# K9 220V Performance Estimates



## Erobison (Sep 14, 2012)

I'm considering using the K9 220v in my conversion of a 91-95 model Toyota MR2 and was wondering if my performance estimates on the motor look reasonable? I'm looking at using a Soliton 1 for motor control and the battery pack should be able to supply the motor with it's max voltage of 220V, and peak current of 1000A.

Based on 220V, and 1000A (220ekW), I'm estimating a peak power of ~157 bhp, which works out to around 52% efficiency. I'm calculating that number based on a torque estimate of 278 ft-lbf at ~2975 rpm; after that I think the induced voltage will cause current to start to fall off. 

Do those numbers seem about right? Is such a low efficiency to be expected? I'm not so certain about when the current will start to decrease as this isn't indicated on the motor characteristic curves.

I greatly appreciate everyone's help.


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## major (Apr 4, 2008)

Erobison said:


> I'm considering using the K9 220v in my conversion of a 91-95 model Toyota MR2 and was wondering if my performance estimates on the motor look reasonable? I'm looking at using a Soliton 1 for motor control and the battery pack should be able to supply the motor with it's max voltage of 220V, and peak current of 1000A.
> 
> Based on 220V, and 1000A (220ekW)*, I'm estimating a peak power of ~157 bhp, which works out to around 52% efficiency. I'm calculating that number based on a torque estimate of 278 ft-lbf at ~2975 rpm; after that I think the induced voltage will cause current to start to fall off.





> Do those numbers seem about right?


Nope, 52% sounds way too low.



> Is such a low efficiency to be expected?


Nope.



> I'm not so certain about when the current will start to decrease as this isn't indicated on the motor characteristic curves.


 
Yep, motor curves are seldom drawn out to 1000A. You could post the curve you use or link to it  Often you can extrapolate the current and RPM traces for estimations at higher loads.

edit * You need to use the actual voltage (including sag) when calculating efficiency, not the nominal (220kW).


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## tylerwatts (Feb 9, 2012)

WARNING! WARNING!

Kostovs do not like high amps for any extended period, even with clever cooling! I wouldn't take the K9 to such high amps! Why so high? MR2 is light and would not need all that power/torque! Look at the stock ICE, the car is a little rocket with those wee motors!

I'd consider the Soliton Jr, with higher voltage (would let you stay in a lower gear for cruise speed and get some mechanical advantage!) as the motor is happier with more voltage over more current. I'd say 600A for short periods (30s) with good cooling management and thermal cut-back on the controller (Solitons are brillinat controllers and won't even let you know they've started this!) and you should be safe, with plenty HP and still better than ICE torque (all from 0rpm and across wide rpm range!).

PS, opinion only, taken from many posts from members using these motors. Anyone wishing to disagree or post Dyno data to disprove me point of view is welcome, just don't want a melted Kostov after the first full power run! Also, that much torque with too much ramp up in a lowe rgear and your MR2 transmission will pop its guts quicker than you hear the tyres spin! Beware!


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## skooler (Mar 26, 2011)

I agree with Erobison,

if you want to use the K9, use a Jr (600Amps is still a lot)

If you want to use 1000amps then get an 11" motor.


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## Erobison (Sep 14, 2012)

Tyler:

With batteries and everything I'm estimating the car weight to be ~2800-2900 lbm and I'm after 0-60 mph in ~6 sec. That's about what the stock MR2 turbo could do with it's 2.0L turbo motor. And I don't know if I'd call it a wee motor; it was small in displacement but it made 200 bhp/200 ft-lbf of TQ which ain't too shabby in my book.

Also right now I'm not as concerned with exactly what equipment I'll be using as I am concerned with how accurate my estimates are of said equipment. Once I feel like my performance estimates are in the ball park then I can work out what I need to hit my performance goals.

Major:

The curves I'm using for the K9 220 are at the following location:

http://kostov-motors.com/files/productattachments/6ff70418861d3230f01fc0340802fb1f_S220E01.pdf

I'm really having a hard time verifying my TQ estimates, and when the current starts to fall off. I'm currently using the generally accepted method of voltage being proportional to RPM, i.e. if voltage is doubled the same current can be achieved at double the RPM.


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## Old.DSMer (May 18, 2012)

Hello Erobinson! Your build goals and performance estimates sound similar to mine (1995 Eagle Talon AWD). You might find this post an interesting read.

In the end, I've decided on a K11-220V with Soliton-1. Its capable of more than my initial battery pack will deliver, but allows for future expansion.

For what its worth, I'm not a fan of continuous over-voltage or over-current conditions on a motor. The manufacturers end their charts where they do for a reason. Like tylerwatts said, continuously pumping 1000A into a K9 probably won't end well. But thats just my opinion - several people have run Warp9s with higher voltages and huge currents for a long time with no issues.

