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Which controller for small autocrosser?

9K views 48 replies 12 participants last post by  rickeolis 
#1 ·
Hi everyone,
I am putting together a 1979 Mazda RX7 to race in auto-X and to be used as a daily driver at times too. I have placed an order for a TransWarp 9" motor, and plan to use Lithium (thundersky or ??) batteries. I am looking at which would be best for my desire for strong power on the track.
The Zilla Z1K-lv, the Soliton, or the Netgain Warp-drive 1200 amp models are my choices, but could use some opinions from those who actually have them installed.
Thanks!

-Rick-
 
G
#2 ·
For racing I'd go with the Zilla Z2K. Go for the top of the line because it is known to live at the race track. It costs money but it is the best for racing. Soliton1 may be ok with a single motor and the Netgain may be good to. Neither the Soliton or Netgain have race proven information. The Zilla does.
 
#6 ·
Sounds like you are approaching this backwards, but maybe it only appears so because you didn't provide too much detail about the project goals. You already ordered the motor, does that mean you already have calculated torque and RPM and gearing numbers to make sure your car will accelerate as expected given your motor torque limits and gain max speed as expected given motor RPM limits and your differential's gear reduction since you are planning on direct drive?

I am not an expert or a racer, but direct drive with 9" motor doesn't seem like a logical choice to me, unless the car will be really super light.

Also, given that you calculated max power the motor can handle, have you decided on battery pack size, both voltage ( number of cells ) and amperage ( cell size ) ? How does your power requirement corellate to your range requirement? Since you want to race and street drive you probably need a balance of both power and range, which turns into a dilemma of the pack size. You need high C rates, especially with direct drive, so large prismatic cells are probably a poor choice, so you are looking at lots of small cells. This means $$$$. You'd be tempted to build smaller and lighter pack, but then you lose range.

As you see, lots of questions, decisions, compromises, etc.

I think the question of which controller to buy is probably the last one you need to be asking. It will become obvious once you figure out pack size and power levels ( volts and amps ) involved.

Hope this helps
 
#7 ·
Direct drive probably isn't the way to go-especially since you want to use this as a dual purpose vehicle.
What kind of top speed are you looking for in racing, and what kind of accelleration do you desire? Direct drive is not conducive for both speed and accelleration (usually one or the other)-sounds like a large AH battery pack will be required because of the current draw, which will not make your car lightweight as you say you are building.
I am not an autocrosser, but it seems like a transmission would be needed.
Mike
www.EV-propulsion.com
 
#8 ·
I am building it for lower speed torque in mind. There is no interior at all, no radio, no heater or A\C, etc. It should be VERY light when I get done.
I have a Geo Metro for my normal daily driving and an '87 Corvette to race with now, and this is a new project I am trying to build, so what I need to know is the advantages of one controller brand over the others.
Thanks-

Rick
 
#9 ·
Note: I am the guy developing the software for the Soliton 1 so I won't touch the controller question with a 10 foot pole since that has been known to be a mine field. Therefore you won't get any controller recommendation from me (even though gottdi's response amuses me :D) but just general tips what to think about.

I agree with Dimitri and EV-propulsion, you have to figure out what kind of performance you need before you decide what parts to get, having a controller that can handle kA doesn't make sense if your pack or motor can't handle the power. We know from experience that a WarP 9" can handle 100kW (1000 Amps and 100 Volt) for at least 10 seconds, but we also know that about that time it looks like a good idea to not stand too close to the motor and we've (well, ok, Tesseract has since I'm on the wrong continent) always made sure to run it at low current for some time to re-settle the brushes before next high power run. If you push the motor too hard or too long it might zorch which, btw, is a bad thing.

Also, those 100 kW have to come from somewhere and 100 kW out from the controller means 100 kW in which means that the pack has to handle that power as well. Since Lithium typically don't like discharges above 5C (there are exceptions like A123, but they come with a different price tag) it means that if you have a pack with 150 Volt nominal your battery current will be somewhere around 700-800 Amps (depending on sag and SoC). This translates to around 200 Ah, which, as EVpropulsion put it, "will not make your car lightweight". A higher pack voltage lowers the needed Ah, but it still won't make your car lightweight.

Another thing to consider is transmission. Loads of Amps means loads of torque. Excessive torque means that thing might break. We've tried that too. :D

So, do you need a drag racer or is a peppy commuter car enough?
 
