openinverter forum

Hey everyone!

Since summer 2020 I have been building on my Volkswagen Golf 3, which in fact is a original CitySTROMer. The first posts of this topic are gonna be a quick recap of the last 13 months. I've been updating on a Dutch Volkswagen forum since I bought the car, where you can see a lot of additional pictures.

http://www.volksforum.com/forum/showthr ... ge=1&pp=20





I bought the car along with its original 20kW motor, but without battery's. The original motor with Siemens inverter was functioning, until I needed to go to the RDW (Dutch vehicle authority) to import the car. At that moment the inverter stopped functioning and we needed to get a trailer.

After I was finished importing the car, I could finally start dismantling it.



This was the new motor, which I wanted to put in the Golf at the time. It was going to be driven by 2 Sevcon's Size6, and an original 02A (Diesel) gearbox.



The Golf was then upgraded with a much better VR6 drivetrain to cope with the weight and power.



We made a custom adaptor plate for the motor.



And then we put on a taperlock with tapped holes to fit on the flywheel.











Work on the batterypack started.



It was build using 1792 VTC6 18650 cells. There were paralleled 28 blocks of 64 cells, which gave it a nominal voltage of 103.6 volts. It had a capacity of about 19.4kWh.



The chargers were fitted.





Fitting the 2 Sevcon controllers to the custom made cooling plate.















Here came the first testdrive, which was in January this year.











Charging the car with 76A DC, 8.3kW.



At this point, the car was more or less finished. I was a little disappointed by the poor range (140 kilometer), the dissapointing performance (90kW) and the charging speed could have been better.

I decided I had learned a lot by doing this conversion, and I now knew what I had to do in a next build...

After driving the Golf for about 3 months, I decided it was time to rip out the 90kW motor. It was time for something better...



First, I needed to test if the Tesla LDU fitted inside the engine compartment.



I needed the reversed oil pump from Zero-EV.



This is the new charger, a 22kW Brusa.



The LDU drop-in board.









I then started working on the new batterybox and motormounts.















The reversed oil pump was also put in.















This is, at the moment, the current state of the project. I am now waiting for 2 custom made driveshafts.

Really nice, reminds me on my first Mazda conversion.
Where did you get 22kW Brusa? Are they still available?

tnx

It's the newer NLG664 model.

https://www.brusa.biz/portfolio/nlg664/?lang=en

I know someone in Germany who has a few of them. I think he still sells them for about 2.5K.

Nice conversion, very clean! Love that there are so many detailed pictures in this threat!

Great read. I’m interested how you get on with the battery pack. I’d love to upgrade the batteries in my Porsche but it’s hard to find the right solution due to space/weight constraints.

Zapatero wrote: ↑Thu Sep 16, 2021 6:01 am Nice conversion, very clean! Love that there are so many detailed pictures in this threat!

Thank you!

Boxster EV wrote: ↑Thu Sep 16, 2021 8:55 am Great read. I’m interested how you get on with the battery pack. I’d love to upgrade the batteries in my Porsche but it’s hard to find the right solution due to space/weight constraints.

With the previous conversion, I chose to build a custom made, custom sized battery pack to completely utilize the space in the original batterybox. With its 19kWh, the range was so disappointing that I wanted to maximize the size of the new battery pack. Therefor, I started with ditching the original batterybox so I could make a custom one. With the 3 large Mercedes battery packs in front and 3 of the same in the back, every millimeter of space is completely utilized. It's just coincidence the battery's fit so snug together.

The battery's are 11kWh each. With 6 of them, the total capacity is about 67-68kWh. The previous conversion used about 12.5/13kWh per 100km. The calculated range should therefor be about 500-530km.

I was aware of the extreme currents the LDU can draw from the battery pack, so before I chose these types of battery's, I did some extensive testing with al available packs.

On the picture, you can see a very big 20kW resistor which is connected to the battery with an IGBT and contactor for redundancy.



With an oscilloscope, I plotted a graph to measure the voltage sag when closing the IGBT.



With those measurements, it was possible to calculate the internal resistance, and thus the voltage sag at even higher loads.

We concluded that the battery pack should have a voltage sag of 62.9v when fully charged (403v), when a current of 1400A is drawn. Quite promising I think.

Interesting stuff. What model Merc were the batteries salvaged from? What are your plans for BMS and cooling?

The batteries are new, originally for a Mercedes EQA.

