AEVA Members: your Forum Login (here) is NOT the same as your new AEVA member login.
You do not need to change your existing Forum login.

Renard's BMW

Post up a thread for your EV. Progress pics, description and assorted alliteration
User avatar
BigMouse
Senior Member
Posts: 600
Joined: Thu, 28 Oct 2010, 02:39
Real Name: Vincent Tannahill
Location: Silicon Valley
Contact:

Renard's BMW

Post by BigMouse »

Exciting! Did you order from Australia, or direct from China? Did they come with the interconnects?

3.07v with 6A draw? That seems like a lot of sag to me. Comes to 37mOhm internal resistance [(3.3-3.07)/(3.07/0.5)]. Is that common for these cells?

EDIT: Nevermind, I see from the thundersky datasheets that the voltage under load is listed as 3.0v, I assume CALB would be the same. Property of the chemistry perhaps?

Anyway, congrats!
Last edited by BigMouse on Thu, 02 Aug 2012, 16:24, edited 1 time in total.

Renard
Groupie
Posts: 219
Joined: Sun, 29 Aug 2010, 18:55
Real Name: Robert Fox
Location: Cobargo NSW

Renard's BMW

Post by Renard »

Big Mouse, I wouldn't take that measurement too seriously as it was just a preliminary poke with two flimsy jumper leads. I just had to get a cell to do something -- even 6A.
I didn't want the hassle of a China order, so the cells came through EV Power. And yes, they came with plated copper 5-leaf interconnectors and s/s M8 bolts, washers and spring washers.
I may substitute something else for the spring washers though.
Renard

Renard
Groupie
Posts: 219
Joined: Sun, 29 Aug 2010, 18:55
Real Name: Robert Fox
Location: Cobargo NSW

Renard's BMW

Post by Renard »

After a month of work, I've finished five battery boxes. I learn as I go. It's amazing what one can forget to allow for as one proceeds, such as the impossibility of grinding a weld in an internal corner, the trouble a millimetre of error can cause, putting something together the wrong way round and welding it up… And then finding the cells don't quite fit for some reason one has overlooked.
Here is more detail than many readers may care for, but it's very possible I've overlooked some important detail which someone may helpfully point out.

The photos show the boxes, two which sit forward of the motor, the one above it, and two under the back seat. The front lower one holds sixteen cells in rows of nine and seven; the upper one holds two rows of ten, the one over the motor holds 24 in three rows of eight. This is how I get sixty 100Ahr cells in the front. The ones under the back seat hold seven and eight cells -- that leaves 37 for the boot.

Image
Fabricated from 25x25x3 steel angle and 20x3 steel flat bar, they reflect slightly different ways of dealing with some problems.
In particular, there must be a way to pack in the last cell, so one box edge has to be removable. In one box, the whole edge is removed and bolted on; in the other, one edge has been cut for a short distance only, and then a strap bolted on to re-enforce it. In one box I used captive nuts; in the other I tacked an extra 3mm strip under the angle to give a tapped hole of 6mm depth, which is only slightly less than the 7mm depth of a M8 nut. The last cell in the three-row box is dropped into the centre. The single row boxes are filled from one end and then the end blocked off with a strap. All boxes have a height of 240mm; the cells are 215mm at the casing, and 218mm at the terminals, so that there is about 18mm clearance over the terminals, and the same under the box upper edge. This means that the box edge gives about 3 to 4mm side containment to the top shoulder of the cell.
Image
The central cell bottom support element consists of 20x20x3 angle with 20x3 flat welded to form a tee. With the cells connected across rather than along the rows, and closely packed, they form an almost solid mass which rests primarily on the outer edges, with the centre element carrying less weight than would be the case if the cells were loose and unbound.

In the front three boxes there are two M8 tapped holes at the mid-point of each short end to serve as lifting points.

