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Conversion of a VW POLO with an AC industrial motor

196179 Views 344 Replies 33 Participants Last post by  cts_casemod
Welcome to my conversion of a VW POLO into an electric car.

The car is an ongoing project, started in August 2011. DVLA registered on February 2013.
The current power is 30HP nominal with 40HP peak (Motor limited).
This is an ONGOING project. Check back often!!​


  • How to use a standard, cheap, Induction motor to power your EV (Including voltage changes);​
  • All you need to know to modify an industrial VFD for high output and closed loop EV Use - Shown in the topics, fool-proof guide to be added by summer 2014!​
  • Using a cheap server power supply as your DC-DC converter (modifications to operate as a true CC supply by June 2014)​
  • Universal voltage charger (Capacitive/Inductive Based) - Cheap way to charge. Superseded by PFC charger however Ill make sure to have one of these as a backup ALWAYS.​
  • Advanced 3KW PFC corrected charger (1.5KW version by Feb 2014, fool proof guide by summer 2014!)​
  • Closed loop control using industrial automation control (On tests, details shown on last controller rev)​
  • Corsa B/C EPAS (Electric power steering) - Details/Pinout on page 30. Modifications to fit the Polo somewhere before (Feb 2013?)​
  • Battery monitoring using a cycle annalist and android app (Hopefully by Feb 2014)​
  • On-Board Backup generator - 3KW (Summer 2015)​
  • Efficient heat-Pump Heating and cooling (Planned!)​
  • Full Stand-alone EV Grade Inverter/Charger planned to be released by 2016​
  • Xenon (Low/High beam) and LED (DRL/High Beam) custom headlights - Tired of Chinese crap and glaring other drivers? (March 2014!)​
  • Solid State PWM heater control Pag. 30
  • VW Gearbox Adapter for 020 and 02a Pag. 30 Its not compatible with the front mount on the golfs, but that should be easy to change. Dimensions are correct to +/- 0.20mm. Other cad files are available by request. feel free to comment and make some changes.​

Other future projects are reverse cycle air con for efficient heating/cooling and interface to an on-board removable the generator.

The topic will be upgraded with more information as the project goes on, so keep checking.
The project was designed on a budget, never compromising safety. Critical parts were thought during quite some time and there are attempts which are not presented here for simplicity.

Efficiency was one of the key components, hence an AC setup together with a latest generation LIFePO4 battery pack. At some point (2016) I plan to take this project to OEM grade with a dedicated controller. Much of the hardware is being tested right now, the missing bits is some kind of interface between modules and the VFD fully replaced by an intelligent controller.

Update: As of Summer 2013 I started rebuilding the car. Higher Voltage battery pack, On-Board PFC Charger and new engine mounts are the main changes.
Final voltage was decided as 410V Nominal (320-500VDC) for several efficiency and safety reasons.

Details about public charging Stations will be provided soon, for those in the UK (Should be similar to other European countries), since the main pack is now on-board and I'm not lucky enough to have off-road parking.

Why convert to electric!?

A commonly asked question...​

On my particular case I will have an investment return due to cheaper insurance and no road tax (£240Year). The savings add up if the fuel cost (£20 instead of 60/month) and maintenance (£100 less each year in oil, coolant, filters, etc) are taken into consideration, and should help make for a better car with features such as air con, instant heating for winter and availability of mains power (230VAC or 400VDC) from the battery pack, saving me to carry additional equipment I often need (Generator, inverter, battery packs...)​

The project will continue slowly as i add updates. The whole setup was built from scratch to my individual needs and as such a lot of time effort and testing is required. Like many I have limited availability, hence progress will be split into several tasks over the course of a few years.

I hope this project is a good inspiration to all those that are thinking in retrofitting a vehicle to electric. You will be able to do your own repairs, which to many people can be a saving on its own considering the prices garages charge and many times the poor workmanship provided (I've been a mechanic myself for over 6 years, gave up due to stress/time/quality related issues and I am taking an engineering degree now).​

If you like the topic and find something useful, please add to the rating on the top right corner.

(Original topic - Aug 2012)

Hi Everyone,

This topic will be for the conversion of my 99 VW Polo.

This Car will have an Industrial Ac Motor with a peak of 20KW. It will be driven in city to commute and the target is to have a minimum speed of 25 Miles over hills and a Maximum speed of 40 to 50 miles per hour with a range of 25 miles.

Yesterday, after driving 450M I got the motor, so my conversion is officially started, but I will probably take a year or so to convert.

Here are some pictures of my new motor:
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I will post a Video of the motor spinning. I have just tested it on all phases (I am using single phase power) and it works lovely!

I am planing to use this crankshaft end attached to the motor, however I haven't seen no one doing it this way. Is it just because no one has one or is the steel to hard? The guy on the engineering shop told me it would be fine :confused:

Yes, I plan to keep the clutch, this is my first EV conversion, if I find I don't need it I may later take the flywheel off.

