Some Days Being Better than Others at EVTV

64 Comments / VW Thing / By

Tough week.

Somebody tell Selsea Chexton et al that this thing about electric vehicles being maintenance free is a fantasy of theirs, not reality.  Jason Horak and I don’t see it that way.

It was bad enough that the transmission in the Escalade imploded.  I find it odd that it did so.  It is indeed a heavy vehicle, much heavier than stock.  And we are putting a bit of power to it.  But frankly, the transmission seemed to be shifting pretty smoothly.  And my driving style is pretty tame frankly.  Picture 0 to 30 in 10 seconds.  And 30 being about it 99% of the time.

Once in awhile, if I coasted downhill for 30 seconds for example, when resuming the throttle, the transmission would kind of “bang” into gear in what I would describe as an unnecessarily hard shift.  Oddly, the experts at LeGrand transmission noted that the gasoline version does exactly the same thing and not to worry about that.

But in the rebuild, they were very confident that what I needed was a HIGHER stall speed, not a lower one.  This is counterintuitive to me.  Diesel trucks all have lower stall speeds.  Lower stall speeds of course lockup the torque converter at lower rpm and this makes the transmission run cooler and last longer.  Diesel engines have more low end torque while gasoline engines tend to develop it at higher rpms – typically 3600 for a V8.  And so to my way of thinking, the electric motor is more akin to a diesel power plant.

But I suffer an ongoing malady.  I probably know more about more different things than anyone you’ll likely encounter in a normal environment.  But about 90% of what I know happens to not be EXACTLY technically correct.  I’m keenly aware of this fact, which is the difference between me and most, who actually believe what they know to be true.    And so in any given situation or conversation, I have some thoughts as to how it might work, but I’m never really certain.

But in the course of things, I regularly encounter people who are VERY certain and VERY confident they have the right answer.  That their batting average over the past five years might be 8% of mine doesn’t enter into it.  THEY are CONFIDENT and I am NOT.

So I tend to concede the point on the theory that they MUST know what they are talking about, because they are confident and that must derive from actual experience or data they are privileged to and I’m not.  Like Charlie Brown and the football, I learn over and over that those who don’t know, generally are unaware they don’t know, and in fact think they do – and all too often with my money.

So we are going back to a lower rpm torque converter.  That may fix the problem and return us to our original state.  And maybe the destruction of the transmission will then repeat in a year, or maybe not.  Or not.  I’m not sure.  I know we have to change the tranny twice, and buy two torque converters.

 

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On the matter of the saltwater rheostat, we actually succeeded.  Up to a point.  At a higher voltage (13 volts) and with a LOT of salt, we managed 50 amperes in a fairly controllable fashion.  That implies that with somewhat less salt, and somewhat more voltage – like the voltage of a car, this would be an interesting way to drain a large pack.  But is largely useless in what I want to do, controllably load individual cells or two or three cells at 1000 amps that I can “tune” at least roughly.  We failed there and I guess we’ll go to a rebar concept next.

A number of viewers were alarmed at the production of hydrogen.   I just generally toss a lit camel into those situations and they more or less resolve themselves.

 

The VW Thing is another matter.  And it is related to the DC-DC converter issues we’ve been having.    The issue is of course inrush current to the essentially infinitely low resistance of the input capacitors that exist in the DC-DC converter, the DMOC645 inverter, and indeed on the output of the Brusa charger.  See our existing diagram.

VWTHING

 

As I said on camera, one of the clues is that when we turn the thing off, it continues to power the JLD404 with 12v for up to 20-25 seconds.  The DC-DC converter input capacitors must of course drain down, and they are likely being aided by the input capacitors to the DMOC 645.

Mark Wiesheimer and Brian Couchene both advise me that inrush currents at these levels can indeed weld contactor terminals and Brian actually has had this experience and measured the current pulse with an oscilloscope.  His solution is an NTC Thermistor on the input to the DC-DC converter.

 

I was under the impression, largely from the Solectria manual, that the DMOC had its own contactor and precharge circuit internal.  Mark Wiesheimer assures me not.  We have had it apart actually and it’s true I don’t recall seeing one.  So in going to the 645 model, apparently they dropped that.

 

An NTC Thermistor is not going to quite cover that.

 

VWTHING2 And so we are going to add a second contactor to the input of the DMOC645 with a precharge resistor.  This contactor will not come on when we turn on the maintenance switch or the emergency disconnect slap switch.  But rather with the ignition switch which will require us to turn on the ignition to engage the DMOC645.  But it WILL precharge across resistor R2 when we close contactor K1.  We’ll do something like 300 ohms and 250 watts on that resistor which will allow 1 amp precharge.  This should charge those input capacitors within just a few seconds.  So it would be unlikely that you COULD manage the slap switch and then the ignition quickly enough to hurt those capacitors.  But you don’t want to re-engage with the ignition switch already on.