Achieving cable entry points is effected by two 20mm holes for conduit entry -- drilled with the 19mm drill bit I bought earlier and filed out to 20mm. In my first box I cut out the holes. In both cases the weakened edge has been braced with 20x3 strap.
The box sides parallel to the length of the car have been diagonally braced in such a way that the 20x3 flat bracing would be in tension, not compression, in a front end collision, in which case the box and contents would -- for the upper box -- tend to twist forward while the box is secured at its bottom. The side bracing may also serve to contain any swelling of the large face of the cells.
Here are the two forward-most boxes.
Image
The rows of cells are separated with 4mm thickness plastic angle from the local hardware store, with one edge cut down. This gives just about the right separation for the cell inter-connectors to connect cells end-to-end. The cell pitch, side-to-side is 67mm, but is only 61mm end-to-end.
Some 2mm thick plastic angle is used at the box edges to pack in the cells where the box size varies a millimetre or two from correct size. (Illustrated here for the three-row box.)
Image
In the three-row box, the centre row cells are held down with 5mm threaded rod brazed onto the bottom tees.
Image
All other cells are held down at the box edge with M5 bolts screwed down onto some peripheral plastic angle. (Not done yet.)
Two small supports are screwed onto the aforementioned rod to hold up the centre of the polycarbonate cover.
Image
The top cover is 3mm polycarbonate sheet.

The Wavesculptor and a contractor box sit nicely on top of the large box with a centimetre or two to spare under the bonnet -- though it's more a case of just touching the somewhat sagging under-bonnet insulation.
Image

The boxes under the back seat are held up by four M8 bolts; the seat sheet metal is strengthened with 60x60 squares of 1.6mm gal. sheet above and below.
Image
Lateral support is by a bracket across to the lower bolt of the transmission tunnel cross-brace bracket. (in the distance, you can see some oxy gear -- very helpful for tweaking steel.)
Image
Here is one under-seat box in position.
Image

One nice little problem I've been pondering, is how to allow some extra cable length to the under-seat boxes before they're raised into position, as once raised, it won't be possible to fasten the cables.

Oh, and no BMS yet.
Renard

User avatar
weber
Site Admin
Posts: 2745
Joined: Fri, 23 Jan 2009, 17:27
Real Name: Dave Keenan
Location: Brisbane
Contact:

Renard's BMW

Post by weber »

You have been busy. Coulomb, Newton and I know well how much work goes into designing, building, redesigning, rebuilding battery boxes such as these. And we didn't mitre our corners, but overlapped them.

That's an interesting idea, using the box to clamp the cells, by putting them in from one end. Have I understood that correctly? And bringing the cables out through the frame and reinforcing with diagonal braces.

Well done!
Last edited by weber on Sun, 02 Sep 2012, 10:25, edited 1 time in total.
One of the fathers of MeXy the electric MX-5, along with Coulomb and Newton (Jeff Owen).

Renard
Groupie
Posts: 219
Joined: Sun, 29 Aug 2010, 18:55
Real Name: Robert Fox
Location: Cobargo NSW

Renard's BMW

Post by Renard »

Thanks Weber, for your kind words. I must confess to some satisfaction when an appreciative comment is made. It has indeed been a lot of work, and needed much thinking. My wife complained justifiably when I would move into mental planning and fail to notice her. Image

As you say, for frame style boxes, as opposed to sheet metal styles, there are some surprisingly tricky design problems to overcome. My approach was, in order to maximise volume, to use the frame itself to contain the cells. This makes it hard for the amateur steelworker such as myself to get the dimensions just right. The plastic angle is to deal with small errors and for packing.
Also, there is the problem of how to get the cable out of the box! There seemd no alternative to cutting into the top frame.

I tried different solutions to the 'putting in the last cell' problem. But yes, the method for the single row boxes -- and these alone -- was to turn two of the end verticals outwards, because I had the space to do so under the seat, and fill the box from the end. A diagonal strap then fastens across the end with a little packing as required. The top and bottom of this end is slightly weaker, with just a flat and no angle, but it's a very short length. You can see this in the penultimate photo.
Last edited by Renard on Sun, 02 Sep 2012, 13:15, edited 1 time in total.
Renard

Renard
Groupie
Posts: 219
Joined: Sun, 29 Aug 2010, 18:55
Real Name: Robert Fox
Location: Cobargo NSW

Renard's BMW

Post by Renard »

The chargers arrived recently. I ordered two TCchargers, each 2kW, which can be paralleled. Strangely, that was cheaper than one at 4kW, and it provides flexibility in charging. Each charger draws just under 10A from the AC supply, and by having two chargers, one can avoid the difficulty and expense of 15 and 20A equipment and circuits, and one can plug into two regular outlets, though preferably on different circuits.

