# Trademe find - donor car



## linz (May 18, 2008)

http://www.trademe.co.nz/Browse/Cat...&18=0&18=0&24=0&24=0&searchRegion=100&x=0&y=0

Various potential donors with blown engines. A couple of Celica's, which have been used as donors before.


----------



## zppz (May 18, 2008)

Spotted this Suzuki Carry van with seized engine going fairly cheap on trademe. There are a couple of these on evalbum, they have the advantage of an easy battery layout like a ute does, but with the advantage of having dry space to carry stuff.

http://www.trademe.co.nz/Trade-Me-Motors/Cars/Suzuki/auction-207592342.htm


----------



## samborambo (Aug 27, 2008)

I understand a few people here have converted Toyota MR2s. Are these cars a good platform to work from? Any major 'gotchas'? I ask because there's an MR2 going for $500 with a blown motor here in Tauranga:

http://www.trademe.co.nz/Trade-Me-Motors/Cars/Toyota/MR2/auction-219070945.htm


Sam.


----------



## linz (May 18, 2008)

Found this on the net-
http://www.mr2dc.com/buyGuideMK2.aspx?navSection=buyerguide

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
Bodywork (top of page)
Firstly check that the paint matches on all panels, if different colours then examine the fixings for that panel and determine if its been unbolted, check for after market welding if any such occurs, theses are signs of accident repair.
In general the Mk2 does not suffer from the same rust problems as the Mk1. But areas to check for rust include the following:- open both passenger and driver doors, look at the point at which the door pillars meet with the floor. Move to the rear wheel arches and check the top sections on both sides. The rest of the arch is made from the plastic trim.
If it is a T bar model you are looking at you might like to check the seals in the roof. Get a hose pipe and whilst sitting inside run water over the roof to check for leaks. If they do leak its normally behind the driver or passenger.
The alloy wheels do go scabby after a few years, they can be reconditioned for around 40 pounds each, original wheels cost around 300 pounds new, so take this into account if they have kerbing marks on them."
<<<<<<<<<<<<<<<<<<<<<<<<<<


----------



## samborambo (Aug 27, 2008)

Thanks for the reply linz. I had a talk to the wife/boss and decided we haven't got the space to start a conversion right now. Oh well.

The auction closes tomorrow. If anyone here is seriously interested in the vehicle from out of town, I don't mind going out this evening to have a look at it for them. You'd have to let me know some time during the day today though.

Sam.


----------



## John (Sep 11, 2007)

samborambo said:


> I understand a few people here have converted Toyota MR2s. Are these cars a good platform to work from? Any major 'gotchas'? I ask because there's an MR2 going for $500 with a blown motor here in Tauranga




I know it’s a bit late to reply to this post so take my comments as for future reference. I like the MR2 mk2 as a platform for a number of reasons, small, light aerodynamic (small frontal area), and the power steering thing is already nicely sorted for you but sports cars with two seats seem to all have a lousy payload. The difference between the GVWR and the curb weight reflects the fact that it only has two seats. This would make certifying it with hundreds of kilo's of lead on board a bit more of a headache than it already is. You would probably need to get a special dispensation to exceed the GVWR and it would be at the discretion of the low volume vehicle certifier wether or not they allow it. If you were planning on a light weight lithium pack this may well be a non issue.

When you convert a car you might sink $10k to $15k into it and a lot of time and effort. You have to like the car for itself and not just because it is cheap. Anything with rust shouldn’t get a second look and if you buy old it should be because you like retro cars. The donor car makes up most of the finished product and determines so many of its finished qualities it is important to get the right one and is IMO not the place to penny pinch. If by some happy coincidence the right one turns up with a blown motor and cheap go for it.


----------



## samborambo (Aug 27, 2008)

I bought the MR2 listed above! Managed to beat him down to $380. The car is in pretty good nick apart from a couple of minor scratches. The interior needs a bit of attention but that's expected too. I'm picking the car up next week to put in storage for a couple of months until we move house. I can't wait to start pulling it apart!

A few details on the planned build:

 The preliminary budget is $7000 to get it pristine, not including motors and batteries. I’m looking at 6 – 12 months project build time.

 This is a project I’ve wanted to do for many years now with loads of modelling and design ideas. I’m using two 400V 3 phase induction motors for each rear wheel and am designing and building a pair of 1200Vx160A VSDs myself. I’ll also be designing and building the charger, battery management system, battery and motor frames. 

