Tuesday, April 27, 2010

April 23 Friday Show

I've posted the April 23rd Friday Show. We had a lot of wind noise I had to filter out so forgive Brain and I in the opening segments. We hadn't been breathing helium or anything, I just had to lose the low frequencies to make the wind more or less go away. We're still learning this video game, and most of it seems to be audio actually.

We did do a walk around of the newly reassembled Mini Cooper. We talk quite a bit about the Speedster Part Duh heater assembly. This is actually a kit from Canadian EV that we used and Brain and Trace did a marvelous job of installing it. It is just factory in operation and fit.

We ground off the fiberglass around the frame in the engine compartment. And I did a bit more in-depth review of the Xantrex LinkPro/TBS E-Xpert Pro instrumentation. It is cheesy looking. But it actually works quite well. It is quite accurate. And it is much more flexible than I realized when I dismissed it out of hand initially. At $250 it appears to be THE extant solution in EVland for the very necessary counting of AH to determine state of charge.











I've since done a bit of testing on the 2009 Mini Cooper Clubman. Yesterday I drove it to Perryville and back at as constant a 60 mph on the Interstate Highway as I could manage. It was 78 miles roundtrip with a consumption of 75.1 AH. It took 42.9AH to get there and a little over 32 to get back, indicating Perryville is mostly uphill from here.

At 60 mph, in the Getrag's 6th gear, I'm loafing along at about 1400 rpm. We did NOT get the Tach on the Mini working yet, but we did install a Summit Racing tach temporarily and the output of the TIMS600 controller seems to drive it admirably using the TIMS default and the 4 cyclinder setting on the tach.

We average about 60 amps at 60 mph on the straight and level, not even breaking a sweat for the 100AH SE cells. I DID mash the accelerator a couple of times - ZOOMING over 85 almost immediately. This drew a maximum of 372 amperes and dropped the cell voltage to a saggy 2.79volts for a total power of about 116kva (nearly enough kilowatts). I took this as a VERY good sign. It's hard to zoom anywhere with such an overdrive gear. The TIMS 600 is SUPPOSED to have a 300 amp limit.

I stopped in Perryville to do a Marine Corp temperature check of the motor and controller. They were at about skin temperature. In fact, the transmission was hotter than the motor. Our AN-8 sized cooling system, using the MIni radiator and fan, do indeed seem to be doing a superb job of keeping things cool and allowing MAX POWER out of the TIMS600 without stress. Probably a combination of the high flow rate and huge heat sink relative to what is normally used with this.

Finished the drive at ostensibly 75% Depth of DIscharge (DOD). However, the average cell voltage was 3.278. This is a bit of a puzzle. The SE discharge curve is quite flat. But I can't imagine it being THAT flat. We did do one measurement when the cells were first installed at 111 amp hours out of these 100 AH cells. It is quite likely, we have much more capacity than it appears. That would somewhat explain such a high resting voltage after the drive.

In any event, though I'm always looking for a bugger in the potato salad, the EV grin is starting to widen. The weight and coilover springs make the ride almost stately - like an Escalade. The performance is quite beyond the ICE engine which was already perky as you recall. The steering is stiff in local quarters but actually pretty good on the road. And with NO regen really on the highway we seem to be doing about 0,96 amp hours per mile. This indicates a "no regen" range of about 80 miles at 80%DOD.

The drive shaft issue (fingers crossed, eyes skyward) seems to be solved for the moment. I'm growing more confident in shifting and driving without fear of throwing a drive shaft. And the EV grin is starting to come on. This is a marvelous car. We have plenty left to do, but it is shaping up as an all weather all season ride with bluetooth and IPOD. Good performance. Good economy. Good creature comforts. And the Getrag transmission verifies our selection of this car. We take off in 3rd and road cruise in 6th for a good solid 4 speed experience.

Jack RIckard

10 comments:

  1. Nice work, Jack.

    I had been waiting for a report like this. It seems that gearing is one of the most important and least often optimized parts of an EV drivetrain. No surprise, gearing is everything to racers of any propulsion type, and OEMs are also obsessed with it. What's interesting is how different an ICE is from an electric motor in this regard.

    Your data suggests that REALLY tall gears, like a smog-era 2.47 rear axle in a rear-drive car, or double-OD gearsets in a FWD car like the Mini, are the way to go with electric motors. This makes great sense, as these motors have a torquey power band like diesels, only even moreso, and down to 0 RPM. Its too bad you can't get really tall gearing for the VW transaxle in the Part Duh.

    I'm no expert, but at least your motors seem to like extremely tall gears- far taller than what is generally available. Most conversions just don't take that on, and it apparently is making a big difference for you on the Mini. I'm guessing you popped for the highest available gear sets and R&P (.70:1 fourth and 3.44:1 R&P?) on the Part Duh to do the best you can there, too. Tall '50s style wheels & tires will help, too, but its all really guessing after you get to the shallowest ICE-based gearing.

    The combination of Brand A motor and Brand X controller at Chosen Voltage Y in a car that weighs whatever is a serious challenge to figuring out this question and optimizing an EV drivetrain gear package.

