openinverter forum

Hello friends of the electric drive.
I discovered this forum while researching the Leaf motor and, like many others, would now like to present my personal project. I am fascinated by how many enthusiasts are out there who want to convert their own special vehicle. I would like to use the forum for inspiration and learn from other members' solutions for my own conversion.

About the project:
The vehicle is a Barkas B1000 built in 1975. These cars were built from 1961 in the former GDR in East Germany as fast transporters. My vehicle was a fire engine in its 1st life. I would like to equip the Barkas with an electric motor and drive it for the next 40 years
I want to use the Leaf EM57 motor. However, the inverter will probably be based on the ID4 front-wheel drive and will be mounted on the Leaf motor with an adapter plate. I would like to do this for the following reasons:
-The ID4 inverter already has an integrated EMC filter
-The power modules are currently still being produced and further developed and are available as IGBT and SiC variants
-The inverter uses 3 current sensors for the phase currents

The motor should not simply be flanged to the existing gearbox. I want to remove the differential from an existing Barkas gearbox and put it in a newly manufactured housing. The manual gearbox and clutch will therefore be removed. The gear ratio of the differential is 5.2857. The maximum speed of the engine is to be limited to 4500 rpm. This corresponds to around 100 km/h. The maximum torque should be around 300 Nm at the motor and I want to limit the maximum power to 40 kW. This means that the drive is 4kW above the maximum output of the original engine, but slightly below the maximum torque of 350 Nm in first gear.

My background:
I have a doctorate in engineering in the field of power electronics. I can design circuit boards and program microcontrollers. I also like classic cars and enjoy working on old machinery in my spare time. Like the Barkas I am from the East-part of Germany.

The timetable:
It should be legal on the road in 2027. That could certainly be achieved sooner, but with a house and two small children, it's a realistic compromise. I also want the vehicle to be exactly how I want it to be.

Current status:
The vehicle has been completely dismantled and the chassis and bodywork professionally blasted and primed. Repair work is currently being carried out on the bodywork. After that, I will continue with filling, sanding and painting. At the same time, I am developing the drive train. I have the motor and inverter on hand. I replace the driver board and the control board of the ID4 inverter with an own development. This will be followed by testing and measurement on the test bench.

I will report my progress and findings here from time to time.

Many thanks for your interest,
Florian

I'm very much looking forward to this project, the Barkas is awesome

Here are a few more pictures of the ID4 front inverter. This drives an asynchronous motor and has a rated output of 80kW. The IGBT power module FS660R08A6P2FLB is used together with the LEM current sensor HAH3DR 660-S07/SP2.
Here is a comparison of the housing sizes between the Leaf inverter and the ID4 front inverter.

Wait a second.. you know that a mismatch of Inverter and Motor, which is your current plan, will possibly be an issue for the TÜV?
The currently practiced regulation says that you don't need EMV tests for matching motor and inverter, because that already has been certified. However mismatching combinations have not yet been certified and therefore need to be tested.

Or do you have access to an EMV Lab, being a Dr.Ing. for power electronics?

1975 is way before 2002!

You're right, an EMC measurement is necessary in this case. However, as you rightly suspect, I have a good contact with a nearby EMC lab. I have already discussed this with the director. However, in the case of a private conversion, a relatively simple and quick measurement of the radiated emissions is sufficient. My advantage is that the director also used to drive a Barkas and also thinks the project is great

Cool project.
So is the plan to do an open inverter control board for the front ID4 inverter?

I would like to adapt one of my existing control boards. With a corresponding circuit to read out the Leaf resolver. So far I have only had experience with encoders. I program on the C2000 series from Texas Instruments. I would like to continue this in the future because I am very familiar with the special features of the microcontrollers and the registers. However, I will be happy to make the schematics available to the community after completion.

Small update: I have finished designing the replacement driver board version 1 for the IGBT module. Piggybacked onto this board are SKYPER 12 R drivers from Semikron. I also managed to remove the original driver board, which was pressed on using a press-fit connection, without damaging the IGBT module.

BarkasFlo wrote: ↑Tue Aug 20, 2024 6:31 am However, I will be happy to make the schematics available to the community after completion.

That would be very much appreciated.

After testing and function verification i will keep my promise.

The adapter boards arrived today. After a short moment of tension, the certainty that all the holes are in the right place

Just out of interest, is there a reason why the board is so large and not limited to the mounting holes and connection pins? Because of the shielding?

To the phase output side it is so large because of the mounting of the current sensors. On the DC-side i could have spared some millimeters, but it was easier and quicker in the design process to just make a rectangular shape. And the cost of the PCB isn't increased very much. I think it also helps with the shielding, but that wasnt the reason for the design.

