A Target Rich Environment – Tesla Reverse Engineering


The Tesla Drive Unit continues to shock and awe – at least us in the shop. And of course, no sooner had we posted the last video than our “Jack Rickard wannabes” sprang to action to note METOO so it is genuinely an area of interest.

We did learn a bit in dismantling the drive unit quite beyond what we’ve done before. Frankly, I was treating it as a black box. Doug Yipp kind of drew us into an examination of the differential. His interest was racing performance and ours more safety. Let me again reiterate that if you DO get a drive unit working, stepping on 350kw at 35 miles per hour with the open differential in the drive unit IS going to result in a launch from pavement into wooded glenn rather inevitably. We have NOT tested this but it is my belief that the Quaiffe Automatic Torque Biasing Differential will address this in Bristol fashion.

The growl has drawn us in a bit further. Jarrod Tuma and a few others have correctly corrected my explanation of the voltage differential between the rotor and frame causing current leaks in the bearings. IF I understand this correctly, it is more a capacitive issue between the common mode voltage on the stator and the rotor – resulting in a signficant difference in potential between the rotor and ground. And as the only connection between rotor and ground is the bearings, there you have it. The brush bearing does indeed appear to be there for grounding purposes. Yet we growl.

Jehu Garcia posted a marvelous video announcing EVWEST’s initiative to develop their own open source controller board for the Tesla Drive Unit. Wouldn’t that be marvelous? As always, Jehu is a little in the weeds technically and factually. It APPEARS that this is Michal ELias long awaited Universal Motor Controller board, thus far NOT open source. And of course EVWEST is developing nothing. But this may be a California alt-left libtard thing that I just don’t understand. Elon Musk seems to subscribe to it. If somebody DOES develop something interesting, and you buy it and incorporate it, then in some sense YOU developed it having had the astute sense to incorporate it. I get it. Cool.

Mr. Elias actually promised us almost immediate delivery of the UMC three years ago. So his timeline management isn’t even as good as Elons, which is famously poor. And even there, the self aggrandizing “I invented a sensorless Universal Motor Controller board is slightly overwrought as well. Texas Instruments introduced a chipset and a reference design to do just that, which appears to be mostly what the UMC is.

All that said, I personally think it’s a great idea. Actually I thought so three years ago But in this application, perhaps more so. Actually what he is talking about now is a little different. A simple CAN controller much like ours but instead of delivering drive units, he flashes the memory of the existing Tesla inverter control board with a known compatible firmware version. In this way, changes to the firmware cannot effectively disable the CAN control or require rework of it.

Most of these FLASH memory controller chips have some sort of “fuse” that can be blown once it is flashed. This is deliberate to prevent people from downloading the firmware in the chip. But it is always optional. And it appears Tesla elected not to set it. Of course once it is set, you also cannot reflash it, and so it is actually pretty common not to set it.

Without doubt, Tesla has the ability to replace the firmware in the drive unit control board via CAN. And indeed there is a bootrom in the multicontroller on the Tesla inverter control board. SO my first choice would be to be able to flash the drive unit over CAN.

Jason Hughes and Michal Elias are rather desperate for us to be stuck in LIMP mode. Indeed, they are telling anyone who will listen that we ARE stuck in limp mode, having no information on what we are doing at all other than what they see in the videos. Their motive here does not seem to be furthering electric vehicles but again – self aggrandizement without apology. They have offered no solutions. Simply accusations based on fantasy.

But we did come across a more recently manufactured drive unit version that indeed would go into drive and reverse and neutral but did not develop any power to speak of when we put on the throttle. It was really lame. And so I assume similarly “limp”. And that was the drive unit we swapped the DOKA inverter into, leaving the remaining DOKA drive unit as the one we disassembled to find the growl – and as it happens in this video to diagram the cooling system.

But that also leaves us with the more recent inverter which we do show in this video. Curious, we took it completely apart. I should have shot video of this. But it started at taking a peek with a couple of screws and we just sort of accidentally kept at it until it was all in pieces. Opportunity missed I guess. Some photos.

