Renard's BMW

Post up a thread for your EV. Progress pics, description and assorted alliteration
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Post by Renard »

Hi guys, out there.

Where are you positioning your inertia switch?
Right next to a (fused) auxiliary battery, or just 'before' the ignition switch?
In the latter case, one would still have many functions available even when the switch is tripped; in particular, hazard warning lights, and only the HV and other 'ignition' functions would be isolated.
The choice is between killing the whole system or just parts of it.
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Post by weber »

NCOP14 Jan 2011 Section 2.10 says in part:
"Disconnection of the traction pack from the rest of the traction circuit must be by a contactor operated by the ignition switch.
An inertia switch should be employed to disconnect the traction pack from the rest of the traction circuit in the event of a collision."

My thinking is that it should not disconnect any extra low voltage circuits other than the one powering the coils of the traction pack isolation and segmentation contactors, as ELV may be useful after a collision, particularly for lights.
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Post by Johny »

Mine just opens all the HV contactors.

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Post by Renard »

Thanks for that. It was what I was thinking, but I wanted to see if there was any problem with it.
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Post by Renard »

Finally I picked up the angle grinder and the saw and cut out the boot base, in order to fit the boot battery box.

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After the base has been cut out, the side compartment has been strengthened with a piece of sheet metal from the rail to the base.

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The box in position:

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As explained earlier, this box holds 33 cells. The groups of six on each side, aligned longitudinally, leave 38mm free space at the end of each group which permits the exit of the cables without cutting into the frame.

The rear view: "Pardon me, madam, but your slip is showing."

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Decorum restored:

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One pleasant aspect of EV conversion is that when one tires of one job, there is always a different kind of work to be done. Hence, here is the smallest box that I could find that just contains a single Kilovac contactor: Altronics H0393. I even had to use a sheet metal internal mounting plate, since using a thicker, plastic one would have caused the contactor studs to foul the cover. As a somewhat unnecessary refinement, I include a small LED to indicate the presence of the LV.

ImageImage

I hooked up the LV wiring to the rear box contactors and heard a satisfying 'clunk' when power was applied.
It was satisfying to be able to screw on the lid and declare it finished.

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Also on the rear of the car, I made up a polycarbonate shroud for the mini-pack of four cells on the side, assembled some HV cable sections, screwed on some 0.6 aluminium sheet that I had in the scrap box onto the exposed face of the battery box. The cut edges around the box will be sealed with foam.

What are people's thoughts on providing some sealing to the base of a box so that road debris is not hurled up at the cell bottoms? Does sealing the base significantly reduce cooling, or is that not an issue?
Last edited by Renard on Fri, 23 Nov 2012, 09:16, edited 1 time in total.
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Post by Richo »

Where does the spare tyre go?
WA local regs didn't want me cutting out the tyre well when I had my BMW.
So the short answer is NO but the long answer is YES.
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Post by Renard »

My engineer, in NSW, will accept a spray can.
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Post by jonescg »

Renard wrote:
What are people's thoughts on providing some sealing to the base of a box so that road debris is not hurled up at the cell bottoms? Does sealing the base significantly reduce cooling, or is that not an issue?


In my experience, if your cells are getting warm enough to need cooling, you're doing something wrong. Seal em up I say. You don't want your terminations getting cruddy and wet if you can help it. By all means leave a small vent hole near the top, but you don't want any moisture getting in there.
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Post by BigMouse »

I'm planning on making my battery boxes a bit different from yours. I'll build them in to the car out of sheet metal so that they are sealed from the beginning, then reinforce on the outside as required to meet the restraint criteria. Depending on how tight you've made your box, you may be able to make a sheet metal insert which you can seal around the top at the floor of the boot. Those tie-down studs might make that a challenge though.

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Post by coulomb »

Renard wrote: What are people's thoughts on providing some sealing to the base of a box so that road debris is not hurled up at the cell bottoms?

