Renard's BMW

Post up a thread for your EV. Progress pics, description and assorted alliteration
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Post by Tritium_James » Mon, 03 Jun 2013, 20:38

Johny: the magnetising current won't be there unless you're 'driving'.

Renard: the motor mass parameter affects only the PID constants for the velocity control loop. I doubt having it incorrect will make much of a difference to anything like this, unless maybe it's continually hunting between drive/regen trying to maintain the setpoint speed.

85-90°C winding temp isn't too unusual. Don't forget it's perfectly happy going to 155.

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Post by Renard » Mon, 03 Jun 2013, 21:41

Thanks TJ, you reassure me.

I will confirm my thermistor's output against the WS's with the Bridge, and keep monitoring for a while.

There's not much space between the motor fan entry face and the lower front battery box, maybe 8-9cm, so that doesn't help the airflow. The gap is visible in the second photo of the post of 22 April on p6.
Last edited by Renard on Mon, 03 Jun 2013, 14:54, edited 1 time in total.
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Post by Renard » Fri, 14 Jun 2013, 22:06

I took the car to the engineer in Ballina the other day

On the way, I drove cautiously and at speeds of no more than 80km/hr along a fairly flat road. Consumption: about 135 watt.hr/km. On the way back, at 90 to 100, consuming about 160 watt.hr/km.

Fortunately a couple of little faults that had been appearing recently didn't surface on the day. The engineer drove on some empty roads, swerving sharply to test the balance.
I got quite scared -- I never do such things -- but I suppose he knew what he was doing.

He was impressed by the document I had produced for him with explanations and photos recording details of the build relevant to the NCOP 14 regulations. So his examination of the car was perhaps less drawn-out than it might otherwise have been. He told me that he had assessed two other electric conversions -- one ute and one sedan.
The main sticking point was the weight over the front axle; it had increased by 100kg to 800kg, as had the weight over the rear axle to 780kg. (200kg increase overall to 1580kg.) But whereas the rear axle had a BMW specified maximum load of 1420kg, the maximum front axle load was 845kg. He was worried that two passengers in the front would exceed this limit by about 20-25kg.

But the Owner's Manual lists several other Series 3 models, and they all had differing front axle load limits ranging from 810kg for the 4 -cylinder to 900kg for the diesel. The question was whether the suspensions were really different or whether this was just paper management. I have heard that the 318 has lighter components, but do the 328 or the convertible or the diesel have heavier springs etc? He was trying to extract information from BMW so far without success.
One possibility: remove six or eight cells from the front upper box. I hope not.

We chewed over this and various other matters for three hours. I was very tired afterwards.
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Post by Johny » Fri, 14 Jun 2013, 23:00

Good going Renard.
I wonder if one of the BMW forums could answer that question of front suspension with any level of confidence.
You would think that a workshop manual might indicate different spring components if it were different between builds.
I've had some success roping in help from car club members that seem to collect lots of useful information.

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Post by a4x4kiwi » Fri, 14 Jun 2013, 23:10

Hi,

Best to compare part numbers. Based on my '91.

Same wishbones. Springs are naturally different parts.

318i
http://bmwfans.info/parts/catalog/E30/2 ... _wishbone/

325i
http://bmwfans.info/parts/catalog/E30/2 ... _wishbone/
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Post by BigMouse » Sat, 15 Jun 2013, 01:11

For E36, the wishbones are the same on all models except the M3.

http://realoem.com/bmw/partxref.do?part=31126758513

Springs are different though, even from one trim level to the other for the same model. I have King springs in my car which are stiffer than stock, but I have a set of stock springs on hand just in case the engineer has a problem with it.

By the way, you can use realoem.com to do part number cross reference for any BMW. It's how I found the electronic pedals that Mal mentioned in another post.

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Post by Renard » Sat, 15 Jun 2013, 02:13

Thanks friends, for that input.

I'm learning things I didn't want to know about front suspensions.

