjust the regen on the fly via a dial inside the car, even better.
For batteries you're probably not going Prismatic, but rather looking at Headway, K2, and the like.

Will be following this thread with interest.
 

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Since you'll be on the picks a lot, a regen-capable motor/controller may be the go


I would say NO - regen is useless on a racer - your brakes will be absorbing 600Hp+ regen will only be able to absorb 100hp (ish)
Regen is good if you gently brake - not what you do on a track!
, if you get regen for free then OK but if you are looking affordable then its DC and regen will cost weight and complexity

With that in mind you're probably looking at 16kWh+ pack (200wh/km*4*20km race)

That is what I said - using the headways or Turigny that is about 100Kg, I am going for about half that (9Kwhrs) using 100kg of TS

The nice thing about the smaller cells is that you can easily increase your Kwhrs if you need to

the total design car weight is about 600kg, with driver and batteries, at the top end. It will likely be closer to 500kg

You should be able to beat that - thats my expectations for my road legal two seater with an 11 inch motor that weighs 102Kg - and my chassis is built heavy cos I'm a coward!

Go light! - but try and retain the ability to add more cells if nessesary
 

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Some more thoughts about energy requirements

20Km - 20 laps of the short circuit at Brands - 40 seconds a lap - 800 seconds

16 Kwhrs / 800 seconds = 72 Kw average - on the throttle 80% of time? = 90Kw = 120hp

That is 120Hp average!

The IC cars have 160hp at peak power - 6000rpm? at 4000rpm ~ 120Hp

Should be enough with no gear changes and max torque available whenever you want it

If you have designed your battery with several paralleled strings you may end up using a 12 Kwhr setup on some circuits and a 16 or even 20Kwhr setup on others

If you don't need the extra energy leave it in the trailer - go light!
 

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I ran a few seasons without doing any maintenance on my hewlands other than dog rings. Compared to $700 a weekned for tires and $7000 each winter to freshen the Pinto engine, the hewland was insignificant. (I was in deep). I still think the hewland would be the way to go since it is meant to be driven without a clutch except to pull away from the pits. Do you up and down shift now without the clutch. I learned it and never replaced a racing clutch. Some guys used the clutch on downshifts. You might want to ponder this one carefully. OTOH, you may be able to get the diff gears right and never shift. I've got some single way adjustable Penske's that I'll donate to the cause if you need them. They are only 10 1/2 eye to eye due to my zero droop crazy stiff setup but I think I might have a set of longer shafts somewhere. I sold everything else.

Our local tracks are more like 1:20 and I think you will have trouble making a feature race to the end. I do agree on the brakes - my telemetry showed higher G's in braking than throttle. My data showed pretty much 100% brakes or 100% throttle. I would do the calcs as if you were flat out all the time.

It's an interesting project. I had a Euroswift FF and a Van diemen F2000. They both had full Indy car style sidepods with radiators. Yours will tight.
 

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Hi xtal,

Nice project. I've read plenty of arguments about the wisdom or otherwise of going with a single ratio versus multi-ratio transmission. It's sometimes said that you need twice as powerful a motor to get the same performance as you would with a smaller motor and gearbox, and that seems about right from my own calculations.

There's a spreadsheet at the top of this page I found very useful for estimating the ideal ratio and comparing results with and without a gearbox:http://www.diyelectriccar.com/forums/showthread.php/dc-motor-charts-ev-performance-spreadsheet-41565.html

Personally I think a single ratio system can make a good compromise for a commuter, but for a race car you really need a two or three-speed box. The trick is finding something suitable.

