# Planning Subaru WRX Conversion



## DavidDymaxion (Dec 1, 2008)

http://www.proev.com/ these guys did a Subaru. They directly drove the front and rear diffs with 2 motors and 2 controllers.

I think it is a good idea to keep your gears and clutch, unless you can afford to go with very high power levels (which usually means 2 motors and powerful batteries, which would about double your budget). Plus with AWD, a 1st gear high torque take-off would be great fun! Good luck not breaking something!

http://www.NEDRA.com is another great resource. You can look at the records, and see what components it took to get that performance level.


yunkingyoda said:


> I am planning to convert my 2003 Subaru Impreza WRX Wagon. I am a fairly competent mechanic (or like to pretend as much). I change all my own fluids and have done a handful of modifications/upgrades. I am also a radio technician by trade and so I have had a good amount of electronics schooling.
> 
> I'm hoping to get over 100 miles per charge and would be content with 175-200. More than miles per charge I am concerned with performance. I bought the WRX because it's a rally car, and I want to try and keep as much power as possible. I don't really have a budget for this, but am anticipating spending around $10,000. Obviously I would like to spend as little as possible, but the car is in great shape and I intend to part it out to fund the project.
> 
> ...


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## winzeracer (Apr 3, 2012)

yunkingyoda said:


> I am planning to convert my 2003 Subaru Impreza WRX Wagon. I am a fairly competent mechanic (or like to pretend as much). I change all my own fluids and have done a handful of modifications/upgrades. I am also a radio technician by trade and so I have had a good amount of electronics schooling.
> 
> I'm hoping to get over 100 miles per charge and would be content with 175-200. More than miles per charge I am concerned with performance. I bought the WRX because it's a rally car, and I want to try and keep as much power as possible. I don't really have a budget for this, but am anticipating spending around $10,000. Obviously I would like to spend as little as possible, but the car is in great shape and I intend to part it out to fund the project.
> 
> ...



I would start with the wiki here on diy ev, from the sounds of it you have not really done any research yet. Start reading other build logs and find out what you think you can accomplish. 100 mile range AND hard acceleration is not going to happen for 10 grand, maybe for $50,000+ with lots genius.

If you post up with a possible setup. Motor, controller, batteries, charger ect... You will get lots of good feedback.

Happy hunting 

Brock
Www.winzeracer.com


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## yunkingyoda (May 23, 2012)

Like I said, I've been reading a lot, but it's been a bit overwhelming. I was looking at parts yesterday and think I would like to go with a Zilla controller--probably the ZK1HV with the HEPA pedal. Also, a 9" DC motor, though I haven't really researched brands yet. Batteries is what's really killing me. I read one of the FAQs on here that was for sizing the packs, but was still confused after reading it. I think I want to go with li-ion. I know they are lighter, are they comparable in terms of performance? I have seen a lot of battery packs once they are made up, and I would be comfortable being more creative than having them all boxed together. I know electrically it wouldn't make a difference if they were all squirrelled away to save space. Would having one motor for the whole thing as opposed to one for each diff affect the AWD in any way other than power/torque?

As far as having range and performance goes, I can dream, can't I?


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## corbin (Apr 6, 2010)

You probably should use an 11" motor, and Zilla 2k to get good performance.

corbin


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## winzeracer (Apr 3, 2012)

yunkingyoda said:


> Like I said, I've been reading a lot, but it's been a bit overwhelming. I was looking at parts yesterday and think I would like to go with a Zilla controller--probably the ZK1HV with the HEPA pedal. Also, a 9" DC motor, though I haven't really researched brands yet. Batteries is what's really killing me. I read one of the FAQs on here that was for sizing the packs, but was still confused after reading it. I think I want to go with li-ion. I know they are lighter, are they comparable in terms of performance? I have seen a lot of battery packs once they are made up, and I would be comfortable being more creative than having them all boxed together. I know electrically it wouldn't make a difference if they were all squirrelled away to save space. Would having one motor for the whole thing as opposed to one for each diff affect the AWD in any way other than power/torque?
> 
> As far as having range and performance goes, I can dream, can't I?