We have managed to eliminate the bootstrap switch to jump the car.  We simply take the aux battery as the input to the slap switch AFTER the charge diode.  In this way the slap switch becomes ON/OFF for the contactor K1 and even without the DC-DC converter it will fire it up.  Once the DC-DC converter comes up, it will actually provide the 13.6v through the charge diode to both the battery AND the contactor.

 

The input to the DC-DC converter is a little more complicated.  Largely because we need to develop something to handle DC-DC converters and hopefully eliminate all the problems we’ve been having.  Understand that while this is a high voltage circuit, it is pretty low current.  To do 800 watts at 13.5 volts is about a 70 amp max output.  But at 330volts, that same 800 watts is more like 2.65 amps.

One of the issues we have with DC-DC converters is the case where you step on the accelerator and the pack drops instantly from 330v to 280v for example.  If we have an air conditioner inverter for example or a DC-DC converter with input caps, those caps instantly discharge from 330v to 280v back OUT of the input to the pack.  This can itself be a rather large current.  Diode D1 is a 400v 100A diode.  It allows current IN to the DC-DC converter but not back OUT and so the caps cannot discharge backwards out into the main battery pack.

We also have a theory from Jeffery Jenkins of EVnetics that noise from the controller/inverter switching can exhibit on the cables from the pack and so at the input of the DC-DC converter – sufficient ripple to exceed the current capacity of those same caps.  We have employed a fairly substantial coil here of about 50 uH to filter that ripple.  But what happens when we remove that voltage with K1 or the maintenance switch.  L1 could very well cause its OWN spike on the input exceeding the voltage rating of the caps.  Fortunately, the diodes we use are actually double diodes.  So I’ll use the other half to act as a flyback diode across L1.  In the event contactor K1 opens, this should allow L1 to discharge safely through the diode.

We are going to adopt Mr. Couchene’s NTC Thermistor as a current limiting device on the input.  But there are a couple of problems.  An NTC Thermistor is a Negative Temperature Coeeficient resistor.  Quite the reverse of the Positive Temperature Coeffcient resistors we use as heaters.  Instead of going UP in resistance as they heat, NTC Thermistors go DOWN in resistance quickly as they heat. So we can start with an 8 or 10 ohm thermistor, but when it heats up, it will drop to 0.1 ohm or thereabouts as it heats up.  So we will limit inrush current but then go down in resistance allowing full voltage to the DC-DC converter.  This is a very conventional approach with such power supplies.

But NTC thermistors have one little problem.  They need some time to cool to become effective again.  So if we hit our slap switch and then re-engage it immediately, we don’t have any resistance to slow the inrush current.

The solution is to put a relay, K3, across the Thermistor.  This is activated by the 13.6v output of the DC-DC converter.  So initially, the Thermistor resists inrush current.   Once the caps are charged, the DC-DC converter will immediately put out 13.5volts and that will engage K3, bypassing the Thermistor.  Once the current is off the thermistor, it will immediately begin to cool.  Subsequent slap switch activations and reengagements will not affect the operation.  And of course the loss through the small resistance of the Thermistor will be avoided as well.

 

Or that’s the theory anyway.  We’ll try to get this wired up this week to see if we have better success.  If we do, we will probably package the diode, coil, relay, thermistor, etc into an enclosure and offer them on our online web store.

But I’m never quite sure… And we’ll have to run some of these for awhile to see if they cut the death toll on DC-DC converters….  Probably throw in a fuse for giggles as well.

 

Jack Rickard

 

 

 

 

 

 

 

 

64 thoughts on “Some Days Being Better than Others at EVTV”

  1. Tim Catellier

    Jack,

    I had a similar problem with two contators welding shut a couple years ago. I was trying to set up system where my DC to DC converters would turn off when the car was off. Providing 12V to turn the car on wasn’t an issue since I carry a small motorcycle battery as a backup, and the 12V side of the car always has power. I was doing this to try and solve a small problem. My DC to DC converters have fans that turn on and ramp up according to their temperature. In the summer time, it’s hot enough here in AZ that they run all the time. They come on sometime late April to mid May and turn off sometime in September. That’s a heck of a parasitic load and I was hoping to stop it.

    I wired them up so that there was a contactor on both the positive and negative side of the high voltage supply, and they closed when I turned on the ignition. I used Kilovacs just like you’re using. It worked great, once. Both contactors welded shut the first time I turned the key. I believe what caused the problem, and this was backed up by Ryan Bohm, was the inrush of current into the DC to DC converters to top off their capacitors. I don’t know that for certain, but I can tell you that every time I disconnect the DC to DC converters from the high voltage supply, that when I hook them back up there is one hell of a spark that scared the pants off me every time. I’ve since learned to put a resistor from the supply side to the inlet for a minute or so before I connect them. That stops the spark.