So to take a break from steelwork, I've been doing some wiring.

This photo shows the fuel door plate with two IEC male connectors.
Image

Yes, I know that the IEC connectors are not waterproof, but I don't expect to be charging in the rain.


Each one is connected to a charger, and each one can be connected with a separate 10A cable, though I happen to have acquired, free, some 25 years ago, 20m of five core 2.5mm^2 flex. I've kept it through several house moves waiting for some ideal use, because it seemed far too good and expensive to discard. It will make a very good double cable with a common earth, all in the one sheath. It is, in effect, two very heavy duty extension leads in one sheathing.

Image

The hole in the top centre of the plate houses the fuel door micro-switch, and the blank centre space is reserved for a possible J1772 receptacle if it becomes desirable to install one. Or if the new AC/DC combination plug takes off, I'll re-work the whole thing.

The rear contactor box in the boot holds two contactors and a terminal post.
ImageImage

The left upper contactor is an inter-pack isolator, the other is the battery negative isolator.
To provide for the eventuality that fast charging takes off, and to avoid crawling around under the car in the future doing re-wiring, I'm running 16mm^2 cable as the charging cable from the boot, just near the fuel door, to the front. This is way over size for the 12A the chargers will supply, but should be good for a 80A fast charge. This cable is secured to the brass terminal post, where it's joined to the charger output.
The brass terminal post is secured underneath by nylon machine screws.
The positive and negative charge lines pass through the black cable gland and terminate in detachable mini-anderson style connectors rated at 45A, 600V. That current rating is, to put it politely, decidedly optimistic. But they'll be fine for the 6A I will put through them. They can slide onto each other, as shown.

Image

These permit the chargers either to be mounted in the boot or on a bench at home. I don't know yet which will be more convenient, but I have the option.

This photo shows the forward end of the BMW 'secret passage' originally used by the fuel filling hose, but now to be occupied by three cables.

Image

Outside of the passenger cabin, it is very difficult to arrange an alternative passage from the front of the car to the boot, though small wires can be squeezed through the grommeted hole at the base of the rear seat where the speedometer wires pass. The 12V wiring, which passes through the grey conduit is small enough that it can be fitted here. I have elected not to disturb the wiring under the carpet in the cabin.
So there are four 20mm conduits passing along the length of the transmission tunnel: inter-pack cable, negative cable, charging cable and 12V wiring. This photo shows the charging conduit and the LV conduit.

Image

The left hand side off the tunnel holds the inter-pack conduit and the negative conduit, (that is, the cable running from the negative point of the battery, in the boot, to the negative point of the motor controller.) I thought it might be better to put these next to each other in case there should be some strange magnetic effects from having them too far apart in a loop. Or am I being needlessly concerned?
Last edited by Renard on Thu, 20 Sep 2012, 18:09, edited 1 time in total.
Renard

Nevilleh
Senior Member
Posts: 773
Joined: Thu, 15 Jan 2009, 18:09
Real Name: Neville Harlick
Location: Tauranga NZ

Renard's BMW

Post by Nevilleh »

How neat is that? Well done!
I don't see how your battery boxes clamp the cells though, or are you not concerned about that?

Renard
Groupie
Posts: 219
Joined: Sun, 29 Aug 2010, 18:55
Real Name: Robert Fox
Location: Cobargo NSW

Renard's BMW

Post by Renard »

Nevilleh wrote:
I don't see how your battery boxes clamp the cells though, or are you not concerned about that?


With the exception of the two boxes under the rear seat which will be packed at their ends, the cell rows have almost no play whatsoever in their boxes. So the only expansion would be end faces, and that only where there's no diagonal bracing strap. The end cells are held on four edges. Would the faces still swell do you think?
Renard

User avatar
coulomb
Site Admin
Posts: 4039
Joined: Thu, 22 Jan 2009, 20:32
Real Name: Mike Van Emmerik
Location: Brisbane
Contact:

Renard's BMW

Post by coulomb »

Renard wrote: The end cells are held on four edges. Would the faces still swell do you think?

Ummm, yes, I think so. Some of our cells are actually swelling, just sitting loose on shelves. They swell about a millimetre each side, so 2 mm total. But they seem to clamp up OK (e.g. just pressing them together by hand).

Do the end cells need clamping? It's hard to say, but the fact that they swell at all bothers me.