The batteries are probably Sky Energy LiFePo4 192x 40Ah 3.7V cells. They will be ordered once the build is nearing completion since the battery market – especially for LiFePo4 – is quite volatile. The company I work for is interested in sponsoring the battery purchase. ABB have quoted me NZ$4000 for a pair of 9.2kW(continuous) aluminium induction motors with 4.5x short term overload. These motors may be over spec but I’m designing to accommodate them for the mean time. The battery and motor controller will be capable of around 70kW in bursts.


At this stage the conversion will add 150kg to the curb weight. The modelled range is realistically 200km (250km max, ideal conditions) at highway driving and around 350km around town. The converted car is expected to have around 20% better acceleration but a lower top speed of 140km/h. The onboard 2400W battery charger will trickle charge the car in under 12 hours. I’m also working on a half hour non-isolated 3 phase charger - I'd like to see how well these Sky Energy cells accept a 2C 80% charge.


With an average commute to work and weekend trips, etc the batteries should pay for themselves in 5 years and last a further 10 years. That’s based on $1.70/l petrol. What's the price of petrol doing over the next 5 years, I wonder? 


Once I start work on the car, I’ll put up a build log.

Sam.


----------



## Hemon Dey (Jul 31, 2008)

Hi Samborambo,

It sounds like you've got a cool project going. Sounds like you're doing quite a bit yourself, I would love to have a look at your blog when you have it up and running. 

I'm attempting an industrial ACIM conversion here in Chch, but using a 15kw motor into a standard gearbox method. Also intend to use LiFePO4 (currently evaluating Headway cells) that will be ~600V 20AHr which should give me about 80km of range. Converting a sporty sedan which I have not decided on yet. 

The 15kw motor is rated to 2.8x torque at full load torque. I have also got a 15kw PDL microdrive elite inverter to play with, however this can only do 22kw peak, and I need more like 45kw peak to get normal like performance. 

It is a 2 pole motor that has a baseline ~3000rpm, max of 4500rpm, 50nm nominal torque 150nm peak. Via a gear box I think this will be similar to the ICE it replaces.

There is another guy on these DIY forums who took a 2hp inveter (in the US) and refitted the smart power IGBT module to be 90hp. He had to do some tweaking of the software internally to trick it into thinking it was driving a 2hp motor, when infact it was driving a lot higher. Here is his weblink:
http://etischer.com/awdev/

I wish you all the best, and keen to monitor your progress.


----------



## samborambo (Aug 27, 2008)

Hi Hemon,

If you want to go down the same route as that guy in the states of tricking out a smaller inverter, www.surplustronics.co.nz has a surplus stock of IGBT six packs I'm using for $99/pc. If you wait for a trademe auction (he usually does one every couple of months) you may get two for $90. You'll also need bigger reservoir capacitors, probably a current amplifier stage for the IGBT gate driver and modify/replace the current sensing arrangement. Is your VSD capable of torque control instead of speed control?

I'm doing away with the gearbox and diff for an anticipated 4-5% efficiency gain. Not using a gearbox means a lot tighter parameters and took a while to come up with a decent solution.

Sam.


----------



## Hemon Dey (Jul 31, 2008)

samborambo said:


> If you want to go down the same route as that guy in the states of tricking out a smaller inverter, www.surplustronics.co.nz has a surplus stock of IGBT six packs I'm using for $99/pc. If you wait for a trademe auction (he usually does one every couple of months) you may get two for $90. You'll also need bigger reservoir capacitors, probably a current amplifier stage for the IGBT gate driver and modify/replace the current sensing arrangement.


Interesting, though I'm not really that sure that will be my route. I'm happy enough to find a 30kw VFD if possible with 45kw peak rating. The PDL one I got was really just for play and testing and I got it cheapish of trademe. 



samborambo said:


> Is your VSD capable of torque control instead of speed control?


Yes, sensored (encoder) vector control is available, though I don't think sensorless vector is supported.



samborambo said:


> I'm doing away with the gearbox and diff for an anticipated 4-5% efficiency gain. Not using a gearbox means a lot tighter parameters and took a while to come up with a decent solution.


Yes, part of the reason why I'm opting for a gb system. Also how many poles are you using? What voltage are your motors rated at? If you're direct driving the wheels, is it via a fixed ratio chain drive? Watch the ratio relative to the baseline RPM of the motors to ensure you don't hit constant power at the top end revs, ie. that may limit how fast you can go as you won't be able to pump more power into the motors the higher you go above baseline. 

I wish you all the best, do keep in touch.


----------



## samborambo (Aug 27, 2008)

Hemon Dey said:


> Interesting, though I'm not really that sure that will be my route. I'm happy enough to find a 30kw VFD if possible with 45kw peak rating. The PDL one I got was really just for play and testing and I got it cheapish of trademe.
> 
> 
> 
> ...