If you are going to go without a gearbox the Warp 9 motor may not be the best choice, as it's redlined at 5,500 rpm. Kostov have just brought out an uprated 9" motor with a nominal rpm limit of 6,800. It might be worth contacting them and asking if it's suitable for your purposes. One of their engineers is an occasional contributor here (Plamenator): http://kostov-motors.com/tractionmotors/kostovevmotors-and-kits/seriesdcmotorsforelectricvehicles/k9220v/
 

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Range wise, a typical race is about 20km
...
My hard limit is weight; more than 200 or 250kg of batteries (upper limit) will stress the chassis beyond safe design limits.
...
The ICE in this car makes about 160hp in good trim from ~2000cc. Will the Warp9 engine offer similar capabilities, properly fed?
You really need some telemetry data from several runs on the course to optimize your design, but you can make some WAGs ahead of time then refine your choices based on the telemetry data collected by the Soliton1. Of primary importance will be average power, total run time, peak power, percent of time at 100% duty cycle (which will indicate you've run out of voltage) percent of time at 1000A (which will indicate you either need more current OR motors that deliver more torque per amp (ie - higher voltage/lower amperage)).

The worst case for the battery requirement depends on the average power demand over the entire race and the total time. If you need 120kW (160hp) average for 20km and the race lasts 15 minutes then you need a ~30kWh battery pack:

120kW x 0.25h = 30kWh

Of course, you don't really use the maximum output of the F2000 engine for the entire race, hence the need for good telemetry data.

My WAG: you'll need 20kWh of battery pack for a 15 minute race. Headway cells (LFP chemistry) deliver about 80-85Wh per kg, so a 250kg budget should get you ~21kWh... should be enough, then.

A single WarP-9 motor probably won't cut it. I'd consider dual 8" motors, or, as was mentioned, the new Kostov 9"/220V (but also two of them). The 1 hour rating of single motors in this size range is approx. 30kW - the i²t relationship means you can pull twice that power on average if you run them for 1/4 the time, but that still won't be enough, I'd guess. BTW - I'd permanently wire advanced timing motors (eg NetGain 8") in series and neutrally timed HV motors (eg Kostov 9") in parallel.

You will almost assuredly need an external blower to cool the motor(s), especially if you stick with direct drive.

I would ditch the chain drive and go with toothed belt instead (higher efficiency, less problematic, less dangerous if it breaks). I believe the HTD profile is especially well suited to this application.

Specify the differential ratio so that you can run the motors at a minimum of 2000 rpm and a maximum of 5500-7000 rpm (depends greatly on the motor - keep the WarP9 below 5500 rpm but the NetGain 8" and Kostov 9" should be able to handle a bit more than that... 6500-7000 rpm should be acceptable for racing applications).

Interesting project, btw. We came within spitting distance of converting a F2000 chassis for the Pikes Peak Hill Climb last year but chickened out over budgetary concerns. Our customers are way more affluent than we are... :D
 

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i agree with tesseract, you will really need at least two 9" motors or an 11", i've seen the warp 9 put out 100kw but only for 20ish seconds. One 9" motor will probably start to over heat if you try and race with it. if you running the soliton 1 it can put out 1000amps continuously and your motor could only handle it for a few seconds, even with added cooling.

Adding another motor will only add 50kg to the car and it gives you plenty more Kw to play with if you can use them.
 

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I would say NO - regen is useless on a racer - your brakes will be absorbing 600Hp+ regen will only be able to absorb 100hp (ish)
Regen is good if you gently brake - not what you do on a track!
, if you get regen for free then OK but if you are looking affordable then its DC and regen will cost weight and complexity
I would hjave thought AC motors were of comparable weight to DC motors (give or take). Assuming that was the case, I expected the 'free' 100hp under braking was worth it.

I could be wrong. Wouldn't be the first time. :D
 

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Hi Bell

I would hjave thought AC motors were of comparable weight to DC motors (give or take). Assuming that was the case, I expected the 'free' 100hp under braking was worth it.

