EV Digest 6857
Topics covered in this issue include:
1) Re: Motor Adapter plate
by "Roland Wiench" <[EMAIL PROTECTED]>
2) Re: Thundersky and calculations
by Ian Hooper <[EMAIL PROTECTED]>
3) Re: Thundersky and calculations
by Ian Hooper <[EMAIL PROTECTED]>
4) Re: Tesla roadster motor philsophy
by "(-Phil-)" <[EMAIL PROTECTED]>
5) Re: Battery Venting
by "(-Phil-)" <[EMAIL PROTECTED]>
6) Re: Tesla roadster motor philosophy
by "(-Phil-)" <[EMAIL PROTECTED]>
7) Re: Battery - Fuel Cell Hybrid Idea
by Mark Freidberg <[EMAIL PROTECTED]>
8) Re: Battery - Fuel Cell Hybrid Idea
by Christopher Robison <[EMAIL PROTECTED]>
9) Re: Battery - Fuel Cell Hybrid Idea
by "(-Phil-)" <[EMAIL PROTECTED]>
10) Re: Tesla roadster motor philosophy
by Victor Tikhonov <[EMAIL PROTECTED]>
11) Re: Tesla roadster motor philsophy
by John Wayland <[EMAIL PROTECTED]>
12) Re: Tesla roadster motor philosophy
by "George Swartz" <[EMAIL PROTECTED]>
13) Woohoo! just finished homemade capacitive discharge spot battery
tab welder
by Jeff Shanab <[EMAIL PROTECTED]>
14) Series/parallel motor clarification
by dale henderson <[EMAIL PROTECTED]>
15) Re: Battery - Fuel Cell Hybrid Idea
by Jeff Shanab <[EMAIL PROTECTED]>
16) Re: Tesla roadster motor philosophy
by Jeff Shanab <[EMAIL PROTECTED]>
17) Re: Tesla roadster motor philsophy
by "David Roden" <[EMAIL PROTECTED]>
18) Re: Tesla roadster motor philosophy
by "David Roden" <[EMAIL PROTECTED]>
19) Re: aluminum wire for EVs?
by bruce parmenter <[EMAIL PROTECTED]>
--- Begin Message ---
Hello Marty,
Both of my motors came with a bore hole for a brass pilot bushing. The GE
which has a 1-3/8 in dia output shaft was bore for the standard transmission
output pilot shaft. The Warps have a smaller hole, but a thinner brass
bushing works.
Find a early model crank shaft in a junk yard. They will normally keep the
good ones lock up in the back room. The early models such as the Chevy 256
or 283 for internal balance engines are forge steel. I luck out and found a
Chevy 256 crank in perfect condition.
Do not use a later large crank flange where the flange is not completely
round, which are use for the external balance engines.
This is a large flange type, where you can have a taper bore put in to it
for a taper lock bushing and still maintain the raise ridge on the front of
the crank flange, so it will center it self into a flywheel, flex plate or a
pump shaft.
It is easy for a machinist to mill a taper in the flange. He sets the lathe
to the specs of the taper which you can get out of a taper lock handbook.
After the taper is cut, the taper lock bushing show fit flush with the end
of the motor shaft, which will be recess some what into the face of the
crank flange. This allows for clearance of a transmission shaft to insert
into it.
I found it was easily to order the taper lock bushings from a Dealer that
handle Dodge Power Transmissions equipment and supply both the crank flange
and taper lock to a machine shop.
To install the set screw holes. the machinist has to make a taper plug to
push into this taper hole in the flange. He than can pilot drill and tapped
the holes for the taper lock set screws. He then removes the mock up plug
and installs the taper lock for a fit.
Normally the back diameter of this flange of about 2 inches in diameter is
ok. My overall length was set to 1.75 inches so the face of the crank flange
has the same references as it was if its in the engine. I also had the
machinist mill a small rig that goes around the shaft at the rear of this
coupler, so it can butt up against the bearing race that also rotates.
This prevents any thrust on the motor shaft which may be cause by the
pressure on a flywheel.
Another way to calculate the thickness of a motor adapter that bolts onto a
transmission bell housing. Is have the taper lock coupler built, install it
on the motor with a transmission pilot bushing install in the motor shaft,
then dry fit the transmission without a bell housing so it goes into the
pilot bearing, but do nut bottom out. Leave a little clearance.
Measure the distance from the face of the transmission to the face of the
motor and add your bell housing width and bell housing back up plate if you
use one. The distance or gap that is left, is the thickness of the adapter
plate you want.