It looks as though the E36s are all much the same, but the springs are different for different models. Perhaps it could be a matter of fitting new springs? And I suppose the shock absorbers should be replaced at the same time?
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Post by Renard » Sat, 15 Jun 2013, 15:05

BigMouse wrote:
By the way, you can use realoem.com to do part number cross reference for any BMW.


Thanks for that reference BigMouse. Further checking this morning confirms that, as you say, the front axles are the same. And the springs are different. That enlightens me about the situation.
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Post by Renard » Tue, 25 Jun 2013, 01:46

The engineer's concern about the front axle load limit would be assuaged, he said, if I installed appropriate new coil springs. I suggested the King springs specified for the model range, to which he agreed. So at some expense I had two new King springs installed in the car. They affected the ride height only slightly -- raising it about 10mm, but they do feel springier. BigMouse writes that they are stiffer than the originals.
Oddly, despite the extra rear weight, the rear ride height is 10mm more than BMW specifications. But I hadn't measured that beforehand so I don't know how it's changed.
Anyway, the engineer was satisfied by my installing these springs, and

PASSED THE CAR.

Now all I need is the pink slip and I can register it. With one day to spare.

Some bugs:
I flattened the auxiliary battery. Rather alarmed, I checked through the wiring and eventually discovered that one of the HAZV leads to the DC/DC converter was internally broken. A relief that the cure was so simple. Probably my last drive had been all courtesy of the auxiliary battery alone.

While investigating, I discovered to my surprise that the DC/DC converter draws 85mA from the auxiliary battery even when nothing is on. That adds up to 2A.hr per day and is obviously unacceptable. I hadn't picked it up because I'd been checking ELV current draw with a clamp meter, and 85mA hadn't registered, but the multimeter told the true story. I can see that it calls for another relay.

This also raises the matter of current draw while charging.
During a long charge of many hours, the contactors which together draw about half an amp, would deplete the auxiliary battery significantly. Nothing's worse than having a flat auxiliary battery which can't bootstrap itself because it won't activate the contactors to access the charge in the main pack via the DC/DC converter.
If only charger manufacturers would have added a 13.8V charge outlet to their chargers.

There are two obvious ways to deal with this: one way is to carry a small 13.8V charger additional to the main charger; the other is to include the auxiliary contactor, which activates the DC/DC converter, in the charger activation circuit. But this means that there would be some HAZV circuit activation whilst charging.
I wonder what people think about this.

The mosfets in the power steering pump controller were overheating and eventually blew up. So I installed a 60mm fan that I had in the junk box, over the heatsink. It had nowhere else to go but on the lid, so it's starting to look a bit clumsy. Maybe one day I'll re-work the whole box.
To power the fan, I had to make up a couple of spring connections for the wiring. These came off the former ASC control switch. The ASC works by throttling down the engine if a wheel starts to slip, and there was a switch by which it could always be electrically disabled. Of course it's irrelevant now since there's no throttle, though annoyingly, the "ASC off" warning light remains on.
The closely related ABS system is a bit problematic. The ABS/ASC Module requires three signals from the Engine Module: ignition cut-off signal; idle speed signal; and crankshaft speed signal. I don't know what the first two signals should look like, though the third is clear enough, I suppose, just a series of pulses at 3Hz per rev I think.

And a few other bugs which I'll deal in due course.

I'm starting to feel more confident driving, no longer worrying that it may stop dead. Particularly pleasing is the smooth and effortless acceleration at higher speeds, for example from 80 to 100. Lower speeds still require a couple of gears for brisk take-off. Much to learn.

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Post by BigMouse » Tue, 25 Jun 2013, 02:12

Congrats on getting it passed!

I've read about the DC-DC converter draining problem before. I've put an output on my controller for a DC-DC converter output relay. You could do something similar with the ignition wire so the DC-DC is only connected to the 12v system when the key is on. I'm also planning to have the DC-DC active when the charger is connected. I don't see any problem with doing that.

