Posts
We had a bit of a visit this week from George Hamstra of Netgain Motors, and took advantage of the visit to interview him on camera - mostly about earlier careers and how he got started with electric vehicles and Netgain Motors. Netgain's Warp 9 is inarguably the workhorse among the conversion community and he continues to innovate and improve on this motor.
A Tequila powered interview, George talked about some of the 26 improvements he's made to the latest build, going on now. These include a new fan blade design to run the motor cooler with a port for an optical RPM pickup. It also features some new brushes good up to about 192v. The previous recommendation was 170v on this popular line of DC series motors. Oh, and 1/2 inch terminals.
The Tequila flowed both directions and I wound up spilling the beans on a couple of our "sekert projeks". The one most likely to cause a stir is the $20,000 contest giveaway. George has signed on as motor sponsor for this event, though we continue to discuss 9 inch or 11 inch motors. We're still designing this event, ergo the lack of an announcement. Current thinking is that we will have an extensive questionaire entry form. From the entrants, we will select 10 and present them online for a popular vote. The winning "Dream Build" project will receive a motor, controller, full set of LiFePo4 batteries, and a charger. So far we have Elite Power Solutions as the battery sponsor and Netgain Motors for the motor. Still to select, charger and controller.
We are also going to convert my 2008 Cadillac Escalade EXT. This vehicle has all the room in the world. We're going to fit it with a massive 67kWh battery pack and TWO Netgain Warp 9 motors with a special automatic transmission. It will also feature a huge capacitor bank made up of Maxwell 3000F Supercaps. George and I spent a good part of the day talking about how to wire up two motors and two controllers and he has a method supposedly far superior to any you've heard about. HE's also actively campaigning for an active hybrid cap/bat pack using a DC-DC converter. No problem George. I just have to figure out how to build a 1600 amp buck/boost circuit with a2/0 gage cable coil and a half dozen 400 amp IGBTs. I can do that. I think.
It's shaping up as the impossible to complete and totally impossible for anyone to fund EV conversion. Don't try this at home. Our goals? 1000 mile range and 723 mph.
That's what Tequila does to me.
Enjoy....
Jack Rickard
Subscribe to:
Post Comments (Atom)
Jack/Brian, my guess is that your ICE sound device doesn't work on your EV because the 12V cigarette lighter plug it is isolated from your bat pack voltage. Depending on the device's current requirement, you might be able to make it work off a resistive divider to 12V from your main pack. I would think that regulating in most other forms will filter out your motor commutation noise.
ReplyDeleteI wanted to hear what George was saying about how much amperage is consumed when driving an alternator and AC compressor off the back end shaft. Did he tell you off camera?
JR
Did he tell us what? He told us it took a surprising amount. Without knowing the power level of the AC compressor, the size and efficiency of the alternator, and precisely what load is applied to BOTH instantaneously, there is not even a ballpark possibility. But he said it was more than most people assumed.
ReplyDeleteWe're not going to try to engineer the car so the $12 toy noisemaker works. I was just surprised that it didn't. But you are most probably correct in that it was getting the alternator noise through the 12volt, and not just through the air. I suppose we could connect the output of our RPM sensor to the 12vdc via the 7.5k resistor instead of to ground and it might just work. We actually use this resistor to dampen the magnetic pickup pulse. We could probably do that as easily to the 12v as to the ground.
Jack Rickard
Hey Jack,
ReplyDeleteIn the video you didn't say much about the idea to use ultracapacitors in your future projects. Could you please talk more it and what challenges it brings about. I think this is a fascinating subject. Here is a paper where a similar concept is described:
http://web.ing.puc.cl/~power/paperspdf/dixon/25.pdf
As you see it relies quite heavily on the software side to control the system which means a lot of debugging. Is there a ready solution for that? If you are going to build it from scratch it would probably make sense to start with a toy project before going full scale.
Waiting for more news on that front.
Thanks,
Nikita
Jack,
ReplyDeleteHave you or George talked to http://www.rinehartmotion.com/
about 3 phase AC inverters? I know Dave Kois is selling the old Ford Siemens AC motors with a Rinehart Motion inverter. As custom builds I think they run around $8-9K but in some volume the price might be better.
JRP3
JRP:
ReplyDeleteHave you known of David Kois to ship any of these and anyone receive one? I have some batteries on order with him now, that I haven't received.
So I don't know yet what's real there or not. I was interested in the Siemens motors about three years ago. Probably not so much now. We need production products that will be produced and supported in the future.
While interesting, Zillas and Siemens and so forth that were once available are really not of a whole lot of interest to me personally. Many will use remnant stuff successfully, but I can't really spend time looking at stuff you can't buy or if you do buy, won't be able to get replacements for. That's my thinking as of today.
Nikita:
ReplyDeleteHopefully we'll be talking a LOT more about it. Thank you for the link. I already had two Dixon papers on the Chilean project, and a book full of others.
The basic determination is passive or active. Passive is simply fronting the cells with super capacitors and it is widely reported that this does no good. I have extensive experimental results from a set I had on a GEM several years ago to refute this. It does a LOT of good.