Roland
----- Original Message -----
From: "Marty Hewes" <[EMAIL PROTECTED]>
To: <ev@listproc.sjsu.edu>
Sent: Saturday, June 09, 2007 9:58 AM
Subject: Re: Motor Adapter plate
> Hey Jeff (and Roland), someone on the same wavelength :). We're either on
> to something, or we're all nuts :). I'm surprised the large Chevy crank
> flange hasn't become more of a standard in the EV world. You can bolt a
> world of goodies to it, thanks to the various race parts suppliers out
> there. Once my motor looks like a Chevy crank, I can bolt in a manual
> trans
> with stock, lightweight race, or no flywheel or clutch, or to one of a
> number of automatics with or without a torque converter, all without
> changing the hub. And a huge variety of transmissions are all cheap and
> available. And information, and parts for modifications to those
> transmissions is plentiful.
>
> What did you do for a pilot bearing, bore the hub center for it? My motor
> just has a bolt hole in the end of the shaft.
>
> I could sure use those drawings. Did you make your hub? Are you in a
> position to make me one?
>
> I'd go with Roland's idea of just cutting the end off a Chevy crank and
> boring it for a taper lock except that forged steel Chevy cranks are
> relatively rare and expensive, most Chevy cranks are cast nodular iron.
> By
> the time it's bored, I'd be a little leary of the strength.
>
> Anybody got a junk Chevy steel crank around that suffered a thrown rod or
> something?
>
> Marty
>
> ----- Original Message -----
> From: "Jeff Shanab" <[EMAIL PROTECTED]>
> To: "Electric Vehicle Discussion List" <ev@listproc.sjsu.edu>
> Sent: Friday, June 08, 2007 8:33 PM
> Subject: Re: Motor Adapter plate
>
>
> > Funny you should mention that.
> > My taperlock presents the pre-"one piece rear seal" chevy 350 crank
> > pattern.
> > Which I mount a button flywheel and tilton racing clutch. Then I order
> > disks with the nissan splines in it since all the racing clutches are
> > the same.
> >
> > If I dust off my old server and transfer the files to a host (I lost my
> > free SDSL connection when I changed jobs) I could provide drawings of
> > it.
> >
> > MY complete adapters for sale idea was simple. (I just don't have money
> > to start this buisness)
> > warp 9 to 350 chevy taper lock adapter
> > for use with tilton or quartermaster clutch off ebay
> > A series of bells that mounts to the 9" that sets back the assembly
> > and adds a 12" diameter register.
> > A flat plate with a 12" hole in the middle and a standard bolt
> > pattern.
> >
> > To make a kit I pull the proper depth bell off the shelf and put it
> > in the box with the crank adapter and clutch
> > I throw the blank plate into the fixture on the cnc
> > it puts in all the tranny mounting holes and the dowels
> > I take it over to the waterjet guy and he cuts the outside profile.
> >
> > I have since decided that a dual motor setup would be better.
> >
> >
> >
> >
> >
> >
>
>
--- End Message ---
--- Begin Message ---
On 09/06/2007, at 10:11 PM, David S wrote:
Ian Hooper said
- ThunderSky and Liteway cost about $0.50/Wh
- Valence Saphions are about $1.60/Wh, including BMS
- A123 M1 cells cost $1.40/Wh
- PHET cost about $0.65/Wh or $1/Wh in packs with BMS
Prices for A123 are if you pull apart DeWalt 9360 packs, which is
sadly the cheapest way for individuals to get them! A123 continue to
disappoint me with their reluctance to sell to the public. PHET were
far more welcoming of private enquiries, and it sounds like their
high power cells aren't all that far short of A123 in performance -
very promising! (My soapbox comment for the day!)
-Ian
What is the Home Depot brand Rigid using in their 48 volt tools?
Not sure, but most lithium cells in power tools are just cobalt
cathode cells, not LiFePO4s, so they won't last particularly long and
are not so robust.
AFAIK Dewalt is the only manufacturer who have a contract with A123
to use their M1 cells, and it's only their 36V 9360 packs.
-Ian
--- End Message ---
--- Begin Message ---
For PHET, I spoke with Mindy Fu ([EMAIL PROTECTED]) and
Daniel Wu ([EMAIL PROTECTED]), who were both very helpful.
For Valence, I got an email from Topher H (valence-
[EMAIL PROTECTED]), though I'll admit after finding out their
cost I didn't really look into them much further!
-Ian
On 09/06/2007, at 9:27 PM, Richard Acuti wrote:
Ian,
Thanks a lot for answering my questions. That's quite a price
spread;. .50-$1.60...
Do you happen to have a point of contact for PHET and Valence?
Rich
Here are some costs per watt hour for various brands of lithium:
- ThunderSky and Liteway cost about $0.50/Wh
- Valence Saphions are about $1.60/Wh, including BMS
- A123 M1 cells cost $1.40/Wh
- PHET cost about $0.65/Wh or $1/Wh in packs with BMS
Multiply by 13000 to calculate the cost of your equivalent pack
(since 128V @ 100Ah = 13kWh). A BMS will set you back about $1K
on top of this for those without.
