openinverter forum

Maybe getting time to "blog" about this.

So I've bought I 2004 VW Touran with a petrol engine and I will convert it to a Nissan Leaf drivetrain. That is the motor, inverter, 2 batteries and various relays. Yes 2 24kWh batteries from 2015 Leafs for a total of 48kWh. Each "cell" will be doubled up and it ends up being a 4P96S configuration. A "cell" actually contains 4 pouches in 2P2S configuration. I have 90% decided against using the Leaf BMS because of the stupid centralized spaghetti wire topology. The cells are distributed too much throughout the vehicle to make use of it. Instead I will use a brushed up version of the Polo BMS, this time with one wire communication instead of infrared.

The controller is hacked with the open logic board of course, I will hook it up to the Touran "motor CAN bus" which already contains useful signals like throttle pedal and brake switch.

I will keep the original Touran 6 speed as mounting the Nissan tranny looked like a daunting task. Bolting together motor and transmission has been done before so I'll go that route.

When I removed fuel tank and exhaust a large open space became vacant, it will now hold 52 of the 96 cells. 8 more will go in the exhaust tunnel, 12-16 below the spare wheel leaving 20-24 cells to go in the engine compartment. As you can see there is a lot of space between hood and inverter.

Finally I have also 90% decided against the original charger and DC/DC converter. For a wimpy 3.6kW I think it's way to big and I will try inverter charging instead and also have a DC charge port. DC/DC converter can just be some Meanwell supply which should happily take the 380V from the Leaf pack.

Gosh, that is a questionable DIY blue wheel lifter. Maybe put a concrete block underneath it as battery weight increases.

I'm not worried about the lifters, I used them on the heavier Sharan with no signs of weakness. And they have a TÜV seal. Like that dam in Brazil

Now I started testing the new BMS slave boards and actually mounted it to the battery today.

• 4 channels

• 1mV resolution from 3.6-4V

• 10mV resolution below 3.6 and above 4V

• 30mA balancing current - balancing is done by programming a voltage set point

• 2mA active current

• 100µA standby current

• 1-wire fail-safe daisy chain bus (it is not dependent of software to pass through messages)

• Self-addressing

• Fully field up-gradable via boot loader

The bus is begun and terminated with an isolator module (first picture). I'm currently clocking it at 7kHz. The isolator is also a protocol converter with a text based protocol over RS485. You can have multiple isolators on the bus and they are also self-addressing. The current sensor module is on the same bus.
I've used that same topology on the Polo except the 1-wire bus (infrared in Polo). Also in Polo resolution is lower and there is no balancing.

Are you rolling your own BMS too?

Oddly enough I started the schematic for the cell modules for one today. Is 30mA going to make a dent for balancing with the large capacity of these cells? I was thinking of putting the resistors for balancing on a separate PCB, but switched from the cell module.

I did a 1-year test run with LFP batteries. Basically I charged and discharged two packs in turn, measured voltage curves, internal resistance curves, and balancing behavior.
What I can say for sure is that balancing is an extremely overrated topic and thus 1A (or more) balancing currents are over speced. What very basic BMSes do is engage big resistors at the charge end believing that something is then balanced. But in fact two cells at the same SoC will reach different top-end voltages due to differences in internal resistance. Messing around with resistors (or even active balancing) in that case is actually counter-productive.

What really disbalances cells are differences in self-discharge. So if you leave two cells at 100% SoC on a shelf for 1 year one will discharge to 90%, the other to 92%. Those 2% within one year is what balancing needs to make up for. That is very little charge.

As a check you will find that the Nissans stock BMS sports 10mA balancing current: http://www.electricvehiclewiki.com/wiki/bms/

Thanks, that's interesting.

I'm mostly familiar with high discharge RC hobby batteries which internally are basically dozens of cells in parallel. I guess there's probably more manufacturing consistency in batteries designed for EVs and probably most low discharge rate LiPos. I have noticed from watching youtube videos (mainly about leaf packs) that it is more likely that one or two cells will be low in comparison to the rest.

One of the more interesting balancing approaches I've seen is using a 'flying cell' to transfer charge between higher and lower voltage cells.

johu wrote: ↑Sun Feb 10, 2019 6:12 pm

I have started testing the new BMS slave boards and actually mounted it to the battery today.

Any plans to release your BMS boards ?

Yes if testing goes well I will be selling the boards in the shop. Open sourcing is also considered.
My cost will be dominated by the assembly fares (because low volume), so hard to estimate now. First offer was 10€ per board for assembly... So I'm currently using the paste stencil to hand-populate 120 boards
I'm hoping to have 24 boards finished in the coming days as that will allow me to test on the 99-cell rear battery pack of the Polo.

Will start a new thread in a yet not created forum soon.

this looks really interesting -how many cells will each board take ?

4 cells bms slave, that's written on the board.