#11 ·
Hi Qer, I really appreciate the input.
I had posted a while back with my desires for this project and nobody had much to say, but you are asking the questions I need to know:
I want the car to be quite powerful for each lap up to 5 minutes, without damaging any related parts (Batteries-motor-controller)
I would like performance specs similar to that of a Spec Miata, such as 0-60 under 5 seconds, top speed does not need to exceed 90 MPH, and on a daily drive should last at least 50 miles...
If you don't think the Warp 9 is the way to go, I would like to honestly like to know what kind of motor\controller package would be good.
Thanks again!

Rick
 
#14 ·
Ok, I'll bite, despite risking being flamed to crisps. :cool:

"0-60 under 5 seconds, top speed does not need to exceed 90 MPH" is not simple to achieve and you WILL be pushing things, probably even blowing things (batteries, motors, possibly even controllers) becasue that's what racing's about. To quote Plasmaboy: "...we blow things up, so you don't have to."

Anyway, the White Zombie does the 0-60 in 2.9 seconds and has a top speed at 1/4 mile of 114 mph. It achieves that with a Zilla 2kA and a siamese WarP but (and this is a big but) it can't keep it up! Drag racing is about seconds (with the possibility to cool things down between runs), you're talking minutes and pushing these kinds of kW for up to 5 minutes will be torture for the whole electric circuit.

So let's start from the beginning; batteries. As EVpropulsion already stated you want voltage, preferably north of 200 Volt, but you also want Ah because the maximum power you can drain by the pack is of course W=V*A and your maximum continuous Amps will be Ah*C. For currents that are getting awfully close to continuous I don't think you want to use more than 3C which means that 200 Ah will give you 600 Amps top and if you want more power you have to raise the Voltage. Your pack will be huge unless you go with A123, but then the price tag will be monstrous. You want to keep an eye on the pack temp too and might even have to cool it with fans because even though increased temperature has the advantage of reducing internal resistance and increasing it's efficiency it'll also kill it in the long run.

Then there's the next step, controller. I think you have two options, Zilla or Soliton (with a possible third alternative, Netgain). Zilla has a peak power of 1kA or 2kA but continuous Amps are "only" 300 versus "over 600". I dare say that since you're talking serious performance your choises are Zilla 2kA versus Soliton (I haven't seen any claims about Netgain so I really can't give you any hints about that one), the Zilla 2kA definitely wins on peak current but according to the specs it might eventually drop down to 600 Amps. For drag racing this is obviously not a problem but, again, seconds versus minutes. I can't really tell you which one's the better one for you because that depends on how long the Zilla will stay above 1kA, how much current you really need and for how long.

Now; motor. With those performance numbers I'm afraid you'll blow up the TransWarP. It will be too much Volt and too much current for too long. You probably want a siamese build since that cuts the power per motor in half which will drastically increase the chance that you make it to the end. You might also want to consider forced cooling too, ESPECIALLY if you go direct drive, since the motors won't get much air flow at all at low rpm's but you'll still force a LOT of current through the motor and thus generating insane amount of heat. If you want to go with the high voltage version or not I'm not competent to tell you, I'd say Major is the guy that can give you that answer. With a siamese the Zilla has an edge since it can do series/parallel shift. It's on the todo-list for the Soliton (and Netgain I think?) as well, but there's no ETA for when...

Finally, transmission. I think direct drive is a bad idea all considered, because you probably want to keep the RPM high to be as nice as possible to the motor(s) and that means you'll have to keep the gear box. Since you probably don't want to wait a second or two when changing gears you probably also want to keep the clutch. But now's the question, can your transmission handle the torque? Pushing 1kA through one motor will give you a torque in the 200 Ft/Lbs-range, using a siamese setup in serial mode will mean 400 and increasing it to 2kA in serial mode will be somewhere in the 800-range! When will the transmission (or it's mountings) snap?

One thing's for sure, you better have a big wallet. :D
 
#15 ·
There are so many things to address here I didn't even try quoting, because the quotes would dominate my whole post. I'll try to just address subject matters, instead of exact wording or posts.

Autocross
I am building an autocroser as well, and also plan to sprint down the drag strip. What kind of autocross are you running in that lasts 5 minutes! :eek: That seems like an awfully l-o-n-g time for an autocross race, and more like a short road course. The autocross races I watched at the local Goodguys car show here in Columbus were completed in less than 30 seconds by the fastest cars, and still under a minute by the slower ones.