Prices for A123 are if you pull apart DeWalt 9360 packs, which is
sadly the cheapest way for individuals to get them! A123 continue
to disappoint me with their reluctance to sell to the public.
PHET were far more welcoming of private enquiries, and it sounds
like their high power cells aren't all that far short of A123 in
performance - very promising! (My soapbox comment for the day!)
-Ian
_________________________________________________________________
Don’t miss your chance to WIN $10,000 and other great prizes from
Microsoft Office Live http://clk.atdmt.com/MRT/go/aub0540003042mrt/
direct/01/
--- End Message ---
--- Begin Message ---
I hate to make this assertion, but the hairball is far from *absolute*
protection. Let's say there is a sudden short on the low side devices, and
the controller is now bypassed. The hairball detects this and attempts to
release the contactor and somehow the huge parallel inductance of a dual
transwarp 9 causes a massive flashover between the terminals, much more then
the arc quenching hardware can handle. Or even worse, maybe the builder
used a surplus 12vdc contactor w/o arc suppression.... The contacts melt
enough to weld on, then you are full blast.
In a DC system the only thing standing between battery and motor is a
mechanical contactor and semiconductor junctions. This means full
acceleration if there are only 2 faults.
If you have AC, and a similar fault happens on one of the 3 T-bridge
low-side sections, the worse case is you could get instant and hard braking,
but braking is not near as dangerous! More likely is a 3 stages fail
catastrophically from the domino effect (don't ask me how I know this =),
and the fault current is enough to blow a fuse or trip a breaker.
This is why it's always a good idea to have a secondary "last ditch"
disconnect as well as proper overcurrent protection. In theory a low side
fault on a controller like a zilla could also have a high-side fault and
create overcurrent easily that might save your ass as long as you have a
good fuse in the circuit.
My point is the Zilla/hairball or any DC solution has only as good of
protection as the rest of the car.
-Phil
----- Original Message -----
From: "John Wayland" <[EMAIL PROTECTED]>
To: <ev@listproc.sjsu.edu>
Sent: Friday, June 08, 2007 7:55 PM
Subject: Re: Tesla roadster motor philsophy
Hello to All,
David Roden wrote an excellent response to this thread:
AC induction and brushless DC motors move the job of commutation from the
motor (mechanical) to the controller (electronic and/or microprocessor
controlled)...AC motors are generally less complex than DC motors. DC
controllers are generally less complex than AC controllers. Seesaw: you
are trading mechanical complexity for electronic complexity...
However, David left out pertinent info below though, that might unfairly
skew safety in favor of AC:
A series DC motor controller, if it fails, is apt to fail full-on. This
can send the EV hurtling forward unexpectedly...Various safety devices can
be introduced to reduce this inherent danger of most DC machines. Most
hobbyists make do with extra contactors and possibly a "big red button."
Some have more sophisticated schemes...
David, there's a brand of DC controller that protects against the above.
Every single Zilla controller cannot run without and is mated to, a
Hairball interface that provides absolute protection against the full-on
runaway you describe. For the record, there's never been a single
occurance of this kind of failure in a Zilla, old or new, but just in case
in the very unlikely scenario of a Zilla's power stage going into full
failure mode and it 'were' to happen, the Hairball's advanced protection
features would instantly shut down all power contactors and the vehicle
would simply cease to operate...just like an AC system failure...well,
almost. You see, some AC controller designs can fail and actually cause
the traction motor to lock up during vehicle travel...something that won't
happen with a DC Zilla controller. GM was so concerned about this with the
Impact prototype, they abandoned the original twin motor / twin inverter
design over concerns about one drive side failing, locking up, and putting
the vehicle into a dangerous out-of-control spin at high speed.
In the context of what many of us Zilla owners already know (many private
emails have been sent by this guy to Zilla owners asking them to open
their controllers and send him spy pictures), please don't give more
ammunition to him by omitting the incredible safety features all
built-into the full line of Zilla controllers! Mr. Frederiksen has already
demonstrated how misguided he is about pretty much every aspect of Otmar
and his fabulously reliable and powerful Zilla controllers. He 'seems' to
think he can build a better mousetrap by copying what's under the lizard's
skin. His latest post continues his assault towards Otmar when he asks
"does Otmar know this?" Does Otmar know about this? Of course he does!
He's done consulting for Tesla, for crying out loud!
By the way, the high voltage system of a Tesla isn't any higher than the
high voltage DC system some of us have been running since long before the
Tesla was even conceived. I was running a Gozilla controller and 336V pack
back in '98, and yeah, Otmar knew about that, too :-)
I love the Tesla and think they're doing a great job with this machine.
