[DRIVING] VW Touran powered by Nissan Leaf [FINISHED]

[uhi22]

Huber Suhner CCS plug

Sorry I had it wrongly in mind. Lot of distance until the knee.

[johu]

And here is an early forum release

[MattsAwesomeStuff]

The amazing Dan Gelbart, in his MIT Prototyping for Engineers class he filmed but had the plug pulled on him, says that people who do R&D spend so much of their career doing and undoing fasteners, that you should use cases with keyholes and slots and spot welded captive hardware as much as possible because of how much time it saves. He says you'll spend about 1 year of your life doing and undoing fasteners, which is the same amount as your life is lengthened by proper exercise and diet, so eat whatever you want and just make sure you use captive hardware and it's the same quality of life difference but much simpler

Dunno if your battery box was thick enough to tap holes, or if you could weld or epoxy nuts on the far side (maybe plus tapping the case holes), to not have that issue of being unable to disassemble it later.

...

I complain about my lack of garage and having to borrow people's garages to get work done, and here you are out in the snow under your car. That would sap my motivation so quickly, bitterly cold aluminum on my fingers, wet and cold.

[johu]

Dunno if your battery box was thick enough to tap holes, or if you could weld or epoxy nuts on the far side (maybe plus tapping the case holes), to not have that issue of being unable to disassemble it later.

The battery pack came with some self-tapping bolts. These hold on amazingly well even to the 1.5mm side angles that I used for fastening the side walls. And in the 3mm main box anyway. But yes I emptied 20 Makita batteries into this project

I complain about my lack of garage and having to borrow people's garages to get work done, and here you are out in the snow under your car. That would sap my motivation so quickly, bitterly cold aluminum on my fingers, wet and cold.

Got used to it over the years. At least I get to breathe some fresh air contrary to sitting in front of my computer.

[arber333]

He says you'll spend about 1 year of your life doing and undoing fasteners...

I noticed German/EU engineers obviously spend several years with fasteners. I remember we studied them to the hilt in my engineering days .
Now with all those slots and buttons bolts are becomming obsolete. However just try to reuse those snap fit things, they will ruin your day...

Myself i tack weld nuts under the steel boxes all the time. It is really easier on my fingers when i need to assemble that...

[johu]

I just drew up my 12V ratsnest for my own reference and thought I should share it here

I have two charge ports because as of yet I was too lazy to wire up the AC part of the CCS port to the OBC. Might change later.
I use the PP pin of both ports to pull down 12V and thereby turn on a PMOS. The various circuits are diode-ORed with 5A Schottky diodes.


Use cases
CCS charging
Turns on

• CCS controller via Q1
• VCU in charge mode via D6
• BMS via D4

AC charging
Turns on

• Coolant Pump, OBC, heater inverter allow, and contactors 12V side via D5
• VCU in charge mode via D3
• BMS via D3 and D4

Driving
Turns on

• Coolant Pump, OBC, heater inverter allow, and contactors 12V side via D1
• VCU in drive mode
• Inverter

When the VCU sees drive mode and charge mode at the same time it will lock out drive mode. The heater inverter 12V supply is also powered in AC charge mode to allow drawing AC power from the car without actually turning key-on. A granny charger plugged in at the car end is enough to enter AC charge mode.

The contactors are not enabled in CCS mode because the CCS contactors branch off before the "car" contactors.

[DVD3500]

Did you use some special software to draw the "ratsnest"?
I am redoing all the wiring on my project from scratch and looking for options...
Thanks!

[johu]

Did you use some special software to draw the "ratsnest"?

Not super special KiCAD

[johu]

What I should have done: make a lid for the BMS box

with the battery already in the car. Not fun.

So what I did instead

Aeromods!

Closed of the two ducts for brake cooling because who needs that when you have regen. And also the duct for transmission cooling. And finally cover the complete underbody rather than just half of it like to stock undertray. Oops. left a little hole. Will close later.

I might also buy moon disks that completely close off the wheel to further reduce turbulence.

[johu]

Time for some software refinements: https://github.com/jsphuebner/stm32-car ... a5f11da36d

I have rearranged the code to explicitly run a state machine rather than in-transparently jumping between states. Now I can transition from drive to quick charge and back to drive (when cable removed) without restarting the car.

I also started refining SoC calculation a bit more. Problem: when cold-starting the only way to find out the current SoC is the floating cell voltages. But if you've just rapid charged and now turn the car on the cell voltages haven't settled and SoC is overestimated by a few %.

Now I found the STM32 has something called "backup registers". Basically 20 bytes of data that is retained by the RTC battery. The advantage of those over writing to flash is that they don't wear out. You never know when the car is turned off and when you should store your data. Just storing every few seconds quickly destroys the flash page.

A hardware mod is necessary. Vbat must be connected to 3v3 via a diode and a capacitor must be connected to Vbat. I tried just 220 uF and it is enough to retain data for 15 minutes or so. By then the cell voltages are settled anyway and we don't need the stored data anymore.

EDIT: in fact I could even tie permanent 12V to Vbat via a low quiescent current LDO.

[jrbe]

Do you think FRAM (FeRAM) would be reliable inside an inverter?