One surprise that wasn’t really a surprise, but is surprising is that the power switching electronics eschews the current fashion in largish very integrated modules such as SkiM in favor of the very common TO247 transistor package. Of course that then requires a number of them for each phase. Again, I have to admire Tesla’s engineering. The TO247 allows them to array the switches along the length of the designed coolant tubes in very Bristol fashion. And so coolant flow per unit of package heat sink area is really quite well optimized in a still very compact package. Comparing the size of this inverter to the DMOC645 or UQM’s behemoth it is a marvel. But three coolant flows going both directions through the heart of the package. Really quite cunning.

The current sensor is also very interesting. They have copper bars as current carriers befitting the high current levels (up to 1350 amps in some of the later models) required for each phase. Two of the phases have current measurement devices. But again, a little designed circuit bridging a manganin metal bridge in the copper bar performs the necessary current sensor duties.

And of course the most interesting part is of course the control board. All the external communications and throttle signals and encoder signals come through the AMPSEAL connector directly to this board, which then drives the power switching circuitry. The brains of the operation.

The task of figuring out the CAN bootloader is a little ambitious. But the multicontrollers on the board feature two 14-pin JTAG connectors. JTAG is the Joint Action Task Group and many years ago came up with this shortcut connector to directly access pins on a chip for programming purposes.

And so, after examining the pile, we sacked it all up and shipped it to Collin Kidder in Sparta Michigan. The mission is to see if we can download the firmware from these chips, and subsequently reflash it onto these chips. If so, we could download one from one of our working drives, and reflash this later manufacturer “limp” inverter back into useful duty.

Actually, Collin has test benches in Sparta and of course has Siemens motors there. The common Siemens motor we have sold for years out of the Azure Dynamics bankruptcy is actually a pretty sturdy 100kW AC induction motor. And so I’m thinking this inverter could be resurrected, connected to the Siemens, and perhaps with a bit of encoder modification, be made to serve as a Tesla test bench without the Tesla motor.

The actual chips used on the Tesla inverter control board are heavily ensconced in a protective conformal coating. This inures it to the vagaries of weather but also has the added feature of totally obscuring the part numbers on the chips. But Collin has already dug into the board and identified the rather expensive Texas Instruments chipset used.

Note that one of the three chips identified thus far is the MicroSemi ProASIC3 A3P125. FPGA’s are Field Programmable Gate Arrays. Early computers were basically logic devices based on AND gates and OR gates and NAND gates and NOR gates and logic inverters etc. I guess modern computers are as well deep in the die. These chips provide massive numbers of them and allow you to write code to configure them in various ways. Picture a hardwired application specific computer. The advantage is that it is lightning fast at performing very defined logic and switching tasks. Tasks such as desaturation detection mayhaps?

The Texas Instruments chip set consists of the TMS320F2811PBQ Digital Signal Processor and the TMS320F280PAGQ Piccolo Microcontroller. Each are gratefully equipped with 14-pin JTAG connectors. We are more likely to find the code of interest of course in the Piccolo Microcontroller – the smaller of the three chips. This is the brains with the DSP and FPGA providing the brawn of the design. (I’m making all of this up, but I’m pretty good at it. Better to baffle you with bullshit than try to dazzle you with brilliance).

Recall if you will our battery work of just a few weeks ago. Jarrod Tuma had a kind of stalled out HACKADAY project to reverse engineer the BMS boards on the individual battery modules of the Tesla. On our announcement of our project, which referenced his earlier work, he was reinvigorated on the project and so we collaborated with him on this project.

Not certain what eventually comes of that, but for the present, seeing this video Tuma contacted us to note that he actually works in Oregon for a company doing Inverter design work. I think we even gave a shout out to the company in our battery coverage. He further noted that IF a junk inverter was to be found at EVTV, he would graciously accede to receive it and store it properly in his garage.