Using a high-revving AC motor and lithium batteries is a great combo, too.
However, rumor has it, that Tesla is currently having a bit of trouble
actually delivering the promised 0-60 'in about 4 seconds' and that the
range per charge is closer to 200 miles than their hoped-for 250 miles. On
the other hand, a siamesed DC motor and a Zilla Z2K would right now,
effortlessly deliver 0-60 in 3.5 seconds in that car, and likely the same
200 miles range because of the DC controller's higher efficiency over the
AC inverter's wasteful use of electricity as it passes through 6 times the
silicon on its way to making three phase juice for that high revving motor
:-)
See Ya....John Wayland
--- End Message ---
--- Begin Message ---
If you have a recombinant type of battery, you don't want to do this, as you
defeat the system and will lose a lot more electrolyte!
The telecom floodies all use catalyst caps to recycle the water, seems like
this is a better solution.
-Phil
----- Original Message -----
From: "Roger Daisley" <[EMAIL PROTECTED]>
To: <ev@listproc.sjsu.edu>
Sent: Friday, June 08, 2007 8:58 PM
Subject: RE: Battery Venting
Why couldn't you replace the cell caps with snug fitting "chemistry type"
rubber stoppers that have 1/4" holes through them? Then you could manifold
the vents together and route the vent tube away from the vehicle. My
lead/acid motorcycle battery has a sealed top, but a vent tube out the
side
with a tube routed under the bike. This seems like a good idea that could
be
expanded for EV's. If you used flexible connecting tubes, the each rubber
stopper could be easily removed for inspection and watering.
--- End Message ---
--- Begin Message ---
I don't buy this, the efficiency of well designed AC drives can be higher
than DC. There are a lot of reasons why, and I don't really want to start
an AC vs DC flame war here, so I'll stop now.
But remember, what happens in the armature of a DC motor *IS* AC! It's
just switched by a mechanical switch rather than an external solid state
one.
-Phil
----- Original Message -----
From: "Danny Miller" <[EMAIL PROTECTED]>
To: <ev@listproc.sjsu.edu>
Sent: Saturday, June 09, 2007 10:01 AM
Subject: Re: Tesla roadster motor philosophy
There is an additional issue though. AC drive systems are affected by
skin effect, DC systems are not.
In addition to the skin effect issue, fundamentally the power is not
moving through all the copper at the same time and this increases the
effective resistance for a motor made of a given mass of copper. Motor
winding resistance is a significant issue at these power levels. Well
that's only the simplest observation of the difference in AC vs DC sizing
and efficiency. I don't have the experience to know much more about the
differences.
I think the overriding benefit of AC remains the regen capability (if the
controller supports it). This significantly benefits in-town driving.
Danny
Bill Dube wrote:
I agree with Victor on this one. An AC system is inherently much safer
than a DC system. A dropped wrench in the right spot can connect the
motor to the battery in a DC system and result in full throttle. Shorted
silicon will launch the car before the safety logic has a chance to
realize what has happened and drop out the main contactors. The
contactors open quickly, but far from "instantly."
In an AC system, the controller must be 100% functional for the
motor to even turn.
There is only twice the loss in the controller, not six times the
loss. There are indeed six switches, but the current flows through just
two in series. The voltage is typically twice as high as it is in DC
systems, so the current is half as much and thus the losses turn out to
be about the same. (The motors folks use in DC cars just can't take the
300+ volts that the AC systems thrive on.)
--- End Message ---
--- Begin Message ---
--- David Roden <[EMAIL PROTECTED]> wrote:
> Sorry to break in here, gang, but this thread is
> somewhat troublesome for a
> couple of reasons.
There's no "gang" present. There are list members who
posted to this thread, and a list administrator who
applied a label with negative connotations to those
members. That labeling was inaccurate and
inappropriate.
> First, although it's talking about batteries, it's
> partly off topic. The EVDL decided several years
> ago to not discuss fuel cell vehicles.
There's no mention of fuel cell vehicles in the
original post. I could appreciate a request for
subsequent replies to not discuss FCVs, but not a
request to discontinue the thread on the list.
> Second, it effectively tips into the area of
> over-unity and perpetual motion devices, another
> area that we've long since agreed
> to avoid.
Simply requesting that subsequent posts to this thread
refrain from dicussing those devices would likely
suffice.
>Please take it to private email if you'd like to
>discuss it further.
I would prefer that list members who wish to post
positive replies to the thread continue to be at
liberty to do so.
What's important here is that even when one person's
idea has no practical value in and of itself, it can
still spark creative thinking and innovation by
others.
> Thanks for your understanding!
You're very welcome.