    So, is this relevant to your situation, I don’t know. But I thought I’d share it on the off chance it’s helpful. Good luck!

    Tim Catellier

    2. Brian Couchene

      Tim, I don’t suppose those DC-DC converters were Iota modules were they? The ones that they have been selling for the past few years have NO internal precharge. These are the ones I have scope data on…

      1. Tim Catellier

        They sure are Brian, I bought them back in 2009. They’ve been very reliable, and I’m quite pleased with them apart from the fact that their fans run all summer and I can’t really shut them off. If I’d actually read the blog entry above before I posted my comment, I would have learned that Jack was able to solve that problem. That’s the challenge with having such minimal knowledge of electrical circuitry. It’s all a mystery to me until someone explains first that it can be done, and then how to do it.

  2. Doug Ingraham

    Jack,

    If I had just waited another hour (before I posted in the previous blog) I would have known that the problem was inrush current mostly to the DMOC. I am surprised that precharge isn’t in the DMOC. What do they do in the Transit Connect van?

    Doug

    1. weisheimer

      They are as clear as mud about that, to be sure…
      What they do is to hand that job over to Johnson Controls/Saft and actually, it appears that the contactor and .pre-charge are done in the battery module.
      It is NOT well documented, but I’ll try to post the link to a document that I found that describes that it is done in the battery module.

      There is no contactor in the Gen2 DMOC645, there is a DC link discharge resistor though, to ensure that you MUST pre-charge it each time that traction voltage is removed.

  4. David Seabury

    Another possible issue is that you are back feeding the DC-DC converter output caps which may slow the rise time on the contactor coil. You could try a large diode on the converter output to prevent this. Just a thought.

    1. Jack Rickard

      Not a bad thought actually. I got lucky and got a shematic of the DC-DC converter. Relatively small input caps but huge ones on the output. Like five 4700 uF caps. I’m warming up to this new DC-DC converter.

  5. Collin Kidder

    You probably don’t want such a large wattage precharge resistor nor so high a resistance. Capacitors can take a lot of inrush current so you almost can’t hurt them with any precharge resistor value. 50 ohms and 50 watts should be sufficient. 50 ohms means that the inrush current will start at 6.8 amps if your pack is 340V. That will dissipate 2.3kW initially but quickly taper off. The RC time constant of this precharge would be 1/2 second. At the end of this 1/2 second the capacitors will be charged to 215 volts which means you will be drawing 2.5 amps and dissipating 312 watts. At the end of 3 RC time (1.5 seconds) you will be 95% charged which is pretty much sufficient to just let the main contactor close. It is unlikely that anyone will beat the 1.5 seconds between operations but if they could then you can always switch to a smaller resistance and a little bigger resistor. Since precharging happens very rapidly you can run a whole lot more watts through them than they’re rated for in continuous duty. Yes, I really do this.

    1. Brian Couchene

      Collin, I’ve designed about 5 different precharge systems for various applications (I’m not counting the NTC’s) so far. I’ve also analyzed precharge circuits from A123, US Hybrid, and Corvus Energy. I’d venture that some of my designs were more robust than the OEM ones and some less robust, but it was a design decision. All that said, You’re 90% there with your analysis. I’ve done the same calcs you did but you missed the parasitic loads. All the HV components have some issue that causes trouble with precharge. While you’re trying to charge the caps there is usually a discharge resistor across the caps in each module. In the DMOC, I think it’s 10K. The higher the voltage rises to, the more current the 10K resistor draws. Also, your DC-DC, what voltage does it start generating 12V at? if it starts generating 12V before your precharge completes, it will draw a couple amps while you are trying to complete precharge, and you’ll never get there.
      Without going back and digging out my design sheets, I would GUESS that the resistors I used for a 300V system were closer to 10 ohms than 50 ohms. This provides more current to compensate for the parasitic loads and also gets precharge completed quicker which has the added benefit of getting the bypass contactor closed before the DC-DC has time to power up. My designs usually have the bypass contactor automated based on HV dc bus voltage, not on operator control.
      You are spot on about the resistor being capable of huge surge currents for short durations under 500ms, however you should carefully check the resistor data sheets and choose the resistor carefully. Some handle surge currents much better than others. Specifically, wire wound resistors are quite robust.
      I’m unsure of what method to suggest to Jack because I’m not sure what his end goal is. What I don’t like about his latest diagram, besides the resistor values, is that the precharge resistor could possibly be passing current indefinitly, and that the DMOC could be powered up indefinitly, depending on the position of the slap switch when you parked the vehicle. It looks like Jack was looking at a Precharge circuit from Curtis when he drew it. The DMOC isn’t a Curtis.
      OK, here’s an option but it has a drawback… Use the GEVCU to do the precharge. Turn on the main power with a GEVCU output to a main contacor which starts precharge to the DMOC. Then, using CAN communication to the DMOC the GEVCU monitors the DC bus voltage and turns on the precharge bypass contactor when the voltage reaches 90% of battery voltage. The advantage here is that there are no additional hardware modules that measure DC bus voltage. The downside is that the GEVCU doesn’t know what the actual battery voltage is, and thus if the battery SOC is low and voltage is 88% of max, and the GEVCU is looking for the DMOC to be at 90% of max batt voltage, it won’t work…. The saving grace here is that Jack is using Calb CA cells which have a very flat voltage curve… I’ve used the above method before, it’s not my preferred method, but it does work. Don’t forget to add a timeout in software that shuts the main contactor off if the precharge takes too long to prevent overheating the resistor.
      This timeout and, having precharge built into a battery pack has advantages. Say, you were working with a pack from A123, not just cells but the entire pack, with built in precharge you could have a direct short pack + to pack – (external to the pack) and when you command the pack to “turn on” it tries to do precharge, which it can’t into a dead short. It faults on a “precharge failure fault” with no damage done. You can ask me how I know this but I can’t divulge where I performed that unintentional experiment.