We have 1 mm polycarbonate under all our cells. [ Edit: except where they are protected by another layer or two of cells underneath. ]

Mud on the cells and BMUs is not a good look, or even a good thought.
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Post by Canberra32 »

Pack the stuff batts in turn cover it all in glad wrap then hand lay Kevlar over the box with epoxy to form a shell.
Once set pull it off then remove the glad wrap and glue or screw it back up in place.
Rally cars Kevlar the bottom of their cars to stop the stones cutting through the floor so it should do :)

Composite addiction yes :)

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Post by Canberra32 »

Hmmm that came out wrong.
Pack the batteries in and cover with glad wrap

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Post by Canberra32 »

Also a piece of 5mm abs plastic and a heat gun to stretch it to shape could work though I would personally drag it to a sheet metal fabricator and have them make and tack in a new boot pan.

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Post by weber »

Good work.
Renard wrote:I even had to use a sheet metal internal mounting plate, since using a thicker, plastic one would have caused the contactor studs to foul the cover.

We had the same problem. Our solution was to cut the contactor studs off flush with their nuts. Ouch!

BTW, In Australia and New Zealand, in DC terms, LV means exceeding 120 Vdc but not exceeding 1500 Vdc. And HV means exceeding 1500 Vdc (AS/NZS 3000 section 1.4.98). So I use the terms ELV and HAZV as defined in NCOP14 Section 2.1.
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Post by Renard »

weber wrote:BTW, In Australia and New Zealand, in DC terms, LV means exceeding 120 Vdc but not exceeding 1500 Vdc. And HV means exceeding 1500 Vdc (AS/NZS 3000 section 1.4.98). So I use the terms ELV and HAZV as defined in NCOP14 Section 2.1.


Thanks for the guide to correct nomenclature.

Does your rearmost box have a base which is open apart from the 1mm polycarbonate Coulomb mentions?
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Post by weber »

Renard wrote:Does your rearmost box have a base which is open apart from the 1mm polycarbonate Coulomb mentions?
Yes. All our boxes are like that, except we don't bother with the PC in the boxes that are well above the road, i.e. those in the upper part of the fuel-tank space, behind the rollbar and over the motor.

We will also put 1 mm PC on the forward face of any battery boxes that might get hit there by stones.

I used to be able to buy 1 mm PC sheet at Bunnings, but I can't find it anywhere now, so I settled for 1 mm clear PVC last time. We're using that in all the box lids. I hope I don't come to regret that.

[Edit: Polycarbonate has excellent impact resistance. PVC is complete crap in that regard.]
Last edited by weber on Sat, 24 Nov 2012, 10:00, edited 1 time in total.
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Post by Renard »

I have cut out my lids from 3mm polycarbonate (not cheap -- nearly $50 for a 915 x 650 sheet at the local Hardware store) to give a secure protection of the terminals and future BMS, and to keep the celltops visible.

But the faces facing the a/c condenser in front, and the bases of the lowest boxes seem to warrant a lower degree of physical protection so I agree that 1mm material of some kind should suffice to keep the mud out.
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Post by Renard »

The last month has been spent organising wiring and figuring out where to put the ELV control circuits.

I have just completed a little circuit designed to interface the BMS (Neville's "Low-cost BMS") to the TC chargers.
Neville's Master unit has two FET switches, one closing when one cell shunt turns on, and the other closing when they all turn on. These are inputs to the circuit, along with +12V (small current supply) from the TC charger. The 12V drives a transistor base which controls the coil of a relay. This places minimal demands on the Charger 12V supply.

The same 12V drives a PIC micro as shown in the photo. Since I have two separate chargers, I had to use an extra input to tell the PIC to reduce the output when in trickle charge mode i.e. when at least one shunt is turned on. The TC charger puts out a current proportional to 1/3 x (V - 2) x I _fullon. Since the dac level outputs around 2V are not suitable for generating currents of 0.5A (one charger) and 0.25A (each, for two chargers), I had to use higher dac levels and pass the output voltage through a buffered divider. The other output generates the 'full on' voltage.

