Of batteries and range and endurance and costs and complexities and batteries….
This week we continue A123 module obsession AND we do some minor work on the Cadillac Elescalade.
Apparently the A123 cell thing is of intense interest to at least some segment of our viewership. If developed, it would appear to offer some alternative cell strategies. However, these are not entirely without difficulties.
A couple of items. We continue to have lab anomalies I’m hesitant to report in detail. The reason I can’t share these with you guys is you guys. You shred me every time I do with a laundry list of how I SHOULD have done the test.
We are accustomed to testing large format cells – 160 Ah and 180 Ah units with the odd 400 Ah cell thrown in. It’s true I’ve done quite a bit of work in the last year in pairing two 90Ah cells for 180 Ah.
Suddenly dealing with 20Ah cells is just a different world. 1/2Ah or even 1 Ah isn’t anything on a 180Ah cell. It’s not really much of anything on a 100 Ah cell. It’s a LOT on a 20 Ah cell. And so our procedures and test equipment, which I am ALSO always testing, gets a little bollixed up on what I’m doing at any given moment.
IS the decrease in capacity from 19Ah to 17.8 Ah due to test equipment or have I damaged the cell? Or not fully charged it in the first place?
As everyone who has gone into real cell testing has discovered, defining fully discharged OR defining fully charged is actually a little squishy. You can fully charge the cell using anything you want. Let it rest a couple of hours, and it will take more using the same metric. Similarly on discharge. A “bit more” starts to get hard to define at 20 Ah.
But we have had some mysteries. Like bottom balancing four cells to exactly 2.50 volts and then charging the pack. When we discharge it, they are all out of b a lance again. So we repeat the process and they are BACK in balance again?
How about draining a cell to 2.50v and then leaving it overnight with NOTHING connected to it. To find the next day it is ruined at 0.85v. Wait a minute. Recharged it works fine again????
We do not see these sorts of things with the larger prismatic cells. I would characterize these A123 cells as about as stable as a burlap sack full of cats. But I don’t know if that’s a good thing or a bad thing.
More reality. Yes, I know you all are all packaging engineering experts and I was made to WATCH the other kids during art class in the second grade. But whatever I do adds 1/3 to the weight and volume of A123 cells. You can pretty much figure that if it takes 10 cells and they weigh .496grams each that will be 4.96 kg. My package will be 4.96 x 1.33 or 6.6kg. So any increase in energy density you “imagine” from these cells is not only not possible, but if I’m doing the packaging there is a penalty here. A half sized pack doesn’t get you half the range. It probably gets you 1/3 the range. So your 100 mile car with a pack that costs slightly MORE than half a pack probably actually delivers 1/3 the range or 35 miles or so.
Similarly the costs. Yes, it’s $100 for resin. Let’s try polycarbonate at $150. Or straw, at $90. Whatever I do, at least in prototype, dramatically increases the cost of these cells which STARTED OUT very pricey themselves. As their price has fallen, the percentage devoted to connectors and resin and molds and so forth has risen as a percentage.
So despite my obsession with these cells and posing them as a low cost alternative because of their high power output, reality keeps intervening to make it clear to me that this will NEVER be my choice for cells in a car. The large format leggo block 180Ah CALB is the battery of choice for me in designing a car at the moment. And I would list A123’s as “problematical”.
But that’s not to say some effort making them LESS problematical isn’t in order.
On the good side, despite my totally ruined mold, the 13.2v 120 Ah battery is testing well at about 113 Ah without any real overcharging or over discharging. I have mentioned some oddities but the cells seem to still be ticking along. But from what I am seeing I can see new insight into why some are so focused on top balancing BMS systems. They are a brute force way of making these cells do your bidding or appear to. I suspect there is another better way, but I’m still looking for it.
And the 13.3v package is looking pretty good to me in camp green and black. It is a little heavy at 36 lbs was it? But obviously durable. All cells are available at the top, perhaps too much so. A dropped wrench on this one would be fireworks. I might put some effort into a soft rubber “cap” made out of the silicon rubber mold material. Pour it on, let it cure, and pull it off. Then you make your connections and mash it back on to secure the terminals. Kind of a soft rubber hoodie for a battery.
All this is kind of stalling out our larger projects. But I confess I am having some fun. ANd it feels like we are just doing some things very differently from the OEM’s and the very elegant high tech style so in vogue. But I kind of think “car stuff” out to be a little more rough and tumble along the lines of the SLI battery, which has evolved over 100 years – in fact we missed the anniversary of Kettering’s electric start automobile 100th anniversary this week.
The 1912 Cadillac Touring Edition was first to eliminate the hand crank and opened up driving to everyone. Cadillac founder Henry M. Leland, who had already pioneered electric lights and electric ignition on his cars, worked closely with Charles F. Kettering, the inventor of the electric starter, to incorporate the device into his cars. The electric starter also was GM’s first electric motor – a core business today anticipating the growth in the electrification of the automobile.
