# Dual motor / Dual controller advice



## mikejh (Nov 20, 2008)

Hi guys,

I am hoping some experts here can give me their thoughts on the correct way to wire up a dual motor setup.

I am still in the dreaming/planning stages and have not bought anything yet.

My thoughts are to go with a single double splined Transwarp 11 initially and then upgrade by adding a second Warp 11 down the track.

The plan is to have a reasonably quick EV that I can drag race occasionally.

Trasmission plans were either a gear vendors OD and low ratio diff, or Powerglide and higher ratio diff.
Can't decide between nice compact trans with no pump etc, electric shift and bolt straight on (GV) or Powerglide incorporating mech reverse and park features.

Anyway, my questions to the knowledgeable...

I was told by one ev parts vendor that dual motors are usually wired in parallel and I should use two controllers (one per motor).
I didn't quite get whether they were saying to parallel the controllers (which I don't think is a good idea) or run each one to its own motor isolated. 

This goes against my thinking of running a single controller (say a Soliton 1), a high pack voltage (say 300v) and wiring both motors in series with each other, meaning each motor "sees" 150v and current is equal in both at 1000A.

I thought most high performance EVs are wired this way (motors in series)?

Can anyone see the logic in running two soliton 1's running a motor each, and two low voltage (say 150v) packs as against a single Soliton 1 at high voltage?
Apart from cooling requirements.

My thoughts are that if the Soliton 1 is good for 350V and 1000A then you would be better of using this high voltage capability. Being an IGBT controller the Vce sat is reasonably fixed and a smaller percentage of the total system voltage when running at 300v compared to 150v so controller losses are lower. 
Of course they may not be rated to 1000A at 300V, I haven't researched them that thoroughly yet, but this is more a hypothetical logical question.
And further (I can here it now), controller losses are the least of my worries if I am going to race it, I know.

Another vendor said... Gee 11 inch motor, you're going to need a lot of controller for that.

Is there any reason why I would need more controller for an 11" motor versus a 9" motor?

I figure even a 500A controller would give similar performance on either motor with the 11" motor producing more torque at the same amps due to armature diameter?

Thanks.

Mike


----------



## Yabert (Feb 7, 2010)

Hi Mike
1- you seem to be well informed.
2- you seem have been misinformed by some vendors.

A Soliton 1 will control very well two 11 inches motors in series and mechanically connected together.
The only thing I know about the Soliton 1 (should be confirmed by Tesseract) is than when battery voltage is over 310v, the motor Amps can only be 900A.
I've never understand what will happen after the battery sag from 310v to 309v.... 900A to 1000A instantly???


----------



## mikejh (Nov 20, 2008)

Thanks Yabert,

Good to know I'm on the right track.

I am sure the step from 900 to 1000A would be ramped nicely.

It would be good if using two controllers gave you the power of two, but in the case described to me, you would still only have 1000A per motor which you would get with a single controller, series wiring and a higher pack voltage.

I guess the other thing to consider is if I wanted to run more than 150v per motor as you are then getting outside the voltage range of a single controller.

Now if only I could afford a Shiva... 

Mike


----------



## Tesseract (Sep 27, 2008)

Yabert said:


> ...I've never understand what will happen after the battery sag from 310v to 309v.... 900A to 1000A instantly???


There's hysteresis in the high pack voltage motor amperage limit function. I don't recall the exact value, but it is either 5 or 10V.* That said, when pack voltage declines below the lower hysteresis limit then motor current will increase back to 1000A at the slew rate set in the web interface (assuming, of course, that full throttle is still applied and that duty cycle is well below 100% [because back EMF is proportional to RPM and flux {ie - current}]).

NB - we (Evnetics, that is) are in the process of selling the Soliton IP and have a few genuinely interested parties. One of them will continue to support DIY sales; the others are OEM customers that have a compelling business interest in maintaining the supply of the controller for their use but whom otherwise probably won't want to mess with DIYers. 


* - I only designed the hardware and this function was added several years ago - probably an old post of mine discusses this.


