Share →

I’ve been obsessing on a new controller design for the Tesla Model S battery modules to such a degree the past two weeks that I’ve rather failed to do a video, or even blog our last one.

Which is remarkable in that in the May 26 video, actually published on May 24, I’ve not only lost complete reference to the calendar, but we’ve reached a new Milestone several different ways.

First, as of May we have been in continuous publication for eight years. We should probably be enjoying greater success by now. But I’m older and slower and we publish less often and indeed I forgot to blog this video frankly. The upside is I get to meet so many new people each day.

We have driven a lot of electric cars in this period. None really approaches the Tesla Model S – a remarkable feat of engineering and I’m reminded of it daily. For a little over two years, I’ve been focused on reverse engineering the Tesla Model S drive unit, and the 1990 Volkswagen Type II T3 Vanagon Doppelkabine is the driving test bed for that drive train. I don’t know what I expected, but a pickup truck that drives like a Tesla Model S was not it.

There were indeed some corrections to the controller software once we had it in a rolling vehicle. But I’m actually stunned by how few there were. We found out the hardware charge enable really doesn’t work and indeed Tesla has replaced it with a charger CAN message instead. A couple of our Speedhut gage scalars were hosed up. And we got into kind of a circular hardware reference between the brake light output and the brake input due to some wiring comedy. Some axle measurements were off requiring a 1-inch spacer to keep the CV joints from coming apart. But in less than two days it was all worked out and rolling. The many months of bench testing and many iterations of the wiring harness payed off big time.

The result is a 480 horsepower VW pickup truck with very positive traction from the Quaife automatic torque biasing differential and you can see the results in the latest video. Over and over actually.

But beyond that, I was kind of shocked and disappointed to get in my beloved Siemens 115kW 154 HP Yellow Thing. After driving the DOKA, it seemed lame, clumsy, and underpowered. Actually, I drove it yesterday quite a bit and it wasn’t long before I was enjoying it again. But when I first got in, the comparison with the DOKA was stark. For a big, too tall pickup truck with goofy suspension, the yellow rubber DOKA is just a scream to drive.

Further testing revealed about a 325 wH per mile burn rate which was encouraging and very much in line with our 10:1 rule with a total vehicle weight of 3530 lbs. But the aging Better Place Renault Fluenze battery pack isn’t really cutting it. It produces enough power apparently. But we are barely getting 49 ampere-hours out of the Nissan Leaf battery cells in it that started life claiming 62.5 Ah. Bill crept the last few hundred yards from a car show in Jackson yesterday after barely 50 miles.

Originally, we used to design our cars for a minimum 100 mile range as that was the number everyone wanted to hear in the early days of EVTV. But after numerous builds, we noticed that in this small town, barely four miles on a side, we were charging about twice a week. And a visit from Damien Maguire of Ireland drove this home. We were driving down the road in the Escalade when he asked when the last time I charged it was. Frankly, I couldn’t remember. And that makes sense because we didn’t make it back to the shop and had to call the flat bed.

Would you believe that if you have TOO much range, you simply quit bothering the eight seconds it takes to plug in in the garage each night? And so four the last couple of years we’ve targeted a more sedate 60 mile range, which we did not precisely achieve with the DOKA it would appear.

So we face a dilemma. Go with what we’ve got or enhance?

On the one hand, I like what I’ve got and Bill did a great job hiding three 128vdc segments from the massively over-engineered Better Place pack. One on each side of the Treasure Chest underneath the pickup, on slides actually, and one under the back seat. The result is you truly cannot tell this is a conversion without a very close inspection.

Of course we have about an acre in back. Which seems a lot for carrying groceries and/or lawn chairs. We could add a second Better Place pack in parallel in the back of the vehicle. I can see getting my buddy Dan Todt down at Southeast Fabricating to gen us up an aluminum box for them, spraying it with bed liner, and mounting it right beneath the rear window. We’d have a kind of “hump back” looking Doka then. But paint it black and it disappears, right?

Of course, we also have a couple of full Tesla batteries lying around for our work on the battery controllers. But the full slab would actually have to hang out the back a foot.