[jrbe]

Now I found the STM32 has something called "backup registers". Basically 20 bytes of data that is retained by the RTC battery. The advantage of those over writing to flash is that they don't wear out. You never know when the car is turned off and when you should store your data. Just storing every few seconds quickly destroys the flash page.

Do you think FRAM (FeRAM) would be reliable inside an inverter?

Looks like FRAM is fine in magnetic environments,
https://www.ti.com/lit/pdf/slat151

Some FRAM has incredible write cycle life too.

[johu]

JLC also has a choice, e.g. https://jlcpcb.com/partdetail/Fujitsu-M ... ERE1/C8739 (2kB, 0.40€). It can endure 10¹⁰ write cycles, so 317 years one write per second

So depends on the goals. Short term storage of a few items can be achieved with a cap and the integrated RAM. Long term with a larger button cell or permanent 12V stepped down. And long term "high" volume could be achieved with FRAM. Just needs power, clock and data.

[jrbe]

JLC also has a choice, e.g. https://jlcpcb.com/partdetail/Fujitsu-M ... ERE1/C8739 (2kB, 0.40€). It can endure 10¹⁰ write cycles, so 317 years one write per second

I checked that JLCPCB had some decent options before recommending it

[jrbe]

The amazing Dan Gelbart, in his MIT Prototyping for Engineers class he filmed but had the plug pulled on him, says that people who do R&D spend so much of their career doing and undoing fasteners, that you should use cases with keyholes and slots and spot welded captive hardware as much as possible because of how much time it saves.

Have you ever attempted to use keyhole pems or spot welded hardware in production? These both shift the time savings to an operation of installing these things to a person or a machine that likely also needs to be programmed.
Then there's the struggle of using the keyhole pems, warped pieces not grabbing them, no lead in to get them started, rattles, etc. Basically all the ones I've tried suck. Production can move too quick and strip / rip them out then the part or assembly is junk.
Pems nuts are ok but still time to install and can be stripped out / popped out.
It's definitely quicker using self threading screws. The coarse, wood looking screws meant for sheet metal with a blunt nose are my favorite if it's a minimal # of times it gets used and there's a torque limiter used to tighten them.

Weld studs can really suck if the welder doesn't know what they're doing or their capacitive discharge equipment is shot. Their welding can be incredibly inconsistent too. They feel ok then break away. They like to fall off at very inopportune times leaving no easy way to fix them.
Clip nuts / push nuts or hex rivnuts if they need some extra strength are my favorite lighter duty and replacable threaded fastener options.
Christmas tree clips, the plastic clips with the push in lock cylinder, or the ball stud and rubber cup work well and are quick too.

[Ev8]

A flat floor has been on my to do list for far too long. It should make a real difference

[johu]

Yes will see how things develop in summer time. Today I drove 31 km and used 9% of the battery. Consumption display was 130 Wh/km. 10°C ouside temp.

[DVD3500]

Does the German TÜV care as long as everything is secure and not protruding too far down or outside the car?
My friend who converted his Triumph Spitfire said adding a "skid pad" to front of his car made a measurable difference...

[Jacobsmess]

Consumption display was 130 Wh/km. 10°C ouside temp.

That seems good, if I'm calculating correctly 4.78miles/kWh, roughly 190mile range with your 50kwh pack (40kwh usable).

[johu]

Yes I still have to find the usable kWh. The pack is nominal 62 kWh but I'm only using 8/9 so 55 kWh. The ID.3 also exists with this 55 kWh pack and it is said to be 52 kWh usable. On the modules it says 158 Ah and it is 96S.

I'm not the kind of guy who just empties the battery just to find out how far it goes So will have to wait till the next road trip.

[arber333]

Yes I still have to find the usable kWh

I have now 7 modules in Mazda for 320V. That ammounts to 47kWh. If i would add another module which i am thinking of i would get those vaunted 55kWh and 300km range !!! But i dont know how to mount Tesla charger... there is not a lot of space in Mazda left...
But i dont want to just add fast charging as i dont have cooling yet setup...

[johu]

But i dont want to just add fast charging as i dont have cooling yet setup...

Yes tell me more about this. You said you were having issues on a road trip.
Were you monitoring temperatures and how high did you let them climb? What happened? sorry I can't find your original post.

[arber333]

Yes tell me more about this. You said you were having issues on a road trip.

That was on a drive to croatia. I was very excited as i managed to charge on chademo at 43kW!!! but after 20min Jaguar cell became toasty as of 45deg. I took control of charging and opened both boxes to outside air.
It helped while driving on highway, temperature went down actually.
This happened several time and i decided to add some fans to the boxes.
On the way back i saw one cell in a 2P plummet and the second one took all the load. Immediately when i stopped it jumped back up.
I had to perform bypass and remove that 8S cell pack from the loop. I drove home in a slower way, less heroic

[johu]

Ok, thank you. I also consider actively venting the box if temperatures go too high. I think I will only ever charge once per day because I expect range to be 300 km or more (when I don't drive heroic )

[arber333]

I also consider actively venting the box if temperatures go too high.

I am thinking of fitting a blower fan to each box in a suction way. I.e. air is sucked via the length of the box and expelled at some hole in the sides. For that i will have to make several holes on one side of the box for the air to enter... I am not sure about cooling efficiency though. Well see. Alternative is liquid cooling but i dont like the complexity...