The biggest point with this subject, in your case, is weight. Even a stripped down unibody car is going to be too heavy to effectively compete in an autocross race without a transmission - or - rear end gearing that is too steep to do anything more than city driving. Those gears may also come back to bite you in the autocross because it won't want to stretch out on the final straight. You will punish your motor and batteries running direct drive, because off the apex of every turn you're going to be asking them for max current to make up for not having enough gearing.

My project, by comparison, is being scratch-built and purposely designed to run direct drive. I am shooting for a final weight of 1200lbs with A123s. I am also using an 11-inch motor, which is capable of a ridiculous amount of torque for a 1200lb vehicle. The goal is that I won't be stressing the motor and batteries so much off the apex because it will actually have more torque than I can succesfully apply. The vehicle is also a dedicated race and show car, with no real-world expectations other than an occasional trip up the street for fun. That allows me to (hopefully) afford A123s. It looks like my pack will be around $15K, and under 500lbs.

I don't mean to go on about my project. I am trying to give you an idea of how the project was planned. Unless we are missing critical details, your plans seems to be a mix of components and ideas that will likely result in disappointment. You have a production street car that you plan to convert to an EV racer/driver, with a mild performance-oriented powertrain combination. It sounds like you will ultimately break a lot of parts, and eventually kill the motor and/or battery pack. Shoving enough current through to repeatedly accelerate the steel-bodied car will stress the batteries and motor, and the high torque loads delivered electric motor style (instantaneously - like a hit of nitrous oxide) will stress the driveshaft and rear end.

Transmission
As noted, running direct drive with a relatively heavy vehicle is probably asking too much from your motor and batteries - in an autocross race environment. If you were just drag racing you could manage it. The converted Powerglide (do a search here) might be a nice option if you don't want to shift, and want a more futuristic "feel". They can be built to withstand over 1200lb-ft of torque and live to tell about it. There are also a number of racing manuals that can handle high-torque racing applications. When I was considering using a transmission, one thing I found appealing is that you can use dog-engagement race transmissions that can be shifted without a clutch. Because an EV can simply select the appropriate gear from a standing start and accelerate without use of the clutch it opens the door for using these transmissions. Whatever route you plan to go, if you choose to use a transmission, be prepared to pay the piper. You need a really stout transmission race transmission because the street models aren't designed to handle the repeated shock of instantaneous torque hits. The phrase "nitrous-ready" is a good thing for an EV racer's parts.

Controller
I'm not pitching for anyone - yet - but have a couple favorites. I have been enamored with Zillas since I first learned about EV drag racing, and then along came a spider named Soliton. I like the Zilla's track record and relentless ability to slam as much current as your batteries can muster up on the motor. I like the Soliton's hi-tech build and ability to deliver whopping doses of current until someone screams "Uncle!" I am split between which one makes the most sense in an autocross race. Until there's a 2K Soliton, the Zilla will win likely continue to dominate at the drag strip, but autocross is a different animal. It's unproven whether one could even get 2K amps into the motor and on the ground, and you're definitely not going to use any substantial amount of current continuously. You're on and off the pedal, from apex to entry point. I watched some 500-700hp muscle cars (with road-race suspension underneath) go through the cones at the aforementioned Goodguys event. They struggled to successfully apply the ramp up of torque their ICE powertrains delivered - even with really wide, sticky, rear tires. The ones who got a little overzealous with that application ended up doing nice little 360s. One guy just enjoyed the moment, kept his foot in it for a couple turns, then emerged from a cloud of tire smoke. This would be even more challenging with an e-motor that's capable of full torque whenever you ask for it.

I look forward to that challenge but, as I pointed out, spent a lot of time designing for the intended mission.
 