While Tesla drive units don’t quite grow on trees around here. As it so happens, I did get taken on a drive unit that had obviously been flooded and apparently blown up as well. SOmetimes good things come from bad behavior and experience. I’m personally wounded that anyone would be so dishonest as to deliberately sell me a damaged inverter and gleefully take off with the money, on the other hand…. We learned a lot from THAT mess as well. And so we have shipped the inverter to Mr. Tuma.

In all honesty I expected the battery project to go on for months. And indeed, properly putting together an actual device you can use is going to take a few weeks. But the reverse engineering fell into place with almost alarming speed. And so I agreed to forward the inverter in exchange for Mr. Tuma’s continued collaboration on the drive unit. The inverter is a mess. But the control board is likely operational, if a tad encrusted with crap. He is busy with the conversion of a 95 Mitsubishi Eclipse and is reverse engineering the Zytek drive train out of Daimler’s SMART ED. Our buddies at Illuminati Motor Werks are involved in that project as well. Indeed, I think EVWEST sent me one of those and I sold it to Nate and Kevin. Or maybe gave it to em. I disrecall. I personally think it’s a dead end. But at $400 a drive unit, an inexpensive one.

In any event, we are hopeful of his participation at least at the kibitz level with our firmware flashing project. And we may have hidden ambitions regarding a perhaps slow and laborious disassembly of the firmware code itself.

Jehu Garcia is all butt hurt at our characterization of his battery bomb in the Kombi van. In fact, the video embedded in the last blog explaining all about that was hastily removed. Unfortunately not quickly enough. Apparently he had a sekert contract going with a large company to do a battery makeover of HIS Samba. Subsequent to our blog, like the same day almost, his contract was cancelled. He bitterly characterizes me as a “senile old man”.

While his intentions are poor, I fear he may be onto something. My energy level wanes. My forgetfulness increases. He may have hit a nerve here.

Disassembly of the firmware in the inverter control board is non-trivial. This is not 8051 code. Indeed it is one of the most advanced embedded processors out there, and pricey at that. I think they’re about $32 each in single quantities. But there are those that like to do disassembly as an exercise. Having done some, I’m not one of them. But if you are, we’d be pleased to add you to the hack team. I probably am old and senile at this point, but if I can enable some young tech stallions to carry on the work, might be good things to come of it for all.

If you are all into self aggrandizement and overawing the aborigines with your hacker magic, posing as an expert and one upping anyone you can find in a forum to listen, you probably won’t be happy with us. But if you sincerely want to further the EV and custom EV DIY end of the world, and enjoy the process and learning along the way, do contact me. No Tesla employees please.

Similarly, in this episode I introduce the Tesla charger. We have for several years done a brisk trade in Chevy Volt chargers. This is actually a charger made by Lear and it was used in the Coda automobile. We obtained some after their bankruptcy. With different firmware it was also used in the Chevy Volt. We decoded the CAN messages needed to set the termination voltage and current. Actually the bare minimum required.
And have then sold them as an inexpensive but very high quality and durable 3.3kw charger – slightly more powerful than the Brusa we had sold and somewhat less expensively.

We have accumulated 10 of the Tesla Chargers intending to do the same but have never really had time to fool with them. I guess we still don’t. But I have one wired up and I’m playing with the CAN and the startup sequence of what has to be hooked up first and before the other thing, which then enables the third thing etc. etc. I get these chargers for $400 or $500 because they are totally useless boat anchors. Nobody has made one work that I know of. It is only rarely they show up. Generally they get SHREDDED with the rest of the car that can’t be sold off in the salvage parts market. Which is a crying shame. It’s a GREAT charger, 11kw in a very efficient and compact package. While I don’t know the current architecture, in the early Tesla Supercharger stations they simply had a dozen of these things stacked up inside running on 3phase.

It’s actually very versatile, effectively working on any wall power commonly available in the world. I suspect it would work on a DC input as well up to a point. It’s 336% more powerful than the Volt charger. And so it would charge any EV from 50 to 430 volts in less than 1/3 the time.