We can always dream.  Unfortunatly we have to be realistic also. My problem with my current build is that did not choose the right batteries, and I am going to be abusing them. If you want performance then definatly go with Li-pouch type cells, not prismatic. I do not think that one 9 inch motor is going to be what you want.

http://www.thunderstruck-ev.com/warp-9.html
This is a pretty standard 9" and it says 34HP that is quite a ways from what you are looking for I am sure. If you are truly going for performance you will want something like dual 11" which means 2 controllers( or one Really BAD one!) and a large 200+ah pack

Here is another motor company that have high HP motors. There is also a pouch cell on this page
http://kostov-motors.com/tractionmotors/kostovevmotors(ac-dc)/seriesdcmotorsforelectricvehicles/

PS. I don't really know that much around here. There are guys that are FAR more knowledgeable than I, to get their attention, post a possible setup like I had said. I think everyone is overwhelemed at the begining of research, just keep going in a few months you will have a decent idea of what you want to do. Building an EV by yourself is not overnight process, just keep at it.

Brock
www.winzeracer.com


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## TigerNut (Dec 18, 2009)

yunkingyoda said:


> Like I said, I've been reading a lot, but it's been a bit overwhelming. I was looking at parts yesterday and think I would like to go with a Zilla controller--probably the ZK1HV with the HEPA pedal. Also, a 9" DC motor, though I haven't really researched brands yet. Batteries is what's really killing me. I read one of the FAQs on here that was for sizing the packs, but was still confused after reading it. I think I want to go with li-ion. I know they are lighter, are they comparable in terms of performance? I have seen a lot of battery packs once they are made up, and I would be comfortable being more creative than having them all boxed together. I know electrically it wouldn't make a difference if they were all squirrelled away to save space. Would having one motor for the whole thing as opposed to one for each diff affect the AWD in any way other than power/torque?
> 
> As far as having range and performance goes, I can dream, can't I?


It helps if you think of the battery as an integral part of your "engine" to begin with. Lead-acid is useless for high performance, especially if you want the pack to last for more than a few recharge cycles. Within the various lithium chemistries and cell construction methods, the internal resistance varies greatly and that influences how much power can be extracted from a given combination of cells.

Each battery cell has a nominal voltage (specified in volts V), an internal resistance specified in ohms and denoted R, and a nominal rated capacity C, specified in amp-hours. The actual current drawn from a cell is denoted by I, and can be specified either in amps, or as a ratio relative to the nominal capacity, in which case it will be written 1C, 2C, etc. Most prismatic lithium cells can be operated continuously at 2C or 3C (which means you'd use up the entire charge in 30 or 20 minutes, respectively), and they may have 'burst' or short-duration capability of 10 seconds at 5C or greater - but extended or repeated burst drains will reduce the battery life expectancy (in terms of for how many cycles you will be able to charge it back to its nominal capacity).

So... if you're extracting power from the battery, its terminal voltage drops in proportion to the current and internal resistance. As an example, for a single 100Ah cell with V = 3.6 volts, and 0.001 ohms internal resistance, drawing 100A is a discharge of 1C and it reduces the terminal voltage by I*R = 100 x 0.001 = 0.1 Volts. So instead of getting the nominal 3.6 volts, you're only getting 3.5V. Pulling 500 amps would be a 5C discharge and reduce the terminal voltage to 3.1V; in that case the power delivered to the controller by that one cell is 1550 watts. If you had 80 cells in series, your total power in that case is 80 * 1550 = 124 kW, which would probably give you about 124 HP at the motor shaft (assuming about 0.75 efficiency through the motor and controller). But, you'd have to get out of the throttle after about 5 to 10 seconds to prevent damaging the batteries - that 500A current draw is causing I*I*R = 500*500*0.001 = 250W of heat to be generated in EACH CELL and you'll melt something very quickly.

A rough analogy is that you have a fuel tank connected to the engine with a fuel line that's too small, and you can only apply so much upstream pressure in order to increase the fuel flow...