#16 ·
Hi guys,
This is great input, I really need it.
Ok, so I agree that 5 minute runs are too long in AutoX, maybe 2 is more realistic. Also, I am looking at a 1500 pound car or lighter when done, which is why I opted or the 9" motor. I can move up to the 11" if needed, I thought about it many times...
As for the performance spec's, the Tesla can do a much quicker 0-60 time (3 seconds??) and is capable of 100 miles. As long as I keep the weight down, I think my spec's (0-60 in 5 seconds and 50 miles), is doable. It's a direct drive too.
A tranny, clutch, shifter, pedals, linkage, and related mounting hardware would add hundreds of pounds, and that alone should help me keep the need for enourmous torque down.
A stock 1979 RX7 weighs about 2400 pounds, minus 12a motor at 350 pounds, minus tranny and clutch and linkage (250 pounds), minus gas tank (40), exhaust system (60), radiator and lines (40), A\C unit and heater (70), entire interior (150), steel motor mounts (30), radio and speakers (20), stock lead\acid battery (50), etc. gets me down less than 1300. Then I can cut out lots of unnecessary heat shields, brackets, battery tray, lines and hoses, but I will also get aggressive about certain panels and brackets.
Given all that, I will then add in the new motor and controller and batteries. No idea how much it will weigh realistically, but I can get it weighed. I still think it will be less that 1500...
This is much lighter that Metros and Festivas using lead acid battreries and still doing 8 second 0-60's and up to 65 MPH for 70 miles using 400 amp controllers. I think 1200 amp controllers and lithium batteries should get me where I want. I could be wrong though...

Rick
 
#31 ·
I'm REALLY happy to find this thread.
I've been kicking around the idea of making a EV auto-xer for a while. (I already do some autocrossing with an ICE car).

I've got some comments / questions:

Have you ever autocrossed before? Admittedly the ones I do are on the small /short side, but they are 30seconds to a minute. Getting up to 2 minutes would be a heck of an autox course.

Removing tranny clutch and linkage is 250lbs? Really?
RX7's were always pretty light cars and without much torque. I'd think they'd have pretty lightweight components too. I'd have guessed closer to half of that 250lb figure. My confidence level on that isn't super high though.


This is much lighter that Metros and Festivas using lead acid battreries and still doing 8 second 0-60's and up to 65 MPH for 70 miles using 400 amp controllers.
Rick
Who is doing this? Don't get me wrong, I'm not doubting you. I'd just really like to see some data points on cars that aren't setup for achieving maxiumum range - which seems like 99% of the EV's out there.

If anyone knows of some other links that might be helpful to an EV autocrosser, please do post them.

Finally, Thanks to all the super knowledgable guys who are taking their time to educate the rest of us!

Scott
 
#17 ·
For performance either drag or autoX you will need the following:
(1) High power battery pack (with high C rating) e.g. A123, Kokam, Headway
(2) Dual motor or large single motor e.g. siamese 8/9, Warp11HV, or 13"
(3) High amperage controller e.g. Zilla, Soliton, Netgain
(4) Best donor you can find e.g. weight, handling.

RX7 is not a bad choice, good luck and report back your performance numbers!
 
#19 · (Edited)
Simple answer:

Because John Wayland's and Dennis Berube's dragsters have high voltage.

Complex answer:

Higher voltage allows for more amps to be drawn at higher rpms. example: 144V will allow 500A to be pulled up until 2000rpm and 288V will allow 500A to be pulled up till 4000rpm... if 500A to a motor is 150ftlbs, then which would you rather have?....

150ftlbs @ 2000rpm = 57hp
or...
150ftlbs @ 4000rpm = 114hp

So lets say you wanted to build a 320V pack that can pulse at 2000A peak

1500 Headway cells will cost about 26K$USD for 320V 150A (15C pulse)
13.33C = 2000A peak
It will also weigh 1013 lbs for the pack

320V*150AH = 48kwh
if your lightweight, aerodynamic car, got 250wh/mile then 48kwh = 192mile range (100% DoD)
 
#20 ·
Just an addition to Bowsers post:

Even if you "only" have a WarP 9" that will probably zorch if you get close to 200 Volt it still makes sense to have a higher pack voltage since this means sagging will have a lesser impact. Pulling hundreds of amps out of a pack will make the voltage drop pretty drastically and if you don't have a margin that means your top rpm will suffer.
 
#21 ·
Sounds like a great project. I plan to autocross my conversion, too, but it's much heavier than yours.

Don't forget about current multiplication. At low rpm, your controller will buck up the current. The motor current could be 3 times the battery current, for example. Your I^2R heating is going to be 9 times higher, plus with the lower rpm the motor's fan won't move as much cooling air.

Also, don't forget the torque curve falls off faster at high rpm for series DC than for AC.