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Also part of the work was to re-tidy the wiring and re-enable the EPAS. It doesn't bother me much to drive, but parking can be a bit tedious at times.

Here the user interface board that converts the analog signal from the electronic throttle to a current source.

The inverter can detect open/shorted/out of range values. At the time I was in a bit of a rush so I skipped the Electric power steering and the isolated tachometer outputs the old system had. That means the cycle analyst is just working as a amp meter. Mileage is not recorded.

In the meanwhile, since I haven't done so in the past, here's a handy circuit to drive the EPAS

Original Full size image here:

Small prototype board with the circuit components for the EPAS:

The clocks are generated by an attiny 13. A main clock is set to 35Hz to simulate engine running. The secondary clock sets the assist power.
The default programmed values go from 55 to 218Hz. The correct range goes all the way down from 0, but I found the steering too sensitive.

LED1 blinks to indicate the circuit is working. There is a 3second delay from the moment ignition is turned on to the moment the EPAS is activated. This is to allow the DC-DC to start first.

The 2 NE555 chips are just a push pull buffer to output a nice 12V square wave. Output current is limited trough a 47R Resistor, just in case.

Diode D1 creates a virtual GND as the 555 only resets below 0.7V. I Think the trigger input could be set for this but haven't quite checked yet.

Regarding the Attiny13:

The attiny can be programmed in seconds and costs pennies. It also allows a startup delay that the 555 would not and can disable the EPAS if the voltage goes to low (Not implemented).

To program, the Arduino Environment can be used with a AVR MK2 ISP or a USBASP programmer. The Attiny13 files are required to add support, which can be easily find online.

Programming is done in AVR GGC style. Code Below:

/* EPAS CONTROL UNIT - Open loop, manually adjustable feedback
 * Designed by C. Silva - Acessory & user interface PCB's - The Electric VW project (2012-2015)
 ** December 2015 **
 * ---------------------------------------------------------------------------------------------------------------------------------------
 * ADC inputs:
 * Analog potentiometer. 0 to VCC, 128 levels.
 * Outputs:
 * Output 1: Engine Running signal, SQUARE WAVE, 35Hz
 * Output 2: Power steering assist level. User adjustable from 55 to 218Hz
 * Output 3: Blinking Indicator

  //Define CPU Clock, to correctly set up the delay function
  #define F_CPU 1200000    // 9.6MHz with CLKDIV8 Fuse Enabled = 1.2MHz
  //Atmel delay function
  #include <util/delay.h>
  byte adc = 0;       // Variable to store ADC result
  // byte output = 0;    // Used to delay EPAS startup
  uint16_t i = 0;     // Variable to store count value for non blocking delay

// ---------------------------------------------------------------------------------------------------------------

void setup() {

  DDRB |= _BV(0); //Make (PB0) an output        // Engine running indicator output
  DDRB |= _BV(1); //Make (PB1) an output        // EPAS control Output
  DDRB &= ~_BV(2); //Make (PB2) an input        // ADC for user selectable assist level       
  DDRB |= _BV(4); //Make (PB4) an output        // Blinking Indicator
  SREG = 128;                                   // Global Interrupt Enable
  TCCR0A = 0;
  TIMSK0 = 0;                             

  //ADMUX |= (1 << REFS0);                      // Set ADC reference to AVCC
  ADMUX |= (1 << ADLAR);                        // Left Adjust the result 
  ADCSRA |= (1 << ADEN);                        // Enable ADC
  ADCSRA |= (1 << ADIE);                        // Enable ADC Interrupt
  ADCSRA |= (1 << ADSC);                        // Start A2D Conversions  

  // PWM Configuration
  // Pag 78 Datasheet, Table 11.3 - Fast PWM (32KHz)
  // OCOA/PB0 - Non Inverting Mode, Clear on Compare match, Set on Bottom
  // OC0B/PB1 - Disconnected, Normal I/O operation (This is toggled by software inside the COMPB Interrupt)
  /* The overflow flag is used by the damm arduino compiler, so without changing registers
  and going crazy we can use hardware PWM as alternative to create a fixed frequency sq wave*/  
  OCR0A = 128;                 // Set Duty cycle = 50%
                               // This is a 73.42 Hz signal to enable the EPAS (AKA Engine Running)
  TCCR0B |= 1<<CS01 | 1<<CS00 | 1<<FOC0A;  // Prescaller = 64, therefore clock = 73.24Hz/2 = 36.62Hz
  _delay_ms(4000);  // Wait 4 seconds for the DC-DC Converter to boot up and voltages stabilize.
  // Enable the EPAS, by turning the PWM square wave signal output on.
  TCCR0A |= 1<<COM0A0 | 0<<COM0B0 | 0<<WGM00;  // SET WGM00 FOR OPERATING MODE. 0 = NORMAL, 3 = FAST PWM, ETC    
  // output = 1;                  // Wait for voltages to stabilize before enabling the EPAS  
  TIMSK0 |= (1 << OCIE0B);                      // Enable COMPB Interrupt