But like everything in the Tesla, it is very tightly integrated with the MCU gateway, the BMS, and even the EVSE on the wall. And as always, so many projects, so little time. Plenty of bizarrely bad advice, and so little actual help. I actually had a man comment on this video offering us the condescending and very knowledgable expert advice on what kind of LIGHT BULB to put in our drop light. Thank you. I didn’t know any of that. Look at me.

I shouldn’t complain. Actually many viewers are quite generous and much more knowledgeable than I. We recently hosted a visit from Randy Lee of Toronto. Randy has a CNC machine shop there and built us 3 sets of stub axles with VW flanges for the DOKA. Very high quality. And so Bill Bayer, in this episode, installs the Tesla Drive Unit and axles into the DOKA using Randy’s pieces.. A very different kind of build with no transmission.

Some yet to go I guess. But I heard an airplane roaring under the DOKA this week and I can only assume a cooling system is going and that indeed the radiator fan in the DOKA is a monster. Even using the wrong drop light configuration, this build is getting very close.

I will be pleased to show you in the next episode our new SPEEDHUT gages. Bill built me a little panel for the Tesla drive unit bench with the DOKA gages and we got them working very productively. The Tesla control unit now drives these gages perfectly to provide MPH, RPM, AMPERES, SOC, INVERTER TEMP, and VOLTAGE. Actually the voltage is currently our 12v. But since I informed Bill that in no way would he ever get these back for the DOKA, order new ones, he has conferred and confabbed with SpeedHut. They actually want us to act as a reseller for these and have agreed to some custom printing so we can use the 12v for 400v, more realistic inverter temperatures, BATTERY instead of FUEL LEVEL, and we intend to make the tachometer do double duty as an analog current display as well as RPM. They are large, easy to read, and eerily backlit.

Yes, I like the 7 inch EVIC display. It looks Tesla. It has all the information. It has a touch screen. But even on the Tesla with a 17 inch screen, I cannot reliably hit the CENTER button on my garage door opener on the screen AT DRIVEWAY SPEEDS. It’s just hard and clumsy to hit. Large automotive gages will be a delightful addition to the DOKA. These new LEGEND CAN SERIES gages from Speedhut finally solves our instrument cluster woes on converted vehicles. Yank the instrument cluster entirely and replace it with these gages.

Jack Rickard

44 thoughts on “A Target Rich Environment – Tesla Reverse Engineering”

  1. William Maxwell

    Congratulations EVTV Team. Great work.
    I’m glad you discovered the growl source. wonderful detection skills. you arrived at the bearing current failure analysis faster than I did once with a 2megawatt diesel ICE motorgenerator, which wiped out the rear main bearings of the 1,800hp Catapilllar engine.
    A neat solution for the stub axels, and great design decisions the well designed final solution that Bill assembled on camera. Good word Bill.

  2. Jack and Bill I’m very pleased that I was able to custom machine the Doka to Tesla stub axles for the effort. I find it very difficult to just sit back and watch someone struggle with something to me, “is just a walk in the park”. Like yourself the the experience you have garnered over many years involved with computer systems, for me it has been the machine business of gulp 39 years. I became very interested in magnetic drive after meeting a man Bob Patterson who had converted a Honda Prelude. The back seat was loaded with lead and the performance was interesting but range, not so much. Fast forward to “Who killed the electric car” and a Chevy S-10 EV (the brother to the GM EV1) for sale un-operational all of which set me on a path. With the inspiration of people like yourself and the DIY mentality the little S-10 is moving again. I may add its sporting EVTV/Chevy volt charger which is working very well.

    I enjoyed my visit to EVTV and wished I could have stayed longer and got my hands dirty. I have a solution for the spline shaft drives on the UQM and Siemens motors almost ready -another week.

    I must clarify Jack I live in the countryside north of the town of Strathroy 220 Km west of Toronto.

    Randy Lee
    Randen Technologies Inc.