Is there a reason for not just using the pre existing driver board?

Reverse Engineering of the Schematic of the existing driver board (Parts, Connections, etc.) is way more complicated for me than just design an equivalent driver board. Some ICs don't have a part number and i don't have a x-ray machine to follow the signal traces.

Ausgezeichnet ! As a former Wartburg 1.3 driver I love this!

After some time has passed, I would like to get back to you with a basic update.

In the meantime, I have had the opportunity to talk to someone who has already converted a Barkas to an electric drive. He used a system from the company Fleck GmbH (https://www.fleck-elektroauto.de/). The company mainly uses industrial drive technology and the on-board voltage is limited to 96V.



I wanted to know whether it is possible to drive up to the maximum speed of 100 km/h with the original gearbox in 3rd gear and whether he has any experience of wear and tear with higher torque in 3rd gear. I don't want to build an electric car where I still have to use the clutch and shift manually and had considered permanently engaging 3rd gear in the original gearbox. After a nice phone call, however, he advised me not to let 3rd gear rev up so high, as it gets very loud in the vehicle from 80 km/h upwards. He then shifts to 4th gear when driving at higher speeds. The load on the gearbox is significantly lower due to the even torque of the electric motor, but Barkas gearboxes are not known for their high mileage. He advised me to look for old Passat gearboxes. These also fit well in the frame of the Barkas and are significantly better in terms of mileage and torque resistance.

After thinking about it for a few days, however, I was not satisfied. A lot of adjustment work, a lot of unnecessary weight (most of the manual gearbox is not needed at all) and the efficiency of the drive system doesn't get any better either.

So I started to measure and compare which e-drive I could possibly install directly in the Barkas. Unfortunately, the entire construction of the frame is designed for a lengthways motor and is not very suitable for a typically transversely mounted e-axle. However, there is one candidate that would probably just about fit, the ID4 front-wheel drive, respectively the front-wheel drive of the MEB from VW. Here are a few pictures of the test placement.
The drive unit has to be tilted by about 13° so that the mounts for the drive axles move far enough back and the drive axles do not collide with the bumpers. I still need to investigate whether this could cause a problem with the oil circuit, but I am slightly optimistic.

Using the ID4 inverter on the ID4 motor is obviously easier than adapting it for the Leaf motor. However, I would have preferred to use a synchronous motor instead of an asynchronous machine. Nevertheless, in terms of overall weight, efficiency, installation space, adaptations, spare parts supply etc., this seems to be the best solution.

Even though I know nothing about Barkas, it seems to be a front-wheel drive with a longitudinally mounted in-line engine and a gearbox behind the engine. The frame is narrow in the area of the drive shafts and widens towards the front. A Tesla Model3 engine should fit. It is originally mounted in front of the rear axle. The Leaf motor is also in front of the axle.
ID4 is of course also good and apparently you already have it. Incidentally, I think your project is good because you're not trying to get the cheapest possible electric car with scrap parts, but are building what you really want.

Yes, that's right. The Tesla Model 3 motor could also be a good fit, even if it would certainly be bored with my 40 kW drive requirement .

Progress has also been made with the driving of the IGBTs in the MEB inverter. I have assembled the adapter board and installed it as a test.
To do this, I had to cut away about half of the intermediate base in the inverter, as the driver board is higher than the original. (I was already aware of this during the design process). The next step is to design the control board with microcontroller, CAN interface and resolver interface to test the driver board. I will try to tackle this as soon as possible.

There is news again. Since my last post I have designed a control board, which is now manufactured and assembled. It fits well into the inverter housing and is already connected to the encoder and temperature signals from the motor and the DC voltage measurement. The biggest challenge here was developing the control circuit for the encoder and I'm curious to see if it works. I want to test this over the next weeks.

Small status update: Resolver excitation and position measurement is working.

Impressive design work!

The inevitable question: open source? Did you do it from scratch or kindof OI based?

Thank you!

I based the excitation on a design suggestion from TI. However, I have adapted my circuit diagram slightly and will be happy to share it here. As a driver for the excitation winding, I used the ALM2402 circuit, which is advertised for this purpose. After some research, I found out that most automotive resolvers are driven in the 10kHz range. This fits very well, as I also want to pulse the IGBTs at 10 kHz and I can therefore synchronize the PWM for resolver signal generation with the IGBT pulsing. The PWM signal passes through a 2nd order low-pass filter so that a relatively sinusoidal curve is created for the excitation voltage. One thing to note here is the phase shift between the PWM signal and the sinusoidal signals of the sin/cos tracks. According to oscilloscope measurements, this is 20µs. This must be taken into account for the ADC sampling of the voltage maximum.