Cheers and good luck with the build!


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## Batterypoweredtoad (Feb 5, 2008)

The WarP motors are designed to be much more amp tolerant. The Kostovs are designed for voltage. I would really like to see someone try overvolting a Kostov the same way people overamp the WarP motors.


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## major (Apr 4, 2008)

Erobison said:


> Major:
> 
> The curves I'm using for the K9 220 are at the following location:
> 
> http://kostov-motors.com/files/productattachments/6ff70418861d3230f01fc0340802fb1f_S220E01.pdf


So your torque estimate looks pretty close. RPM is more dubious. But run with your 157 hp output. Include sag in your input and get 174 kW for efficiency of 67%. More believable.




> I'm really having a hard time verifying my TQ estimates, and when the current starts to fall off. I'm currently using the generally accepted method of voltage being proportional to RPM, i.e. if voltage is doubled the same current can be achieved at double the RPM.


I don't know what you mean. Verify  Current starts to fall  Torque and current are a one to one function regardless of voltage and RPM.


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## Jordysport (Mar 22, 2009)

A K9 will take 1000Amps for about a second, 500 amps is about the peak limit for the motor (1 min) absolute max.


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## Erobison (Sep 14, 2012)

Old.DSMer:

I obviously wouldn't be continuously putting 1000A into the motor; only if I was trying to blow the doors off someone at a stoplight or something. And as Tyler said earlier, the TQ developed at 1000A would probably shell the transaxle the first time I goosed it. I'd probably be running something like a few hundred amps maybe lower for normal driving, (higher under acceleration obviously). 

Think I'm OK with that level of current (or slightly lower, maybe 8-900A) for a 5-10 seconds?

Major:

The voltage I gave would be the estimated "sagged" voltage at 1000A. The pack voltage would be somewhere around 260V.

Should have clarified what I meant about the current falling. I'm good with the current-torque relationship, but as you said, estimating the induced voltage as RPM increases is tricky and that's where I'm having trouble. I still think my estimate of 157 hp is a bit low but I don't really know how to confirm.


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## Erobison (Sep 14, 2012)

Whoops, Jordy answered my current question while I was typing my reply.


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## Jordysport (Mar 22, 2009)

Erobison said:


> Old.DSMer:
> 
> I obviously wouldn't be continuously putting 1000A into the motor; only if I was trying to blow the doors off someone at a stoplight or something. And as Tyler said earlier, the TQ developed at 1000A would probably shell the transaxle the first time I goosed it. I'd probably be running something like a few hundred amps maybe lower for normal driving, (higher under acceleration obviously).
> 
> ...


a 260v pack with 1000A you would fubar the motor in less than a second, you can forget that. 600A is the max i would take it for 5-10secs

as for the power side of things, a good estimate, Peak Power (hp) = ((Voltage after sag) x (Peak Amps) x (Motor Efficiency)) / 745 ....... eg. Kostov 250V Alpha motor is 88.7% efficient and can take peak 1000A, = 250 x 1000 x 0.887 / 745 = 297 hp


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## Erobison (Sep 14, 2012)

Thanks Jordy. That matches up pretty well with the results for the warp 9 in EVTV's speedster here (Speedster redux, 3rd gear):

http://blog.evtv.me/2011/04/the-graphs-is-always-greener/#

145V*1000A*85%/746=165 bhp They're showing 157 bhp; close enough....


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## tylerwatts (Feb 9, 2012)

Erobison

I had not realized you were after MR2Turbo performance! Kosovo Alpha at ~300V would be my recommendation, and a Soliton Jr can hold 500A continuous and peak 600A so if that doesn't match your ICE yours is tuned something special.

Re the trans, the Solitons have excellent torque ramp up control, giving the right, smooth ramp up and it would be no problem for the trans. And these electric motors mean you can start off straight from 3rd so no gear change till over 60 which will save over a second on 0-60!

MAIN QUESTION does the MR2 have clearance for the 10.5" Kostov motor at the diff and CV junction, and enough width? Knowing the Kostovs are really short by DC standards you should be fine, just that clearance is bugging me now...


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## Erobison (Sep 14, 2012)

Tyler:

What makes you choose K11 Alpha over WarP 11HV? Just curious.

I'm not sure about clearances yet as I'm still planning. Don't even have the car yet...


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## tylerwatts (Feb 9, 2012)

Personal preference. Warp will soak a lot more amps. Kostov likes higher voltage with interpoled rotor. And the Kostov runs cooler due to the interpoled rotor also. Plus as a result the Kostov is more efficient at producing torque from what I understand, but I may be corrected. And finally the Kostov is a bit smaller, a lot shorter and considerably lighter! All good things and plenty capable in an MR2

Edit: by soak I mean the Warp can handle more Amps for longer, they are tough motors! Hence their weight.


