To an optomist, the glass of water is half full. To a pessimist, it’s half empty. Kind of a point of view thing. Of course, to an engineer, we have a curious instance of a water glass that’s probably twice the necessary size, and undoubtedly mounted in the wrong place anyway. And is there any REAL necessity for it to be constructed of expensive and failure prone glass. ABS plastic would likely contain the water as well, within certain temperature constraints.
This week we DO indeed present for your edification, education, consideration, and approval, one each MILSPEC video, color green.
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We had failed in the previous week to do so. And I suppose we should explain, though I’m not certain why there is such a necessity to do so. There is no program or plan here. We simply reached a Friday and had nothing to say.
We also had nothing done. I’ve been spending a stupid amount of time playing with something I’m not very good at in the first place, physical machining and packaging for these A123 cells. That causes me to rush a bit on the bits I SHOULD be doing and as a result, I’ve actually blown up a bunch of test equipment. I don’t know if these were run of the mill failures or my failures in every case, but I’ve lost a couple of loads and a power supply in a week.
Throughout the week we work on various little things and either shoot pieces as we go along, or get them all set up to shoot quickly on Thursday and Friday. By Friday afternoon, we had NOTHING – everything we had tried to put together either had some weird failure with no explanation or we were waiting on a part, a vendor to explain why, or something similar. We went down the list Friday afternoon and all had incurable delays or halts to everything we had had a notion of doing that week.
So I went home. Had a lovely evening playing bridge and drinking wine with some friends of ours until quite late. And awoke Saturday morning with no video to edit. Nothing more complicated than that.
I must confess, that in recent weeks I’ve been a bit removed from our overall process and there are few cues in the shop that anyone is watching anyway. My e-mail load had dried up over the holidays as people, I guess, were enjoying the holiday. And I was feeling a little bit of end of year reflection on why we are doing this, what we are accomplishing with it, and whether it is really worth a 24×7 365 day effort. After all, I do have electric cars to drive at this point. What’s the emergency, what are we REALLY accomplishing here, and why am I working this hard at age 56. Truth to tell, we’re probably leading this industry by a full two years from where I had thought/hoped we were.
I know that is a bit hard to accept with daily announcements of OEM electric car offerings literally pouring from the screen. Hasn’t the electric car revolution already happened and we are just mopping up the last of the late adopters and conservative majority on this one?
I fear not. More like we don’t have the early tinkerers and innovators sufficiently and properly organized to sponsor an outdoor cookout even WITH the assistance of the Boy Scouts of America (BSA). I’m actually a bit discouraged that we have been unable to move that token any further than it currently lies on the ground.
In any event, it’s the end of the year. I think I’m going to slow down the pace and play with what strikes me. This week it is the simple addition of an experiment with green chroma key. I was all wired up for a prolonged battle with Final Cut Pro X over green chroma key. We got a largish piece of green muslin and a frame to drape it over behind us and shot the show on faith with nothing to look at.
There were a couple of tricks but really within an hour on Saturday morning I had figured out pretty much how it worked. And lo and behold, Brain and I could be ANYWHERE in front of ANYTHING with the flick of a mouse. I know this is a very basic technique to any of you advanced video professionals. But to us country boys trying to make our way in the big city, this is astonishing. And to have a weather map that is really a schematic diagram is pretty cool for some of these discussions. Without a schematic, my talking doesn’t really make any sense at all.
I have also been hard at work on TWO different A123 modules. The first, actually described to me by Kevin Wong worked quite well actually. It had a couple of minor problems but was very easy to assemble. Unfortuantely, there’s no point in showing it as we’ve already moved on.
The second was originally described somewhat vaguely by Celso Menai of Portugal. Celso IS kind of the battery guy with a small OEM that is developing a kind of tricycle car that is really quite captivating in the video he showed us at EVCCON. This theme was expanded by Mic of Oz – an Australian who provided an animation of it on Vimeo that I rather liked.
Actually in the time I SHOULD have been making video, I’ve made this module THREE TIMES in prototype form. The last has some 48 cells in a 4P12S configuration for a 40 volt 75 Ah module. It is 19.75 inches long, about eight inches high and about nine inches wide and weighs about 75 lbs. It represents a 3 kWh pack.
The prototype has spaghetti wiring on it for the Cellog 8S modules to monitor individual cell voltages. We bottom balanced the entire set of cells at 2.75 volts during assembly. We’ll be charging it and discharging it to see what happens to the individual cells. Under load, poor connections and so forth show up.
This is kind of a leap of faith. We used nylon threaded rod and some pvc nuts and by following Mic’s instructions and including a nut with every insulated piece, we think we’ve managed the clamping forces as well as they can be managed. But we do not want flexing between the tabs and the spacers in the vibrating environment of a vehicle. So we’ve cast the ENTIRE thing in the urethane resin we’ve been playing with.
Actually for the prototype, we have the opaque resin in the bottom and some nearly clear resin in the top and we want to see where we are. But the thing winds up looking like a 75 lb block of ice with spaghetti wiring out the top.
A123 is of course having their own problems with their over engineered cooling system. We did something quite different. I procured some thin 0.30 aluminum sheet from our ONLINE METALS supplier done in gunmetal anodize. Anodized aluminum is kind of peculiar in that it really doesn’t conduct electricity very well, but it DOES conduct heat. So we made little panels of it with a 90 degree bend at the bottom just wide enough for two cells. We slipped those between each TWO cells with the leg pointing IN toward the center.
When we put the battery in the resin form, we pulled the panels down slightly to where the feet touched the form box ends. Then we poured the resin.
