The Struggle Continues

We’re having a time in the short days of winter. Here at the end of January, there is a bit of light at the end of the tunnel as the winter at this point WILL end at some point. But we struggle.

This week, we look at the final touches on the Electric Swallow. This is a neat little car with a neat little body and we had fun doing it. I was a little annoyed over the throttle issues but we more or less solved it with a 12v to 5 v converter even though it wasn’t as it should be by the book.

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We did do something we are going to try to incorporate in all future builds, including the Elescalade. That is interlock our controllers using the little relay on David Kerzel’s J1772 board that we use. This little board is $37 and it makes your car respond to proximity switch and copilot signals from J1772 EVSE. But it features a little relay. On this build, we routed a 12v interlock signal through the normally closed contacts of this relay. In this way, if you plug in the charging plug, the car is disabled and you can’t drive it away.

We actually routed the same signal through the Xantrex so it could also disable the controller when the SOC got down to 10%.

The car drove well and Lee took off for Denton with no real issues. If you stepped on the throttle all the way the controller kicked out. I showed him where to put a little resistor on the 5v DC-DC to fix that. And he seemed happy when he left Saturday afternoon. The car drives very nicely and as predicted, by using the 100Ah cells and the AC-50, it is very spritely.

We were hoping for additional reports when he got home on actual range and acceleration as we had no time for them here before he needed to be back to work.

Unfortunately, he apparently towed the car all the way to Denton with the VW tranny in gear. On arrival, he found transmission fluid all over the passenger compartment and nothing working. We’re hopeful he can get all that turned around but it’s a setback after all this work.

Meanwhile, I blew experimental A123 module La Troiseme number two WIDE OPEN.

I’ve already heard from a number of viewers DEMANDING to know what happened. Well, I’m not sure and I’m not sure we’ll ever know. We don’t have a “script” like House. Whatever happens happens and I don’t always know what caused it.

Before casting, the cells measured 77.75 Ah which I thought was quite good. We cast it in resin and let it cure a few days and discharged it – but we really only got 65 Ah out of it and that was down to 24volts or 2 volts per cell. We probably over discharged a couple of cells at that point. Then we put the charger on it. After 80 Ah it never did reach above 41 volts but it DID split the resin wide open and the most positive set of cells were hugely swollen and leaking electrolyte. Later, another set split it in another place. So at least two cell segments failed.

No fire. No smoke. But some heat. And the module did split wide open.

Module one failed in an interesting way as a result of something I just did wrong. I’ve been playing with these new light object voltmeter controllers. They have a voltmeter that sports two relays with two voltage set points each. You can use these for all sorts of things.

I was using it to switch the first prototype Troiseme to a load. Of course the load is very low resistance. The cables to the load are also very low resistance. But we were sampling the voltage at the wrong place. So when the controller closed the contactor, the voltage dropped to under 2 volts because of the drop across the cables. The ratio of cable resistance to load resistance is very low. When it goes to 2 volts, the controller opens the contactor. With the load removed, the voltage shoots up above 3 volts. This causes the controller to close the contactor.

And so what I set up was a series of perhaps 50 cycles from zero to several hundred amperes all occurring in 30 seconds until I could figure out what was going on and get it stopped. This caused a lightning display inside the battery module. It now shows full voltage, but any attempt to draw the least amount of current results in a total collapse to zero volts – maximum internal resistance possible.

With Swallow finished,we are working more on the Elescalade and have good progress there really. Rod fabricated a couple of 3/8 inch polycarbonate covers for the massive 76 kWh battery pack and box in the back of the Cadillac. We’ve mounted an Manzanita PFC-75 to this cover and a Vicro Megapack power supply we will use with six 5v 40A modules and one 15v 10 Amp module for a 15 volt output at 90 amps for our 12volt system.

We also moved the Aurora Inverter down to the shop. This allows us to hook up the 192v pack to this inverter and drain about 36 amps from the pack to produce 21 or so amps of 240vac right into our panel. iN this way, we can use the truck to power the shop. Because of anti-islanding circuitry in the Aurora, this will do us NO good as far as backup power goes because it won’t make any if we lose grid power. Why they have done this mindless thing makes no sense to me. It does not achieve the safety issue they sought.

But in any event, it DOES let us drain down a pack and instead of wasting the energy as heat, we can use it to run the bandsaw and the lights. That’s pretty cool.