[ Edit: not sure if it was our 16 newer cells from EV Works or not. ]
Last edited by coulomb on Sat, 22 Sep 2012, 05:24, edited 1 time in total.
Nissan Leaf 2012 with new battery May 2019.
5650 W solar, 2xPIP-4048MS inverters, 16 kWh battery.
1.4 kW solar with 1.2 kW Latronics inverter and FIT.
160 W solar, 2.5 kWh 24 V battery for lights.
Patching PIP-4048/5048 inverter-chargers.

Nevilleh
Senior Member
Posts: 773
Joined: Thu, 15 Jan 2009, 18:09
Real Name: Neville Harlick
Location: Tauranga NZ

Renard's BMW

Post by Nevilleh »

I made my sheet metal boxes to be a snug fit so the cells are hard against each other and the box walls and didn't I have a job and a half getting them in! I tried to remove some about six months later and it was too difficult so I just removed the whole box and did my tests with the cells in place. Its going to be a real problem if and when the time comes to replace any of them. I wish I'd thought to make the end plates removable, but they are welded in. So the cells definitely swell to fill the available space.

User avatar
weber
Site Admin
Posts: 2745
Joined: Fri, 23 Jan 2009, 17:27
Real Name: Dave Keenan
Location: Brisbane
Contact:

Renard's BMW

Post by weber »

Nice work as usual, Renard. You wrote: "I thought it might be better to put these next to each other in case there should be some strange magnetic effects from having them too far apart in a loop. Or am I being needlessly concerned?"

I don't think you are being needlessly concerned. I think your intuition is good. The bigger the loop, the more inductance it has and the more it will radiate high frequency noise introduced by the motor controller's PWM. We will be putting our go and return cables in the same conduit. Each cable will be single-core double-insulated to 0.6/1 kV.

[P.S. I agree with Nevilleh and Coulomb and recommend adding more diagonal braces or something to stop the end faces of the end cells from swelling.]
Last edited by weber on Sat, 22 Sep 2012, 05:50, edited 1 time in total.
One of the fathers of MeXy the electric MX-5, along with Coulomb and Newton (Jeff Owen).

Renard
Groupie
Posts: 219
Joined: Sun, 29 Aug 2010, 18:55
Real Name: Robert Fox
Location: Cobargo NSW

Renard's BMW

Post by Renard »

Thanks, the three of you, for your thoughts on cell-swell.
At the row ends, even though the cells are hard up aginst the box, there is still a 1 to 2 mm gap in which I could insert some steel. (The radius on the inner corner of the angle from which the box is made, holds the cells slightly away from the angle face.)
Or perhaps I'll weld on the 3mm flats that I have already used. Not sure yet.
Meanwhile I've been pre-occupied mounting the power steering pump, following in Nevilleh's footsteps, both with respect to type of pump (Toyota MR2) and location.
Renard

Renard
Groupie
Posts: 219
Joined: Sun, 29 Aug 2010, 18:55
Real Name: Robert Fox
Location: Cobargo NSW

Renard's BMW

Post by Renard »

Slow work this last month. I visited family in Perth and unfortunately just missed the monthly AEVA meeting.

I have now bought a Toyota MR2 power steering pump. (1993 I think.) There seems to be agreement among wreckers that these are worth $300. Everything about it is very solid -- casting, wiring, connectors. Somewhat over-engineered, I'd say, but good on them.
This has been mounted in the free volume on the LH side of the motor. I've used the original support strut from the MR2 to hold the rear end, and for the forward end, two rubber bushes on a bracket attached to the rail. New hoses have been fitted at a non-trivial expense. It draws about 20A at 12V.

Image

My other current work is fabricating the 33-cell battery box which fills the space previously occupied by the spare tyre. Since this box will weigh 110kg, I've strengthened the chassis rails with 50x50x4 angle, bolted through the rails. The original rails are formed from two pieces of 1.2mm sheet metal into an octagonal cross-section. Presumably this form crumples well in a collision.
I have inserted crush tubes to prevent the rails being squeezed by the bolts. Lacking suitable ready-made tubing for these tubes, I found some 12mm rod in my scrap box and drilled it out to 8mm ID on the lathe.
The odd placement of the holes in the angle bracket as shown in the photo is due to the pre-existing holes in the chassis rail which I employed for the fixings. The only new hole is the rearmost one.