The issue is that AC motors (and controllers) are a LOT more expensive than DC

if you are looking affordable then its DC

and regen will cost weight and complexity

A powerful AC system would cost ~ $25K - Motor and controller -not batteries
An equivalent (but much less sophisticated) DC system ~ $8,000 or less
Mine has cost $700
$100 for the motor
$600 for the Open-revolt controller
 

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If you haven't see it yet, check out www.proev.com for a 4wd electric racecar. I don't know what kind of tracks your vehicle races on, but I would think regen braking is very important, particularly if you are on the limits of battery capacity, you'll need to be stuffing power back in when braking, the ProEV guys say it is critical to their car, they have 4wd, that can shift the juice with braking in front, power in back.
Now if you run in an oval thing were you don't brake much, it might not matter.

Similiar issue with the trans, what are the speeds? Do you have to slow significantly for tight turns, or can you optimize gearing for a narrow mph range? Higher voltage means lower current, so if you don't run a trans and need lower rpm power, you might need a lot of current.
Generally a trans is worth its weight, gears can be very lightweight if designed for it, you'd generally only need 2 speeds, no reverse?
Might see what is available in a CVT these days.
http://www.wrightspeed.com/specifications
Don't know if you've seen this car.

I recently posted up a drivetrain design that uses two torque converters in a direct drive setup for the smart car. Maybe you can give this design a try, I'd love someone to fund the building of a prototype of my design.

The A123 cells are quite powerful (but expensive), and the ProEV uses Kokam cells which are also powerful but expensive. I don't know what your budget is, but you probably know racing can get costly, and much more so when you are not using off-the-shelf standard parts!




Since you'll be on the picks a lot, a regen-capable motor/controller may be the go


I would say NO - regen is useless on a racer - your brakes will be absorbing 600Hp+ regen will only be able to absorb 100hp (ish)
Regen is good if you gently brake - not what you do on a track!
, if you get regen for free then OK but if you are looking affordable then its DC and regen will cost weight and complexity

With that in mind you're probably looking at 16kWh+ pack (200wh/km*4*20km race)

That is what I said - using the headways or Turigny that is about 100Kg, I am going for about half that (9Kwhrs) using 100kg of TS

The nice thing about the smaller cells is that you can easily increase your Kwhrs if you need to

the total design car weight is about 600kg, with driver and batteries, at the top end. It will likely be closer to 500kg

You should be able to beat that - thats my expectations for my road legal two seater with an 11 inch motor that weighs 102Kg - and my chassis is built heavy cos I'm a coward!

Go light! - but try and retain the ability to add more cells if nessesary
 

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Discussion Starter #16
The speed ranges from 50-60kph (very tight turn), followed by a uphill drag race, to 230kph+ high G turns. Unfortunately I do not have any telemetry and cannot easily get it until spring.

Regen will not help me much and will add weight and complexity. Weight makes me slow, and complexity makes the car break. Most of my braking takes place over very, very short distances and can only be described as violent. A mechanical system may have benefit but I'm not BMW Williams .. and a huge portion of the appeal is the reduction of mechanical complexity and a shift into my own area of expertise, electrical engineering.

I think I am sorted on most issues but the critical one, and that is the transmission. Work has kept me away for a week or so, but I will be figuring that out this weekend. Most advice has been to keep the transmission. This makes some things easier but others harder. Shifting costs time and adds the possibility for error.

Gearsets are relatively inexpensive to buy, but I would much rather go to a LSD direct drive scenario. That is another consideration; I am open diff at the moment, as the car cannot deliver enough torque to break the slicks free when they're warmed up without doing something stupid.

I have found two sponsors for this project, there's been a lot of interest. That's encouraging. :D
 

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I don't understand what weight does regen add?
A motor can brake violently, all the power doesn't have to go back into the battery, but even a smaller amount could make a big difference in how much battery weight you must carry.
Friction brakes create enourmous heat, and it has to be removed. If you can move all the heat where it can be cooled better, it could be more efficient. You could use a smaller lighter rotor with less friction braking.

The speed ranges from 50-60kph (very tight turn), followed by a uphill drag race, to 230kph+ high G turns. Unfortunately I do not have any telemetry and cannot easily get it until spring.