After taking the pack down to 170 volts, we’ll trim from there manually using a little setup from the batt lab.
I basically mounted a 12v supply, a 0.1 ohm 250 watt resistor, a contactor, and this voltmeter controller all on a little piece of the aluminum aircraft decking we’ve been using. We have one set of cables to carry the 30 amps or so of drain current and a SECOND set of voltage sense wires with alligator clips we will connect DIRECTLY to the batt terminals to prevent the oscillation that caused so much trouble with the A123 module. In this way, we sense the actual battery voltage instead of the voltage after the current drop. Again, this is caused by the very low 0.1 ohm load. It’s actually about the same amount of resistance as we see in the connections.

We’ll set the lower limit at 2.60v and the upper limit at 2.77v. In this way, the cell will discharge into the resistor until it reaches 2.60v. At that point, the controller will disengage the contactor. The cell voltage will creep back up slowly. When it reaches 2.77v, the controller will again engage the contactor and take the cell down to 2.6v again. This cycle will be repeated until the cell just can’t make it to 2.77v. That should be about 2.75volts near enough.

In this way, I can connect this device to each of the 57 cells in turn and basically walk away. An hour later, that cell should be at 2.75v. At some point, they all will be. Then we’ll charge the pack and set our Manzanita for the top voltage.

The J1772 receptacle has some pretty stiff wiring but the 75 Amp Manzanita will certainly heat that up. Fortunately, it is just a foot or so long. We’ve terminated that in some terminals under the truck right where the J1772 comes in at the gas cap. We’ll run 4 AWG cable from there to the Manzanita to handle the 75 amps this charge really can draw if you put it close enough to a panel. And of course, we have 4 AWG cables from the Manzanit to the cell terminals, although with the charger mounted on TOP of the battery box, those cables are quite short.

Again, we’re going to use David Kerzel’s little AC31 board to do the magic and make use of his relay to do a couple of things. Interlock the controller again of course. We’ll also probably use it to turn on the heater pump through a seasonal switch. In this way, in winter with the seasonal switch set, the charger will cause the pump to come on circulating our glycol in the system. We’re going to put two little 250 watt rubber heater pads on our system that run off of 240vac. When the J1772 connector is in, this will use wall AC to gently heat the system – all night long in most cases. So the pump will run and the very low level of heating should keep both cabin and batteries reasonably above freezing and I suspect, running all night, really quite warm which is why we are using such weenie heaters.

During the day while driving, our much larger 14 kw heater running off pack voltage can be used as desired. But I don’t want THAT much heater running all night. A thermostat failure and we could really heat things up and cause a fire.

So we’ll have an alternate system powered by AC when charging.

Today’s video is of a bit more reasonable length. Our 3 hour mini series are just too much editing for me, and two much video for you.

Warmest Regards;

jack Rickard

http://EVTV.me

53 thoughts on “The Struggle Continues”

  1. Jack,

    Great show again this week.

    I would like to see John Goodenough speak at EVVCON. It would be very interesting to hear his take on where batteries and alternate transportation technology is headed and his attendance to EVVCON may also spark the interest of some of the battery manufactures and actually get them to attend.

    As you said, this is not about the EV, it is about the battery.

    Regards,

    Randy Hardesty

  2. Hey Jack!

    I don’t think the threaded nylon rod is the right material for the job. From the “General Design Principles for DuPont Engineering Polymers” at

    http://plastics.dupont.com/plastics/pdflit/americas/general/H76838.pdf

    “However, in a metal/plastic assembly, the large difference in the coefficient of linear thermal expansion between the metal and plastic must be carefully considered. Thermal stresses created because of this difference will result in creep
    or stress relaxation of the plastic part after an extended period of time if the assembly is subject to temperature fluctuations or if the end use temperature is elevated.”

    If the curing temperature of the resin didn’t loosen the connections, temperature cycles during use eventually would have. Unless some care is taken to accommodate the thermal expansion issue, stacking plastic with metal and tying it together with plastic won’t work for long.

    Mike Kaindl

  3. Jack:
    What do you think about back tracking? Perhaps connecting the cells together strapping them together with heat sinks between each, without the potting; then running them through a few charge/discharge cycles, at rest will help identify the problem. Then, if there is a University near by, test the unit the same way on a cycling vibration table.