      1. Per Eklund

        I plan to use the voltage meter that Jack has in store to do a precharge circuit,
        This one: http://store.evtv.me/proddetail.php?prod=FourRangeVoltmeter
        That together with the right sized resistor.
        Sense the voltage over the unclosed contactor terminals and when that has fallen to a good value (10v?) just pull the second relay and disconnect the first relay. The second relay in the meter will pull the contactor and the first relay will pull the precharge resistor.

        That way you will have a fully programmable precharge solution for pack voltages between 0v to 500v.
        Then just choose the right resistor for your pack voltage.
        You might have to have a larger relay outside of the meter to pull the contator if it draws to much amps.

        The second relay could also in addition turn on a ready light, or the opposite way the first relay could do some kind of interlock so that you cannot do anything with the car until the precharge is done.

        Regards
        /Per

      2. CollinK

        Thanks for the detailed analysis. Yes, I was trying to be really conservative. Normally you wouldn’t use even 50 ohms but rather something smaller like the 10 ohms you mentioned. The lower you go the more nervous it makes people. Of course, once you start going down the road of having such a small resistance and a power resistor rated nowhere near the peak power you absolutely must have a way to drop the precharge resistor out of the loop in case of trouble. That leads to two relays – one to control the precharge resistor, and one main contactor. I had thought to ask the DMOC for the voltage it sees and stop precharge when it gets close but, like you said, it has no way of actually knowing the current system voltage. A battery monitoring system of some sort could report that but he doesn’t have one. So, you are left hoping that the pack is close to its nominal voltage. Or, given R and C guess how long to precharge and keep the precharge contactor closed for 5RC just to be sure. That has its own problems. I’m going to guess that these things are the reason that the Transit Connect Electric handles precharge in the battery pack where the BMS is. I’d imagine they measure both system voltage and the DMOC bus voltage and stop precharge either after a timeout or when the two voltages are close – whichever happens first. So, yes, there are options but it depends on how rebust he wants the precharge to be and how complicated he would like to get. Precharge can be simple or complicated and, like you said, there are tradeoffs to every single method.

  6. jehugarcia

    And all this time I thought you didn’t like Inrush Current Limiters Jack, http://www.digikey.com/product-search/en?x=12&y=9&lang=en&site=us&KeyWords=570-1023-ND

    BTW, pretty clever use of K3 relay, I might have to do something similar as I really don’t like those ICLs on my charger running hot while I charge my pack, especially once I start charging at 12kw, so If I can bypass them with a 120V relay electrified by the charger once it gets going, then they wont have to run hot.

    1. Jack Rickard

      Yes. Well it does improve efficiency of course but there is also a problem with Thermistors in that they need a minute or so to cool down before they are again effective. By bypassing, it immediately begins cooling down as soon as the DC-DC output comes up.

      Jack

      1. Brian Couchene

        Jack, that’s a novel design using a relay to bypass the NTC. I don’t think I would do it that way but it’s certainly not a bad idea, and I’m warming up to it. I’ve never seen it done that way anywhere, maybe it’s because the purpose of using the NTC over other precharge methods is to eliminate the more expensive contactor with moving parts. I’d say a resistor and contactor with control electronics controlling the contactor is a more robust system, but more expensive and more complex.

        Everything is a tradeoff, and the right solution is the one which fits your priorities the best, not one which someone else tells you is the best solution. Often the solution that someone else tells you to use is the one that makes them the most money. I think Jack said something to this affect when talking about his transmission woes.