    This is all so much easier to do on a RWD car with separate trans and rear differential. It would be very useful for a serious conversion shop to build a RWD car with a quick-change rear axle just as a mule to dial in its various available motor/controller configurations at different chassis weights and voltages. This would be essential information for the whole community. Not likely to happen, though. Moreover, what would people do with the data?

    Most conversion guys couldn't pick the correct gears for their motor, controller, voltage and GVW anyway, because they don't have the gearing choices in the available auto parts, or the resources to make new choices for themselves. Its enough of a wake-up call to make me rethink the drivetrain of the Lotus Elite I'm planning to do, and go with a separate rear diff and trans primarily for the gearing options. I'm guessing there's enough gain there to justify the extra weight and packaging problems compared to a transaxle.

    At any rate, its now clear that a pretty substantial efficiency (performance, range, probably also thermal management) gain is usually being left on the table in EV conversions by not being able to really match the drive system's output characteristics to the glider's gearing.

    This is one spot where there's a whole in 80 years of automotive development as it applies to electric power, and it can really only be filled by the OEMs with their superior resources and developmental capabilities.

    Still, you've minimized the problem as much as could practically be done in your latest cars. Nice to see your attention to detail there, Jack.

    TomA

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  2. Yes, Tom. It's a classic and very visceral mismatch. Most of the motors available to us develop peak torque from 0 to about 2500 or 3000 rpm. While this is a 10x wider power band than the ICE engine, it is in precisely the wrong place. Modern vehicles are geared under the assumption that the sweet spot in the engine would be somewhere between 3600 and 4600 rpm (in some cases higher yet as I'm sure you know).

    As garage converters, it's difficult for us to just "put in a work order" for a different geat set to try it out.

    But yes, Speedster part duh features a 3.44 Ring and Pinion in place of the original speedsters 3.88:1. And we have gone to a 0.70 4th gear and of course the highest available in the others. I think it will make a huge difference.

    Rather than taking off in 3rd gear and shifting to 4th at 55mph and topping out at 95 mph, I'm hoping it allows us to take off in 2nd gear and get up to 110 mph at the top.

    jack

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  3. Agreed, but I'm not sure the electric motor power band isn't always wider than an ICE. My 465 CID Pontiac makes fantastic torque from under 3000 to 5750 redline. Of course, thats far broader than most ICE torque curves. More importantly, 0-2500 is actually far more manageable.

    I've been thinking for a long time that a GM Powerglide automatic, which is a 2-speed planetary (1.85 1st, 1:1 2nd) gearbox with reverse, paired with a quick-change rear would be an excellent choice for a RWD EV. Now your experience with the Mini, and your thoughts about the JRSE(P-D) Speedster are pushing me over the decision point.

    There's a company just starting to make one with no torque converter and an external pump to compensate for the no-idle electric motor:

    http://www.kansasev.com/evglide-powertrain.html

    I would probably skip that, use a regular 'glide without the TC, and just idle the DC motor, which would also give me power for a/c, ps, pb (through hydroboost) and an alternator. Pretty hard to beat those well-developed OEM devices for what they do, and I think the "inefficiency" of slowly turning the drive motor is overstated compared to separate power systems for everything it will run with a single accessory belt. That's a bonus of this driveline configuration, and goes a long way to paying for the custom 'glide and QC diff.

    The 2-speed gearing seems very good when paired with the quick-change, for which there are available cog sets in small steps down to 1.95:1. This as also a bulletproof set-up, well able to take all the torque even an 11" motor could dump into it.

    Until Getrag actually starts making their Electric Drive systems, I'm thinking the PG/quickchange a is flexible (though not particularly cheap) way to efficiently set up a RWD EV with a big (10" or 11") DC motor in a heavier-than-most EV. It solves other problems (like accessories) cheaply too, and a bigger, heavier car should be able to offset the losses of these various compromises with more space and payload for a disproportionately bigger pack, like the pick-up trucks do. That would give me a 4-seater with some carrying capacity, just what my every day needs are.

    Anyway, that's my evolving strategy...

    TomA

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  4. Tom and Jack,

    I suggest looking at Gear Vendors. They have some nice solutions for EV's. http://www.gearvendors.com/racing.html

    Michael

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  5. Well, GV make high quality planetary components, but they aren't well-suited to electric motors. The problem is that their .78:1 ratio is only about a 25% spread from engaged to disengaged.

    That's perfect for splitting the gap between the existing gears on an ICE drivetrain, and really dialing in a narrow powerband to optimize acceleration or, say, climb a long hill at a given speed.

    That's what an overdrive is designed to do. It makes the transmission even "closer-ratio" than it already is, which is important if your motor really only makes power from 1800 to 2100 rpm. That's a diesel torque curve, and the reason trucks have 8 to 11 forward speeds (and use lots of overdrives.)

    Electric motors, with their very broad power band starting from 0 rpm, need a very different gearing strategy. If I could choose the gears, I'd want 50% wider gearing between speeds than most ICE gearboxes, and have the final drive maybe 35-40% taller than normal. That puts the electric motor in its powerband all the time, and eliminates the surplus ratios. Two forward speeds is probably all you need. That's all Getrag is doing on its multi-speed Electric Drive units, anyway.