My car doesn't have ASC, but if you want me to sniff around with my scope for the other signals, I'm happy to. It'll be something I need to address when I do my conversion anyway, so having the "before" snapshot would be useful. I do have ABS.

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Post by weber » Tue, 25 Jun 2013, 02:13

Renard wrote: Anyway, the engineer was satisfied by my installing these springs, and

PASSED THE CAR.

Now all I need is the pink slip and I can register it. With one day to spare.
Woohoo! Congratulations.
the other is to include the auxiliary contactor, which activates the DC/DC converter, in the charger activation circuit. But this means that there would be some HAZV circuit activation whilst charging.
I wonder what people think about this.
That's what we do. Whenever the battery pack breakup contactors are powered up then so are the DC/DC converters, to power the contactors. You have HAZV then anyway.
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Post by unheardofinstruments » Tue, 25 Jun 2013, 02:22

Well done renard, must be agreat feeling to be past the engineer! I hope he is kind on me...

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Post by jonescg » Tue, 25 Jun 2013, 02:23

Just wondering about the virtues of a large capacity AUX battery which is charged from it's own 13.8 V charger through the AC plug. Saves the need for a DCDC which is potentially always on. Provided everything is off when the car is turned off (no phantom loads) it could be a bit simpler than a DCDC?
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Post by Renard » Tue, 25 Jun 2013, 04:09

BigMouse wrote: Congrats on getting it passed!


Thank you, and also to the others who have congratulated me. It's been a two-year journey with ups and downs, but I'm glad I did it.
BigMouse wrote:
My car doesn't have ASC, but if you want me to sniff around with my scope for the other signals, I'm happy to. It'll be something I need to address when I do my conversion anyway, so having the "before" snapshot would be useful. I do have ABS.


In retrospect, I should have done that research before I pulled the engine, but hindsight is a wonderful thing.
I would indeed be grateful if you could find out something about those signals. The ABS needs them to work. Without them, the main ABS relay doesn't close. The ABS warning light stays on, though I admit to having put in a transistor and a PIC micro which turns the warning light off when the car reaches 10km/hr.
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Post by BigMouse » Tue, 25 Jun 2013, 04:38

Tell me where I can find the wires in question and I'll stick a probe on it. MY ABS light goes off soon after I start the engine. It doesn't wait until I'm moving.

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Post by Johny » Tue, 25 Jun 2013, 15:07

jonescg wrote: Just wondering about the virtues of a large capacity AUX battery which is charged from it's own 13.8 V charger through the AC plug. Saves the need for a DCDC which is potentially always on. Provided everything is off when the car is turned off (no phantom loads) it could be a bit simpler than a DCDC?
There is a huge amount of extra confidence in having the 12V system running at normal capacity. A 12V battery that was slowly discharging would have you worrying more about whether your headlights would keep lit than if you actually finished the trip. Headlight range anxiety.

Renard, let me add my congratulations. I think the engineer's sign off is the most significant landmark during a conversion.

I used a 150A Tyco relay (free sample - long story) that follows the HV contactors to isolate my 12V battery from the DC-DCs. I run my motor fan off the DC-DC side of the relay as well - just to be sure.

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Post by Renard » Tue, 25 Jun 2013, 15:35

BigMouse wrote: Tell me where I can find the wires in question and I'll stick a probe on it. MY ABS light goes off soon after I start the engine. It doesn't wait until I'm moving.

I looked up the ABS wiring diagram in Bentley for the 1992 model. Alas, it is a simplified version without the inputs I need. So your warning light must go out after certain other self-checks which don't require engine input.
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Post by BigMouse » Tue, 25 Jun 2013, 16:17

Renard wrote:
BigMouse wrote: Tell me where I can find the wires in question and I'll stick a probe on it. MY ABS light goes off soon after I start the engine. It doesn't wait until I'm moving.