There may be a drawback to this arrangement insofar as the angle bracket will not telescope as well as the rail in the event of a rear end collision. But I don't see how a conventional car, not designed for the purpose, can be stuffed with batteries and still be as collapsible, at least for the boot.

Image

Image

The photos were taken before the surgery on the boot floor.

There are four cells and the auxiliary battery to the right of the big box, in the position previously occupied by the lead-acid battery. All up, I expect there to be about 130kg of cells and box installed in the boot space.
I have removed the spare tyre and old battery - 40kg in total; the exhaust - maybe 10kg; and there is also an expected maximum loading of 65kg (5 x 13kg) attributable to luggage. So there should not be a load placed on this section of the vehicle which is much in excess of that for which it was originally designed. (I am not expecting heavy luggage.)

The cells in the box are disposed in a way so as to optimise the volume between the rails. It's a close-run thing; I have only 2 - 3mm of clearance on each side between the box and the support brackets. These brackets are also 4mm angle welded to the big angle and gusseted. Extra metal is welded to provide 8mm of thickness for the tapped bolt hole. (There would be no way of fitting a nut.)
The three central rows hold 21 cells, and there are six cells in each side row. The cells are retained by the diagonal braces. An example can be seen of the heat-shrinked aluminium strips that hold the cells down. The strips will be fastened to ten judiciously placed M5 threaded rods brazed onto the base supports. This photo shows three cells in the side row and two each in the central rows for illustrative purposes.

Image

I could have been more relaxed about fitting in cells into this box, but then I would have had to build yet another box to fit on the LH side of the LH rail, but after six boxes, the joy of steelwork is starting to fade.

The last four cells and the auxiliary battery (17Ahr gel cell) are shown in the next photo. A cell-top cover will complete the fittings.

Image
Last edited by Renard on Sat, 03 Nov 2012, 11:33, edited 1 time in total.
Renard

CometBoy
Groupie
Posts: 313
Joined: Fri, 20 Jun 2008, 02:59
Real Name: Bruce

Renard's BMW

Post by CometBoy »

Nice work Renard.

Just wondering if the engineers in NSW are happy with you putting the front battery box in what appears to be the frontal “crumple” zone of the vehicle?

Maybe I have missed something in looking at the photos above??

Cheers
Bruce

Renard
Groupie
Posts: 219
Joined: Sun, 29 Aug 2010, 18:55
Real Name: Robert Fox
Location: Cobargo NSW

Renard's BMW

Post by Renard »

CometBoy wrote:
Just wondering if the engineers in NSW are happy with you putting the front battery box in what appears to be the frontal “crumple” zone of the vehicle?

Although those boxes are close to the front I don't see more than about 10-15cm of difference from the original six-cylinder engine which pretty much filled the engine bay. The car body was the same for the four cylinder version, and they stuffed the six in without much room to spare.
Nonetheless, it's about time I confirmed with my local engineer.
Renard

Canberra32
Groupie
Posts: 238
Joined: Wed, 13 Jun 2012, 04:25
Real Name: Damian butcher
Location: Canberra

Renard's BMW

Post by Canberra32 »

Make sure there is a frosty Eskimo of beer in eyeshot ;) if you catch the engineer looking or you hear "nice for some" offer one :)
Don't call it a bribe just more of a make sure they are in the best mood possible :)
If they are a none drinker smash the end of one and... Lol

Renard
Groupie
Posts: 219
Joined: Sun, 29 Aug 2010, 18:55
Real Name: Robert Fox
Location: Cobargo NSW

Renard's BMW

Post by Renard »

Well, I saw my engineer this morning, and after having crossed his palm with silver -- or gold -- Image    he didn't seem too concerned about crumple zones, particularly after I pointed out that the six-cyl. engine left so little space anyway. Measuring again, I see that the crumple space is reduced by about 5cm.
Renard

Nevilleh
Senior Member
Posts: 773
Joined: Thu, 15 Jan 2009, 18:09
Real Name: Neville Harlick
Location: Tauranga NZ

Renard's BMW

Post by Nevilleh »

Renard wrote: Well, I saw my engineer this morning, and after having crossed his palm with silver -- or gold -- Image    he didn't seem too concerned about crumple zones, particularly after I pointed out that the six-cyl. engine left so little space anyway. Measuring again, I see that the crumple space is reduced by about 5cm.


