Eeee Geee

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inaglasshouse
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Re: Eeee Geee

Post by inaglasshouse »

In other news I tried driving with the brake servo vacuum hose disconnected. Just to see how bad the brakes are without the assistance. Answer: predictably terrifying, so I will definitely need to implement a replacement for the directly-engine-driven vacuum pump. In version 1.
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Re: Eeee Geee

Post by RobFrost »

inaglasshouse wrote:In other news I tried driving with the brake servo vacuum hose disconnected. Just to see how bad the brakes are without the assistance. Answer: predictably terrifying, so I will definitely need to implement a replacement for the directly-engine-driven vacuum pump. In version 1.
I assumed braking in an EV would be via energy recovery, seems I was wrong.

Also, I was expecting the project to be in Yorkshire.

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Re: Eeee Geee

Post by BILLY BEAN »

RobFrost wrote: Sat Sep 10, 2022 4:13 am
inaglasshouse wrote:
Also, I was expecting the project to be in Yorkshire.

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Nah! It's in the Saaf. Yorkshire people are far more sensible. However, despite myself I am learning something from Richard's adventure.
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inaglasshouse
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Re: Eeee Geee

Post by inaglasshouse »

RobFrost wrote: Sat Sep 10, 2022 4:13 am
inaglasshouse wrote:In other news I tried driving with the brake servo vacuum hose disconnected. Just to see how bad the brakes are without the assistance. Answer: predictably terrifying, so I will definitely need to implement a replacement for the directly-engine-driven vacuum pump. In version 1.
I assumed braking in an EV would be via energy recovery, seems I was wrong.

Also, I was expecting the project to be in Yorkshire.

Sent from my SM-G988B using Tapatalk
Quite right re energy recovery. Regen is a fine thing. And one of the nice things about coding it myself is that I get to choose the logic, and level of driver real-time control, over regen.
It's certainly true that, in an ideal world of energy efficiency, the brakes (which turn kinetic energy into heat and dust, rather than something useful) are never needed. But, you know, stuff happens! I need proper brakes too.

I don't think they sell G Wagens in Yorkshire, do they? They're all in SW3.
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inaglasshouse
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Re: Eeee Geee

Post by inaglasshouse »

One slightly unexpected benefit of the (Citroen) battery pack I have chosen is that the BMS architecture is very neat.
We need to monitor every cell. In some cars (eg Nissan Leaf) you end up with a mass of small wires, one to each cell, coming back in a huge loom to a central unit. Ugly, especially if you are wiring it yourself.

The modules I am using require much less wiring spaghetti. Each has its own dedicated chip monitoring the cells in that module, and then the chips daisy chain together via a comms loom (see pic).

I have that loom from the original car, so can just plug into each module. Leaving only the minor issue of how to create a master to talk to the slaves...

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Jonny Hart
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Re: Eeee Geee

Post by Jonny Hart »

inaglasshouse wrote: Fri Sep 09, 2022 10:48 pm In other news I tried driving with the brake servo vacuum hose disconnected. Just to see how bad the brakes are without the assistance. Answer: predictably terrifying, so I will definitely need to implement a replacement for the directly-engine-driven vacuum pump. In version 1.
I wouldn't faff around with a vacuum pump. It's a kludge and the car will sound like a fish tank.

Fit the Gen1 IBooster electric brake servo from a Tesla Model S. I have it on the 914 and its the best brakes I have ever had on an old car. The IBooster is on a 72mm square bolt pattern and I will wager the G is too.

In fact, come and have a go in it if you fancy. I have a spare IBooster you could borrow too.
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inaglasshouse
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Re: Eeee Geee

Post by inaglasshouse »

Jonny Hart wrote: Sat Sep 10, 2022 1:23 pm
inaglasshouse wrote: Fri Sep 09, 2022 10:48 pm In other news I tried driving with the brake servo vacuum hose disconnected. Just to see how bad the brakes are without the assistance. Answer: predictably terrifying, so I will definitely need to implement a replacement for the directly-engine-driven vacuum pump. In version 1.
I wouldn't faff around with a vacuum pump. It's a kludge and the car will sound like a fish tank.