        1. Jack Rickard

          Its not that novel Brian. I found about four or five examples of this using Google. In fact, I sent you a schematic of the DC DC converter and that’s basically what they are doing internally. So all that for nought. I think the DMOC645 is the issue.

  7. zak650

    Hi all,
    This may be a dumb question from someone who doesn’t know enough about electronics but here it is. Would putting a pair of the double diodes both plus and minus diodes protecting their prospective lines, one double diode on the input of the dc-dc converter and one double diode on the output of the dc-dc converter. I think I’d skip the inductor entirely and make it a practice of not turning off the pack disconnect until after the car has “calmed down” and the various capacitors in all the systems have drained down like they normally when turning off the car overnight or when you go into the store.
    Thanks for your patience.

  8. Andyj

    I’m using a magnetically switched contactor with a key for the starter circuit. (Fresh out of contRactors). It will be wired to make & release when the potential difference is low enough.
    If you spy contactors in any electrically assisted car, they are laughably small because they do not switch loads, only take them.
    The hard bit is building it completely bug free for any situation. Too many items can initiate or open while high…. It can be very scary.

    1. Klaus

      Contact. It’s like jabbing a welding rod into the workpiece and the welding rod sticking tight. Magnetic blowout contactors are for breaking the connection when there’s an inductive load that wants to keep the current flowing.

      1. Allan Høj

        Klaus, I’m aware 🙂

        I think that it is because the voltage is raised to twice what speester run with and a voltage of 320VDC. It will make a somewhat more substantial spark.
        I find it odd that the DC / DC converter is able to weld contact pair together, as it has a coil in front.
        The coil is going to act as a timer switch-on delayed, but maybe the coil does have the proper size?

  11. Randy C.

    My only suggestion on the contactor problem is polarity. Is the open circuit voltage of the correct polarity across the contactor? A mid pack contactor has to be hooked up backwards from the label. When open the 2 ends of the pack come together effectively reversing the voltage on the contactor.

    1. Brian Couchene

      I believe Jack has found his contactor welding problem and now may only have to determine what his ultimate solution is. I, along with others had originally suggested it was the DC-DC converter however I was wrong. Instead of going out to the garage and opening up my DMOC, I checked the OLD manual and it indicated that precharge was built into the DMOC. Others have since confirmed that the AZD DMOC’s do NOT have precharge built in. Seems that AZD removed it in this hardware revision. Jack has further verified that the problem wasn’t the DC-DC by analyzing it’s schematic and found a quite robust precharge built into it. I have personally observed and documented a DC-DC converter cause power contactors to weld on closing. However the specific DC-DC converter jack is using has a precharge circuit that prevents this. If he had a different DC-DC, his problem might have been both the DMOC and the DC-DC.
      Different contactors wouldn’t help, he needs a precharge system. If you check the contactor data sheets they list a maximum current on closing, and without a precharge system the DMOC’s caps have thousands of amps inrush current, only for a couple miliseconds, but that’s enough to spot weld the copper contacts closed. After I welded a couple Gigavac contactors closed with a DC-DC that lacked precharge, I cut one open to analyze and photograph the contacts.

  12. Jeff Pollard

    Hi Jack,

    If you haven’t given up on the water resistor yet, you might want to try copper sulfate as the salt instead of sodium chloride. That should keep your electrode from corroding. The disadvantage is that it is more expensive http://www.coppersulfatecrystals.com/

    I don’t know if it will help you get more current through or not but it might be worth a try.

    Jeff

  13. Allan Høj

    News but not really ….
    ABB has made ​​a high-efficiency motor IE4 SynRM without permanent magnets. The rotor is special when imagining the field lines in the rotor, one can see that makes sense. The engine was at the exhibition last year and they have not been able to deliver the engine, but they can now.

    The only downside is that it must be controlled by an ABB Drive

    http://print.rosendahls-schultzgrafisk.dk/abbbesog/kataloger/IE4%20synchronous%20reluctance%20motor.pdf

    Allan

  14. Marlou Jasmin Madrio

    Hi Jack

    Watched your video regarding the Liquid Salt Rheostat

    I believe you’ll have better results using the HHO brown gas generators

    Some are massive and available as DIY kits

    I think you can get away with 2.7 to 3 volts at very high currents if you parallel these HHO generators

    I think it’s all about surface area of the plates in contact with the electrolyte as well as the distance from plate to plate

    Regarding your mysterious contactor getting welded shut, pls try to shunt the contacts with a condenser much like the contact points of an automotive ignition system

    Otherwise use a high power MOSFET to drive your high power relay in conjunction with a bounce less digital on off switch

    I think it’s the high power bounce which fries the silver contacts inside your contactor

    The coil needs to immediately lock into magnetic saturation without any bounce

    I’ve been following your show for 4 years now and I’ve been enjoying watching your program even the archived episodes

    Life after Singapore career for me I think would be pursuing EV builds like you guys