    Also, since your first prototype failed because of human error and your second failure cause is unknown, it may indicate the problem is because of your connecting method in the second module.

    Thirdly, I note that often the cylinder-type cells are spot-welded with straps connected to each cell, this removes the problem of increasing oxide resistance at the junctions. I don’t know that much about laser welding but it seems ideal for what you are attempting; the problem: where can you get it done without costing a ton.

  4. After hearing this news, I’m abandoning the A123 cells for my dragster and I’m going to refocus on the FlightPower batteries that have been successfully used to set records already. Should be much easier to connect up. Sorry they’ve given you so much trouble, Jack. Here’s an approach being taken by one dragster builder using prismatic packs similar to the A123 AMP20s you have been using. http://endless-sphere.com/forums/viewtopic.php?f=14&t=33121

  5. Hey Jack!

    As you ease back into the Cadillac project, I remember a concern I had about the hydro boost brakes. Is vacuum used in the Escalade to actuate any valves/doors in the HVAC ducting? If so, is there a work around? Might you lose the AC up your skirt?

    Mike

  6. Without wishing to drop names, “Bottled Lightning” was recommended to me by a Fellow of the Royal Society with a research interest in Lithium batteries. It is a good (and largely untechnical) read

    +1 on Goodenough. One of the most underated scientists of the last half century. He can also presumably speak English as he was a professor at Oxford for a while

  7. Thoughts on A123 direction. I guess I’m thinking to go back to the basic design of large prismatic cells and put six or eight A123’s together in parallel with a device to form strong terminals. We might cast those in resin or some sort of box to make a single 3.35 v cell of 100 to 200 ah.

    Strap those together quite normally.

    The large module was attractive but losing cells 48 at a time is a little expensive.

    Jack

  8. Hi jack
    That’s terrible news about the swallow he must have been very upset
    Transmission oil is terrible stuff to clean off.
    While it was being towed I presume the motor would have been power.
    Does the regen only work when the brake is pressed?
    Or would he have overcharged the battery’s like mad

    Nick

  9. Since it was an AC motor, it wouldn’t generate significant power unless the field were active. Same goes for a DC motor the doesn’t have permanent magnets.

    As an aside, you can watch “Revenge of the Electric Car” on Hulu for free. They inserted a few ads and I’ve heard it’s only available to US viewers.

  10. Regarding the Aurora Inverter. The reason it shuts down is that during a power failure the juice produced by the Aurora can back feed out of the building. It goes up to transformer on the pole where it gets wound up to around 4kv to 26kv and proceeds down the wires to the electrical workers trying to fix the problem. This produces severe electrocution dangers for them. Also your inverter will be attempting to power all of your neighbors still connected to the wires requiring lots more amps. That’s why back up generators have a transfer switch that disconnects the building to prevent the same back feed.

    1. Oh I forgot to mention. Since the unit wasn’t designed to be part of a back up power source it has no provisions for the transfer switch. It has no guarantee that it has been disconnected from the grid. So the safest thing is to shut down.

  11. RandyC

    We KNOW why they do it. I think it is mindlessly stupid. We already have auto disconnect switches. If Grid power is lost, these relays disengage and we are positively disconnected from the grid entirely. There is no possibility of what you describe.

    Unfortuantely, with this idiotic anti-islanding, the Aurora inverter is useless as a backup power option. If we lose power, it won’t work at all. The very CONCEPT of a power inverter on site that relies on GRID power to operate is a technological oxymoron.

    IN any event, it does allow us to drain our large packs and use the power to power the shop instead of just burning it off.

    But as always, I deeply resent the meddlesome do-gooders saving us from our selves.

    Jack Rickard

  12. No, of course the AC motor did not overcharge the cells. However, when he tried to fire it up, he heard a pop from the controller and nothing. He thinks it blew something trying to turn the motor. I didn’t really understand his description.

    He’s kind of sick over it of course. Easy enough to put it in neutral.

    I don’t really like towing myself. Put it on a flatbed or a trailer for me.

    Jack Rickard

  13. I love it when my thoughts get verified by your research Jack.

    I thought, “In an automatic balancer, I would probably have a few second delay in switching to keep it from overcycling the relay.” I’ve blown big diodes with NiCd batteries and imagined the same thing happening here. And sure enough, you try it and it happens.