Mark Freidberg
--- David Roden <[EMAIL PROTECTED]> wrote:
> Sorry to break in here, gang, but this thread is
> somewhat troublesome for a
> couple of reasons.
>
> First, although it's talking about batteries, it's
> partly off topic. The
> EVDL decided several years ago to not discuss fuel
> cell vehicles.
>
> Second, it effectively tips into the area of
> over-unity and perpetual motion
> devices, another area that we've long since agreed
> to avoid. The physics of
> the idea aren't supportable, as some responses have
> tried to make clear.
>
> I wouldn't have said anything, but the thread is
> beginning to take up a
> significant amount of list bandwidth. Please take
> it to private email if
> you'd like to discuss it further.
>
> Thanks for your understanding!
>
>
> David Roden - Akron, Ohio, USA
> EV List Administrator
>
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____________________________________________________________________________________
Pinpoint customers who are looking for what you sell.
http://searchmarketing.yahoo.com/
--- End Message ---
--- Begin Message ---
On Sat, 2007-06-09 at 11:24 -0700, Mark Freidberg wrote:
> --- David Roden <[EMAIL PROTECTED]> wrote:
>
> > Sorry to break in here, gang, but this thread is
> > somewhat troublesome for a
> > couple of reasons.
>
> There's no "gang" present. There are list members who
> posted to this thread, and a list administrator who
> applied a label with negative connotations to those
> members. That labeling was inaccurate and
> inappropriate.
While I don't really agree with the vitriol in Mark's response, I also
don't understand why this subject is inappropriate or why it seemed to
be a "perpetual motion" idea.
When flooded batteries are used or charged, they split the water in
their electrolyte into hydrogen and oxygen, and release it. This wastes
energy. Sealed batteries with a catalyst can recombine the two, but the
energy is still wasted as heat. Using a small fuel cell to recombine
the two and capture the energy probably wouldn't yield that much, but
how could the setup possibly be less efficient than just the battery
alone? It might not be enough of an improvement to be worth the
complexity, but I don't think it was an objectionable idea. After all,
we're still talking about a car that runs on batteries, and gets charged
from the grid.
Or did I misunderstand something about the original idea?
--
Christopher Robison
[EMAIL PROTECTED]
http://ohmbre.org <-- 1999 Isuzu Hombre + Z2K + Warp13!
--- End Message ---
--- Begin Message ---
If you are taking the energy that is otherwise wasted, then it's not a "over
unity" claim. But if you are "optimizing" the battery to produce extra
hydrogen, so you can burn it in a fuel cell, you will lose more than you
gain by this "optimization". Any claims to the contrary, by the laws of
physics and thermodynamics, must be over-unity and thus "perpetual motion".
In truth lead-acid batteries (with proper charging) don't waste that much
energy in electrolysis to be worth reclaiming by this proposal.
IMO, don't think the discussion up to the point of over-unity is a taboo
one. It's good to talk about these things and share knowledge before you
see one on a late-night infomercial! =)
It sometimes takes a lot of digging to determine that a new idea is, in
fact, based on over-unity calculations. This one, to me, is cut and dried.
-Phil
----- Original Message -----
From: "Christopher Robison" <[EMAIL PROTECTED]>
To: <ev@listproc.sjsu.edu>
Sent: Saturday, June 09, 2007 11:52 AM
Subject: Re: Battery - Fuel Cell Hybrid Idea
On Sat, 2007-06-09 at 11:24 -0700, Mark Freidberg wrote:
--- David Roden <[EMAIL PROTECTED]> wrote:
> Sorry to break in here, gang, but this thread is
> somewhat troublesome for a
> couple of reasons.
There's no "gang" present. There are list members who
posted to this thread, and a list administrator who
applied a label with negative connotations to those
members. That labeling was inaccurate and
inappropriate.
While I don't really agree with the vitriol in Mark's response, I also
don't understand why this subject is inappropriate or why it seemed to
be a "perpetual motion" idea.
When flooded batteries are used or charged, they split the water in
their electrolyte into hydrogen and oxygen, and release it. This wastes
energy. Sealed batteries with a catalyst can recombine the two, but the
energy is still wasted as heat. Using a small fuel cell to recombine
the two and capture the energy probably wouldn't yield that much, but
how could the setup possibly be less efficient than just the battery
alone? It might not be enough of an improvement to be worth the
complexity, but I don't think it was an objectionable idea. After all,
we're still talking about a car that runs on batteries, and gets charged
from the grid.
Or did I misunderstand something about the original idea?
--
Christopher Robison
[EMAIL PROTECTED]
http://ohmbre.org <-- 1999 Isuzu Hombre + Z2K + Warp13!