----------



## mikejh (Nov 20, 2008)

Oh man...

Does that mean there is the potential that Soliton controllers may not be available anymore?

Before I even get started?

I had only just decided to forget about designing my own and just buy one!

Mike


----------



## Tesseract (Sep 27, 2008)

mikejh said:


> ...
> Does that mean there is the potential that Soliton controllers may not be available anymore?...


It is possible that the Soliton won't be available to DIYers anymore, yes, but that does not seem to be the most likely outcome at this point (mainly because the DIY EV vendors want all the IP for all the models, while the OEM clients only want the IP for one model or another). 

I should note that I haven't been involved in the negotiation process (just like I am not involved in the day-to-day operations) so can't really say more about it at this point. I am, however, not terribly pleased with the pace of negotiations and might be barging in on them next week if I don't see some progress on Monday.


----------



## mikejh (Nov 20, 2008)

Thanks Tesseract,

Good luck with it and I hope it goes the way that the DIY EV community would be happy with.

These are the best controllers I have seen in a long time and I would hate to see them disappear.

I don't have an EV yet but I have been researching them since the 400a Curtis was as good as it got. 

Mike


----------



## dougingraham (Jul 26, 2011)

mikejh said:


> Is there any reason why I would need more controller for an 11" motor versus a 9" motor?


One motor and one controller can do 170 motor volts and 1000 amps assuming enough battery to not sag below 170 volts. This is 170 kw or 228 HP peak. If you double this you get 340kw or 456 HP. A single Soliton 1 driving two motors with the motors wired in series will give at most 300kw or 402 hp assuming the batteries are good enough. If you wire the motors in parallel with a single Soliton 1 each motor sees only 500 amps and 170 volts so you would be limited to 170kw or 228 HP. The difference in this last case is you would only need a battery that doesn't sag below 170 volts instead of the series battery requirement of not sagging below 300 volts.

It all depends on what you want to do with the car. For street use as a daily driver a single controller and motor are probably more than plenty. If you want to do street racing then you might want more. If you want to go to the drag strip then you have a completely different situation.




mikejh said:


> I figure even a 500A controller would give similar performance on either motor with the 11" motor producing more torque at the same amps due to armature diameter?


500A will give you less than half the torque of 1000A on these motors. A single motor at 1000 is better than two at 500.

Probably a better single motor Soliton 1 config would be with a Warp 11 HV motor run at 288 volts and 1000 amps. The torque is a less than a Warp 11 but more than a Warp 9. You get a wider torque band and with correct gearing you would see a peak of 288 kw or 386 HP. Put in a 340 volt peak pack and go have a good time.


----------



## mikejh (Nov 20, 2008)

Thanks Doug,

Yes that is basically what I was asking and why I couldn't see the logic in connecting motors in parallel. You are basically wasting half the watt capability of the Soliton.

I see your point about 1 Soliton with two series motors only giving 300Kw and this is due to exceeding the max voltage limit of the Soliton and only being able to send 150V to each motor.
Would be nice if it could just stretch to 340V... The IGBT's are probably 600V. Who needs a 2:1 safety factor. 

My question about the controller for an 11" versus a 9" was just to check I wasn't totally wrong in my thinking.
As far as I can tell, you don't need a bigger controller to run an 11" motor.
500 or 1000 amps through an 11" motor would be the same as a 9" motor except for the slightly higher torque in the 11".
You can't break a small controller by putting a big motor on it providing the current limiting is working properly. A 500A controller should just come up to 500A and hold there even if you're driving a 3 ton truck with it. Slow yes, but shouldn't break if the cooling is sufficient. (And obviously will de-rate with temperature as no controller that I know of can do their "claimed" current continuously except for the Solitons).

I am not sure I get the point of the 11HV.
I understand that you can run a higher voltage and therefore get more RPM out of it before BEMF kills it, but it has the same diameter armature of the 9" motor so you have lost the advantage of the 11" diameter (longer torque arm).
Maybe in practice that broader torque band translates to more overall performance. I would have to experience it to be convinced. 