    I thought, “I’d probably do smaller packs, just in case something bad happens to a cell. Don’t want to lose a whole pack at once.” Sure enough, this conclusion is also reached.

    You have my dream job Jack. You spend your days tinkering in your garage with your friends. I envy and respect you and your work. If I could only find a way to pay the bills doing that…

    – Doc

    1. DOc:

      I’m kind of having the same thought Doc.

      The interesting thing about this one was the issue of the voltage drop across the cables carrying the current. When your load is 0.1 ohms, the resistance in the cables can be half the drop. So you have to be careful where you measure.

      We’ve talked about this with regards to chargers and charging in the past. Indeed we rejected the Current Ways charger because they could not manage accurate measurement of pack voltage over this issue.

      The “calibration” issue on the EMW Charger we just reviewed is interesting. But if I get some time, my intention is to modify the code where this charger charges for 3 seconds, shuts down for 25 ms, measures the voltage with no current, and then resumes charging – hopefully I can derive a function this way to take cable drop out of the equation.

      Jack

    1. No possibility there. I don’t know that the controller is blown. He can’t get the motor to turn. The tranny is probably locked up but he provided very few details.

      He’s of course sick over it and noted he was going to take a few days before even assessing it. He had taken a week off to come up and be part of the last of the build. I think he was pretty happy with the results. We had seats in it where he could get in and drive it.

      It was very perky. Nicely balanced. Some minor issues to work off and some interior work – a little carpeting really. We had built some neat features into it. I could hardly wait to get some video of his daughter driving it.

      As I say, we’re struggling here.

      Jack

  14. Jack – re the A123 module failures: a long shot because I’m sure you have thought of it: if you have the spec sheet for the resin you used, do you have a resistivity value (ohm-cm)? Also I wonder what the resistivity of the uncured resin is?

  15. Hi Jack,
    Love the show. You and Brian keep me inspired on my own ev project.
    I seem to recall that a few other people working with these pouch cells,(I’m using the A123 cells myself), found that if you don’t isolate the cells from each other they can short out at the edges where they are folded over very easily. Maybe someone else who has a better memory can chime in.
    Also, I’m wondering if the heat generated in the curing process of the resin might be compromising the pouch casings and causing them to short out. Just food for thought.
    Is any of that Honey mead going to be available at EVCon?

    1. Oh yes. Remember metric mind’s box that came to the doctor? “first do no harm”, he said, but I can’t think of his name. The cells were kocham (spelling?) and carried current, to the doctor’s surprise, along the side edges of the pouch. The current was small but when placed in the aluminium battery box it arrived at the doctor’s door ON FIRE almost.

      There must be a simple way of testing this. If it’s not the close placement of the cells, maybe it’s the resin. Perhaps, someone (jack preferable) can seal a nylon rod in the same resin, and see if it will carry a small charge while encased in the resin? Maybe a terminal at each end. I know this sounds a bit mad, but it’s worth testing. Other modules not encased in resin didn’t seem to want to blow up. It’s simple to do. And at least eliminates a possible culprit to a degree. There’s no point thinking about it-test it.

      Padraic McDonnell

    2. Padraic:

      The fundamental issue here is that they were KOKAM cells. No relation to A123 cells at all. Different chemistry. Different price. Different everything.

      Victor Tikhonov with Metric Mind felt qualified and able to design an entire module with incorporated BMS, but was unaware the pouches were conductive at the edges and when KOKAM refused to honor the warranty since the cells were misused, informed the customer that he couldn’t’ possibly be held responsible. This was his same line when we had a cracked motor face plate on an MES-DEA 200-250 motor.

      Alex Smith was the customer in that event. He had invested I think something like $48K in the development of this battery pack. And it came off the truck with evidence of sparking and smoke damage out of the box.

      Other than also being a pouch cell, the A123 cells share nothing with the Kokams.

    3. Yes that’s all correct.

      I wish I on worte this on its own: “maybe it’s the resin. Perhaps, someone (jack preferable) can seal a nylon rod in the same resin, and see if it will carry a small charge (test resistance) while encased in the resin? Maybe a terminal at each end.”

      Is that a plauseable way of testing if it’s the resin?

    4. I know when you say exothermic event, you’re concerned that the cells are damaged in such a way that electrolyte leaks.