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The other exciting event was the arrival on Monday of the cell module pcb's I ordered from pcb cart. These look very nice and the only fault is mine in that I omitted to tell Neville, before he re-designed his board, that the 100Ahr cells use M8 bolts, not M6. I will have to drill out the holes. Fortunately, there is still through-plating in the two inner, unused holes.
For my 112 cells, I ordered 120 boards, at a cost, for 120, of $1.45 each.

The programmed micros are at the Post Office awaiting collection, and there are still a couple of components to come from element14 - ones which I couldn't get from Mouser and for which I didn't want to risk a substitute.

So when they arrive I begin the SMD adventure -- new territory for me, but I am heartened by the fact that some people, much more experienced in electronics than I am, have not themselves previously undertaken this mode of fabrication, and yet seem to have managed.

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Post by Nevilleh »

Hey, you are to be congratulated for having a go at this!
I think that you will wonder why anyone bothers with thru-hole stuff once you've successfully made some smd boards.
Get an oven!

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Post by Renard »

Nevilleh wrote:
Get an oven!

Fortunately, I have an oven of just the right size sitting in the shed.
(Oh wonderful cornucopian shed that has such things within it!)
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Post by Renard »

Today I installed the DC/DC converter. I have used the place previously occupied by the engine control module; it is well protected from water and dirt, and its only disadvantage is that it will be troublesome to get at it if the unit should fail.
(If that happens, I'll re-locate it to the boot. With the BMW battery having been in the boot, there is already a heavy duty ELV cable from there to the engine bay, and I have added a pair of wires to the conduit taking the charge current from rear to front, which deals with the HAZV requirement.)
The converter is mounted on the control module carrier. Underneath it is an active zener. Since the HAZV could be as high as 400V, and the converter is rated only to 360V, as a precaution I have added a little micro to switch a FET when the voltage exceeds 360V. In which case the active zener, which knocks about 32V off the applied voltage, is put into series with the converter. It consists of two high voltage NPN transistors in series, with the collector-base links being themselves suitably rated active zeners. Over the top perhaps, but I don't want failure. The transistors are mounted on heat sinks for a worst case dissipation of 50W.
The photos show the location at the LH rear of the engine bay.
The orange conduit through the firewall carries the heater cables.

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Post by Renard »

Slow work this last week or so, as the shed gets very hot in this weather.
I've been working out how to wire up all the ELV functions, and it's a messy business.
For one thing, the BMW fuse box is just STUFFED with wiring. I had to get into it to pass a few wires through it and to get a lead for the Accessory signal. Hard work to get everything back into the box.

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I've mounted a box next to the fuse box to hold various circuit boards and junction posts. The boards were made up over quite some time, so they could be streamlined -- another time. The RH board is the heater control with two FETS -- for the left and right parts of the ceramic heater -- which suits the BMW which has two corresponding control thermistors. The middle board controls the coolant liquid fan and the motor fan, and also monitors ELV voltage and the coolant in-line flow gauge. The LH board controls the power steering pump.

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The DCU will sit under the centre console, and extra wiring was needed to pass from there to the engine bay. Some wires from the main harness which would have been used for the automatic transmission controls can be employed for this, and also wires have been passed through the holes which had been occupied by the water pipes.
I put in the auxiliary battery and turned on the ignition, and I'm happy to say that most things seemed to work. The only hiccup was that the ABS warning light stayed on. The ABS may still work, but evidently it's upset that I chopped off its connections to the ICE engine control module. Further research is needed on this.
I've used the oil pressure warning light for a vacuum pump warning, and the alternator warning light for ELV warning, specifically, a check on the DC/DC converter. If this fails, the voltage will drop from 13.8 to nearer 12, and the light will come on.

From the fuse box there used to issue two large wire bundles linked to the engine harness at connectors X20 and X69. For the latter, which was mostly for the auto transmission, the manual version has only four wires connecting, but the X20 has two dozen wires which have to be dealt with. Some have just been terminated but there are still quite a lot that are needed in the new box as can be seen in the photo.