--- End Message ---
--- Begin Message ---
Danny,
Danny Miller wrote:
There is an additional issue though. AC drive systems are affected by
skin effect, DC systems are not.
The fundamental frequency AC drive generated is something like
240Hz. The PWM carrier frequency to form sine wave is typically
in 6-18kHz range (which BTW is no different from the PWM frequency
DC controller operated at), which is far too low to be affected
by skin effect. You start having impact from hundreds of kHz and
higher.
In addition to the skin effect issue, fundamentally the power is not
moving through all the copper at the same time and this increases the
effective resistance for a motor made of a given mass of copper.
Huh? First, the power is not moving, the current is. So what else the
current moves through if not copper? If you mean entire wire crossection
is not used equally and current density is higher hear surface, this
IS skin effect and as I mentioned has no practical effect at the
frequencies used in AC EV inverters.
If you mean inductance (e.g. inductive resistance) for AC current
vs "laminar flow" of DC current, there is no power loss in inductors
other than IIR on their wire, which is no different than DC loss
('of course comparing same current level and same wire)
Victor
--- End Message ---
--- Begin Message ---
Hello to All,
Victor Tikhonov wrote:
John Wayland wrote:
David, there's a brand of DC controller that protects against the
above. Every single Zilla controller cannot run without and is mated
to, a Hairball interface that provides absolute protection against
the full-on runaway you describe.
John, what David meant....
Victor, the point I was making wasn't about 'what David meant'...it was
about 'what David omitted'...that being the fact that not all DC
controllers can cause an EV to run-away. He completely over-looked the
Zilla's built-in safety features that totally prevent this. You cannot
hook up a Zilla without this feature enabled.
Not to spoil it John, but as Roger usually puts it you "conveniently
forgetting" (tm) that, unlike Tesla, WZ has really two motors.
Surely it's a fair comparison to bring up an $8000 DC drive and talk
about what it can do against, what, a $20,000 AC drive?
A DC system based on Otmar's high performance controller & installed in
the Tesla however, would turn it on its ear blowing away its current
performance with way more power than it presently has. Would DC be the
best choice to try to warranty to picky high dollar customers who will
be out there pushing their Teslas to the top end speed limits? With the
fireball monster always around the corner at extreme high voltage-high
DC performance levels? Probably not. AC is great. we all know this. It's
also way more expensive than DC when acceleration per dollar is figured
in. Some of us know this and openly talk about it, others act like it
doesn't exist.
A wise man once said:
>if identical raw power DC and AC systems would
>cost the same, everyone in their right mind would choose AC.
David often speaks glowingly about his AC powered Geo Metro. What he
doesn't talk about too much, is that his car was a ridiculously priced
converted econo-car that Solectria made for the bargain price of just
$40,000!!! Who (to quote Victor) "in their right mind" pays $40,000 for
a Geo Metro that's even slower than a stock wheezer Metro? Now, getting
one used for 1/4 that price? Maybe :-)
I do agree with Victor's statement. So Victor...where's that 350 kw AC
system for $8000 that I can replace my DC system with? You know, it's
the one installed in my steel bodied car that holds the world record for
the quickest 1/4 mile ET for a street legal car that still has doors on
it. This 2580 lb. DC car is more than a second quicker and nearly 17 mph
faster through the 1/4 mile (12.1 @ 106.5 mph) than the early version
highly touted $75,000 fiberglass kit car AC powered tZero with its 13.24
@ 90 mph ET when it had lead acid batteries and was 130 lbs. lighter
than WZ at 2450 lbs. Even when fitted with 700 lbs. of exotic lithium
batteries...vehicle now priced at over $100,000 and weighing just 1950
lbs. ... the tZero's beefed up 165 kw AC system still can't
out-accelerate my 2580 lb. Datsun with its DC system powered by lead acid.
When we try the A123 lithium pack a month from now, the sub-1900 lb.
WZ's ET will probably dip deep into the 11s, and if it does we'll
actually have NEDRA - NHRA certified time slips to back up our ET claims
(unless we get thrown off the track for lacking a roll cage for sub 11.5
second runs)...no goofy flag waving rolling starts needed. Barring any
electrical-mechanical problems, White Zombie should be able to eclipse
all validated 1/4 mile ETs for street legal electric cars...even the
'skeleton' tube frame 'thing' that's being foisted as a real car to
everyone, the Wrightspeed...all on caveman DC!
Would WZ be quicker and faster with a 250-300 kw AC power plant capable
of spinning up to 12k rpm? Absolutely! Maybe, some day :-) Until then,
AC takes a back seat to DC at the track when used in a full bodied car.
They want to build very good performance car, but not the purposely
race car like yours. It's like comparing different classes.
So it's not quite apples to apples, you know.