    Currently I’m working for the railways industry as a Sytems and Controls engineer for the biggest underground robotics train in the whole world built by Alstom and Operated by my company for the Singapore Land Transport Authority

    Marlou – Singapore

  17. Allan Høj

    Jack …
    Nice Show 🙂
    It is a well-thought-accelerator system.
    But what happens when icy and slippery?
    Will not it be a bit of a balancing act to avoid blocked the wheels.
    If you had two options 1.norm and 2 slippery
    1 = Agrasiv braking 2 = Smooth braking
    Allan

    1. Jarkko Santala

      That’s a good point Allan! It’s very slippery here for a good part of the year and having aggressive regen without some sort of anti-locking would be really dangerous during the winter.

      1. Michael Neuweiler

        Just had the same thought when I watched Jack’s whiteboard session. Regen (especially without a clutch) might become dangerous. But how to solve it? A switch might be a good idea..

        And another thing: When starting from a dead stop, I don’t want to have to push the throttle half way down to get started. I’d like it to be more responsive and start moving when pressing the pedal a few milimeters. But this would mean we’d have to include the vehicle or motor speed to shift the acceleration/regen-map. But this would result in the coasting-zone to move around.. probably also not desired.

        How is it done in the Model-S or a Leaf? I’d imagine the coasting zone moves in relation to the engine rpm, just like it does with an ICE.

        1. Jack Rickard

          Michael:

          I would urge patience. You’re about to thought experimetn yourself into a tizzy.

          Today we did get the THING to roll finally. There were some errors in the throttle code where it was not saving TPOTS into EEPROM and it would not produce a throttle output with TPOT=2. Changing it actually did little good. You had to do everything in a very defined order to get the motor to spin. The latest code fixes this and we can now spin motor.

          I have a pot range of 0 to 2345. I set T1MN to 300 and T1MAX to 2350. The TRGN is at 18^ and TFWD=24%. This gives me TWO coast zones, throttle full off, and between forward and regen. We don’t even start the pedal until 24% on forward. Sounds like a lot? You want it instantly responsive?

          The difference between dead pedal and start is almost imperceptible. Feels perfectly natural. And we seem to have excellent control.

          Unfortunately, Shane mounted the new throttle where it interferes with the brake pedal. SO instead of driving, I’m typing while he remounts it.

          But I’m’ pretty excited. Very smooth control backing off the ramp???? Ok. Not a thorough test. But the beginning of a grin.

          Point being, we do have to go through all this. But the entire pot throw is 20 degrees typically. HOwever you map it, you have to feel it and redo it a dozen times or so. In GEVCU, we want to be ABLE to do all that. BUt let’s keep it simple for now and once we get a basic throttle map going, if more is needed we can certainly add it. But it is not quite as critical to the foot as it is thinking about it.

          Jack RIckard

          1. Grumpy_b

            I recently drove a new Smart, a renault Zoe, Ford Focus and a BYD e6, all very different and all have different regen characteristics. I loved the way the smart uses the flappy padles on the steeringwheel to increase (RH) or decrease (LH) the level of regen on taking off the accelerator. The Zoe and Focus have limited Regen on the accelerator pedal. And the BYD is such a huge vehicle that I havnt a clue how it was performing, but it did go well.
            My son works for Jaguar Landrover on the Hybrid side, and he commented that the industry is moving to doing most of the regen on the brake pedal, and what feels like conventional brakes is mostly heavy regen. So Miles etc got it right when they did brake pressure regen some years ago on the little Diahatsu copy Ev. This being a similar vehicle set up to the Van Jack got the pressure transducer set up off. So the industry way forward appears to be very limited regen on the throttle, regardless of how quickly you come off, and heavy regen on the brakes only relying on physical brakes as a final step.
            Grumpy-b

    2. Andyj

      And if the pack is fully charged. The Leaf for instance has no regen at all until its allowed to, regardless if its on cruise, going down a hill or eco mode.
      I suspect the throttle/rpm/regen can be set based on rules, avoiding a map in data but that’s down to preferences.

      1. Jack Rickard

        I have never had an incident where the voltage spiked because of regen on a fully charged pack. Regen varies from 30 to 90 amps typically with 90 being a strong decel from 70 mph. Acceleration can easily be 500 or 600 amps for a few seconds on a residential street.

        You have to pretty much fall out of your garage in free fall for this often cited scenario to actually come into play.

        As to the trend toward brake regen, I like having it on the brake. But I’ve grown accustomed to having it on the throttle as well and I have to tell you I like it a lot, as long as I have a notch I can easily find to free roll. Gives a bit of technique to the driving and something to play with.

        I’m planning on having one analog input for a zero to five volt signal from a dashboard potentiometer. We’ll use it on GEVCU to adjust total REGEN torque from zero to max. In this way, I’ll be able to actually “tune” the regen fairly finely by feel.