Did I read somewhere that Netgain was not going to keep making the 11HV?

I have been fascinated with the EV drag racing scene for many years and would like to have the option to try that. Hence the 11" Transwarp now and then add a second motor later when money permits.

Thanks,

Mike


----------



## dougingraham (Jul 26, 2011)

mikejh said:


> Would be nice if it could just stretch to 340V... The IGBT's are probably 600V. Who needs a 2:1 safety factor.


It does go to 340 but derates to limit to 300kw. However when you drive from batteries you will get sag. No way around it. Sag from 340 volts to 300 is only 12 percent so it takes really good batteries to only sag that much. The IGBT's are probably 450V.



mikejh said:


> I am not sure I get the point of the 11HV.
> I understand that you can run a higher voltage and therefore get more RPM out of it before BEMF kills it, but it has the same diameter armature of the 9" motor so you have lost the advantage of the 11" diameter (longer torque arm).
> Maybe in practice that broader torque band translates to more overall performance. I would have to experience it to be convinced.
> 
> Did I read somewhere that Netgain was not going to keep making the 11HV?


Warp 11HV is between the 9 and the 11 as far as torque goes. If you get the gearing right the peak power of the 11HV is going to be close to twice that of the WarP 11. The WarP 9 and WarP 11 peak power output is essentially the same. This is why drag racers use the lighter motor. You can run the 11 at a higher continuous power level. But this doesn't matter in a street car or on the drag strip. You never run at those power levels for more than short periods or you will find yourself in felony speed ranges. Because of that you are just hauling around extra weight. The only time to use the 11 would be where you need the torque and can't change the gearing. But the 11 has a lower rpm limit which you need to keep in mind.

I don't see anything indicating that they are discontinuing it.



mikejh said:


> I have been fascinated with the EV drag racing scene for many years and would like to have the option to try that. Hence the 11" Transwarp now and then add a second motor later when money permits.


I have a WarP9 in my car right now. Even with only 52 cells that sag badly the car is overpowered. I have been backing down the motor current to find the point where I don't like it. I am still happy at 800 amps. Going to try 700 amps tomorrow. If I were going to do it all over again today I would use close to the same weight in batteries but (52 100AH cells at 7.5 lbs each = 390 lbs) but go to a higher voltage (94 60 AH cells at 4.45 lbs = 418 lbs). Currently I see a limit of about 120kw because of the battery sag. Going to the higher voltage would eliminate all the sag and let me run up to 170 volts and 1000 motor amps. A small upgrade would be to replace the Warp 9 to the 11 HV because you get more torque. But with my 60AH cells I can only pull 600 amps from the batteries. 600*288 = 173kw. So input power is about the same but the torque is higher over a large portion of the rpm band. To take advantage of the 11HV I would need batteries that can do 1000 amps. For your situation I would consider instead the Transwarp 9 and add a second Warp 9 later instead. If you need more torque change the rear end ratio to a higher numerical ratio.

Another option is to use a Zilla HV 2k. You can get more torque from a Warp 9 at 2000 amps than you do with a WarP 11 at 1000 amps.


----------



## mikejh (Nov 20, 2008)

Hi Doug,

Thanks for the explanation of the 11" vs 9" motors. It does make a bit more sense now. I must say it's not easy interpreting the motor performance curves when the current axes are different. The two 11" graphs are ok because they both see 500A but the 9" transwarp graph tops out at about 350A.
Although I just looked again and found the warp 9 graph goes to 500A.
So it looks like the 9" is 100ft/lbs the 11" is 160ft/lbs and the 11HV is 140ft/lbs, does that sound right?

I probably should have mentioned in the original post that the donor car initially is an 87 Fairmont (Australian) which is 3200Lbs as an ICE. Bad choice I know, but its sitting here with no engine or gearbox and will make a good development platform for now. I can always pull the running gear and put it in a smaller car sometime.

I guess I am comparing to cars like the Black Pearl 944 and the new Black Zombie Mustang both running Transwarp and Warp 11's .