// ---------------------------------------------------------------------------------------------------------------

// the loop function runs over and over again forever
void loop() 

// ---------------------------------------------------------------------------------------------------------------

  // Select ADC3 (PB3) - Pag 135 Datasheet
  // Let Justify the result (8bit reading)
  ADMUX = (1 << MUX0)|(1 << ADLAR);

         DEFAULT PRESCALLER = 64 <-> 9600000/8/64/256 = 73.24Hz
         OUTPUT toggled on each cycle, therefore 73/2 = 36.62Hz
         The 8 bit ADC reading is shifted once, giving rise to a 0 to 127 read.
         Chose the minimun frequency value = 170
         9600000/8/64/170/2 = 55.14Hz
         Choose the maximun frequency value = 170-127 = 43
         9600000/8/64/43/2 = 218Hz
  adc = (170-(ADCH>>1));     
  ADCSRA |= (1 << ADSC);     // Start A2D Conversions 

  // Togle Pin 
  PINB |= _BV(PORTB1);       // This is the speed signal for the EPAS, to set assit power level
  OCR0B = (OCR0B+adc);
  //Set up a non blocking delay
  if (i>255)
      PINB |= _BV(PORTB4);   // Blink a LED to indicate operation   
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There are many advantages to move outside an urban center, including the fact I can now charge the car at home, conveniently.

The 1.5KW charger is not an issue anymore, and charging during off-peak period from any available 13A socket costs pennies.

The only issue here is whenever the 35 miles on the tank are just not quite enough and with most driving being motorway or equivalent, they go quick!

80% of the cases one has to make a de-route of at least 10 miles to charge and the 4 charges required to travel 116 miles, for example, turn into 6, with a total just above 150 Miles. Quite frequently I also had to pay to charge in private car parks, despite being a member (and paying already) for the charging scheme.

The local charge point company
has done an absolutely fantastic job in convincing me to use the diesel car instead. The 3 charge points within a 30 mile radius are often unusable, the phone app doesn't work as it should and now they charge £1,20 for charge where most charge units have a 2H park restriction. Hum... Now petrol starts to make sense, specially because I dont want to pay full insurance for a car and have a need a second.

Anyway... Back in summer 2013 I actually bough a generator, but the plans to install it were scrapped...

This unit is a variable speed, variable frequency generator, capable of supplying 3KW with a typical rectifier PF of 0.7.

Charging is as simple as controlling the alternator field, which even leaves the charger free if I need to plug to an AC supply to top up at 4.5KW, for example, where timing restrictions apply or I want to make a long journey in a reasonable amount of time. Ah... the wonders of an hybrid :)

Here's a video of the thing actually working:

I should start this work in late January
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The generator video doesn't work. Youtube says it's "private".

I'm designing the ability to use a generator in to my conversion as well. I'm expecting it'll either take the form of a trailer or (if it's light enough) mount to the back of the car on a tow hitch. It would only be installed for long trips.

The steering failure is terrifying! I would have expected that steering columns would be designed to work indefinitely if the power steering fails.
The generator video doesn't work. Youtube says it's "private".

I'm designing the ability to use a generator in to my conversion as well. I'm expecting it'll either take the form of a trailer or (if it's light enough) mount to the back of the car on a tow hitch. It would only be installed for long trips.

The steering failure is terrifying! I would have expected that steering columns would be designed to work indefinitely if the power steering fails.
Fixed the video :)

The good thing is that if failed progressively. I started noticing the steering slipping at certain angles on the last 80 miles. Hopefully serves as a warning to always double re-evaluate what is already there when making modifications.

That's a good idea, if only I had the tow bar I would be doing one myself with a cheap small car engine.
A three phase alternator is a must, it can provide near DC output and be started from the battery pack. I'm still working on that for this one.
As promised, I started to perform the tests with the generator.

Nearly 3 years later I had to do a full service, the carburetor was full of rubbish and the engine stalled randomly. I also got a bad arm from pulling the cord. That's a 200cc engine with a PM alternator! I am happy to say that it now idles fine and can feed a 600W load with a DC output of 250V. Very silent too (well, at that power, at least!)

But, as always, this did not came without another new set of problems.

Much to my surprise the alternator is a permanent magnet type. So in practice, the only way to regulate the output voltage is either by loading it or changing the engine speed using the throttle, which is far too slow to avoid some 500V peaks when a load is suddenly removed.

Since DC doesn't have the dead times associated with a sinusoidal supply the charger output nearly doubles for the same input current. So for the time being the thing simply stalls the motor or makes it run very unhappily.

So the solution is to reduce the peak current rating, as to get the same 1500W with the higher average voltage. Problem is, this will reduce the charge rate from a 230VAC supply, so I'm investigating the easiest way to have both...

The cool thing about this is that once the optimum current is set, I can simply vary the engine speed to obtain more or less charge current. So I can bump it to at least 2KW or I can idle it at 500W, as required.
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