  3. I LOVE Speedhut gauges! I discovered them during my eBugeye build (https://sites.google.com/site/fredbehningsebugeye/build-progress/01-08-26-2011-dashboard-and-12-volt-controls) and put a set in the evTD (http://evtd.blogspot.com/2012/07/dashboard.html) as well. The dash in the PorschEV (http://porscheev.blogspot.com/2015/11/a-pinch-of-this-dash-of-that.html) has a digital GPS speedometer with the EVIC for all of the other read-outs, but I’d prefer a more traditional analog gauge set. Since the EVIC’s battery SOC and Amp hour counter needs some debugging that is understandably low on the priority list, I’d love to the replace the whole thing with the original panel and analog Speedhut gauges. Any chance they’ll work with the CAN bus feed from my trusty old DMOC/GEVCU?

    1. Fred:

      It’s about getting a ROUDTUIT. But yes, porting the code in the Tesla Controller to work with Speedhut gages in GEVCU is relatively trivial. The problem with GEVCU and SOC – it isn’t on all the time. We can measure current and track kWh pretty easily. But only when you are driving. And we can save it and retrieve it on startup. But if you charge, we aren’t even ON so it’s hard to know how much got in without a current sensor on the battery itself and power on during charging. That’s really the issue.

      The Tesla Controller is part of a kit. It includes an ISAScale IVT current sensor. It has the same power on issues, but we can at least measure current.

      Then too, GEVCU doesn’t really DO speed. In the Tesla drive unit, our gear ratio is fixed and the Inverter actually gives us speed and rpm, even though they are kind of in lockstep.

      So whipping up the code to the drive the gages is trivial. But dealing with things like speed and charge state is not.

      1. My thinking was to get a Speedhut GPS Speedometer with a face that matches their CAN Tach, repurpose a mini-tach for an ammeter, and add the voltage, inverter temp, and perhaps Fuel (battery) mini gauges you describe above. I’m well aware of the challenges of capturing the current in and out and may just resort to an Orion BMS for that purpose as well as taking heed of your warning on the Leaf (Better Place) cells.

    2. Fred:
      One solution to driving your analog gauges might be to use the Cluster driver box I developed for Jack a few years ago. It will drive One pulse driven Tach, 3 analog gauges, and two idiot lights. You select the can ids, data ranges, and set the gauge range. Just a thought. Its listed in the store.
      David Seabury

    1. Look quick at SHOPCAM2. Dylan and I are very very lucky guys this morning in that we are still alive. I swear, 1/4 pedal and this thing jumped straight up into the air, flipped over and came at us with both wheels and axles spinning.

      Better to be lucky than good. So much for these lame wannabee LIMP MODE theories.

      Jack Rickard

      1. Well, Jack, it seems as though you all are having fun with all things electric, and specific, Tesla. I on the other hand am stuck, with a wish. and no way to ever afford to do my own build. But as part of the prime directive of the Star Trek show, wanting is far more pleasing than having. Just to let you know I am deriving some pleasure from watching you guys work on your stuff. I guess what I want to say is. Thanks for the videos and the reading material.

  4. You don’t need a tachometer in an EV with a single speed gearbox. Once the system is setup the motor RPM will be always proportional to the vehicle speed and irrelevant. You see this in the Tesla Roadster. Both gauges do the same thing at the same time, a waste of precious dash space. A tachometer is needed in a multi-ratio transmission since there is a possibility of over-revving the motor which I know from personal experience is a bad thing.

    Imagine the commutator exploding, the attached wires being flung against the stater, instantly ceasing the motor, this promptly turned the differential into confetti. In addition brush parts flew out of the motor and punctured the 2 PbA batteries in either side.

    I do like the idea of re-purposing the tachometer as a current indicator. More useful information in an EV and it has the same size ratio as the information relevance. The bigger the gauge the more often it is read and the more important the information is. The only bad thing is the scaling. The information requires both positive and negative indications.

  5. I got to thinking about the Tesla inverter that runs slowly. Could it have come from a dual motor Tesla? The rear drive would be expecting positive responses from the front drive. With no front motor, go into limp mode to get the vehicle off the road. The both motors do have to work together to drive the car after all.