As you have correctly stated though, none of it matters if you don't have a good battery pack to supply the current.
I was thinking the CALB 180's as I can't see me affording an A123 type pack, but they should be ok for 1800A for short runs. But heavy....

I noticed that the Black Pearl is running a 396v pack and 2 Z2K EHV controllers.
Would they be over volting the motors or running 198 to each?
If they are running 2 controllers they must be running each motor at full pack voltage minus sag? Unless the pack is split, but then you wouldn't need the EHV's?

The other reason I like the idea of the Transwarp 11 and Warp 11 is the method of mechanically coupling them. You can use a splined coupler between them and George said the 1.375" shafts are good for 2200ft/lbs shear strength.
I hate the idea of using keyed couplers (due to their potential to come loose and wreck the shaft) and I am not sure you can get the warp 9 or 11hv in double splined shafts.

Mike


----------



## dougingraham (Jul 26, 2011)

mikejh said:


> So it looks like the 9" is 100ft/lbs the 11" is 160ft/lbs and the 11HV is 140ft/lbs, does that sound right?


Those numbers seem reasonable. The only hard number I have is 266 ft-lb at the wheels on a WarP9 at 1000 amps as measured at the dyno at EVCCon last summer.



mikejh said:


> I guess I am comparing to cars like the Black Pearl 944 and the new Black Zombie Mustang both running Transwarp and Warp 11's .


There are lots of ways to skin the cat. Twin Warp 11 motors have a lot of torque. Using your example above of 100 ft-lb for WarP9 and 160 ft-lb for Warp 11 you get the same effect changing the rear end ratio from 3.5:1 to 5.6:1 for the WarP9. Of course this means that 5000 rpm on the WarP 9 is the same as 3125 on the WarP 11. You need to keep this in mind when figuring top speed. I have been over 90 mph before I came to my senses and slowed down. It seemed like it was more than willing to exceed 100 mph. And for my car this is great plenty. It might not be for what you want to do.



mikejh said:


> I was thinking the CALB 180's as I can't see me affording an A123 type pack, but they should be ok for 1800A for short runs. But heavy....


What you might want to do is put in enough pack for one motor and then when you decide to add the second motor double the pack. This assumes the single pack would give you enough range. This would also keep the weight down and save you a bunch of money up front.



mikejh said:


> I noticed that the Black Pearl is running a 396v pack and 2 Z2K EHV controllers.
> Would they be over volting the motors or running 198 to each?
> If they are running 2 controllers they must be running each motor at full pack voltage minus sag? Unless the pack is split, but then you wouldn't need the EHV's?


They need the EHV because they are running the high pack voltage. They are trading voltage at the pack for amps at the motor. You set the motor voltage and current limit in the controller to whatever you are comfortable with. I would guess they set the motor amps to 2000 and the motor volts to maybe as much as 190. They need two so they can do 2000 amps on each motor. Say 170 motor volts and 340 battery volts the batteries will see 1/2 the motor current. John Metric has upgraded brush holders in his WarP 9's and I believe he has run them at 210 motor volts at 2000 amps each. Input power is 840kw (1126 hp). For a street car this would most likely be considered excessive. Maybe 70% of that makes it to the ground.

You look like you are facing the same problem I did when I was planning my project. I didn't want a dud. I wanted it to be fun to drive. So whenever there was a choice and I thought something would be good enough I would tend to upsize it. The motor was the one thing I had decided on and didn't upsize. And I don't need more motor. It is way overpowered for a street car. I have it backed down to 700 amps and it is still fine for use as a daily driver. This is probably about 60% of the full 1000 amp torque. I think I might actually want to start using first gear when I get it turned down to 500 amps. (100ft-lb is about the same as the wankel motor originally in the car.)

So without going to a second motor (and I don't know where I would fit one in this car) I have plenty of upgrade options. Switch to Zilla 2k controller for the extra torque. Go to a WarP 11 HV for the extra torque and power. But before any of that I would want to upgrade my batteries because they are my current limiting factor. And it was what I overlooked when I was originally planning. I needed the higher voltage pack to get rid of the sag.