That said, it IS a pickup. If we removed the individual six-cell modules, we could kind of stack em in back and wind up with a much smaller or at least shorter package. The cell voltages are actually pretty compatible with the Nissan Leaf cells which are actually a different chemistry but feature the same nominal and charging voltages of 3.6v and 4.2v. So I could see putting them in parallel, and well, hold my beer let’s see what happens.

But it is kind of going from one extreme to another. The problem with the Tesla modules is that they are not very granular. You can’t really subdivide them. They are 235 Ah and you need all sixteen to get to the same voltage. That’s 893 lbs of battery in the back of a half-ton pickup truck. We probably have about 17 kWh of storage now, and with 85kWh from the Tesla modules, that would bring it well up over 100kWh. Even if it bumps our weight to 4500 and our burn rate to 450, that’s a 226 mile range. For what? The thing doesn’t even have air conditioning… And it certainly wouldn’t be as spry as it is now with 1000lbs in it. Tough enough with 300lbs of Jackmeat onboard.

Range wise the second Better Place pack would make more sense, bringing us up over 100 miles. But when and in what sort of vehicle would I EVER get a chance to actually use a full Tesla Model S battery pack in a build?

Well one candidate would be the 2008 Cadillac Escalade. Recall we spent 2010-2012 on this build with our first run, sans front hood, in July 2012. I am chagrined to report that it has burned up it’s SECOND six-speed automatic transmission, or third, I forget. Our experiment at marrying electric motors to automatic transmissions appeared to initially be a success. But if you have to change the transmission every two years, I guess I would mark that down as a FAIL over time. Durability is a desirable trait and the marriage of electric motors with existing transmissions has simply been fraught. I’m not alone here. Even manual transmissions have been smoked across the land by the much faster application of torque the electric motor provides.

A couple of months back we received a kind of all-day visit from Mark Buttgereit of Impatient Creations in Alabaster Alabama. It’s a custom car shop and one of many “West Coast Creations” type operations. He wanted to get into electric vehicles and specifically muscle cars using a Tesla Model S drive train. I attempted to explain the vagaries of fabricating a means to implant a full Tesla Model S independent rear suspension subclip in an existing vehicle, but he assured me he knew all about it and he started describing how to take it all apart, cut it into pieces, weld them all back up, and make the 75 inch track shorter and get it all to hang together. I was genuinely horrified by what he described.

But also reassured that he seemed to know what he was talking about and certainly unafraid of unusual builds. He was a bit daunted by the pricing of the components and has been studying on that for several months.

So when the L6 transmission went out AGAIN, I had kind of had it with the DC motor, low voltages, and transmission problems of the Escalade. But I really like the truck. It is just very comfortable for me to get into and out of, great visibility, and great roadability. It just glides down the road. Good air conditioning and heat, which were the main build objectives at the time.

Subsequent to the very good outcome on the DOKA, I’m again enthused to spend a stupid amount of money on a build I’ve already done once. And I called Mark and he was glad to give me an estimate for a stupid amount of money to transplant a Tesla Model S full subclip into the ass end of my Escalade. Indeed, he’ll pick it up, take it to Alabama, engineer the transplant, and deliver it all for barely the cost of a used Leaf.

The aging 400Ah Thundersky cells in it barely make 200v, totally appropriate for a dual Netgain 11inch with dual Solitons, but totally useless for a Tesla drive unit. We’ve already removed them from the car. But I believe I can get all 16 Tesla battery modules into the same space. Picture an Escalade with 85kWh battery pack and 480hp Tesla Drive Unit. That actually DROPS the battery weight from 1620 lbs down to 893 – nearly in half.

One of the ongoing problems on the Escalade that I meant to address is the airbag suspension. Touted as just the thing by Cadillac, it has proven to be just the thing NOT. The onboard air compressor does indeed level the ride automatically, but they leak. We had them replaced once and it was good for a month or two. Then they started leaking again. Turns out ALL Escalades have leaking airbag suspension and there is a cottage industry into converting it to Silverado coilovers. We just never quite did it. Mark and I have discussed how the Tesla implant will NOT feature those monsters in the design.