        Jack Rickard

      2. John Hardy

        @ Grumpy_b. What did you make of the e6? BYD say that it can be charged at 44kW from 3 phase AC using the controller backwards. BTW I live in Redditch – if you wanted to pop in for a cuppa sometime I can be contacted via the Tovey Books website

        1. Grumpy_b

          Hi John, they are currently quoting an onboard 30kw charger, with little details, I didnt get chance to go into the bits and pieces, once I was out of the car on the test drive, it went out with another person on board. Iget the feeling that some ofthe original hype has been toned down on the final delivered product. Im just north of Colchester, a small stone throw in US terms. If you need parts do get in touch. Im slowly buildig up an inventory of EV bits.

      3. Peter Dambier

        Our i-MiEV has three forward gears or regen switches: “D” behaves like an automatic would. “B” behaves like an 8 cylinder gasser with shift gear would and “C” is for coasting and I guess economy. To me it does not make sense shifting. I can do everything in all three of them. So feeling at home in one of them makes more sense to me.

        People I know mostly agree on “B” including me. I am told the Peugot Ion only has “D” but it behaves like “B”.

        It is tricky at first and it has become even trickier since I have put styrofoam/aluminum foil isolation between doors inside and trim. The car lets less noise from the road and from other vehicles inside. So watching the amp meter and speed is a must. I can do coasting but my right foot has become bigger than my left in the process.

        Cheers
        Peter and Karin

        1. John Hardy

          The Ampera (and I guess the Volt also) has a D, N and L just like an auto. L is stronger throttle regen. Apart from P, I only use D and R.

          I do enjoy driving it. I blew off some kind of Subarishi Imprevo the other day from a standing start entering a roundabout. I backed off at 30 or so and he came straining past with all valves bouncing and no doubt the lad driving it had to drive dangerously all the way home to recover his self respect. He had plenty of time to read the lettering on the boot (trunk) lid and I hope he googled it when he got home.

          I don’t usually drive like that: perhaps Jack with your contacts you could arrange an Indulgence for me?

          1. Jack Rickard

            Technically, as long as you were in all electric mode and that nasty little ICE engine didn’t come on, non sin and so no indulgence necessry.

            Jack

          2. John Hardy

            The ICE is only on rarely. Currently 226 mpg on the meter since it rolled off the assembly line. Most of the time I treat the piston engine like a flat bed truck

          2. palmer_md

            I wonder how the Calb CA cells do on the 3x9mm test. I’d like to get a copy of the official protocol for this test.

  19. Bruce Telker

    Forgive me Father, for I have sinned. Being ‘off the road’ for a few days I found myself at the Du quoin fair watching Kansas somehow enjoying pizza-on-a-stick. Then the SEMO fair for a funnel cakes and foot-long-corndogs. Next thing I know, I’m in the tractor pull, with beer in each hand. I know not what I do ! ! ! Hail Mary . . . .

  20. Will Brunner

    Hi Jack,
    I am bringing my 5-year old TS cells out of mothballs and am using a large FET and a CPU heatsink to discharge cells while measuring capacity. 50 amps easy, 600 should be possible with a water block. I have a cobbled-together Arduino setup for doing the ah counting, but it looks like your JLD 404 is a nice way to go. For a next step I plan to use the Arduino to set the gate voltage to get constant current load, instead of turning knobs on a bench supply.

  21. Steven Young

    On the new Thing, green, have you decided on the motor and controller yet? And the number of batteries? I think you should go with the HPEVS
    75 or 76 motor with the Curtis and CA 180 batts thus making another test bed for the GEVCU.

  22. Per Eklund

    Hi Jack !

    I can see that the new thing is in !
    Have you had any problems dealing with TCCH.
    I have had some misfortune when bying a charger from them.
    Now theey seem to have banned my email from their server.
    I guess they got fed up with me trying to get in contact with them.
    Have been trying to get the charger sorted out for over a month now. No answer since mid august from the salesrep.

    I have a thread on DIY about it.
    Seems I have to go over there in person to get some action.

    Regards
    /Per

    1. Jack Rickard

      Yes, we now have a gasoline powered Green Thing and we are successfully driving and testing our Yellow Elelctric THING.
      If you notice, at night the shopcam shows all the lights down low. We are hopeful that they WILL breed in captivity. This is our plan to produce the first EVTV HYBRID ELECTRIC THING.

      Yes, we have had some problems with the TC CHargers – their TLP181 optos are apparently very fragile and blow easily. We received one charger that was already blown when we received it. The original person we were using to order these was very bad about warranty issues offering to give us a “good price next time” instead of replacing the charger. SHe was fired. I am using my gal at Chennic these days with some better success.