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## Frank (Dec 6, 2008)

Jordysport said:


> a 260v pack with 1000A you would fubar the motor in less than a second, you can forget that. 600A is the max i would take it for 5-10secs


...just curious... how do you know 1000A would fubar the motor? Do you have direct experience with this? (hope not!)


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## Tesseract (Sep 27, 2008)

Frank said:


> ...just curious... how do you know 1000A would fubar the motor? Do you have direct experience with this? (hope not!)


It took 14 seconds to cook the 144V version of a 9" Kostov at 900A, so it should take approximately 11 seconds to cook the same motor at 1000A (this is an I²t function).

A 220V version of the same motor will have approximately 1.53x more resistance and so should take 1000A for 1/1.53x times as long (65%), or, say, about 7 seconds. A bit better than a couple of seconds, but still short enough I'd definitely think twice before subjecting the motor to that kind of abuse.

The usual disclaimer applies here: you blow up your motor, don't blame me, etc.


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## Bowser330 (Jun 15, 2008)

tylerwatts said:


> Personal preference. Warp will soak a lot more amps. Kostov likes higher voltage with interpoled rotor. And the Kostov runs cooler due to the interpoled rotor also. Plus as a result the Kostov is more efficient at producing torque from what I understand, but I may be corrected. And finally the Kostov is a bit smaller, a lot shorter and considerably lighter! All good things and plenty capable in an MR2
> 
> Edit: by soak I mean the Warp can handle more Amps for longer, they are tough motors! Hence their weight.


The Warp11HV is also an interpoled motor...


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## Frank (Dec 6, 2008)

Thanks Tess, I know you've cooked at least one on your dyno. I don't know anything about Jordy though. It seemed a very strong statement to make but obviously has some basis in reality!


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## Jordysport (Mar 22, 2009)

Frank said:


> ...just curious... how do you know 1000A would fubar the motor? Do you have direct experience with this? (hope not!)


I Haven't blown one up no, but speaking closely with manufacturer, they are adamant that bursts of 10-20 seconds of 600A on the K9 220V & 1000A on the K11 is the very limit for any sort of reliability and those figures are subject to forced cooling as well. and when the OP wants to run 260V AND 1000A the motor will spit its dummy out very quickly. 

you have to consider also that the Kostov 220V is nearly 3x overloaded already, overloading the volts AND amps on a motor is only going to end up one way. 



Tesseract said:


> It took 14 seconds to cook the 144V version of a 9" Kostov at 900A, so it should take approximately 11 seconds to cook the same motor at 1000A (this is an I²t function).
> 
> A 220V version of the same motor will have approximately 1.53x more resistance and so should take 1000A for 1/1.53x times as long (65%), or, say, about 7 seconds. A bit better than a couple of seconds, but still short enough I'd definitely think twice before subjecting the motor to that kind of abuse.
> 
> The usual disclaimer applies here: you blow up your motor, don't blame me, etc.


There you go then.  I personally wouldn't want to subject the motor to 7 seconds at 1000A over and over again. as its a road car your going to want reliability, and frankly subjecting the motor to those sorts of amps for long durations (burning up people at the lights) is not going to be reliable. my 2p use the K9 220V at no more than a pack voltage of 250V with a soliton jr 600a. job done!


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## Tesseract (Sep 27, 2008)

Jordysport said:


> ...
> There you go then.  I personally wouldn't want to subject the motor to 7 seconds at 1000A over and over again....


Right - I should have emphasized that just because a K9-220V motor *might* survive 7 seconds at 1000A doesn't mean you should subject it that kind of abuse. Not unless you consider motors disposable, that is...


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## Frank (Dec 6, 2008)

Check and double-check.

The WarP series seems able to survive higher currents for longer lengths of time. They are a lot heavier though.


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## Ziggythewiz (May 16, 2010)

Tesseract said:


> Right - I should have emphasized that just because a K9-220V motor *might* survive 7 seconds at 1000A doesn't mean you should subject it that kind of abuse. Not unless you consider motors disposable, that is...


Where exactly does one find the space (legal and road) to use 1000A for 7 seconds?


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## Jordysport (Mar 22, 2009)

Ziggythewiz said:


> Where exactly does one find the space (legal and road) to use 1000A for 7 seconds?


depends on the weight of the vehicle surely, would be very easy to achieve in a tank or hummer.


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## Frank (Dec 6, 2008)

0-60 mph/0-100 km/h.


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