So the way to get a battery pack that can deliver more power, is to put cells in parallel, and/or to use cells that have less internal resistance. Putting "N" cells in parallel reduces the pack's internal resistance by a factor of N, while increasing the effective capacity by N; for example, paralleling 3 hypothetical cells of 100 Ah capacity and 0.001 ohm resistance gives a total resistance of 0.00033... ohms, but a capacity of 300 Ah.

The lowest resistance cells currently on the market are the (A123) pouch type cells, followed by the various cylindrical (Headway) cells - they have various combinations of capacity and internal resistance.


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## somanywelps (Jan 25, 2012)

corbin said:


> You probably should use an 11" motor, and Zilla 2k to get good performance.
> 
> corbin


Isn't 2k a bit much to put through an 11" on a street car?


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## Yabert (Feb 7, 2010)

Hi Yunk

Just by reference, a battery pack able to output 300 Kw (that mean roughly 300 motor HP) and move a WRX for 100 miles (when driving gentle) will need to carry around 40 Kwh of energy.
That represent 15-16k$ just for the battery.

A 850-900 lbs battery...


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## corbin (Apr 6, 2010)

somanywelps said:


> Isn't 2k a bit much to put through an 11" on a street car?


No way! 2k would be awesome (assuming the batteries can do it).

Plus, he didn't say he was aiming for a street car... LOL 

corbin


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## somanywelps (Jan 25, 2012)

corbin said:


> No way! 2k would be awesome (assuming the batteries can do it).
> 
> Plus, he didn't say he was aiming for a street car... LOL
> 
> corbin


I meant the motor's not going to like that.


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## corbin (Apr 6, 2010)

somanywelps said:


> I meant the motor's not going to like that.


Ah, good point! But people do it; I wonder what the limits are? I've heard that 2000 amps can be run through (with a blower) for 10 seconds or less.

corbin


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## yunkingyoda (May 23, 2012)

For clarification: I am talking about a street car. I would like to be able to track it and have a good time, but am not planning on dragging or even tracking it competitively. Couldn't I build a battery with cells in both series and parallel to find some middle ground between extreme performance and extreme range? I'm not looking for an outrageous top speed, I would be content with 80-90mph (or even 70), but having quick acceleration is a must. Because of this I don't see it being necessary to have all the cells in series, but rather make up several smaller batteries in parellel and then have those in series. Not sure if that makes sense, later today I'll look at a few different batteries and come up with some examples. The car weighs a little over 3000lbs stock, and I intend to lose not only the motor, but the A/C as well. Also, there are more components than a naturally-aspirated engine: the intercooler and turbo. Not sure what all that weighs, but if I came out with the same weight in the end, I'd be okay with that.


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## Yabert (Feb 7, 2010)

To have quick acceleration (0-60 mph > 6 sec for example), you will need high power battery...
To have a range of 100 miles or over, you will need high energy capacity battery...

Both ways, the cost will be high!

Anyhow you build a battery with cells in parralele or in series the peak power and range can be the same if the capacity is the same.

Example: 
96s 1P (307v and 100Ah) give 31 Kwh of energy capacity and a peak power at 10C of 307v x 1000A = 307 Kw (excluding sag)
16s 6P (51v and 600Ah) give 31 Kwh of energy capacity and a peak power at 10C of 51v x 6000A = 307 Kw (excluding sag)

The difference is find a motor and controller to pass 1000A is way more easy (realistic) than one to pass 6000A.

The result with smaller capacity cells in parralele will be the same:
96s 10P (307v and 10x 10Ah(100Ah)) give 31 Kwh of energy capacity and a peak power at 10C of 307v x 1000A = 307 Kw (excluding sag)

With lower energy capacity, the range and possibly the peak power will be lower.
Hope that will help.


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## somanywelps (Jan 25, 2012)

corbin said:


> Ah, good point! But people do it; I wonder what the limits are? I've heard that 2000 amps can be run through (with a blower) for 10 seconds or less.
> 
> corbin


I would say 5 seconds through an 11" if it's cold before you stand an extremely good chance of permanent damage.