  6. Hi there,
    Actually what causes the bearing condition is pretty well documented on the est-aegis website and they are probably not the only ones to manufacture bearings E.S.T. protections. The large surface of the casing’s backplate is certainly a nice path for electrons, especially if the bearing is already worn, not only by the flow of current. I suppose the gears on the shaft are helical (N.V.H.),as a result there could be an axial load that only this end bearing would sustain, we would need to check the cut and rotation of the motor. In addition, it’s interesting to notice they choosed a classic coded wheel design instead of a coder bearing, probably because of the shaft’s current that could jam it (hysteresis?or just the voltage). Just a few thoughts…
    All the Best
    Guilhen CROISSANT

    1. Stanley A. Cloyd

      At work when large motors were rewound for invertor duty they all got a brush kits installed. Is there a ceramic bearing to replace the eaten one? Ceramic is an insulator right?

      1. guihen croissant

        Ceramic is an insulator, and there are ceramic fitting rings ( outer fitting for sure, maybe inner as well ) . I’ll have to look for ceramic bearings, i don’t know. Anyway, it looks like there could be various strategies to overcome these problems: ceramic fittings+microfiber brushes, preferably on both ends of the shaft. An other one, that of bearing manufacturers, fill bearings with conductive grease to ensure a continuous flow of electrons and therefore prevent build-up and discharge cycles. I’ve seen papers about the subject related to alternators for mild-hybrid systems, so just 48 volts.
        Another one would be to have some sort of “anodes”, pretty much like the ones you find on boats to prevent damages to the propellers. Anyhow, differences in potential will always exist, proper pairing of materials will be found, it’s exactly why there are no carbon fiber tubs with direct contact with steel mounting brackets, inserts, the stronger will always win. Aluminium vs carbon are more equal and live better together.

      1. When the speed of the vehicle is from GPS and with different vehicles having different tire diameters one universal scale for the tachometer and speedometer can not be used.
        Mark Yormark

  7. I just watched the Tesla Battery (17 MAR) video again. I got to looking at the photograph of the BMS module. I’m wondering how the high voltage side is powered? Is there a DC/DC converter on the other side? Or do they power the high voltage side from the cells being monitored? Which is a bad idea especially if you don’t regularly use and re-balance the cells. No matter how identical your design is you will never draw down to the nano-amp the exact amount of power from each cell in a pack. Over a long time the pack will get out of balance just because the modules can never be identical.

    Another question I have about the bad module where a cell is measuring 0.13 volts. Is that cell truly bad or is it an instrumentation fault? Did the BMS module short out and drain the cell to zero? I’m curious if there is any kind of damage to explain the zero volt cell.

    1. First, we can observe ALL the cell voltages of up to 62 modules, and we can bleed any cell to bring it to anything we like. They don’t have to be balanced to the nanovolt. Just brought into line.

      The bad cell in our module is not instrumentation. We can measure the voltage of that cell with a handheld Fluke meter and it matches the reported voltage exactly. It’s just dead.

      There was no visible damage to that module.

      Jack Rickard

      1. As we learned from the Celllogs. When you power from the cells you’re monitoring any difference in the power consumption throws your pack out of balance over weeks and months of operation. The first 6 cells were powering the entire Celllog and the last 2 were powering only the bias circuitry. This holds true for the individual Celllogs they can never be identical due to variations in the component tolerances.

        I was just wondering how the Tesla BMS modules were getting powered. The low voltage side is simply powered by the external 5v supply. Where does the 8051 and the BQ76 get their power? I would think a company with that amount of engineering expertise would know you don’t power your BMS with the monitored cells. How do they disconnect when there is a low SOC situation to keep from damaging the cells?

        It’s interesting how just one cell bank could be drained down to zero. I’ve seen strange things with 18650 cells including one where it refused to accept a charge. It would continuously draw a low charge current and as soon as the charging was stopped the voltage started dropping. I guess that is what happened to one of those 18650’s. Where did all of those amp-hours go? No telling how long that pack sat on a pallet, with no one checking on it, waiting to be sent somewhere.

        1. My early hamradio experiments with NiCD mignon cells and charging with biased AC resulted in stalagmites and stalagtites stabbing through diaphragm and shorting the cell. A short circuit could fuse the short but no way this cell was doomed.