I think you will find the single motor is more than you need to blow off most anything normal at stop lights.


----------



## mikejh (Nov 20, 2008)

> There are lots of ways to skin the cat. Twin Warp 11 motors have a lot of torque. Using your example above of 100 ft-lb for WarP9 and 160 ft-lb for Warp 11 you get the same effect changing the rear end ratio from 3.5:1 to 5.6:1 for the WarP9. Of course this means that 5000 rpm on the WarP 9 is the same as 3125 on the WarP 11.


True, but I guess with drag racing I would reach peak RPM at about 1/2 track with 5.6 gears. I think the 11's have so much torque that you can afford to go higher in gearing. Trouble is, the quicker you get off the line the sooner you run out of RPM and you don't want this to be before you reach the end.
The Black Pearl runs a 2.75 rear _with_ a Gear Vendors overdrive. Now that needs torque... 



> They need the EHV because they are running the high pack voltage. They are trading voltage at the pack for amps at the motor. You set the motor voltage and current limit in the controller to whatever you are comfortable with. I would guess they set the motor amps to 2000 and the motor volts to maybe as much as 190. They need two so they can do 2000 amps on each motor. Say 170 motor volts and 340 battery volts the batteries will see 1/2 the motor current.


Ah, I get it now. I should have known that. 
I forgot that the top end controllers let you set the motor volts.
This effectively means though that the controller will only get to 50% duty cycle on the PWM in order to limit voltage to half pack voltage.
Thats also why the batteries only see half motor current.

I have always worked around running a pack at the same voltage as what you want at the motor, but then the pack has to be capable of full motor amps.
Thanks for pointing that out.



> You look like you are facing the same problem I did when I was planning my project. I didn't want a dud. I wanted it to be fun to drive. So whenever there was a choice and I thought something would be good enough I would tend to upsize it.


Yep, you're a mind reader. 
I like the idea of a stupidly powerful EV.
I am used to a 500HP supercharged 4L Falcon. I still want fast, just over the petrol engine thing (straight propane actually). And having raced that a few times with a decent 11.0 I would like to be able to match it with an EV. 
In fact I'd be happy with 12.0 from an EV. I think 11 is a bit much to ask without a $30k battery pack.


----------



## Yabert (Feb 7, 2010)

mikejh said:


> ... I think 11 is a bit much to ask without a $30k battery pack.


Maybe take a look here: http://www.diyelectriccar.com/forums/showthread.php/power-capability-chevy-volt-battery-109698.html

For 4-5K$ you can buy 2 used chevy Volt batteries and probably obtain over 500 Kw briefly.
A 700 lbs battery pack will slow you down a bit, but be super fast instead of ultra fast, I think you could have fun!


----------



## mikejh (Nov 20, 2008)

Hi Yabert,

Thanks for that.
I read your thread and it was very interesting.

Unfortunately for me in Australia, Holden has only sold 250 of the Volt since they were launched so there may not be many in the wrecking yards.

Even more disappointing was that I just read they are not going to bring in the second generation of Chevy Volt. Apparently General Motors have decided not to continue the right hand drive program for the Volt. Probably too costly for the sales that they are getting. 

I think the reason for the slow uptake is the price at $60K AUD.
Most people can't justify that when you can buy similar sized cars for $20K.

Mike


----------



## jubjub (Jun 10, 2015)

Yabert said:


> Hi Mike
> 1- you seem to be well informed.
> 2- you seem have been misinformed by some vendors.
> 
> ...


Ok so after researching the Solition 1 controller on this site and in the Solition 1's manual (v1.4) I understand that the controller can run two motors in series and not in parallel. In your post you said that the soliton 1 controller can run two motors in series and mechanically connected to each other. Why is that they must be mechanically connected to each other? Is it because of the potential torque load difference to the motors?