I've already made a schematic for the heating and cooling. I'll be using the Tesla 3-way valve to control heating/cooling for the batteries, and the Tesla 5kW heater for heating the interior and the batteries in series. This way, I can even set the valve to "heating", but keep the heater powered off to use the battery heat to warm up the interior.

Awesome battery box!

RetroZero wrote: ↑Mon Sep 20, 2021 6:16 am Awesome battery box!

Thanks!

Fabricating a lid for the batterybox that doesn't touch the bonnet is gonna be a little bit challenging, but it was the only possible way to fit all 6 of the batteries.

You're lucky. I have to respect original weight of the constructor. Not going to get much under the bonnet or in place of the fuel tank, but will maximise all available space.

Because it's an original CitySTROMer, which had 520kg of lead acid batteries, it's allowed to weigh 1410kg. That's a lot more than the ~1100kg of a normal Golf mk3.

I don't know why it was allowed to have that much more weight, since it's still the same chassis overall. I'm hoping the new weight of the car is gonna be in the 1350-1400kg range.

If you can publish the registration documents which show allowed weight for the car and individual axles, and if it's possible to get an official list of the suspension and brake part numbers from somewhere, it might be possible to upgrade the weight of Golf 3s in some countries. That would be interesting.

I think here in Finland it might be allowed. They might also require documentation regarding to whether or not the chassis was reinforced at some points and you'd have to modify it to match. Is there any information about the chassis compared to the regular one?

Very good point. However. I'll stick to original as much as I can. Don't need to piss off French administration . Weight wise, I calculated approx 120 kg of battery. Looking at you setup, that's 1. 5 EQC modules. A worry for me both in range and nominal voltage of 300vdc

celeron55 wrote: ↑Wed Sep 22, 2021 1:59 am If you can publish the registration documents which show allowed weight for the car and individual axles, and if it's possible to get an official list of the suspension and brake part numbers from somewhere, it might be possible to upgrade the weight of Golf 3s in some countries. That would be interesting.

I think here in Finland it might be allowed. They might also require documentation regarding to whether or not the chassis was reinforced at some points and you'd have to modify it to match. Is there any information about the chassis compared to the regular one?

That would be a little bit difficult. The mk3 CitySTROMer was produced in such a limited quantity (120 cars) that documentation is very scarce.

RetroZero wrote: ↑Wed Sep 22, 2021 5:44 am Very good point. However. I'll stick to original as much as I can. Don't need to piss off French administration . Weight wise, I calculated approx 120 kg of battery. Looking at you setup, that's 1. 5 EQC modules. A worry for me both in range and nominal voltage of 300vdc

The batteries seem to be EQA packs, not EQC. Each 16S 188Ah pack weighs about 55kg.

EDIT;

The 19kWh 18650 batterypack I've build for the previous motor in the Golf weighted 115kg.

Thanks for the info

Golf_mkIII_E wrote: ↑Sun Sep 19, 2021 8:28 pm The batteries are new, originally for a Mercedes EQA.

I've already made a schematic for the heating and cooling. I'll be using the Tesla 3-way valve to control heating/cooling for the batteries, and the Tesla 5kW heater for heating the interior and the batteries in series. This way, I can even set the valve to "heating", but keep the heater powered off to use the battery heat to warm up the interior.

Fun project! How are you controlling the Tesla 5kW battery heater? As I understand, it is HV PWM controlled.

Any chance you could link where you got the Merc EQA batteries from? Interested to use them myself and it wont let me PM you

Thank you for sharing your hobby project with such a good quality! I checked this volksforum thread also, your workmanship is top quality. I like how you make all the metal parts and welding work. I see that you are also good at elecronics. Didn't you consider smaller drive units? Even Leaf motor would have been good enough for this car. Isn't this motor overkill to this small and light FWD car? You will spin both of the tires on every start. Your steering wheel will shake and rattle all the time you push the throttle even a little. I have driven heavier car then yours KIA e-Niro 150kW and 400Nm factory production car even it felt like too much torque for FWD, you will get much more - this is crazy.
Battery that you use is very interesting, would you like to share where to get those modules and what is the price? Do these modules have inbuilt BMS and can you read their data?

If you are looking for these EQA 16S modules, I currently have 6 for sale due to some change of plans. You can contact me by PM.
They have nicely integrated watercooling. Celltap-connectors included, no BMS.