          John Hardy has seen those same minor shorts with lithium. Horse manure happens and those shorts come from the factory – undetected except when bottom balancing.

        2. The individual module BMS boards do indeed power directly from the cells they monitor. I think there are some sleep modes that reduce the drain dramatically, but they are absolutely powered by the module cells.

  8. Jack, great work as always.

    I just want to say that you have it backwards as regards the differential.

    In the absence of traction control, a less open differential INCREASES oversteer.

    An open differential will only spin one tire, leaving the other available for cornering traction.

    A Quaife or other locking differential will spin both tires leaving no traction for side forces, thus increasing chances for redirection into the aforementioned wooded glen.

    I think it is great that you have made them available, definitely a sporting upgrade, but they don’t negate the need for traction control, they increase it.

    The Speedhut gauges are going to be a big seller.

    1. Is the Quaif really a locking differential or more of a automatic torque biasing (ATB) limited slip differential (LSD) ? It is my understanding that the Quaif uses helical gears instead of plates so never actually locks and does transfer power and torque away from a spinning wheel to the wheel with the most traction. It appears the Quaif isn’t an open differential but is not a fully locking differential either.

      1. Differentials?
        All I can tell you guys is what I’ve experienced with Seven and our many different diffs in the same car.
        We’ve had three types of diffs, four total in the car.
        The original diff from the 5speed Geo contained only one set of spider gears and was refered to as a limited slip diff.
        Remembering this is a front wheel drive car, without ‘slip’ turning the steering wheel is a challenge.
        When we stomped on the accelerator with this diff the car pulled HARD to the passenger side. Counter steer of about 15-20 degrees was necessary to stay on the road.

        The second diff doubled up the spider gears like what I think Jack used in his VW builds. This was also a limited slip differential but with notably less unwanted slip. All torque steer virtually disappeared with this diff when stomping on accelerator. No counter steering was required to prevent leaving the road.

        The third diff was like Jacks current fully enclosed Quaife, and until it broke a few teeth, worked nearly undetectably different from the doubled up spider gear we previously had.
        It was also a limited slip diff, but with torque biasing…but since it operated the same as the doubled up spider gear style, e.g. No torque steer, they are probably both to some extent are ATB devices.

        However, once a few teeth broke in the quaife it became a fully ‘locked’ differential…which made steering a front wheel drive car virtually impossible while the car was moving at any speed.

        The forth diff is the same as the third diff only not broken so adds nothing to our tail of three diffs.

        So as far as Seven goes:
        A quaife is not locking, it is more stable than a single spider gear style but makes no noteable difference over a double spider gear style.

        Hope that helps


        1. Some additional info.
          So why not use the doubled up spider gear instead of a quaife? The doubled up spider gears are a straight cut gear and started to ‘growl’ under low load after a few thousand miles. Upon inspection it was discovered the high torque loading, both forward and regen, was too much for these gears and lots of wear had occurred, creating slop and the growl sound.
          So we upgraded to quaife.
          The first quaife had a flaw in the metal in one of the gears which caused it to break. Ower machinist made us a new set from a chrome Molly aloy and it’s been working perfect ever since.
          So from my experience Jacks right on this one, sorry Jack.

          1. Actually I profess no particular knowledge of differentials or anything remotely mechanical. Doug Yipp and the guys at Quaiffe kind of worked all this out.

            I do believe that running the Tesla Model S with the open differential it has and no traction control is a death defying act and quite dangerous.

            I believe the Quaiffe differential addresses this issue as well as it can be resolved.

  9. I selected the Quaife ATB as the differential of choice for our Tesla Cobra race car for a number of reasons. 1) Great reviews from anybody who has ever had one, 2) Quaife’s reputation as a quality manufacturer of Motorsport drivetrain parts, 3) Quaife’s willingness to work with us on this custom application.