By the way id like to run two electric motors in series in an awd hybrid track vehicle designed from the ground up to accommodate this system. I envision a system with a hyabusa motor(with its transmission) and a warp 7 mounted at and driving the rear through a torsen as well as another warp 7 mounted at and driving the front. Motors in series of course and connected to their respective axles at the same fixed gear ratio. I realize it's an extreme setup but my inspiration is the Ultima gtr, a 2000lb 640 hp car that is 2wd and thus highly temperamental. Im after the same performance but with more controllability.


----------



## Tesseract (Sep 27, 2008)

jubjub said:


> Ok so after researching the Solition 1 controller on this site and in the Solition 1's manual (v1.4) I understand that the controller can run two motors in series and not in parallel. In your post you said that the soliton 1 controller can run two motors in series and mechanically connected to each other. Why is that they must be mechanically connected to each other? Is it because of the potential torque load difference to the motors?....


The manual doesn't say anything about dual motors; you sure you got it from there and not from reading old posts on here? More specifically, I've answered this question numerous times in the past. For example: one of my old posts.

And this one.

And one by Jozzer who points out it is possible to parallel PMDC motors, but the process is not very practical.

And another one.


etc.


----------



## jubjub (Jun 10, 2015)

Tesseract said:


> The manual doesn't say anything about dual motors; you sure you got it from there and not from reading old posts on here? More specifically, I've answered this question numerous times in the past. For example: one of my old posts.
> 
> And this one.
> 
> ...


Ok thank you. I saw discussion of dual motors here and regarding the manual what i mean is that there is clearly enough power to power two motors. Ill look at the links in your response right now to find the answer and thank you.


----------



## jubjub (Jun 10, 2015)

I have another question about dual motor setups for those who are knowledgeable. Specifically I'd like to know is if it is possible to have an ac motor and a dc motor, each with their own appropriate controller, mechanically coupled to each other so that they can run the same axle.

The motors I have in mind are the Curtis AC-76 which comes with its own controller, and the Warp 11 dc motor which i would pair with a zilla 2k.
http://www.evwest.com/catalog/produ...ucts_id=176&osCsid=0505r12ugc82isl7manag9u1k7



My instinct tells me that pairing motors in this way would not be a good thing to do, but when i think about further it i wonder if it will be ok since the motor that is putting out the the greater horsepower or torque at a given rpm is the motor that will be dominant. In cars like the mclaren p1, the porsche 918, and koeniggsegg regera for example, the ICE and the electric motors turn together on the same crank and thus always spin at the same rpm. But then again, Internal Combustion Engines behave completely differently than electric motors so that may be the reason why pairing them in this way is possible.

The reason I want to mix motors by the way is because I want the regen that AC motors offer and the torque and high power that the warp dc motors (which cant do regen) offer. I am designing the vehicle this electric drivetrain would go in from the ground up with a friend. Its meant to be a track focused car. He wants to put both motors at the rear so they can both run through a powerglide transmission. I on the other hand want to have the ac motor in the front and the dc motor + powerglide at the rear because of weight transfer factors in deceleration and acceleration respectively and because i don't want to couple these two completely different motors to each other.

What do you recommend and why?


----------



## jwiger (Oct 18, 2014)

jubjub said:


> I have another question about dual motor setups for those who are knowledgeable. Specifically I'd like to know is if it is possible to have an ac motor and a dc motor, each with their own appropriate controller, mechanically coupled to each other so that they can run the same axle.
> 
> ...
> 
> What do you recommend and why?


I have been wondering the same thing: http://www.diyelectriccar.com/forums/showthread.php?t=142674

I understand your thought process with the AC fwd and the DC rwd. 

For my Mustang the motors would be coupled together in line. I suppose the money I would spend on the AC motor could go to more batteries, and give more range. However my car will be a street/strip car. It's pretty obvious that AC is ruling the street and DC still rules the strip. For a performance oriented car, having the most average torque across your RPM range will yield the best acceleration. 