I have autocrossed about 50 times. The top speeds vary hugely, from 1st gear courses (40 mph in my car) to 3rd gear courses (~80 mph). If you do a single gear ratio, you'll be heating your motor more on the slower courses than you would with a transmission, plus have less acceleration (unless you have a really strong pack, controller, and motor(s)). Remember, you don't compare directly to drag racers. They go for < 15 seconds, and the "course" is repeatable, and they spend very little time at low rpm.

There are various ways to attack the problem:

  • AC -- it's a bit more efficient and has a broader torque curve
  • Light weight
  • Keep the tranny to optimize for the speeds
  • Extra cooling
  • Twin DC motors or a single big motor
 
#22 ·
Based on suggestions here, I've decided to go with the NetGain controller for one reason: I can start with 144 or 156 volts to run the Warp9" now, but if it looks like I need to move into the Warp-11" HV, the controller allows me to add high voltage in later.
This way I can go ahead and buy the HD plumbing kit too and should not have to replace the controller whether or not I go with different batteries or motors.
I also plan on being dramatic when it comes to shedding weight off of the car...
More to follow-

Rick
 
#25 ·
http://www.evsource.com/tls_warp9.php

1000A = 237 ftlbs of torque

Thing is, with 160V, whats the maximum rpm you can pull 1000A?

By the looks of this comparable 168V Kostov 9" graph...

http://kostov-motors.com/files/productattachments/817455860674b455566486badd21c31d_9-168V.pdf

The bold data is data that came from the graph and the underlined is data that was assumed in accordance to the trend... Looks here like 1000A will only be available until 900rpm..

Amps RPM
250
5000
300 4750
400
4000
500
3500
650 3000
720
2475
820 1950
920
1425
1020
900
 
#26 ·
http://www.evsource.com/tls_warp9.php

1000A = 237 ftlbs of torque

The bold data is data that came from the graph and the underlined is data that was assumed in accordance to the trend... Looks here like 1000A will only be available until 900rpm..
This is a really good point. Torque (which is in relation to current) will fall off as the RPMs increase. But because speed is increasing, horsepower can still increase.

Series wound motors (and possibly other types of motors, but I'm limiting the discussion to series wound) will draw whatever current is necessary to produce a certain speed (which is a function of the specific motor) for a given voltage. That is, apply 12V to the motor, and it will "want" to spin at a certain RPM. With no load on the motor, it will draw very little current to do that. As you increase the load though, it will still want to spin at the same RPM, but will require more current to do that.

When you get into racing, it gets more complicated than this. For one thing, your battery pack is sagging under the load (assuming lead-acid - other chemistries might exhibit this more or less), so the maximum available voltage is diminishing.

The attached data file is from a test run with the WarP-Drive. The pack is 240V, the controller is set up for 1200A, and the clutch slips with too much power applied. It's has an ImPulse 9 motor. You see that as the data starts out, motor amps are decreasing, motor voltage is increasing (and consequently motor RPM - sorry, this graph doesn't have RPMs), but motor power is increasing. You see some weird stuff after the shift to the next gear takes place, because the throttle had to be feathered to keep the clutch from slipping! :)
 

Attachments

#28 · (Edited)
Headway pack:
320V
150AH
48kwh
2250 max pulse amps
100% Range @ 250wh/mile = 192 miles
Weight: 1013lbs.
Cost: ~25.5K$

Thundersky pack:
320V
200AH
64kwh
2000 max pulse amps
100% Range @ 250wh/mile = 256 miles
Weight: 1320lbs.
Cost: ~22K$

Thundersky is cheaper, with nearly the same peak amps, and 60 more miles of range, but 300 more lbs...
 
#32 ·
Hi Scott, OK, a rough estimate for weight, but that's everything related to the tranny system. (Tranny, bellhousing, arm, pressure plate, disk, T\O bearing, flywheel, master\slave cylinders, lines, shifter, pedals, brackets, crossmember, etc) Plus I never have to worry about clutch problems, :) and in autocrossing, the huge time advantage of not having to shift would be quite an asset.
In the past, I have won regional events using a WRX and have since gotten into road-course racing at a local paved track with my Corvette.

As for batteries, the type of racing I am looking to would be on and off over and over and rarely all the way to the floor for very long. On a typical auto-x track there is rarely but one long straightaway for less than an eighth of a mile.
Since I am running 156 volts, I could get away with half the range, weight and cost of the 320 volt packs... I just don't know what to expect from the different styles. So, the Headway's release more amperage faster than Thundersky's? What about A123's?

Thanks again everyone!

Rick
 
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