    So, I found that GM made a pretty stout 2:14:1 rear axle, which would work perfectly behind a wide-ratio 2 speed Powerglide (especially a beefed one with the lower 2:1 1st and 1:1 2nd gears) and that seems like a pretty ideal and strong drivetrain for a big, heavy RWD EV powered by a big Warp11 HV motor.

    I have already built such a car. I did a motor swap and suspension upgrades on a 1980 Pontiac Grand LeMans Safari wagon about 7 years ago. I sold it, but these things are everywhere. Great, comfortable, sturdy, full-frame cars, and the 2:14 rears are dirt cheap because the ICE guys don't want them. Sure, its 3500lbs dry, but I could get at least 700 of that out by removing the ICE, upgrading the suspension, etc. I think the GVWR was over 4500 lbs. If the Warp11, controller, glide, cooling and all that put 350lbs back in, that car could easily swallow another 1200+ pounds of LiFePO4 under the hood and rear floor. That's about a 60kWh pack. $25k, yes, but even if it sucked up 500Wh/mile, it would still go 100 miles on a charge.

    I could run the A/C, ps, pb, alternator and even a water pump or two off the snout of the motor. It would seat 5 adults. Everything on it would work normally and my wife could drive it every day. We could fill it with groceries and kids stuff. I could probably pull a utility trailer. I can put such huge brakes, stout crossmembers and suspension parts on it that closing in on the GVWR wouldn't worry me at all.

    But back to the gearing, which is how this all got going... That big Warp 11HV makes a ton of torque. It could probably snap most any driveline, and you'd even have to dial back the controller to prevent that with any transmission you tried, but the powerglide can be made very robust, indeed, and the GM 10 bolt is similarly up to the task. Better yet, the gearing seems very close to ideal: two widely spaced forward gears, (2:1 and 1:1) reverse, and a 2.14 final drive ratio.

    For a guy like me, this is getting to be extremely attractive. Expensive, yes, but also a real, usable, every day electric car. Plus, this thing would burn rubber until the tires popped. I like that...

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  6. I suggest you take some time and look at Gear Vendors. I think you have some preconceived notions about what they have to offer. They are not just an overdrive solution. They can provide a complete transmission solution that can mate to anything you want. They have been building custom EV transmissions for quite a while. The EV drag racing scene has been using them for years.

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  7. Do you work for GV?

    I have been all over their site, and I can't find anything but conventional transmissions with GV overdrives mated to them. I've been into these planetary ODs for over 25 years. I have held a GV unit in my hands and I know what it is. Hasn't changed in decades. This is the one and only product Gear Vendors actually makes- everything else is an adapter, tailshaft, control switch or, as you point out, a "complete transmission solution," e.g. a sourced conventional transmission with a GV OD mounted on it.

    There is a reference on the GV site that they made "several transmissions" for the Dodge TEVan, but I can't find any documentation of either the two speed clutched unit with reverse that the DC-motored TEVans used, or the single speed non-reversing transaxle in the AC EPIC version of that vehicle, and I've never examined a TEVan. I don't know what a "custom EV transmission" would really be, other than what Getrag has begun to develop.

    You seem to be missing my original point. I'll drop it after this, but its very simple: Most conventional car transmissions and differentials aren't geared appropriately for electric motors.

    My second point, to your suggestion of an overdrive, is that the OD is also poorly geared for an electric motor. Its two available ratios are too close together to be useful. Combining the OD with a conventional car transmission and differential compounds all of these issues, creating even more unnecessary gears without solving the final drive ratio problem.

    Thanks for sharing, though; it was a good thought.

    Over & out,

    TomA

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  8. David HerringtonMay 19, 2010 at 7:56 AM

    Jack - In this weeks video you mentioned that the TIMS600 EMI "wiped out" the EVision. Can you shield the EMI by simply placing the inverter in an appropriate enclosure?

    Also, did you address the "controller set-up" for the inverter in one of your previous videos? It is supposed to be done with the inverter "unloaded." I am trying to determine if doing it with the tranny in neutral will be good enough or if I need to break down my power train, and remove everything attached to the motor output shaft. Thoughts

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  9. I had a comment with an MES-DEA engineer. He suggested grounding the case by scraping away some of the anodized coating and strapping it to the vehicle ground. He said this in such a way that I have to believe it's a common and known problem, though not mentioned in any documentation anywhere.

    Yes, we did our autotune setup in neutral with the transmission engaged. It seemed to work well. The car is actually running beautifully.

    Jack Rickard

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  10. David HerringtonMay 24, 2010 at 12:20 PM

    Now that you have had some experience with driving the car, what is you assessment of the optimal configuration for the regen feature? Begin regen as soon as you are off throttle, as soon as you touch the brake, only after considerable brake travel? Also I must have missed how you tied the regen pot to the brake pedal travel. Is it in one of your earlier videos/blogs?

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