I agree with you on this. I repeat...AC is cool, it's certainly the way
to go for production vehicles. I have no complaints about the
synchronous pm rotor AC motor in my Honda Insight, and I loved the EV1's
AC squirrel cage induction motor system. I am not, have not, and never
have been anti AC. As I've stated in a past email, I am covertly working
on a few AC projects right now....shhhhh!
In the forklift world, AC is pretty much taking over. The difference
here though, is that it's priced right in there with the DC it's
replacing and offers superior 'everything'. The newest products from
Crown are the AC powered rider pallet jacks, and the brand new stand-up
rider forklifts that replace the old DC powered RC3000 series, that have
twin AC drive motors fed by a dual inverter/controller and an AC lift
pump motor with its owner inverter..awesome machines!
See Ya.....John Wayland
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Couple of minor points:
1. There is AC in the armature windings of a DC motor so skin effect is
possible in both AC and DC motors.
2. A chopper or inverter running at 1000hz, for example, has current
components at higher frequency harmonics due to non sinusoidal waveform. In
any event, I agree that skin effect is negligible at practical frequencies
we run. I will try to look up the formulas.
2. Litz wire is sometimes used in traction motors, for example, the Aurora
solar car brushless motor. Litz wire is used in this application to reduce
eddy current losses and improve motor efficiency rather than for skin effect.
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I saw the plans for this on many a website. I opted not to do this for
my project because the research showed I would damage the 26650's with it.
What are you planning on using it on ?
>From what I am understanding a 2ms pulse at 12V and a couple thousand
amps to clean the zone just a few ms before the 4ms 400A pulse is how to
weld these 26650's(or 18650's) IF the pulse is half that amps and twice
as long the battery will be damaged.
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Im sure Bill can answer this, but Ill open it up to
group as well:
If I want to switch two motors between series and
parallel and Im using contactors to accomplish this
task. Can I switch them all at the same time or will
I need to turn one set off before I can turn the next
one off?
For example if I have one contactor A between negative
of motor1 [n1] and positive of motor2 [p2] and two
more contactors B and C with B between the negative of
motor1 [p1] and controller negative [C-] and C between
on the positive of motor2 [p2] and the controller
positive [C+]
Then,
Can I switch off A at the same time as switching on B
and C [to go from series to parallel] and similarly
switch of B and C at the same time as switching on A
[to go from parallel to series]? or will I need to
switch off A then pause before switching on B and C
[and vise versa]?
Albuquerque, NM
http://geocities.com/hendersonmotorcycles/blog.html
http://www.austinev.org/evalbum/1000
http://www.austinev.org/evalbum/1179
http://geocities.com/solarcookingman
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I have always been fascinated by the pre-cursor to the nimh, the
Ni-Hydrogen. they are good for 100,000+ full cycles! Used on low earth
orbit satellites for years they would go from full charge to full
discharge as often as every 90 minutes. Almost give a capacitor
competition. The state of charge is directly measurable by reading the
pressure sensor.
There are two problems. They are considered trafficing in arms and
people have been working years to get them de-classified. and They have
been charged for the mean temperature for space and the excessive
pressure when above 70 degrees F, prevents furthor chargeing. I haven't
checked back with the guy about if that meant just need to cool them to
charge, or if i can't use them at temps above that. It was indicated to
me that the Koh concentration can be adjusted for terestial use, just
no-one has had a need to do so yet.
Anyhow, as the new lipo4 starts to make its way on to satellites they
are becomeing less popular, maybe that will make them easier to get,
maybe more scarce.
For those who share my curiosity:
http://www.eaglepicher.com/EaglePicherInternet/Companies/Technologies/Power_Group/Space_Applications/Products_Services/
look at the datasheet for the SPV cells
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I believe this is true, but would like to make sure.
AC systems are more efficient than DC systems.
Not becuase of anything inherint to DC vs AC but becuase AC systems are
designed for operation in a car. They take the operational window and
try to keep the motor in a sweet zone. They also end up needing better
magnetic materials to keep losses low so they don't melt down. Our DC
setups are operated outside their designed zone where effiency is lost.
Since they are overbuilt for the environment we use them in, they can
handle the abuse better, creaping from a stop at a stoplight on a hill,
than AC would if it wasn't designed with better materials and smart
controls.
I think a good adjustable commutator driven off of a servo and dual
windings could level this playing field. I have even considered
designing an inside-out dc motor. A hell of a lot more windings to comm
bars that are stationary on the inside of the case to the armature
windings that are inside this case, it would look like the windings of
an induction motor. The rotating field runs off of 4 brushes on a
rigging that advances like a distributer based on rpm,counterweight, and
springs. The feeds for the brushes now have to ride on a set of slip
rings :-( so that introduces a new loss, but maybe it will be
outweighed by the increased rpm capability and the perfect timing.