I have a feeling Robert Turner AKA forum member "rwt33" works for your VSD's manufacturer in Napier (see thread http://www.diyelectriccar.com/forums/showthread.php/dc-brushless-ev-project-progress-24613.html). He may be able to offer advice should you decide to modify your VSD. If the drive has accurate phase current and bus voltage measurement, sensorless mode might be available as a firmware upgrade. 

It would be such a weight lifted off my shoulders if I retained the gearbox. I'm stubborn and am out to prove the point that it can be done with a more efficient fixed ratio toothed belt reduction drive. Goodyear EP have a good tool for calculating optimal pulleys, belts, etc.

I've narrowed it down to ABB's Industrial Performance Motors (IPMs). At the moment I'm tossing up between a pair of 2 or 4 pole aluminium frame motors from ABB. I heard back from ABB today that I probably can't over rate the Tmax of the motors - even for 10-15 seconds. The ABB sales engineer started out with "I'd say you probably can't..." which isn't exactly condemning, however, its the most information I have at the moment. ABB don't give any indication in their datasheet as to what conditions Tmax is at. Is it stall torque? Is it short term torque?

I'm having trouble with the proportion of constant power to constant torque regions. In my acceleration model, the further down the constant power region extends for a given power rating, the better the acceleration. As you probably know, the baseline is roughly the changeover point from constant torque to constant power. Problem is, above baseline the BEMF also increases proportional to speed. This has become my limiting factor. I want to overspeed a 4 pole 380VAC motor to 4500 RPM (as per ABB datasheet) but my minimum 600VDC bus becomes the limiting parameter due to the sine wave peak. I could switch delta/star on the motor windings to give a bit more head room and bring me to 690VAC RMS. That would ideally require a 980VDC bus.Would it be OK undervolting the motor at full speed and with insane odd harmonics AKA square wave? I'm an HV lines engineer and am not that experienced with induction motors.

After typing the problem out I think I've come up with a satisfactory solution. ABB rates the top end speed about the same for 2 and 4 pole motors. That's why I was drawn to the 4 pole motor - slightly heavier but offers slightly more constant power region. However, the 4 pole is only rated for Tmax/Tn=2.8 while the 2 pole is rated for 3.4 times the nominal torque. I figure that the top end speed, in my situation, is proportional to bearing wear. These motors are rated for between 25k-40k hours - I don't need anywhere near that reliability. So why not overspeed them to, say, 8000RPM? The ABB datasheet notes the systems designer to take into consideration max torque, bearing construction, balancing, shaft seals and fan noise when overspeeding. I'll email ABB about how far I can push the speed for these particular motors.

Following that logic, I'll go with a 2 pole motor baseline 2900RPM, top speed 8000RPM (ABB spec 4500RPM). Minimum operating voltage for 2900RPM is 380VAC RMS (star). With a 5.5:1 ratio, it'll hit constant power at 50km/h. That gives me 137km/h top speed, cruise at 100km/h and 6000RPM. My acceleration model shows 9 seconds flat 0-100km/h and 16.6 seconds for the quarter mile. At top speed, the required BEMF will bring the operating voltage to 600VAC RMS (delta) minimum. My DC bus will be 600VDC minimum. The question remains - will the motors overheat with square wave at RMS amplitude?

Rereading, this is far more than you probably wanted to know. I'll probably repost this on my blog in the morning. By the way, I've started the conversion blog. Check my profile for info.

Thanks for reading - this has been a worth while exercise bouncing my ideas off... the keyboard! I'd really appreciate any feedback/ideas these forum members can offer. 

Sam.


----------



## Hemon Dey (Jul 31, 2008)

samborambo said:


> I've narrowed it down to ABB's Industrial Performance Motors (IPMs). At the moment I'm tossing up between a pair of 2 or 4 pole aluminium frame motors from ABB. I heard back from ABB today that I probably can't over rate the Tmax of the motors - even for 10-15 seconds. The ABB sales engineer started out with "I'd say you probably can't..." which isn't exactly condemning, however, its the most information I have at the moment. ABB don't give any indication in their datasheet as to what conditions Tmax is at. Is it stall torque? Is it short term torque?


Hmm ... good point. Not sure if stall torque is meant to be continous or not. I had thought that stall torque is the peak torque, but this may not be necessarily the case if your controller and battery is happy to give more amps to the motor. It becomes a thermal dessipation issue and the power point is given when the motor melts itself/insulation to destruction based on the air cooling available to it. Also if the fan is a shaft one they will derate max stall torque based on zero airflow for the motor (fan not blowing) - having an always on fan would improve this figure dramatically I think.




samborambo said:


> I'm having trouble with the proportion of constant power to constant torque regions. In my acceleration model, the further down the constant power region extends for a given power rating, the better the acceleration.