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The main contactor box is getting busier. It's nearly full and lacks only some 25mm^2 cables. The main positive cable will pass through the small blue transducer on the right which will provide an input to a JLD404 amp-hour meter.
On the left side is a small board which switches off the adjacent FET, thereby passing the supply to the DC/DC converter through an active zener in series as described in my previous post.

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Post by coulomb »

Renard,

in that last photo, I'm seeing a circuit breaker that seems to be handling pack voltage, but not very high current.

Does it have a suitable DC rating? Otherwise, you're not protecting all those thin-ish cables, and you could have a fire hazard.

Some AC intended circuit breakers do have DC ratings, but usually you need two or more poles in series for > 120 VDC operation.

[ Edit: I can just make out the part number: MCB6220DC; it seems to be rated for 500 VDC and 20 A, breaking up to 6 kA DC. I guess this is made for the long solar array strings people have these days. As a point of interest, was it expensive or difficult to get? ]
Last edited by coulomb on Mon, 14 Jan 2013, 17:11, edited 1 time in total.
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Post by BigMouse »

coulomb wrote:[ Edit: I can just make out the part number: MCB6220DC; it seems to be rated for 500 VDC and 20 A, breaking up to 6 kA DC. I guess this is made for the long solar array strings people have these days. As a point of interest, was it expensive or difficult to get? ]


You can get them at Jaycar for $25: http://www.jaycar.com.au/productView.asp?ID=SF4156 but they're supposed to have both poles wired in series as you described. The Jaycar ones have polarity labeled as well, with apparently opposite polarity labeled from one end to the other. This is their way of telling users to put them in series and loop through. Very confusing, and we actually pulled them off the shelves at our store until we could figure it out (some people might hook up only as per the +/- labels and effectively reverse the polarity of their supply without realizing it... some people). Renard, I'd double check the recommended hookup for your breaker in order to realize the full 500vdc rating. It may not actually be a 2-pole breaker as you seem to have it hooked up.

As for the ABS, many cars will have the ABS light on until the car starts moving above a certain speed and the computer is happy that it's getting a good signal from all four wheels. Might check that before you spend too much time chasing wires.

Looking good overall. I can relate to the E36 fusebox wiring situation. I'm not looking forward to breaking in to mine. Otherwise, all the nitty-gritty wiring and "feature" implementation that you're doing now is a big part of the fun of an EV conversion to me, but I'm weird. Image

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Post by Renard »

BigMouse wrote:   Renard, I'd double check the recommended hookup for your breaker in order to realize the full 500vdc rating. It may not actually be a 2-pole breaker as you seem to have it hooked up.

As for the ABS, many cars will have the ABS light on until the car starts moving above a certain speed and the computer is happy that it's getting a good signal from all four wheels. Might check that before you spend too much time chasing wires.


On the ABS, I read the Owner's Manual and it says the light doesn't go off until the engine starts. That signal can probably be arranged.

On the circuit breaker, yes I think it came from Jaycar (bought in 2011 so I can't quite recall). I had indeed assumed it was a 2-pole breaker. There is a discussion about this confusing item at http://forums.whirlpool.net.au/archive/1642279
The opinion there seems to be that it is two single breakers bonded together, with the + and - marks being poor labelling. As long as they're not polarised, it shouldn't matter how they're wired. The way I have them, they're still in series, just with the load between the two poles.
At that time it was the only modestly priced DC breaker I could find, but I notice that Jaycar's 2012 catalogue displays a different brand, and also a 10A version. There is a brand listed at http://www.electriciansupplies.com.au/s ... th=418_466 which is non-polarised, for $22. Might go for that, since a 10A version would be right for the 1mm^2 wiring I have to the heater and the DC/DC converter.

Thanks guys for pointing out this issue.
Last edited by Renard on Tue, 15 Jan 2013, 06:55, edited 1 time in total.
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