We’ll wire brush the resin off these thin feet, exposing the aluminum.
In this way, each cell makes contact with a full sized plate of thin aluminum. That plate extends to the END of the battery where it hooks into this 1/2 inch foot spanning the height of the assembly. I do hope this wicked any heat from any of the cells to these exposed feet. At that point, for some applications this will be adequate. But you COULD attach a chill plate, a finned heat sink, or just place the battery in an aluminum box with contact at the ends between the feet and the box.
The resin, once hardened, should effectively isolate the clamps and tabs and cells and panels from rubbing, chafing, loosening, and otherwise wearing. This is what I consider and important and unfortunate part of the design. We no longer have discrete cells to work with here and no real access to them (other than the spaghetti on the prototype).
I’m actually ok with this. We don’t have access to individual foils in the CALB prismatics we use. So not having access to individual A123 cells is not so very different, except that we have some in SERIES in this battery making up a 40 volt module.
Note also the lack of BMS. I intend to use these as true batteries. If they go bad, they go away. By bottom balancing them on assembly, I’m hoping to prevent failures. : But a single bad cell in this bunch means inevitable and almost immediate failure. We should really capacity test these as well before assembly.
I’ve ordered a little voltmeter with programmable relay from ColdFusion. I intend to hook this up to a contactor and load situation where I can connect a cell and walk away. When it gets down to a specific voltage, ti will disconnect the cell from the load. Assuming they arrive at nearly identical state of charge, this should take them down to an identical state of low charge. I should be able to read our AH meter to detect “short” cells. And the resulting cells can be combined into an already bottom balanced assembly this way with a pretty good confidence on the capacity as well.
Three such batteries would be a 120volt 75 AH assembly and would drive one of the HPEVS systems very nicely with 9000 wH of storage in a scant 225lbs of batteries. We think this would be a 40-50 mile total range or maybe 32-35 mile range at 80% DOD. That’s not far, but many people do drive less than that each day, including yours truly and frankly. The bare cell costs, delivered to us circa 1/1/12, look like about $1250 per module or $3750 for the pack. With resin, threaded rods, hardware, etc, you might be looking at a round $1500 per module or $4500.
Why is this important? Well, lead acid batteries reportedly cost $2500 and offer a 40 mile range. We happen to know that delivered to your driveway, they are more often $3000 unless you are near a battery store where you can get a deal and pick them up yourself. And the 40 mile range is almost entirely made up – wishful thinking. Lead cell cars usually get 25-30 miles in the first two months, and then it drops horrifically over the remaining two years of life. And they weigh a 1000 lbs.
Three of these modules weigh 225 lbs. They really will do 40 miles. They have the advantage of long cycle life – over 3000 cycles. And 650 amps is nothing for these cells. Our tests indicate about an 1850 ampere power output from this module.
So instead of $10,000 for batteries, you pay a 50% premium over lead, and get the same range (actually better) , MUCH lighter weight, and much longer life. If you WANTED to add more cells later in parallel to double the range, it is trivial to do so.
We did order and receive some excellent braided straps from China to replace our EVWorks source in Australia. The shipping and duties from Australia had become really quite onerous and our final cost per strap was over $5 via this avenue in all cases and in the case of the 55 mm straps considerably so.
The shipping and so forth from China is actually pretty steep as well, I think our UPS was $686 on this batch and then UPS came up with some strange $131 brokers fee on the import of these. In any event, I got 1000 of the 70 mm straps we always use on the 100 and 180Ah CALB cells. And a couple of hundred of the straps for the larger M12 bolts on the Elescalade.
We mentioned that it looked like that put us in the strap business whether on purpose or by accident. THree of our viewers have ordered in the first twelve hours so I guess this will be worthwhile. We’re going to put together a set of one 70mm strap, two 18-8 stainless 16 mm M8 bolts, and two zinc coated M8 Nordlock washers for $7 plus shipping. We’ll work on getting some sort of page up that calculates shipping and totals and so forth to make it easy. The larger set for the 400 Ah cells would be $10 per set, but I would be astonished if anyone but us needs those at all.
What I call 70mm straps have 8x13mm holes on 70mm centers. The strap is actually 98 mm long and 24 mm wide of tinned copper braided wire with tinned copper on the ends. We’ll put some photos on the web page when we get it up.
In the meantime, all of you that did send e-mail and Paypal donations this past week, fearing our demise, we deeply appreciate them. It IS true enough that if we don’t find some economic basis for doing this, it cannot continue forever. But that’s not precisely why we missed a week now. But operating with Brian and I and Rod in a dark shop in the cold of winter, we kind of lose sight that anyone is watching or that anyone cares. There’s no shortage of video on YouTube we are well aware. And so our confidence in our mission naturally wanes. The encouragement is actually as important or more important than the donations, but encouragement in DECIMAL is of course the most sincere. I only contribute actual ducats when I actually want to support something. It’s not just happy talk. And we assume you all do the same. So I was encouraged this week. Our viewership appears to be growing and we appear to have the requisite “stickiness” among a set of viewers that keep coming back. That means eventual success if we simply persevere.
We’re hardly alone in our struggles. George Hamstra has 100 motors with no aux shaft as the result of an OEM failure (I’m telling you selling to OEMs is not all as great as you think guys) and Sebastien Bourgoius reports costs on the Shiva have driven them to an atmospheric $9500 for their megawatt controller. So everyone is having their version of a bad hair day at the moment.
But stay with us. If this thing with Iran doesn’t get resolved here pretty soon, we could ALL be heading for a bad hair day at the pump. And we’re just not sufficiently far enough along with all this to deal with it.