Hmm I'm not sure I understand what you mean by "further down the constant power region"? does that mean higher RPM or lower RPM? When you go higher RPM above baseline, you get a reduction in torque, - power is conserved (ie. RPM x torque). For a 4 pole this occurs rougly at 1500rpm, 2 pole at 3000rpm. So if you heading up with RPM, you get poorer acceleration past baseline. The way to improve this would be to increase the voltage within the insulation ratings of the motor. I think this is pretty much what you were saying anyway 

Here is good thread on the AEVA forums that discusses it ... it's pretty long tho:
http://www.aeva.asn.au/forums/forum_posts.asp?TID=585



samborambo said:


> As you probably know, the baseline is roughly the changeover point from constant torque to constant power. Problem is, above baseline the BEMF also increases proportional to speed. This has become my limiting factor. I want to overspeed a 4 pole 380VAC motor to 4500 RPM (as per ABB datasheet) but my minimum 600VDC bus becomes the limiting parameter due to the sine wave peak. I could switch delta/star on the motor windings to give a bit more head room and bring me to 690VAC RMS. That would ideally require a 980VDC bus.Would it be OK undervolting the motor at full speed and with insane odd harmonics AKA square wave? I'm an HV lines engineer and am not that experienced with induction motors.


Bearings and balance of the rotor will give you max RPM capable ... I think that's why you'll find that 2 and 4 pole motors both tend to have max RPMs at 4500 rated. If you change the bearings to high speed low loss ones, and ensure that the rotor is balanced at that speed then you might be able to drive it that high. However note that if you're using a stock industrial 415Vac motor, voltage is going to be your enemy. Rewind the motor for lower voltage and you may be able to partake in higher speeds at the same voltage, albeit at higher amps throughout the range.



samborambo said:


> After typing the problem out I think I've come up with a satisfactory solution. ABB rates the top end speed about the same for 2 and 4 pole motors. That's why I was drawn to the 4 pole motor - slightly heavier but offers slightly more constant power region.


Not sure why you want to stay in constant power region ... I'd want to stay in constant torque region as long as possible. So much so I'd want my inverter to be the limiting factor, not the motor.



samborambo said:


> However, the 4 pole is only rated for Tmax/Tn=2.8 while the 2 pole is rated for 3.4 times the nominal torque.


Not bad really ... but look at the absolute peak torque, not just Tmax/Tn as a 2 pole will have 1/2 the torque capability of a 4 pole. ie. if say 4 pole tn=100nM, tmax is 280nm - but 2 pole tn=50nm and tmax is 170nm according to those ratio numbers. 

Low speed torque is not the problem, its high end torque - that's why I'm going for a 2 pole so I get the higher RPM for the same voltage. However do size the motor for continous rating, not just the peak. Peak ratings are for short term only. Twin 9kw motors sound quite adequate though.




samborambo said:


> I figure that the top end speed, in my situation, is proportional to bearing wear. These motors are rated for between 25k-40k hours - I don't need anywhere near that reliability. So why not overspeed them to, say, 8000RPM?


You might like to check how detrimental this is, is it linear? or exponential?




samborambo said:


> The ABB datasheet notes the systems designer to take into consideration max torque, bearing construction, balancing, shaft seals and fan noise when overspeeding. I'll email ABB about how far I can push the speed for these particular motors.


As for fan noise, pull off the shaft fan and put some "always on" fans - it will enable you to dissipate heat at zero RPM which is very beneficial for an EV motor that starts and stops often.



samborambo said:


> Following that logic, I'll go with a 2 pole motor baseline 2900RPM, top speed 8000RPM (ABB spec 4500RPM). Minimum operating voltage for 2900RPM is 380VAC RMS (star). With a 5.5:1 ratio, it'll hit constant power at 50km/h. That gives me 137km/h top speed, cruise at 100km/h and 6000RPM. My acceleration model shows 9 seconds flat 0-100km/h and 16.6 seconds for the quarter mile. At top speed, the required BEMF will bring the operating voltage to 600VAC RMS (delta) minimum. My DC bus will be 600VDC minimum. The question remains - will the motors overheat with square wave at RMS amplitude?


As you have control over the fixed ratio, you could make the ratio smaller and upsize the motor to meet the torque ... this way you may be able to get the speed more in the band that is easier to achieve without modifying the motors. This will come at the cost of weight, but it the penalty may not be that much greater for the returns.