    Is their ATB the only differential that would work in this application? Of course not, that’s like saying that Microsoft Windows is the best operating system for everybody! I just personally think the Quaife unit is right for ourselves and most of Jack’s customers.
    Here’s a couple of random links I selected from the Internet: A thread from the Boxster/Cayman forum, and a couple descriptions from vendor pages. I am not associated with any of these groups.


  10. Just watched the 28 April video. The reason there are 2 processors, 1 DSP and 1 regular, is to spread the processing load. The DSP version is controlling the inverter to the motor and interacts with the car minimally, basically reports I’m OK. The other processor controls all other functions of the inverter. You don’t want your controller getting distracted in the task of controlling 1000+ amp IGBT’s. It would be bad to forget to turn the IGBT’s off while telling the rest of the car the value of 6 different operating parameters. Microsecond timing is important here.

    You might say the DSP sees all of the CAN traffic. But there are several hardware masks and filters built into the processor CAN interface that only allows a few select messages to be seen.

    1. Yes, it is very likely that you’ve articulated their reasoning. However, it’s still a bit odd because the processor doing the PWM has all the relevant information you’d want to send on the CAN bus – voltage, current, phase angle, etc. It also needs the information from the CAN bus – target speed, target torque, upper limit torque, regen limits, etc. So, really that one processor needs all the information anyway. I suppose you could offload some of the busy work on the CAN bus to a second processor but it would still be somewhat inefficient to do so. It is possible that the main CPU only has CAN so that it can be directly firmware updated. Then, the second processor could deal with the outside world while the two talk over a high speed serial link. On the same board you could use a multi-megabit serial connection and thus transfer info faster than 500k CAN. But, I still wouldn’t do this. A properly programmed and sufficiently fast processor should be able to do it all. PWM is done via hardware interrupt so really it doesn’t get delayed.

      1. Consider that CAN bus. How many messages per second are being shoved up and down it? When you’re on a busy bus, there becomes a point where your node spends as much time dealing data traffic as it does performing its primary function.

        When you’re turning an induction motor with a very high power inverter you want absolutely smooth operation. This is best achieved with a dedicated processor. Not one that has to spend half of its time receiving CAN data, interpreting it, providing responses, measuring temperatures, formatting outgoing data, analyzing stability control data etc. Also as the size of the control program increases the chance of a minor code change or a glitch having disastrous effects increases.

        Calculating the phase currents in an induction motor is not a simple task. The more time you spend computing them the better. Parameters like the temperature of the rotor are irrelevant to the computations and better processed by the safety processor which is trying to keep things from going up in smoke.

  11. Just watched the April 28th show Very informative. I think you supplied the information on the immobilizer bit. I got to thinking what if this bit operates as if it is the 12 volt supply in a contactor. Thus a 1 supplies the voltage to turn the contactor on, then a 0 removes the supply and turns the contactor off. Also I got to wondering if Tesla sends over the air a 0 for this bit to shut down the cars that they do not want to be running? Steven

  12. I’d love to get my hands on some of this random junk the auto recyclers shred or tinkers discard. Australia has such a low EV take up however, postage from the US makes it mostly too expensive (or difficult).

    I wouldn’t worry too much about Jehu, it’s just as likely the battery manufacturer didn’t like his plan of inviting hundreds of random people over to solder batteries. Given they don’t recommend anyone solder to their cells, that alone is a bad idea.

    1. Actually that is Damien Maguire. You might recall we did some CHAdeMO work with Damien many moons ago and today we support his work through his Patron account. I think he’s onto something here.
      He’s done an Arduino Due replacement control board INSIDE the charger that controls the three charging units inside the charger. That kind of eliminates much of the externalities required to work this thing.

  13. OH! Ok. I now can make an informed guess of where Damien’s recently run TESLA Model S front motor is being shipped to for a certain all wheel drive EV conversion that is in desperate need for a magnetic drive front axle.
    Also, I am still in need of a TESLA 11kW charger if it fits into my build. What are its dimensions?
    Mark Yormark

  14. Pingback: A Target Rich Environment – Tesla Reverse Engineering | Car News, Reviews, & Pricing for New & Used Cars.

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