      I know epoxy resin is an insulator, and used as such in electronics.

      My idiotic idea is to test the insulating property of the resin, after curing, you are using. It’s chemisty, who knows what’s going on?

      Padraic McDonnell

  16. Mike:

    I’ve chased these actuators quite a bit. I see electrical connections and a shaft socket. As soon as you leave the diagram you cite, the VACUUUM label is dropped. It is listed as an actuator motor everywhere else. What information do you have that this is actually vacuum actuated?

    Jack Rickard

    1. Jack,

      Just that a google search on “escalade A/C vacuum actuator” leads to some forum entries, ebay offerings, etc. about A/C vacuum actuators for the escalade, including model years at least through 2011. There is apparently both a vacuum and an electric variant, and you may well have the electric actuators. I know in my car (old VW) I had to include the dashboard in my vacuum system to get it all to work right, and wondered if you had eliminated the possiblity of needing ANY vacuum in your car. In my car, what gets actuated deals with defrost and vent, two functions I like to have. I don’t own an escalade, and so wouldn’t get a complete repair manual for it, but I was curious, and thought you might know or could look it up in your manual, if you have one. I’m interested in eventually getting rid of the noisy vacuum pump, and so I’m following your progress on the complete impact of going vacuum free.

      Thanks,

      Mike

    2. Mike:

      We’re on the same page Mike. But a google search doesn’t quite cut it. I have a full set of manuals on the beast, but that doesn’t necessarily cover it in any definitive fashion either. I don’t want a vacuum pump.

      When I chase down the actual AC Delco part number you referenced in the exploded view, it does NOT appear to be a vacuum valve. It appears to be an electric actuator. That was why I was inquiring.

      I don’t KJNOW at this point if we need vacuum for the environmentals, and you haven’t really told me how I could make that determination. You’ve raised the point, and now leave me hanging.

      We have never used a vacuum pump on a car yet. I would be disappointed to have to have one on this one but as stated, the priority is for the ac and heat to work. If it also rolls, so be it.

      Jack Rickard

  17. Orion:

    Possibly and perhaps. I have not been able to duplicate the concept of leakage from the edges of these cell pouches with a meter. I’ve read accounts, but I cannot duplicate the results.

    The exothermic heat of the urethane resin curing is kind of a suspect at this point.

    Jack

    1. Hi Jack,
      Well I know on my design I’m not going to risk it. I use very thin sheets of fiberglass reinforced plastic between each cell. I’m also not going larger than 60ah groups. If I get a chance I’ll try and get you some pics. I also thought you might like a video of the 1967 Cougar I’m doing.

  18. Dear Jack,

    Thanks for your rapid reply.

    Actually, all the A123 20Ah cells are made in Korea. Because the factory of A123 20Ah in Korea. Those cells with “made in Korea” are the old version. And the picture I send in my last mail is the new version. All of our A123 20Ah prismatic cells are genuine and new.

    Adam Tang

    I received this from General Electronic Battery Company in China and we are discussing the origin of the cells. He insists ALL 20Ah cells come from Korea no matter what is printed on them.

    I thought this sufficiently interesting to share. No concept of if it is true.

    Jack

  19. Interesting to note that GM went with LG cells, a Korean company, for their Volt cells. Now we find that both LG and A123 cells are made in Korea and these were the same companies that were under consideration for the Volt contract.

    Hum!, Where’s my tin hat?

  20. Jack:

    On the Escalade, I thought you sprung for the HELM factory Service Manual set for the truck. If so, it should have complete vacuum diagrams in there to quickly check everything you are needing vacuum for. Cruise control is the one most people forget, but on such a late model car, I really don’t thing there’s anything but the brake booster that uses vacuum. The trickier question is what is SENSING vacuum, and why, like the transmission PCM or power steering system. That’s another page or two of the HELM manual…

    IIRC, when I looked into this a little two years ago for you, I’m pretty sure that all the vacuum controls were phased out of the climate control systems in GM trucks somewhere by 2006. I remember being concerned about it, and then discovering that everything on your vintage of Escalade was a solenoid or a motor actuator controlling it. The easy test is whether there’s a hiss when moving the blend or heat controls. No hiss; no vacuum power.