I looked up the ABS wiring diagram in Bentley for the 1992 model. Alas, it is a simplified version without the inputs I need. So your warning light must go out after certain other self-checks which don't require engine input.
Lucky for me! Sorry I couldn't help.

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Post by Johny » Tue, 25 Jun 2013, 19:15

Renard they appear to check a pump(s)?
Is this any use?
http://www.m3forum.net/m3forum/showthread.php?t=341672

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Post by Renard » Wed, 26 Jun 2013, 01:44

Johny wrote: Renard they appear to check a pump(s)?
Is this any use?
http://www.m3forum.net/m3forum/showthread.php?t=341672


That's quite a good thread, but the writer deals with faults that I assume do not occur for me, because the system seemed to be working OK before the engine was removed, so everything points to issues with the DME module signals no longer being present.
I will just have to experiment - some time.

Today I had the car registered, so I am now fully legal, and can drive it without any fear of the traffic police.
I am looking forward to getting some data on its performance.
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Post by Renard » Wed, 28 Aug 2013, 02:15

A couple of months since my last post, and I've been getting experience driving. (And getting the rest of my life back.) The more I drive, the more relaxed I feel and the less I'm feeling the parts of the car as if I were sensing with my nerves into every component waiting for something to misbehave.

I have been fixing a couple of faults which turned out to be dodgy connections, and I fitted a stronger fan over the PS pump control mosfets which had blown up. They've been replaced with a pair of AUIRF1324 types.
The power steering now works well: it's full on up to about 30km/hr, half on up to 60km/hr, and off for higher speeds. It's working very smoothly so I'm mostly not aware of it.

One issue I notice is that the accelerator pedal must be depressed smoothly; jamming it down causes jack-rabbit hiccups.

I'm also getting a feel for the right gear to engage according to the situation for the appropriate degree of response to acceleration, but it's quite forgiving in that except for starting up a hill, one can start in almost any gear, even -- gutlessly -- in 4th. Just not in 5th. The best gear for acceleration is similar to that for the ICE. Normally I start in 2nd and shift to 4th unless I'm climbing a hill.

On the 21st August, the longest drive so far : 128km. Flat drive at a steady 95 - 100 km/hr, about 155w.hr/km

I've collected some whr/km data at differing speeds and have been assembling a graph of the relationship.
I run a set course on the flat at constant speed without wind, heater, lights etc, so my figures represent a best case.
In order to provide a theoretical picture of how the data should look, I quote from my earlier file 'Vehicle_Dynamics-1.pdf'. \\
Edit: This jpg has disappeared from here. It was showing up earlier.

Pardon me if I put the next part of the post into a screen shot; I do so because, just as Weber detests imperial units, I detest badly displayed maths.

No. Here it is as a pdf:

Blogmaths.pdf


Here is the method for measuring rolling resistance!


Image

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Post by Renard » Wed, 28 Aug 2013, 02:26

I make this a separate post.
The first major problem was an experience of being stranded 10km from home with a persistent Wavesculptor HWOC error.
At the same time, the coolant was leaking from the WS block, but TJ assures me that there's no connection. Anyway, the WS is off to Tritium for repair.

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Post by weber » Wed, 28 Aug 2013, 04:56

Renard wrote:One issue I notice is that the accelerator pedal must be depressed smoothly; jamming it down causes jack-rabbit hiccups.
I assume you've tried changing the mass figure in the WaveSculptor configuration. What is it set to? What else have you tried?
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Post by Renard » Wed, 28 Aug 2013, 14:05

weber wrote:
I assume you've tried changing the mass figure in the WaveSculptor configuration. What is it set to? What else have you tried?


The mass figure is set to 1500kg, so that's not it. Neither is it fully removed by setting regen to zero.

I drive sedately anyway, so it hasn't bothered me.
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Post by Renard » Wed, 11 Sep 2013, 19:01

I've managed to get the file about consumption and efficiency displayed:

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