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planning 1994 Renault Twingo conversion

120K views 168 replies 23 participants last post by  etlaare 
#1 ·
My first ev-conversion

Skills: semi-professional car mechanics, welder, metalworker, system engineer, programmer, ICT-architect
Required range: 10 KM/charge
Perf: 40-50 KM/hr
Budget: 1000 Euro's
Hoping to get it street legal which is supposed to be easier for conversions of cars registered before 1998 as the official institute in my country (The Netherlands, Europe) assured me.

Donors:
-Renault Twingo 1994 obtained as a real bargain for 250 euro (tip-top shape apart from a defective crankshaft bearing). It's a small car but will only need to be used as a 2 seater with the batteries covered in the extended back having the seats removed).
-Hyster Forklift 48V motor with fuse, emergency switch, controller (but considering the gate driver part of Paul and Sabrina's Open Source controller with my own microcontroller, 68HC11 based (as I built most of my robots with them and it has programmable pwm pins as well)) although seriously considering an Altrax controller as well (laziness).
-Got me some second hand agm batteries already which for the initial requirements might still be sufficient (I heard the other day that the company that I work for seems to start a new development on Lithium air batteries but I doubt I will ever get my hands on any of those :)
http://www.technologyreview.com/energy/22780/ ).
-Collecting transformers for a custom charging managent system (but maybe my laziness wins as well there causing some strain on the budget which my wife guards so thoroughly).

remaining challenges:
-an affordable vacuum system for the power brake assist (you knew that one was coming I guess)
- machining down the existing hubs from the clutch and the drumbreak from the Hyster and adapting them to the lovely joints (still keeping an eye open for those).

no power steering required with the old model I got.

Bought the car a week ago, fuel tank, exhaust and engine are gone by now, cleaning and small exterior repairs on the way, I got myself a service manual for the car today as well.

ok question:

If the motor indicates 48V is that for a parallel setup ? And if I serially connect the field and armature coils, does that mean I can run it on 96V ?

I read about the robustness of the forklift motors and tend to go for 6x12V and indeed serial anyway but just curious.

thank you all for creating such a wonderful and resourceful forum.







ok I need some cleaning on the motor too....
 
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#40 ·
More and more components are dropping in from all over the world.

I am happy as a child every time I reveice a package. Each and every one of them feels like a Christmas present to me.

And best news of the day, I found my desperately needed plate of aluminum, to be modified to connect the motor with the gearbox, which will be ready to be picked up tomorrow.

 
#41 ·
Hey you got a kilovac! Is that the igbt on the heatsink? If so your going to need a bigger one!:D I used a 300mm square of 12mm thick aluminium. I like the open source controller board. It works well and saves reinventing the wheel. Building an ev is difficult enough:)
 
#43 ·
:)
It's so nice to see you all recognize the bits.

And yes the heat sink is too small, it comes from an old robot on my attic and I certainly agree, although they say that mainly the surface counts and not the volume, I will still use a much bigger one, but for testing the controller with low currents I hope the igbt will survive. Unless I find me some more aluminum to make a proper heat sink before that.

I would not consider the coupler to be my design, I copied it mostly from Electric Lemon: http://www.electric-lemon.com/?q=node/213

Almost tempted to give up my skiing vacation so I could keep working on the conversion :)
 
#46 ·
yes I kept that one, and I also liked your setup with the lamp in your thread :)

I was looking a little more into safety though and found the intertia switches, but also the earth leak to detect if one of the main power cables touches the chassis. Seems a nice safety in case of an accident, but the only way I know this is implemented is with two coils inbetween the mainstream to drive a core that will switch off when they are not the same forth and back.

Now that would be hard to implement with the currents we are facing here I guess ...
 
#49 ·
Looking good.
It sounds a little rough in the video but that could just be the sound quality. It won't do any harm to run it without oil as it is slow speed, short duration and the gears will still be a little oily anyway.

You progress is good, it woon;t be long before you have it back in the car and turning wheels on 12v.:)

I still don't have a motor. I was going to go shopping for one but Santa delivered some hefty utility bills so I am £700 down on the EV budget again.
 
#50 ·
Yes, the microphone of the camera was quite close and seems to have amplified the sound a bit, but I do agree it could be smoother. I took it apart again and indeed it seemed that the top spline hub was off center for some reason. I am trying to figure out what caused it , it was not much, less than a tenth of a millimeter and it could be just the springs of the connector, but I will do some very accurate measuring before I put it together for it's final assembly (I did not "locktied" it yet).

In the meanwhile I was toying and tinkering a little with my IGBT and I have already put a pwm signal on the motor from my own micro controller.. (the components for the cougar-controller have not arrived yet (I can be so impatient sometimes:rolleyes:)). That seemed much easier as I had expected (I used the controller that had been in one of my old (she RIP's) robots which was already programmed for a smooth startup). I am beginning to like this IGBT version, that I think I got as a bargain, quite a lot, it seems so easy to implement, although I did not do any serious measurements to be honest. Yet, while drawing less than 50 amps atm there seems no saturation temperature issue whatsoever. I used a capacitor from the old forklift controller, but I still need to do my maths there.