Fit the Gen1 IBooster electric brake servo from a Tesla Model S. I have it on the 914 and its the best brakes I have ever had on an old car. The IBooster is on a 72mm square bolt pattern and I will wager the G is too.

In fact, come and have a go in it if you fancy. I have a spare IBooster you could borrow too.
Hi Jonny

I hope all is well with you.
Thanks so much for the advice and the extremely generous offers. I will take you up on those - will give you call.

That Tesla brake servo does look like a very good solution.
One thing I need to check is that the G has a few other things connected to the vacuum. One is the (MFI pump!) fuel shutoff - amusingly with the vacuum disconnected the engine keeps running when you remove the ignition key. World of diesel. I think there is a solenoid to enable fuel flow which pulls agains the vacuum. Obviously that's not required in future, but TBH I'm not sure what the other taps from the vacuum line are for... investigation needed.
Maybe do the brakes properly but keep a small (fishtank!) pump for the ancillaries...

Best wishes, R
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inaglasshouse
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Re: Eeee Geee

Post by inaglasshouse »

Back to the BMS. We had established each module has a BMS chip, they daisy chain together, need to figure out how to do the comms.

Luckily, as usual, most of this problem had already been solved. The chip in each module is a MAX17852. Lots of lovely proper documentation available online - thank you Analog Devices: https://www.maximintegrated.com/en/prod ... 17852.html
... and the product line includes a master comms chip, designed to do the job of talking to the daisy chain of slaves. It's a MAX17841B: https://datasheets.maximintegrated.com/ ... 17841B.pdf

It was not even necessary to make up a little PCB for the master. By the wonders of the internet, I found my new friend Anton in Sweden, who has already done it. In exchange for some Euro currency he sent me one, and it looks like this:
Image

It's easy enough to talk to the master MAX chip from a microcontroller (via UART) using Anton's board. Some progress.
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Re: Eeee Geee

Post by inaglasshouse »

And then, to cut a reasonably long story short, I wrote some code to talk to the BMS chips.

Here's the end result, running on a microcontroller with a small display:
Image

Although in the final installation this will be buried away somewhere (probably in a box in the engine bay), I couldn't resist doing a little UI. Just a simple visualisation for test and debug purposes.
We have max and min cell voltage, max and min temperature, and the grid shows status of each cell. In this test I have 9 of 16 modules connected, hence the last 7 columns being grey not green.
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Re: Eeee Geee

Post by Gary71 »

Awesome stuff! I understand all the concepts you refer to, but as to actual implementation I have no idea.

The devil is in the detail with all these things and it’s great to see.
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Re: Eeee Geee

Post by Ian Donkin »

Still lurking on this thread... and still enjoying seeing the progress that you are making. Clever chap indeed!
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Re: Eeee Geee

Post by inaglasshouse »

Thanks Ian.

Progress has slowed of late, while life has been getting in the way, but broadly I have "finished" the code for motor control, BMS, charger control.
Recently I have made up various control wiring looms and packaged the microcontrollers into waterproof boxes ready for installation. Control software and electronics side is now fairly neat and tidy, with plug and play connectors etc.

Mechanical aspects next. Not done much there, yet.
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Re: Eeee Geee

Post by Gary71 »

And whatever you do don’t drill a hole to mount anything…
https://www.pistonheads.com/gassing/top ... &t=2007342
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Re: Eeee Geee

Post by inaglasshouse »

Gary71 wrote: Mon Oct 31, 2022 7:05 pm And whatever you do don’t drill a hole to mount anything…
https://www.pistonheads.com/gassing/top ... &t=2007342
That's a worthwhile tip off! Thanks Gary.
It does seem that the 5 points for unmodified chassis, when wishing to keep original reg and avoid the need for IVA, is going to become increasingly important. Only a matter of time before DVLA started tightening up on we chancers with our amateur conversions, and I guess that moment is now here...

In the interests of reversibility it was never the intention with mine to drill holes. The motor can mount using the previous gearbox mount and some conveniently pre-existing chassis features. Battery box will use engine mounts. I will be extra careful now.

Cheers, Richard.
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Re: Eeee Geee

Post by Jonny Hart »

^ Yep, it’s what I was ranting on about a couple of weeks ago.

DVLA have put a whole industry in jeopardy because they have no way of dealing with classic EV conversions.
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