----------



## samborambo (Aug 27, 2008)

Hemon Dey said:


> Hmm ... good point. Not sure if stall torque is meant to be continous or not. I had thought that stall torque is the peak torque, but this may not be necessarily the case if your controller and battery is happy to give more amps to the motor. It becomes a thermal dessipation issue and the power point is given when the motor melts itself/insulation to destruction based on the air cooling available to it. Also if the fan is a shaft one they will derate max stall torque based on zero airflow for the motor (fan not blowing) - having an always on fan would improve this figure dramatically I think.
> 
> 
> 
> ...


I don't agree that you should be trying to optimise the constant torque region. Your battery pack power should be the limit of how much acceleration is available. Lets say your battery is capable of 75kW. In an ideal world, you want 75kW available from a standstill. However, the torque required to develop 75kW from a near standstill would mean the motor would be huge and expensive.

Size and weight of an AC machine isn't proportional to power. Its proportional to torque since motor power is the product of torque and angular velocity (speed). A well balanced rotor, good bearings and better winding insulation should, in theory, increase the power due to higher speed and voltage - effectively moving the baseline up in the speed range. Gearing can then be used to make extra torque available.

To go the next size up in motors, gaining 15% torque, adds 50kgs.

Anyway, I solved the BEMF problem. It just goes to show the limited experience I've had with induction motors. Above the baseline, the voltage can be kept at constant which explains why the torque tails off - field weakening. Unlike permanent magnet motors, the stator voltage sets up the BEMF too. The control algorithm just needs to take into account the field weakening to balance the torque required. I've still got at least 20% headroom in voltage above the baseline so I can make sure the torque doesn't drop off too much. I'm not that worried about increasing the voltage above the baseline since the motors are designed to take at least the bus voltage of the inverter.

Sam.


----------



## Grant_NZ (May 28, 2008)

Hi guys, 

Most of your thread goes over my head but I noticed you mentioned ABB. I had a look at their website as I would like to use an AC motor as well and they have a large selection. 

Did you narrow down something suitable from them to use for an EV application and if so what model? and obviously a controller would be needed, so would Curtis or Kelly controllers or any other make work or do they have their own?

Thanks
Grant


----------



## Hemon Dey (Jul 31, 2008)

Grant_NZ said:


> Hi guys,
> 
> Most of your thread goes over my head but I noticed you mentioned ABB. I had a look at their website as I would like to use an AC motor as well and they have a large selection.
> 
> ...


The problem with industrial AC is that you are stuck with industrial voltage, which is ~600V DC battery bus. This has complications of its own and certainly challenges the AC industrial conversion.

However I note from your other thread that you have a bit of money to spend on your conversion. Might I suggest that you look at this link:
http://www.evcomponents.com/SearchResults.asp?Cat=43

This is an extremely good price for this Azure dynamics AC motor + controller, and the good thing is it is built for an EV and you don't have to tweak anything. I enquired and it is $700USD to ship to NZ - though I believe it would be the same price to ship 2 or more of them, should might be beneficial to get some one else interested. I'd be keen to buy it too, but alas my budget doesn't allow it.

You'd still need a higher DC bus voltage - but that comes with the territory of AC systems, however it is a blessing in disguise because your system losses are much lower for the same power output. 

Hope that helps.

Best regards,
Hemon


----------



## samborambo (Aug 27, 2008)

Grant_NZ said:


> Hi guys,
> 
> Most of your thread goes over my head but I noticed you mentioned ABB. I had a look at their website as I would like to use an AC motor as well and they have a large selection.
> 
> ...


The motors I'm considering are from the "Industrial Performance" aluminium frame "new" motors. Download the catalogue and have a look for yourself. I recommend that if most of my rant went over your head that you find an engineer to help you size the motor for your application. For reference, my Toyota MR2 will have 2x 11kW IPM in 132 frames. ABB have quoted me NZ$2000 each.

High voltage DC bus makes the best engineering sense as long as safety measures are put in place. I'm looking at installing earth fault protection coupled to the car body to isolate the batteries in the event of current leakage of a leathal level. Basically, the same way a domestic RCD works.

Finding a motor controller of a high enough power rating for cheap may be your biggest challenge. I'm building my own controllers from scratch but if you decide to buy an industrial VSD drive of adequate size, you'll be up for a lot of money. I've seen someone here on DIYEC upgrading a small 2hp VSD with high power switching devices but I think even that ended up being quite expensive.

With upgrading a VSD you want to make sure the VSD supports vector control with overspeed field weakening. Also it needs to operate in commanded torque mode, not speed mode.

Sam.


----------