  21. Two questions came to mind during this show. Has there been a shift in thinking re safe state of charge–I thought the line was 20%, not the 10% mentioned? I espied what appears to be a scooter/motorcycle in EVTV land: is it a gasser you are converting or a battery electric you are optimizing to get in on some best project in the world* action?

    * http://a4.sphotos.ak.fbcdn.net/hphotos-ak-snc3/32224_129701923710250_100000113296487_340916_4634978_n.jpg

  22. Sorry to hear about the woes with the A123 cells Jack.

    I’ve been inspired to go get a lithium pack for my solar power system after reading about your various sucesses with the Winston cells. I’ve got 8 of the 400Ah cells winging (well trucking actually) their way to me from the GWL EV Power warehouse in Prague in the Czech Republic. So although you can’t get them now in the US from Balcon (or whoever it was you said), you might be able to order them from these guys in the Czech Republic (but the shipping and customs duty might break the deal for you). As I’m importing from within the EU, it isn’t a problem for me as there’s no duty to pay and the shipping was not to expensive.

    I’ve ordered one of the CellLog8 things to use as a low voltage cutoff for my inverter load, as the Cellog8 will monitor each cell and trip an alarm relay output if one cell gets to the LVD cut-off voltage. Hopefully that’s all the BMS (as in Battery *Monitoring* System) I’ll need – as you’ve demonstrated that you don’t need all that expensive and dangerous active balancing stuff.

    An interesting thing on the GWL power blog was their new advice that most BMS balancers actually do serious damage to cells by holding the weak ones for too long at the top Voltage (anywhere over 3.65V) and this causes cumulative damage even when supposedly protecting the cell. They recommended it is far better to just short cycle the cells between 10% and 90% charge and not try to get the pack to 100% all the time!

    http://gwl-power.tumblr.com/tagged/TechReport

    Your experiments (and also mine with multiple lead acid batteries) also convinced me to go for the more expensive option of 8x 400Ah cells rather than 16x 200Ah cells in series-parallel because it’s always more difficult to ensure equal current balancing in parallel cells.

  23. If you review the video where you built the A123 pack, I have a sneaky suspicion that you forgot a spacer in your rush to finish the stack. Check the vid, it’ll be the segment where you’re finishing it off, I think that lost you some conductivity and explains why those specific cells failed.

  24. This paper strikes me as one more statement of half-understood and sort-of-right ideas that really doesn’t advance the discussion. The authors seem to acknowledge exactly that in their note on Page 6, which sets the tone…

    Lots of conclusions in that report, with no data or description of the “long term testing” which is the basis for the conclusions. Interesting point about overcharging based on duration, and likely true, but no cogent description of why this is the case, let alone a demonstration of it.

    I think these guys are feeling a portion of the elephant and more or less accurately describing it. OTOH, they don’t seem to have the big picture, and they reach several wrong conclusions as a result. Their “suggested” top balancing scheme in Fig 9 almost gets there, but they brush this impossible multi-cell voltage scheme off on a charger/bms somehow being able to dynamically manage the mythical “relaxed voltage” level. Why don’t they just say to drop the CC voltage from 3.65V to 3.55V? That mostly gets where they want to go, with no equipment.

    I don’t think the authors of this paper understand the ultimate implication of their observations and suggestions, particularly where this ~3.98V “full charge voltage” isn’t referenced to a charge current level, rendering it a rather meaningless number.

    I triangulate that opinion with a look at their “6 tips” to happy cells. Tip #1 is to manually top-balance. I think that’s clearly about the riskiest way to put a new pack into service, no? Tip #5 seems also to misunderstand CC/CV charging protocol, and suggests that GWL charges to 3.65 or whatever, and shuts off the charger. I hope that implication is just something lost in translation, but I doubt it…

  25. I have used LiFePO4 cells with a shunting BMS. I didn’t have any issues with the system but it wasn’t doing much of anything either, so I removed it.

    This self-promotional piece from GWL is bull. Cell shunts do NOT increase the time any cell spends at max voltage. You build your pack with initially top balanced cells if you are using a shunting BMS (if you don’t the shunts will slowly push it that way.) The shunts remove more from any cell that hits target voltage early so they are less likely to go there first next time. Over a few cycles the amount of time the shunts are on gets closer to the same. You can make it as short as you want.