Well, the solution is obvious! Don't crumple!!

How'd your pwr steering pump driver work out?

Renard
Groupie
Posts: 219
Joined: Sun, 29 Aug 2010, 18:55
Real Name: Robert Fox
Location: Cobargo NSW

Renard's BMW

Post by Renard »

Nevilleh wrote:
Well, the solution is obvious! Don't crumple!!

How'd your pwr steering pump driver work out?


So simple. Why didn't I think of that?

I fried the micro I was using and have had to wait for another. But the mechanical system works: I put the wheels on the floor and applied 12V to the pump and hey presto! the wheels turned effortlessly as I turned the steering wheel.
Renard

Nevilleh
Senior Member
Posts: 773
Joined: Thu, 15 Jan 2009, 18:09
Real Name: Neville Harlick
Location: Tauranga NZ

Renard's BMW

Post by Nevilleh »

That's good, I originally tried my pump with a couple of Li cells giving 6.4V and it had enough grunt to turn the wheels easily. Then I upped it to 3 cells and the steering was very light. My driver is set for 8V and that gives quite nice steering. I've added a switch so I can turn it off completely at anything over about 35 kph as you don't really need it then and it consumes lots of power as well as making noise. I'd like to find a speed signal from somewhere and make it automatic, but that's in the too hard basket at present.
Speaking of crumple, my "other car" was a Jaguar XK and I severely crumpled it last week, so don't do as I do, do as I say!

Renard
Groupie
Posts: 219
Joined: Sun, 29 Aug 2010, 18:55
Real Name: Robert Fox
Location: Cobargo NSW

Renard's BMW

Post by Renard »

Nevilleh wrote:
Speaking of crumple, my "other car" was a Jaguar XK and I severely crumpled it last week, so don't do as I do, do as I say!

Oh I'm sorry to hear that. Bummer! and I hope not for my Beemer.

I've just breadboarded my pump controller front end. I have two set-points where the pump supply is to drop from full to medium, and from medium to off. These set-points are adjustable via trimpots. The temporary speed signal is from my square wave generator, and varying this signal frequency gives the three distinct voltage outputs from the micro corrsponding to the the three states of the pump.
I wonder if I should add a magnet/hall effect device on the steering shaft to monitor rotation from 'straight ahead', but this may be an unnecessary complication.
Renard

User avatar
Johny
Senior Member
Posts: 3729
Joined: Mon, 23 Jun 2008, 16:26
Real Name: John Wright
Location: Melbourne
Contact:

Renard's BMW

Post by Johny »

Renard wrote:I wonder if I should add a magnet/hall effect device on the steering shaft to monitor rotation from 'straight ahead', but this may be an unnecessary complication.
I wouldn't. You risk the hall device alignment slipping and the steering doing something unpredictable. It may also act a little crazy as the steering goes from heavy to light when the pump kicks in. You can always re-visit it when the car is on the road if you find the steering pump annoys you in stop/start straight-ahead traffic. All IMO of course.

Nevilleh
Senior Member
Posts: 773
Joined: Thu, 15 Jan 2009, 18:09
Real Name: Neville Harlick
Location: Tauranga NZ

Renard's BMW

Post by Nevilleh »

When you get that speed control working properly, would you share it with me? Just waht I need on mine and if you can discover where to find the square wave, I should be able to add it in easily.

Renard
Groupie
Posts: 219
Joined: Sun, 29 Aug 2010, 18:55
Real Name: Robert Fox
Location: Cobargo NSW

Renard's BMW

Post by Renard »

Neville, yes, of course.
I can certainly let you know about my speed signal when I've got the rear wheels spinning.
The question is though, what is the difference if any, between my 1998 instrument cluster and yours.
I have a circuit diagram for mine, complete with connector pinouts and colours.
Renard

Nevilleh
Senior Member
Posts: 773
Joined: Thu, 15 Jan 2009, 18:09
Real Name: Neville Harlick
Location: Tauranga NZ

Renard's BMW

Post by Nevilleh »

Your '98 model may not be much different to my '88 model! BMW have always been pretty conservative. Anyway, maybe you could send me a copy of the relevant part of the wiring diagram and I'll compare it with mine.

Post Reply