There were no sensors on the robot-controller so after startup I could not turn it off in a programmed way, then it seemed when I disconnected it, it left the gate in a set state. Hence the motor started running at full speed (well on 24V) and I had to connect the gate to mass to reset it and turn the motor off. I had not expected that, but I guess there's either some capacitor at the gate as well, or the IGBT maybe just acts as a flip-flop which afterwards seems a quite logical explanation too, since the functions it's designed for (DC/AC motor controller and emergency power supply) only needs two states.

I don't have too much experience with IGBT's .. (yet) :D but I like them.
 
#51 ·
...it seemed when I disconnected it, it left the gate in a set state. Hence the motor started running at full speed (well on 24V) and I had to connect the gate to mass to reset it and turn the motor off. I had not expected that, but I guess there's either some capacitor at the gate as well...
Yes there's some capacitance on the gate and emitter that keep it charged. That's the reason why you usually should put a resistor between gate and emitter, so the gate can never be left on uintentionally. 10k would be fine.

I would recommend that you read some IGBT theory before burning them up (pretty easy even if you know what you are doing, even more easier if you don't =)) , using IGBTs at this power levels is not as easy at it seems.

Good luck!
 
#52 ·
The gate of an igbt is basically a capacitor. Charge it it turn on. Disconnect the supply it stays on. Discharge it and it turns off. You need a gate driver chip to effect correct control. The driver on the open source controller is rated at 9A drive and works fine with my igbt.
 
#53 ·
ok ok did some more reading about igbt's :)
Still think it's a wonderful device.

And finally (the customs kept it for almost a week) the parts for the controller board have arrived. Did some soldering today.
And here's the result ...well ... I guess most of you have seen pictures like these before but still ...



I always intended to use the potentiometer from the forklift, but I am suddenly wondering if there are more elegant ways to transfer the throttle pedal movement to a potentiometer. Are sliding versions with a spring common in EV's ?
 
#56 ·
Glad to help. The revolt controller can be programmed to accept many different throttle pots via rtd explorer. For example my bmw throttle body ranges from 1.3k to 4.5k. Depending on the igbt you choose I'd recommend using 8khz switching frequency and use a miller clamp diode / resistor setup on the gate resistor to aid turnoff and reduce switching losses.
 
#57 · (Edited)
I was actually looking at the TD350 IGBT Driver IC for protection, optimization and to overcome the Miller effect. The RTD explorer was already installed on my laptop :) I calculated this igbt could handle higher frequencies, but to avoid the skin effect I will keep it lower. Mainly again because you told me before that the noise would hardly be hearable *smiles*
 
#58 ·
oohhhh

I can't resist sharing the little milestones with you all :rolleyes:

The controller-board is working nicely now, just had some silly problems with the usb-RD232 converter. When I first installed it, it connected to COM4.
When I had the board connected a while later and configured the RTD-explorer to the same port again it never got a connection. Afterwards it turned out that if my cellphone was in the neighborhood of my laptop it connected that through bluetooth and simulated COM4 for that as well (even on 3 additional ports) degrading the usb-rs232 converter to COM8. aarrghhhh..

I finally got it all hooked up now, adapted the raw-throttle to a slider pot (I am running into an issue here with scrapyards, they have all their stock in databases now and when I don't give them a brand name of a car that has the parts I need like a throttle potentiometer for instance, they can't find me any part I am looking for (the modern era I guess :rolleyes:)).
Anyway, I did some testing with the IGBT and some of the diode's and capacitors which I finally recovered from the attic. No proper gate driver yet, and well.. I got some spikes already even without a heavy load, but nevertheless, I had to share it so ...

http://www.etlaare.demon.nl/throttle.wmv

Not enough light, but there is my slider-potentiometer and a running motor ...and my arm...

Without load probably using amps is not the best setup but I still had a big smile on my face and was demonstrating it proudly to my family.

I did not like the connectors too much, the one on the hall sensor as well as the one used for the rs-232 caused some minor problems already so I soldered them to the board and the sensor. I think I will consider integrating the usb-rs-232 in the housing of the controller too so I can use an usb-connector to hook up the laptop (or shall I add a bluetooth transmitter to avoid any connector whatsoever :D ?).

That reminds me I am slowly running out of budget by the way... but having an awful lot of fun nevertheless.

And indeed Jack, I now seriously need to look for a proper way to cool the IGBT, it got a little warm already even with hardly any load, ah well 50Amps is already quite a bit of course.
 