At that level of power neither forced air nor internal fans are going to be able to help due to the very rapid heat build up.

The forced air WILL help it cool off afterwards though, and is good for running at quieter low rpms when cruising.


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## yunkingyoda (May 23, 2012)

With 210 3.2V, 100Ah cells I could run three groups of 70 cells in series at 224V each. I could then connect them in parallel to give me 300Ah. It's a lot of batteries, but I would be comfortable fabricating something to put some of them underneath the body of the car where the gas tank is now. I realize it wouldn't cool well, but I could run a liquid cooling system through it, and there would be ample room to separate them to begin with. Also, the entire enclosure wouldn't need to be watertight, there could be vents from a 1/4" -1/2" from the body of the car (maybe, I'm only theorizing). In any case, I'm not sure of all the math to get the power and range with battery capacity and everything, but I'm going to have a look over a couple of the FAQs and see if I can't work some of it out.

Here's an 11" HV motor, though I'm not sure how much voltage it's actually rated for. I do see it says 32.2 continuous HP @ 144V and 173lbs of torque at 600A. Would this fit my application?
http://www.go-ev.com/PDFs/002_05_08_WarP_11HV_Sales_Sheet.pdf


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## Yabert (Feb 7, 2010)

Yes Yunk, the Warp 11 HV is a good motor for a high performance application. Some guys here have builded 300-500 hp car with this motor.
It is rated to 288v and can output 290 lbs-ft of torque at 1000A.

224v x 300Ah = 67.2 Kwh of energy storage. That represent:

-180-220 miles of range (good thing)
-Over 25K$ (bad thing)
-1500 lbs battery (really bad thing)
-Over 435 liters of space (really bad thing)
-Only 220-230 hp of peak power with 1000A controller (caused by the relatively low voltage)

I suggest to you to design around an higher voltage battery pack if you think use an high voltage motor. 96S (307v nominal) for example. You can also keep your eye on Kostov motor.


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## somanywelps (Jan 25, 2012)

Yabert said:


> Yes Yunk, the Warp 11 HV is a good motor for a high performance application. Some guys here have builded 300-500 hp car with this motor.
> It is rated to 288v and can output 290 lbs-ft of torque at 1000A.
> 
> 224v x 300Ah = 67.2 Kwh of energy storage. That represent:
> ...


*
Kostov 11 Alpha(5800rpm nominal & 75kg & $2700):*

295A 500A
100nm 194nm
0.4585365853658537x + -35.26829268292684

312ft*lb per 1 @1000A
624ft*lb per 2 @1000A
177ft*lb per 1 @600A
354ft*lb per 2 @600A
143ft*lb per 1 @500A
286ft*lb per 2 @500A

*Kostov 11 250V(5600rpm nominal & 81kg & $2500):*

210A 77nm
500A 215nm

0.47586206896551725x + -22.93103448275862

334ft*lb per 1 @1000A
668ft*lb per 2 @1000A
193.67ft*lb per 1 @600A
387ft*lb per 2 @600A
158.57ft*lb per 1 @500A
317.14ft*lb per 2 @500A

*Netgain Warp 11 HV(3000rpm nominal & 5000rpm redline & 101kg & $3500):*

398ft*lb 1090A
449 1200A
173 600A

0.45918367346938777x + -102.51020408163265

1000A 357ft*lb

*Kostov 9" 220V (6800rpm nominal & 50kg per motor, 100kg for 2; you'd want them in siamese configuration, which is $4000):*

(look at the per 2 numbers, you'll need to run in parallel for full voltage)

176A 500A
44nm 176nm

Torque=0.4074074074074074*Amps + -27.703703703703695

300ft*lb per 1 @1000A
600ft*lb per 2 @1000A
159ft*lb per 1 @600A
308ft*lb per 2 @600A
130ft*lb per 1 @500A
260ft*lb per 2 @500A


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