Spark surpressors can now be added to furthor reduce arcing (although
not to much, no arcing is as bad as to much)
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On 9 Jun 2007 at 12:45, John Wayland wrote:
> David ... over-looked the
> Zilla's built-in safety features that totally prevent this.
Nope, that's what I was talking about when I mentioned more sophisticated
external safety devices.
I said they weren't numerous, and I think that's a fair statement. There
are far more conversion EVs on the road using Curtis controllers than
Zillas.
An EVDL member might not think so. There's a great deal of discussion of the
Zilla on the EVDL, and with justification - it appears to be a very fine
controller (easy there, I have to say "appears" because I've never used one;
absolutely no offense meant).
But there are plenty of people driving EVs who are NOT members of the EVDL.
Curtis has been around for a long time and has sold a lot of road EV
controllers. I'd be very surprised if more than 5% of the Curtis
installations have any safety gear beyond a single main contactor and
perhaps a somewhat accessable main breaker. You find this sort of setup
even in some 1980s-vintage commercial conversions.
David Roden - Akron, Ohio, USA
EV List Administrator
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On 9 Jun 2007 at 12:01, Danny Miller wrote:
> AC drive systems are affected by
> skin effect, DC systems are not.
I'm not a EE, but I thought that skin effect became significant only 'way up
in the RF range. Of course I don't know them all, but I'm not familiar with
any AC drive that operates above the high end of the audio range.
> I think the overriding benefit of AC remains the regen capability (if
> the controller supports it). This significantly benefits in-town driving.
As I pointed out, regenerative braking isn't exclusive to AC drives. They
almost always have it because by the time you include all the other hardware
and software, it's trivial to add regen too. But a separately excited DC
motor also does regen very nicely, and adding it to the controller doesn't
take much extra hardware.
Silicon isn't free or even cheap. We're all fooled by the nosedives in cost
of microprocessors. As I understand it, that's fueled by improved
fabrication techniques that allow ever more transistors to be added to a
single die, not by cheaper silicon.
Again, my understanding : a high power semiconductor is a different critter.
You don't need more flip-flops on the die; you just need lots of mass to
handle the power. At this scale the materials cost is in the silicon
itself, and I doubt that it will get much cheaper than it is now. I
wouldn't be surprised if the opposite happens. This obviously hits AC
controllers harder than DC controllers.
OTOH, AC induction motors are appreciably simpler and cheaper to build than
DC motors. Thus, if we can ever get an AC controller in large-scale
production so that the huge engineering costs are amortized over millions of
units instead of hundreds, it's quite possible that AC drives will become
competitive even for hobbyist EVs. The quantity is the key, though.
David Roden - Akron, Ohio, USA
EV List Administrator
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Hi Mike,
I agree with Joseph on his points.
Though I have no direct EV experience using aluminum cabling,
I have heard similar comments by electricians and I had
indirect experience on the use of aluminum cables for power
years ago at a hp site.
Another story (EV saves my day)
The computer repair dept. was next to the site electrician's
Facilities Dept. at the PTP hp site in Sunnyvale. The site
consisted of three long rectangular buildings that hp was
leasing (at the time).
According to my co-worker electrician chums, the building's
owner went cheap during construction and used aluminum
power cables from the step-down transformer in the rear to
each of the buildings main power distribution panels.
The electricians were always complaining of having to do a
lot of maintenance to keep the cables in working order. From
my perspective, it caused our team a lot of headaches too.
The site's power was unreliable. These were back in the days
of pre- windows 3.1 PC's and people were still using dumb
terminals connected serially to lots main computers. To lose
power anywhere on the site meant many people lost the day's
data (because they did not manually save it often enough and
software then was too dumb to save it regularly).
It also mean main computers had to be re-started and that
took a lot of time to get everything back up and running.
One power fail back in those days meant the loss of more
than a half of a days work, and most Engineers stayed late
to make up for the slip in their project's schedule.
With the power down, it not only meant I had a lot more work
when the power did come back on and I could not do any
repair work in the shop, but during the down time I could
not even do the boring paperwork to kill some time.
Except a few times during a major power outage, I ran power
from my EV outside the shop door to my desk where I ran my
PC off a DC2AC inverter. The power was off at the site but
the phones were still ATT hardwired and on (pre-VoIP days).
I used a 1200 baud modem to slowly complete my day's
paperwork (yup, I wasn't as dumb as I looked).
I had enough of these bad power experiences to set my mind
against using any aluminum cabling. High maintenance or
unreliability was what I was told by the site's electricians
and what I experienced indirectly.
My EV's cabling is all copper and solid as a rock.
: Knock on dashboard :
Bruce {EVangel} Parmenter
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