    1. I have not read the promotional piece from GWL. But by definition cell shunts certainly DO increase the time any cell spends at max voltage. They basically hold it there bypassing the cell and feeding energy to the remaining cells. They are kept there until the others catch up.

      We do not use shunts and haven’t since some very early experiments with Thundersky cells. They are essentially the hallmark of amateur BMS wannabes that have no clue how these cells work. They are unnecessary and in most cases dangerous.

      We advocate balancing the cells at the bottom ONCE on installation and slightly undercharging them thereafter. It appears to work on multiple cars, many cells, and many thousands of miles.

      ALL of our cell complications have derived from our clumsy attempts at cell monitoring or BMSing. They work much better if you leave em alone.

      Other views are welcome, they just aren’t welcome HERE. We’re no longer guessing, and are singularly disinterested in finding new ways to burn cars to the ground.

      Jack Rickard

  26. Well it sounds as if the gearbox is seized
    There was a lot of this happening a few years ago in Sydney
    Cars being towed by tow trucks and arriving with seized or blown gearbox’s
    I am pretty sure that there are no tow trucks left in Sydney because of this
    They are now all flatbeds

    On a different issue
    now the model S is here (or soon to be)
    what is the situation with spare parts
    Can you ring up Tesla’s spare parts department and order a motor and controller??
    Be nice for an EV conversion

  27. Jack, have you had any thoughts about doing a segment on your Ford Edge? Maybe just a short overview. If it am right on my facts I think you bought this car at some stage of conversion and completed it, that is just what I put together in reading and comments I’ve heard you mention on a couple of shows. I was just interested in the conversion, what parts were used and how it performs.

    David

  28. Jack:
    Last year, I switched my 5.5hp ICE Honda irrigation pump over to a 3 horse electric pump, bought a Leaf and converted my lawn tractor, that I use to cut 3 acres of pasture grass, to 48volt 100ah Pb electric. I hate the Pb batteries but used them to prove my design. As suggested by you, I priced out the 160ah Li cells…ouch!

    I read recently about a company that had solved the chemical problems with NiZn batteries and they are making wild claims about their use in micro hybrids (start/stop technology). Lighter, more power, and longer cycling life, etc.

    If their claims are true, perhaps they will work in an short-range EV as well as my tractor. Hope it isn’t just more vapor.

    http://www.powergenix.com/?q=node/74

  29. When I look at the video “GoElectricDrive.com: A123 video presenting prismatic battery pack” on YouTube which Jack has shown in his shows as well, they put “Heatsink Plates” in between each 20Ah Pouch to wick away heat. And I read on this blog about phantom edge voltage on each pouch. And if that’s so, then how can they use a metal (presumably Aluminum alloy) heat sink plate that is in contact with both the pouch and the heat sink and each heat sink is in contact with the next? Even if they connect a phantom edge voltage to the ground side of the cell, in theory that does seem self defeating to me electrically. But I find it interesting that they use a metal heatsink on both surfaces of each pouch to wick away heat, at least in this instance.

    Jim

    1. A lot of swing thoughts going on there Jim. The only “phantom edge voltage” I’m aware of was on Kokam pouch cells not A123. We have been unable to duplicate the concept on these cells.

      They have a lot of heat control in the A123 module. We’re not seeing any dramatic heat, even under pretty high currents. We’re learning to HEAT cells, not cool them.

      Jack Rickard

    2. Not really straightening anything Jim. We’re all learning here. These cells are new. I can tell you that ASIDE from the mechanicals of putting them together, I have had some cell losses along the way unexplained. I continue to charge and discharge some, and things are not really getting any better. Some very bizarre anomalies and I struggle to duplicate anything twice in a row. So I’m constantly second guessing procedure, test equipment and cells. These are of course a very different SIZE in capacity than I’m accustomed to testing and dealing with . But strangeness continues and I’m starting to wonder if we haven’t started down a garden path that will waste time and resource without good outcome.

      On the physical end of the modularizing it, we just have to continue to try things. So far, my latest connectors work well and I like the 12volt motif in cast resin. Kind of pricey. A little heavy. But durable and doable still having access to ALL cell terminals.

      Runs cool. Even under current. Not bad.

      Working on supra sekert FLATENUM SERIES module now. Hope to have something to show next episode.

      DON’T TOUCH THAT DIAL. We’ll back in a minute with MORE UNDERDOG adventures…

      Jack

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