I'm making very sophisticated plans for coupling motor and transmission. I will use my trusty jigsaw to make a 10mm alu plate that matches the transmission and on the other side bolt standard alu profiles to the Leaf motor. And then bolt the plate onto the profiles. I'm thinking 6-8mm wall thickness of the profiles should be sturdy enough.

The drive shaft *just* stays clear of the motor.

I have done just that in the past with no problems. Recently I have used a single 20mm plate but cutting it out to shape is a pain.

I had the same idea for the transmission plate on my Mazda some years back. And it works. You just make a template from some wardrobe back or plywood and translate that to alu plate. While you saw it with jigsaw get someone to spray some WD40 on the blade in regular intervals. It helps with alu sticking to a blade immensly!

I am less enthusiastic about those profiles. I dont think you will be able to get the center of both assemblies accurately that way. You have to get an accurate position of transmission center and make two smooth holes for guiding pins. There are two pins that lineup transmission with engine. Those pins allow you to attach the plate the same way every time. You have to carefully drill so transmission center and both guiding pins align.
On the other side motor has to meet the same center as transmission. So best way is by another plate (both planes align). You then have to worry only about center point.

Make sure you are alligning motor to transmission vertically with assembly out of the car . It is easier that way.

You could also cut the engine case behind the front bearing and get it to machine shop to be leveled with the front plane. Then you can even use the front part of the shaft and clutch.... Just an idea.

Thanks
Well if I tilt the profiles a bit I can actually use the existing guiding pins of the Leaf motor. Of course it can still twist but not shift.

I can use another set of guiding pins between the profiles and the 10mm plate.

The Leaf motor is slightly tilted to stay clear of the drive shaft.

Hello,

Also I'm on the way to join together Leaf EM57 and BMW E87 together. Specially for this we did digital measuring in XYZ coordinates. If anyone needs those info or dxf with coordinates - give some info in this topic. I will put them here.

damian.lo wrote: ↑Tue Feb 26, 2019 7:57 pm If anyone needs those info or dxf with coordinates - give some info in this topic. I will put them here.

I'd like to get a dxf with the measurements. Would save me some time and would likely be more accurate than my measuring tools.

Yes please do publish the info

johu wrote: ↑Tue Feb 26, 2019 1:48 pm Thanks
Well if I tilt the profiles a bit I can actually use the existing guiding pins of the Leaf motor. Of course it can still twist but not shift.

I can use another set of guiding pins between the profiles and the 10mm plate.

The Leaf motor is slightly tilted to stay clear of the drive shaft.

As long as it is tilted around longitudal axis .
That is why i recommend the second piece of adapter being an alu plate also.
1. You could assemble both parts easily if needed later on, even more if you use a male/female step in design
2. You also fit the motor exactly in center by using guiding pins
3. It is straight under loads unlike profiles.
4. It is easier to get a straight hole than with profiles

If you use profiles, you have to make good supports so that motor will not move/twist under loads.
If you cut off front part of the engine you still have to make something to fit the motor to.

A

Well, there is a problem with the front part of the engine... I sold it (I mean the whole engine). Didn't even drain the engine oil before taking it out

How you project going Johu,

Did you manage to connect up the Leaf motor, what coupler did you use in the end ?

Painfully slow progress. The shaft coupler is not ready yet neither is a battery in
Only thing I got done is a wooden mockup of the "face coupler". Bad weather and work on the new BMS has been holding me back but both is coming to an end

johu wrote: ↑Tue Apr 02, 2019 6:41 pm Painfully slow progress. The shaft coupler is not ready yet neither is a battery in
Only thing I got done is a wooden mockup of the "face coupler". Bad weather and work on the new BMS has been holding me back but both is coming to an end

Yeah, i still havent made any progress on Peugeot 406 either. But I know i have to move! I keep getting stalled by some troubles with inverter brain or other electronics.
If you have a problem getting coupler done, i can offer you our services. You would have to send the intended coupler part to me, but i would be able to bring you completed coupler at end of april...

I will at least try to assemble the charge pump by then.

A

Thanks for the offer but I think I'm getting close. I asked a very perfectionist mechanical engineer to help me and he makes a perfect coupler now. That takes time

Today was the first time I powered up the Touran system since I removed the engine and ECU. So: STOP! check engine oil pressure, check coolant and of course it noticed the missing head lamps
Even playing back a CAN recording from when the engine was still in didn't solve this so I'm thinking I just have to short out the oil pressure switch and put some resistor into the coolant sensor jack.

With the ECU disconnected it looks like the throttle signal disappeared from the CAN bus. Luckily everything else is still there, start signal, brake signal, cruise control signals. Apparently the throttle is actually connected to the ECU old school. So I either have to bring it to CAN or connect it to the inverter directly.

Made a wiki page with findings so far: https://openinverter.org/wiki/Touran_Conversion

Everyone please feel free to so the same. We can then collect these pages on a "vehicles" landing page.

That's an excellent idea. I have a boat load of information on BMW wiring and CAN. Just need to learn how to edit the wiki now:)