We will complete the build here. There will be plenty for Bill to wrestle with in installing our Tesla controls and without the front motor, driving the hydraulic steering and brakes and the A/C compressor.

Which brings me back to our latest project, or again latest project. Recall that with the assistance or leadership of Collin Kidder and Jarrod Tuma, we had kind of decoded the vagaries of the BMS boards on the Tesla Battery Modules. Well, that’s all good. But it doesn’t precisely do very much. You need to actually couple that with hardware and software to control contactors and disconnect the battery if any of the voltages or temperatures or cell imbalance etc and you need to be able to configure all that in a variety of ways.
We’ve been working on a device and software to do that with two or four modules for a 48v home solar “Powerwall” I suppose. But it could easily be adapted for vehicle use. And without it I wouldn’t even load the Tesla modules into a vehicle for transport. They are simply horrifying compared to the LiFePo4 cells we are accustomed to using – at least in terms of safety.

The project is not completed. I just sent off for our third (or maybe its fourth) set of prototype boards for this. But I have done some very PRELIMINARY work on the manual. It rather illustrates how easily an apparently simple concept quickly gets off into the weeds. It’s over 50 pages and not DONE yet.

But it will also give you an idea of the capabilities and possibilities. SOME level of safety can be achieved using Tesla’s own BMS boards and some aggressive monitoring to shut things down if there is any sign of distress. And I think I could ultimately integrate this into the Tesla Drive Unit software such that we would have a pretty tight system between the drive unit and batteries. The Escalade is probably where we should experiment with this->.

And now a word on maintenance free electric vehicles NOT. The Tacoma had an ancient PWM controller termed a RAPTOR. I hated the Raptor. Actually it worked admirably as a controller but it used some sort of inductive slug throttle mechanism that was entirely too amptly named. It was like stepping on a pickle. Mushy. It finally blew. Bill and Dylan worked all week to install a Soliton on the little ADC8 motor and did a yeoman’s job of it I might add. Dylan drove the truck Saturday and ran completely out of juice ostensibly at 79Ah from the 200Ah cells. Kind of hard for me to picture. And I find reports of when things are charged and when meters are reset curiously unreliable around these parts. But this pack has been run to zero so many times I think its’ starting to LIKE operating below 100v and indeed we’ve replaced a few ancient Thundersky 200’s, which are of course no longer available, with CALB 180’s, which do run about 200Ah, so we have a mixed pack of old and new, different chemistries, just a mess really. But it is a small Toyoto Tacoma truck that Mr. Botteron of Heber Springs Arkansas converted as a brand new truck and it is itself in great shape.

And Saturday, I drove my beloved yellow 1974 VW THING to the shop and it died right there. When I turned it back on and attempted to back out of the shop it was completely dead. Incredibly, a GEVCU. The only known failure of one of these units. We’ve never replaced one from the field. They just work. But this one died rather totally. So we had to install another one and of course the hard part was to find the settings we had used to configure it. It runs again.

Bill had done his Ford Ranger and watched carefully as we described the necessity of having the flywheel and clutch and pressure plate balanced. But he was in New Jersey at the time and after calling around couldn’t find anyone who even knew what he was talking about. Here they do them at NAPA down the street. But the “buzz” finally got to him so he pulled his motor to have it balanced. Again, the culprit was the DOKA. The “buzz” was fine until he drove the DOKA a day or two and then it was unbearable in contrast.

So some days it seems it is raining failed electric car parts. If ANYONE tells you that electric cars are maintenance free, run, don’t walk. They live a life REMARKABLY like every car I’ve ever owned. But cleaner and with less greasy grime and odors. And actually I find them much easier to troubleshoot and repair. But that could be my background.

I know that all sounds whiney and you should all feel sorry for the wretched life I lead. But I have to tell you that I can’t wait to get out of bed each morning to live it. Thomas Edison was purported to have said that all you needed to invent was a good imagination and a pile of junk. I have 14,500 square feet just piled full of junk – and I know how to use it. My main problem is people keep coming in wanting to clean it all up for me…