I see proper throttle management of each motor as the largest challenge. the DC motor can make more Ft/lbs per amp, so when max torque is desired you want to divert as much of the battery pack as possible to the DC side, yet you want enough going to the AC side to that it isn't contributing resistance to movement. For cruising you would want a happy medium. AC motors build less heat while cruising, but DC motors need some voltage going to them anytime they are spinning to preserve the commutator (do not dry spin the motor for long periods e.g. towing in gear). Low load situations shift the focus in another direction, you want the DC motor to be producing zero torque any time the AC motor is in regen. 

Typically the PWM of a DC controller will increase amps to the motor fairly proportionately to an increase in traction pack voltage. If the AC system is in regen it will cause a rise in pack voltage. If there was DC motor is running any current when the regen kicks in you have a loop which is no good, the motors would fight each other a bit. 

I haven't thought of everything, but I'm stubborn and won't yield to most of the guys saying don't do it. I see a small window of advantage. It's just a lot of details to work out.


----------



## dcb (Dec 5, 2009)

it is in theory, and perhaps limited production, possible to get regen out of a series wound motor:

http://www.diyelectriccar.com/forum...l-and-regeneration-series-wound-dc-75751.html

with as many solid state switches as there are in a 3 phase controller, it isn't hard to imagine building one being "simpler" than 2 different motors and motor types. You might need to figure out how to turn them and the motor wiring into a boost converter and sort out excitation. 

You might want to look into sepex (shunt wound with separate field control), might be possible to rewind a series to sepex for that matter. With sepex you can control the ratio of rotor current to field current, and tune for power or efficiency and be able to achieve regen as well. More complicated than plain series or shunt, but perhaps not as complicated as 3 phase, and probably lots of maths and experimenting required if you don't get a motor/controller as a package.

http://curtisinstruments.com/?fuseaction=faq.listall

admittedly I don't see many large format sepex, but I don't see any dragsters with regen and both an AC and DC motor and controllers either


----------



## dougingraham (Jul 26, 2011)

jubjub said:


> What do you recommend and why?


Instead of mixing motor types just put in a large enough AC system that will do the whole job.

Or just put in a big enough DC system to get the job done. In a performance arrangement you are not overly concerned with efficiency so the lack of regen is not going to be missed.

The big problem with mixing types is going to be getting the control system right so the correct amount of power comes out of each system.

And it would be fine to run most of the time on just one of them and turning the other on only when you have the first maxed out. The losses due to friction are negligible so you don't have to apply anything when it is turned off. Just let the other motor spin it.

Best wishes!


----------



## jwiger (Oct 18, 2014)

dougingraham said:


> ...The losses due to friction are negligible so you don't have to apply anything when it is turned off. Just let the other motor spin it...


I would be more concerned with accelerating the mass of the other motor, more than the friction. 

For cost is no object builders, going with a big AC system would be the obvious choice. But since EV hot-rodders (myself at least) want to get regen for engine braking into a corner, and the most torque possible to get to the next corner as quickly as possible.


----------



## aeroscott (Jan 5, 2008)

I was thinking about the duty cycle of the dc motor.


----------



## dcb (Dec 5, 2009)

I "suppose" if you had an ac system you could do most of your driving around on, say driving the front wheels (good for regen), and had a dc motor attached to the rear wheels, you might be able to save a couple bucks for the desired performance, but it will still be a fraction of the battery costs and be kinda convoluted. finding a suitable pair of motors for a given pack voltage is a challenge, and the commutator likes a certain amount of current while it is turning (creates a film).

http://www.helwigcarbon.com/assets/files/pdf/English/comm condition guide broch ta4 hi res web.pdf


----------



## jwiger (Oct 18, 2014)

aeroscott said:


> I was thinking about the duty cycle of the dc motor.


Really depends on the cooling method. The one thing that will kill a motor dead is too much heat. John Metric regularly makes four digit hp numbers while dragracing, but that is down to less than 9 seconds of hard use (correct me if I'm wrong, John)

Michael Bream climbed Pikes Peak with tandem Warp 11s using good fan assisted air cooling. 

The Warp series has a good construction and a decent amount of thermal mass, but sustained (minutes) of higher power ratings will build heat that could cause problems if you don't take steps to mitigate it.


----------