Point is, that battery has been “evolving” for a century now. It looks the way it does for a reason, or a million reasons. It arrived in Darwinian fashion to be exactly what it is. And so using that as a starting point is not a bad, if slightly blind, strategy.
But new ideas are good too. And so we are casting about. We have used several. We used the alternating cells on the nylon threaded rod. I liked that, but it buried our terminals. We kind of stress tested it, which on reflection may not have been good medicine. But it got us to a pretty gruesome failure quickly which prevents spending more time on such a thing and then having it blow later.
We then mimicked the individual cell thing we already get from China. A word about that. I’ve heard a lot about just using similar boxes and similar terminals from China. Well, I’ve looked for them on Alibaba and I can’t find them. If you can find who makes those, yes, I wold prefer to just buy the existing hardware and plastic extruded boxes, even if I had to cut them down a bit. Haven’t found a source.
And this to the concept of ideas. An idea is not a general piece of shit on a napkin. They work better with measurements, specific product recommendations, and sources. “Expanding foam” is fine. But there are a brazillian. Similarly urethane resins, polycarbonate, silicon rubber, etc. ALl have different cure times, shore hardness, tensile strength, exothermic reaction, temperature tolerance, etc etc. ad nauseum.g
This is why I can be a little short with some of the arm chair theorists. If you’ve really thought this through by looking up at the ceiling, you’re not in the same category as someone like Nabil or Peter who have hooked some of this up and then had an idea they don’t have the resource to implement. And then if you’re a Damien Maguire or Paul Holmes are someone in that category, just send me a list of parts you need and a delivery address and we’ll wait for YOUR video.
I did include a segment of Damien Maguire’s in this episode. If you were looking for someone to liven up the pace of conversation, Damien is more in my camp than out of it. But he does some interesting and of course tedious work on bottom balancing and shows you the ugly end of it on his BMW and so I included the entire video he uploaded to YouTube. I think he will find bottom balancing surprisingly effective in a lot of ways, and no easier than he thought.
I was reminded by the head of REAP systems, a leading BMS developer at the EVCCON that while bottom balancing might be more effective than top balancing, at least arguably, it was not very convenient. My response to him, and to Damien, is that in all the battery testing we’ve done, across several years and now locations, I’ve never once had a SINGLE LiFePo4 cell express ANY interest at all in my convenience. They are just curiously agnostic and apparently have no feelings for MY feelings whatsoever. But on the other hand, if I ask one to do the dive for the cause at my behest, they will head toward zero volts so fast you think they actually LIKE to give their lives in order to save mine. Valient. Just valiant. Splendid behavior.
This week I’m working on a new supur sekert module project. We are code naming this one the FLATENUM SERIES. It will be a flat pack designed to slide under Speedster Duh and ultimately get hooked up to it to provide 120v of juice at 60Ah. I have kind of a theory that this small Ah pack will act as a pack stiffener – holding the voltage up on acceleration. After acceleration, it would be restored by the larger prismatic pack to an identical state. This appears obvious. But it either may or may not be TRUE. We haven’t really done such a thing. I would THINK it will work and instead of plunging to 106v on a hard acceleration we should maintain up at about 114 or even 116volts. This means more power through the controller to the wheels.
it should add about 200 lbs to the car, but in theory another 25 miles as well.
To make all things fair, i’ll just quietly mention in passing that we are considering an addition to the Drag Race and Autocross at EVCCON this year. It will be a two hour race we will call the EVTV ELECTRIC ENDURO. It will run through a very SCENIC fall drive from Cape Girardeau up the hilly twisty U.S. 61 to Perrryville Missouri, thence across highway 51 to Illinois, where it will pick up Illinois highway 3 down the banks of the Mississippie before recrossing at the Cape Girardeau Bill Emerson Bridge back into town. And it looks like 127 miles on the map.
I think Speedster Redux can make it now and Speedster Duh likely will make it after the A123 addition if it works. But if you’re working on an extender pack, battery trailer, etc there may well be a showcase for it in the EVTV Enduro. Probably a timed race rather than a true road race. Time and the ability to complete being the issue.
I may try to arrange some charging in Perryville for those who want to try half of it, and still get back to the festivities without a flatbed. Yes, the entire concept is for this very beautiful scenic country drive to be just beyond your reach. An electric road race no one can finish. That’s just the way my mind works. I would have been different had I been born a TALL instead of a ROUND. But I’m still around.
One other element that will apply to drag race, autocross, and endure – anti homolugation. If you have produced over 100 of these vehicles, you cannot compete other than exhibition only. It must be a custom conversion or VERY small run OEM with less than a hundred instances on the road. We remain TEsla Fanboyz too, but that’s not really what EVCCON is about.