One of the issues we have with these cells is that they sag in voltage when we try to take that much current out of them. With the caps, they don't sag. They don't sag at all. And it has to do with the way the cells and caps interact in a very different time constant than that used in accelerating the car.
The other issue is life extension, which is much more difficult to measure. But there was a guy in Australia, using NO electronics, just buffering the cells with caps, that claims over 100,000 miles on a LEAD ACID pack. If this were applied to LiFePo4, you essntially have a battery that after you wore the car out, you would move to the next car.
So I'm a big fan of passive cap buffers.
George posits an actual extension in RANGE from an active system. It's a little hard for me to swallow, as you have losses in the power electronics. But I could be persuaded.
ReplyDeleteThe central issue is not the software. I can write software while I'm asleep.
The issues revolve around high current semiconductors and most seriously, around the boost coil.
We intend to do something like 1600 to 2000 amps on acceleration in the Cadillac. This is a heavy vehilce at a little over twice the Mini's weight. And it is going to take some serious power to move it.
IF we did the batteries at a HIGHER voltage than we are going to draw from the caps, and that's certainly an attractive notion, we could get by with current devices somewhat smaller than that. About all we can buy at the moment is 1400 amps. And we would have to run a pretty high frequency to keep from blowing those up.
Otherwise, we're looking at a bank of those in parallel. They need gate drivers, and we wind up with odd power supplies like 15 v or 24 v for the drivers.
At the heart of it is of course a microprocessor. Dixon's theme was about having the caps DOWN in voltage to accept REGEN and UP in voltage anticipating acceleration and trying to predict the future in software. It's the software version of perpetual motion With enough processing power I MUST be able to tell the future. Simply gather all the variables in the known universe and mash em toether with enough MIPSand voila - easy..
He never got there with that part.
If you don't try that, your microprocessor is doing very little more than running a 555 timer with some fault inputs. It's not hard at all.
And then there's the coil. Dixon used 266 turns of flat sheet. I need 2/0 to do these current levels. Do you know what 266 turns of 2/0 would look like? A cable spool. ANd you'd need a forklift to heft it into the truck.
ReplyDeleteWorse, when I turn it on, it might cause the car behind me to lunge into the back of the truck and stick there. Yes, of course we'll go air core, but you can imagine.
So its non-trivial.
Even a passive system has to have some controls to limit the initial charge of the caps, to discharge caps for maintenance, and so forth.
What I'd personally like to do is put a 1400 AMP IGBT between each three cells of battery to each 4 caps and then draw off the ends. So all I need is about 20 lGBT's at $850 each.
The simple step is a buffer. The next step looks easy, but the more you chew on it, the worse it gets. I keep reading. And I'd like to do it. But it gets hugish quickly.
Sometimes the simplest answer is the best. And I think we're looking at a two year project to find that out one more time.
Jack Rickard
Jack,
ReplyDeleteI too am waiting on a few cells from Dave, but I have sent him no money and the wait was expected. I don't know if Dave has sold any of the Seimens motors, but I wasn't suggesting that you try to get one. I was just suggesting that you or George might be interested in the Rinehart motion inverters that Dave is using with the Seimens motors. I'm assuming George could easily build an AC motor but without a decent inverter there would be little point. Rinehart might be an answer.
JRP3
Would switching capacitors from parallel to serial configuration replace the need in an enormous DC-DC converter? Let's say two 125V 63 Farad modules (like this: http://cgi.ebay.com/63-Farad-125V-Ultracapacitor-Supercapacitor-Module-NEW-/370416666039?pt=PCA_UPS&hash=item563e8dc5b7) and a 144 battery pack are used. Would it make sense to charge the capacitors connected in parallel from the battery pack or regenerative braking to 125V and then switch them into series to get a 250V source?
ReplyDeleteAs for a pack of 3 battery cells + 4 capacitors would it be possible to employ a similar configuration to the BatPack (http://www.redrok.com/ev.htm#batpack)? In that scheme cheap low voltage switches could be used. For instance, 24V 280A MOSFET costs around $6 (http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=497-7614-1-ND&enterprise=44)
Thanks,
Nikita
I did a bit of noodling on the DC-DC converter. For this project, the currents required sort of lead us to a coil 38 inches long and a foot in diameter, quite a bit larger than the motor.
ReplyDeleteIn the cap switching, you have to have a large cap or coil to smooth the 250v while you switch back to the parallel. The slightest overshoot and the whole thing turns into a fireball.
And speaking of fireballs. These caps are strictly limited to 2.7 volts. ONE of those$6 MOSFETS opens and we'd probably lose most of the cells in our $10,000 cap bank. If it shorts, we couldlose someof the batteries as well.
At this point, we're probably looking at a simple cap bank buffer for the batteries with no advanced switching circuitry. We will be able to activate it or deactivate it at a switch, precharge it or discharge it, and fan cool it. That's about what I have planned.
Having been through this before, I think it will be very interesting to measure a 0-60mph in a 7200lb vehicle with and without the cap bank. I think you'll be in shock and awe aat all the things you thought you knew about cap banks, that just is not precisely so.
Jack Rickard