      We are gaining confidence a bit in our controller for the charger. Main weak point is the very fragile USB ports on the Arduino Due. We’ve increased the current limiting resistor size to try to treat the charger a bit more gently as well. We have about 20 in the field and they are working nicely for the most part.

      Jack RIckard

  23. Mathieu

    I am working on a main contactor system between the two battery packs in my ATV projekt. No big deal, but…
    The basic idea is pretty the same. OFF should be “off”. No losses on the battery pack while parking.
    In the next step I decided to connect the Brusa Charger as simple as possible. Directly on the battery terminals at the Soliton. But this causes an arcing problem at the main contactor. The solution is clear. Pre-charge.
    Only, I want to keep things as simple as possible.
    Maybe you are more advanced with the Arduino variant. Maybe it is getting to far in the electronic Labyrinth…I don’t know.
    I’ll try a simple time delay circuit with a fixed number of seconds.
    Open to any advice..
    Mathieu
    http://www.conrad.com/ce/en/product/195901/?insert=62&insertNoDeeplink&productname=Conrad-Verzoegerungs-Ein-Ausschalter-Bausatz-12-VDC-Ausgangsleistung-8-A35-V-Zeitbereiche-05-s-150-s

    1. CollinK

      A timed switch will usually work for precharge. You must know the capacitance of the input bank on the device you’re precharging as well as the resistance of your precharge resistor. Then you can multiply them together (use full units, farads and ohms) to get the RC time constant and multiply that by 5. That’s how long the precharge should take. The potentially unsafe part about this is that you have no idea if it is really working. This all assumes that everything worked. If it didn’t you might have troubles. Still, it will work pretty reliably.

      1. Mathieu

        You are completly right.
        The potentially unsafe part about this timer circuit is what I don’t want. A blown resistor or a bad contact could kill my EV200n contactor before I see it.
        So what can we do? I have been thinking about this today…
        We can take a look at the voltage. I have a JLD404 that shows me my “switched” battery back already. I can have a look that it is running fine.
        But what if I use a relay output but from the JLD to switch on the main contactor when the pre-charge is ready to go.
        Sound pretty easy and perfect to me.)
        Or did I miss something…?

        1. Per Eklund

          That is exactly what I suggested earlier on this page. BUT that you use the 4-digit voltmeter instead.
          http://store.evtv.me/proddetail.php?prod=FourRangeVoltmeter
          Measure the voltage over the contactor terminal. Just like Jack showed with the multimeter in the latest show.
          Use that voltage to determine when the precharge is done (voltage has fallen to 10v?)
          Use the two relays in it to do the precharge.
          One relay pulls the precharge resistor, and when the voltage is OK the pull the second relay which energizes the Contator also release the first relay to disconnect the precharge resistor.
          Then you have a fully configurable 0-500v precharge solution.

          You can also set it up to do interlock features with the relays.

          Best regards
          /Per

  24. Andyj

    You would think any circuitry that has a huge capacitor bank on the input to have it own pre-charge current limiter then be continually connected to the main pack regardless of the unit switching on or off which ought to be soft start *after* the capacitors. Whether its the DC-DC converter, main contactors, the drive circuitry – everything.
    Shameful.

    1. Matt

      Inside the case there seems to be ample room for an EV200 contactor – just need to tap into the +12v to drive a ZEVA Smart Precharger… Stick it near the battery inputs…

  25. Anthony Kiszka

    Jack,
    I just got off the phone with a very helpful tech at Hughes Performance. Pete, confirmed that a lower stall speed was the way to go for the electric motor and has helped a few other people build torque converters for these tough applications. I was giving them some hypothetical HP and torque numbers based on the BMW’s dyno run from EVCONN. He seemed to think they could play with the converters internals a bit and lower the stall a bit more, around 1000 rpm. As I haven’t done business with them I can’t endorse, but at least they are willing to work with a customer to meet their needs. Good luck!

  26. Steve Davis

    Sorry to hear that your Escalade transmission imploded. One thing in your description caught my eye – “”this makes the transmission run cooler and last longer” This is only true to an extent. Most automatic transmission have the transmission cooler inside the engine radiator. Why? This heats up the transmission fluid to operating temperature (about 180F) more quickly than by just torque converter waste heat alone.

    My guess is the Escalade transmission has been taking too long to get to operating temperature. In fact, from the way you describe driving it, I’d be surprised if it ever reached operating temperature. The transmission shop’s solution of a higher stall speed on the torque converter would give you more waste heat and a faster warm up.

    My truck has the transmission cooler separate from the radiator. Below 180F, the transmission cooler is bypassed completely. Even then it takes about 10 miles of driving to get the temperature up to normal. Before I added the transmission bypass, the transmission never reached operating temperature unless I was towing or on the freeway for an extended period.

    Good Luck
    Steve

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