#59 ·
Good video. In terms of the scrapyards tell em you want a throttle body for a bmw 316 93 to 98. Easiest option as we know it works and at that age should be cheap. Cooling the igbts is easy enough i used a 300mm plate of 12mm thick aluminium and a pc case fan. Do you have dc bus caps? Are you running at 8khz? Remember an igbt has a reasonably high vce sat of about 2v so at 50 amps your disipating 100w:eek:. Also its worthwile incorporating the miller clamp with an extra fast recovery diode and resistor to reduce switching losses. Don't forget to have the thermistor connected to the heatsink for thermal monitoring and cutback.
 
#60 ·
Thanks Jack, I'll have a go with the BMW specs. The little Twingo will blush from pride at the end as it will also host a vaccuumpump of a Saab 9000 Turbo already. Which made me wonder is if the gold plated cooler of a MacLaren could make a nice way to reduce the temperatures of the controller.

And yes I found some nice 400V 4700uF Elco's that came from some old mainframe computer power supply. In the same box where some helium cooled core's (no idea why I ever brought these home ..) but it does not seem to make much sense to use them :rolleyes:. I go for the regular pc power supply fans I think.
I am still looking for a proper igbt gate driver to reduce the miller effect. It is all just bolted together a little snappy at the moment, but from here I will focus on a nice setup to construct it in a decent and robust way and then will figure out the best position for the temperature resistor.

ah, almost forgot the switching frequency question. Today it was still 16KHz, but I indeed intend to go for 8KHz by your recommendation.
 
#61 ·
* sigh *

waiting for parts atm... I will need a programmer to upgrade the firmware of the atmega168, ordered parts for the nice and small one Jack indicated here.

Still waiting for my power diodes, heatsink and some more capacitors to arrive ...

Ordered a tool to remove the ..ok.. I only know this in dutch so here's a wild guess... tie rod ball ... ?

ah well, at least I could take a picture of some of the parts that has to be put together soon for the final controller version.



Getting a little impatient to lower the motor into the car now the weather is improving. Would be so nice to drive silently in spring already... :rolleyes:
 
#62 ·
Looking well. You will however need a *much* bigger heatsink. Dont forget to have you dc bus caps as close to the power rails as possible to minimise inductance and keep the igbt gate terminals as short as possbile also.

Your building the little ponyprog circuit?
 
#63 ·
Thanks Jack and yes, I have a huge heatsink on order as well :) still waiting for it to arrive though.
When I am putting it together the caps (a ripple version will be added too) will be bolted as close as possible to the busses, but I really have to wait for the diodes to come in before I can do the final placements of all components. They will need to be arranged on the heatsink as well. The controller board will turn 90 degrees and be at the side of the igbt, so the gate connections should just be a centimeter or so.

And yes I ordered some missing components for the little interface You showed at ecomodder to the ponyprog program. The atmega168 I received still only had firmware version 1.7 installed and it turned out that in combination with a 168 that version could not bootloaded yet with the rtd explorer. In time I need my own programmer anyway, but for now it is just to get the latest 8KHz version of the program installed asap.
I hope to be ready next week after some final measurements to lower the motor inside the car, but maybe I am a little too optimistic there now.
 
#64 ·
bbrrr I am way too impatient to wait so long for parts coming in.
But finally the diodes arrived yesterday. Together with some fuses and a fuse holder, underneath is the little programmer I built during the weekend, with which I could finally test the controller at 8KHz PWM switching. I loaded firmware version 11b :) Now maybe one motor differs from the other, but with mine the brushes really make an awful lot of noise at 8KHz. It is a very annoying and loud beep I'm afraid which I am pretty sure the firewall will not reduce totally inside the car...
That will require some serious second thoughts ...

Anyway. I welded and painted the hoops to connect to the original engine supports. And should be ready soon to lower the drive unit in the car. The weather should improve a little for that as I should at least leave the garage door open to have the car with the hood underneath the hoist.


 
#65 ·
Like the programmer! and usb powered! very neat. Were you running the motor at 12v traction power for the 8khz test? I had the same issue with lots of "squeal" from the comm end but was much reduced at 24v and my recent tests at 48v I have to actually try to hear it.
 
#67 ·
Made an aluminum shoebox around the controller today.
Almost finished... At the back there will be 2 pc-fans to force some extra airflow. Crossing my fingers for a day with nice weather still, although I started to clean up the workshop as well in case I get too impatient...





The heat sink is 400x200x20 millimeters now Jack :)
And thank you for that hint about trying it at a higher voltage. It certainly reduced the brushes to vibrate. I think I will keep it at 8KHz for now. Ik had some problems with the connector I made. I think I did not center it properly when assembling it last time which caused one plate to bend a little. I don't think I will try to bend it back but am looking for a replacement frictionplate now. But then it turns out to be harder to find as I had expected.
 
#68 ·
Putting it all in a box make it look even smaller then it did before.

I'm surprised there is, physically, so little to it. Maybe I should get a kit and have a go at building one myself.

Well done.:)
 
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