Regen will not help me much and will add weight and complexity. Weight makes me slow, and complexity makes the car break. Most of my braking takes place over very, very short distances and can only be described as violent. A mechanical system may have benefit but I'm not BMW Williams .. and a huge portion of the appeal is the reduction of mechanical complexity and a shift into my own area of expertise, electrical engineering.

I think I am sorted on most issues but the critical one, and that is the transmission. Work has kept me away for a week or so, but I will be figuring that out this weekend. Most advice has been to keep the transmission. This makes some things easier but others harder. Shifting costs time and adds the possibility for error.

Gearsets are relatively inexpensive to buy, but I would much rather go to a LSD direct drive scenario. That is another consideration; I am open diff at the moment, as the car cannot deliver enough torque to break the slicks free when they're warmed up without doing something stupid.

I have found two sponsors for this project, there's been a lot of interest. That's encouraging. :D
 

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Discussion Starter #18
I assume I'd need either to change proposed motor configurations or controllers in order to do this. Anything that increases complexity needs to be looked at carefully. I am looking for a proven design that will tolerate abuse.

Keep in mind how little time is spent in braking - the car drops from 200+kph to 90kph in a few seconds. The transition back onto power happens in 2 seconds or less during turn in just prior to apex. Then it's flat on. Looking at the charge rates of the batteries, I don't see this contributing to the range, and I can see it complicating things like braking bias.

If it's easy to do sure.. but I don't see it being a big make/break in a 15 minute sprint race.
 

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For low-cost and off-the-shelf parts, a DC motor is the way to go,
and as others have suggested, probably dual smaller motors to increase surface area for cooling and increase the RPM limit. It also lowers the cg slightly by having smaller diameter motors lower in the car, although they will weigh a little more than a single big motor.

But I'd think you might actually be able to remove the rear brakes if you have regen,
and this would not only save weight, but remove unsprung and rotating weight from the rear wheels. If you can use capacitors to absorb the braking, it can then dump the power back in immediately at much higher rates than any battery can to get the car back up to speed fast using the high current needed, and then use the high voltage from the battery to get the high speed. Then you can eliminate the transmission.
This is what I'd try to do, take full advantage of what an Electric car is capable of and the advantages it has over a gas powered engine. Of course, it is more complicated and costly, but then what is the point of going electric?

I used to race electric cars, 1/10 scale R/C cars. :)
They have no mechanical brakes, they were faster than gas cars, accelerate faster and brake quicker.
Check it out, very exciting:
http://www.youtube.com/watch?v=Ngv2toDTQw4&feature=related

I assume I'd need either to change proposed motor configurations or controllers in order to do this. Anything that increases complexity needs to be looked at carefully. I am looking for a proven design that will tolerate abuse.

Keep in mind how little time is spent in braking - the car drops from 200+kph to 90kph in a few seconds. The transition back onto power happens in 2 seconds or less during turn in just prior to apex. Then it's flat on. Looking at the charge rates of the batteries, I don't see this contributing to the range, and I can see it complicating things like braking bias.

If it's easy to do sure.. but I don't see it being a big make/break in a 15 minute sprint race.
 

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...I don't see this contributing to the range, and I can see it complicating things like braking bias.

If it's easy to do sure.. but I don't see it being a big make/break in a 15 minute sprint race.
I'm building a autocross/drag racer and seriously considered regen, but came to the same conclusions you just stated. Good brakes can handle the task easily, and extra complexity is just asking for unnecessary problems.

The best bang for the buck, as has been stated, is going to be a series DC setup. You don't need the transmission either. It wouldn't hurt to have it, but you don't need it. With dual 8s or 9s, as suggested, and a stiff pack, you're going to have more torque than you can put on the ground in that lightweight of a race car. That means you can gear for the top end you need and have fun. I think the concept of being in motion and at or near WOT for the overwhelming majority of the time is escaping people here. Your setup will be more comparable to the electric race bikes than a street car. No shifting, just go:
 
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