EV Digest 6750
Topics covered in this issue include:
1) Re: Questions regarding an EV
by "Mark Karatovic" <[EMAIL PROTECTED]>
2) Re: Batteries or Charger funny?
by mike golub <[EMAIL PROTECTED]>
3) Re: PFC-20
by Jeff Shanab <[EMAIL PROTECTED]>
4) Motor equations
by Steve Peterson <[EMAIL PROTECTED]>
5) NI-Cad STM5-180 Auto watering hookup
by "Mark Hanson" <[EMAIL PROTECTED]>
6) Re: EV Drag Racing Ideas
by [EMAIL PROTECTED]
7) Re: EV's on Local Talk Radio
by "Deanne Mott" <[EMAIL PROTECTED]>
8) Re: More Tweety (NmG) fun...
by [EMAIL PROTECTED]
9) Re: Colorado EV'ers
by [EMAIL PROTECTED]
10) Re: Electric Mini Cooper Videos
by Bill Dube <[EMAIL PROTECTED]>
11) RE: Over voltage in a pack
by "George Swartz" <[EMAIL PROTECTED]>
12) Re: NI-Cad STM5-180 Auto watering hookup
by "Evan Tuer" <[EMAIL PROTECTED]>
13) g wiz safety
by Steve O <[EMAIL PROTECTED]>
14) Re: g wiz safety
by "Evan Tuer" <[EMAIL PROTECTED]>
15) Re: EV's on Local Talk Radio
by "Timothy Balcer" <[EMAIL PROTECTED]>
16) Parallel strings of unlike batteries
by "Marty Hewes" <[EMAIL PROTECTED]>
17) Re: Motor equations
by Jeff Major <[EMAIL PROTECTED]>
18) Re: Electric Mini Cooper Videos
by Jack Murray <[EMAIL PROTECTED]>
19) Re: Motor equations
by Steve Peterson <[EMAIL PROTECTED]>
20) Magazine article FYI
by Bruce Weisenberger <[EMAIL PROTECTED]>
21) Re: Electric Mini Cooper Videos
by "Timothy Balcer" <[EMAIL PROTECTED]>
22) Re: Can anyone recommend a machinist in Los Angeles?
by "Lawrence Rhodes" <[EMAIL PROTECTED]>
23) Re: Electric Mini Cooper Videos
by "Timothy Balcer" <[EMAIL PROTECTED]>
24) Field weakening basics
by Steve Condie <[EMAIL PROTECTED]>
25) Re: Motor equations
by Jeff Major <[EMAIL PROTECTED]>
26) Re: Field weakening basics
by David Dymaxion <[EMAIL PROTECTED]>
27) Re: article: Driving Michelin's Zero-Pollution Car
by "Lawrence Rhodes" <[EMAIL PROTECTED]>
28) RE: Over voltage in a pack
by "Dale Ulan" <[EMAIL PROTECTED]>
29) Re: Motor equations
by Steve Peterson <[EMAIL PROTECTED]>
--- Begin Message ---
Thanks everyone,
To clarify that would be my two way range. And it isn't everyday
driving, but on the odd occasion it may be (say once every two weeks).
It's more for emergencies then anything else.
I was thinking of a ute as well. Electro Auto have some adapter plates
that I can see, but maybe not for the cars in Australia? But as always
I'm concerned about the shipping cost for something that large. There
may be someone local that may be able to do something in regards to
it, need to go to a demo somewhere. I will take a look at that site in
the hope of getting an idea on the plates.
In any case I will need to look at the cost and find a donor vehicle
appropriate. It's good to at least have a feel for the limitations of
my decision before moving forward.
BTW I live in Western Sydney. Townsville is quite a distance from
here, another state in fact. At least a 15 hour drive from here non
stop.
Slightly off topic does anyone here make their own PWM controllers? I
have worked with much smaller motors using PWM and an analog signal
input into a Freescale chip and a PIC to control the speed. I'm sure
that with the high power there is a lot more to it then that. How do
controllers implement the next step? Is it just high power mosfet's as
switches or what?
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--- Begin Message ---
do you have spacers between your batteries?
--- Mike Willmon <[EMAIL PROTECTED]> wrote:
> Been running twenty Crown CR-225's in the truck now
> for 5 months.
> Over the winter the batteries have been kept around
> 75*F to 80*F by keeping the lid propped open
> appropriatley to regulate the
> temp. Recently outside temps started to rise for
> the summer and I came out and they were 104*F and
> the charger did not shut off.
> It was still running full open at just under my
> regulation voltage of 145V. OK so a little thermal
> runaway. I pulled the
> insulation out of the lid, let the truck sit outside
> without the lid for the weekend. Battery temps back
> down to 75*F. A few more
> days running without the insulation in the lid and
> temps are normal; I still prop the lid open at work
> to cool. Because its
> warmer out and the likelyhood of the batteries
> running over 80*F I've dropped the Reg voltage to
> 143V. But the last few days as
> I've watch the end of charge the voltage gets up to
> 143V, the blue Reg light (1500 "Mega"candella ;-)
> flashes on the PFC-20 and
> an hour later voltage drops to 141V, Reg light goes
> off, charger continues full tilt until I shut it
> off. Battery temps barely
> 80*F. Its time for a water check and Equalize anyway
> so I refill all the cells (all of them need a
> little). It hits 143V and drops
> to 141V a couple more times, then it hits Reg and
> times out normally a couple times. The last 3 days
> though it will not reach
> 143V at all. I'd like to run an equalize charge but
> I cannot get them over 143V. I'm only running
> 110VAC so I can only charge at
> ~10.5 amps. The last 3 days I've just shut it off
> manually when the KillaWatt meter says I've returned
> 120% of what I calculate I
> use during the day. The calculation is verified by
> a couple data pulls from the Zilla. At 380 Wh/mi
> its slightly higher I figure
> because I have the summer treads on that run 35psi,
> while my winter treads were 44psi (I notice steering
> is a little harder with
> the summer tires too, but thats expected). I don't
> seem to be using more power than I expect. I don't
> seem to be losing any
> range. It doesn't seem to be losing any steam after
> 15 miles of driving. All the driving seems normal.
> Battery temps seem
> normal. All batteries when at the top of charge are
> average 7.11V with one highest at 7.2V and two
> lowest at 7.02V (all other run
> 7.08V to 7.15V).
>
> What am I doing wrong?
>
> Mike,
> Anchorage, Ak.
>
>
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--- Begin Message ---
Maybe a plastic shroud fitted over the pot and up against the case would
be a good long term fix. It is all that freedom that gets us in trouble?
ie
xxx | | yyyy
|__|
-----------||------------ board, x and y hazards
========== =========== case
Added shroud
xxx | | yyyy
|__|
----------||||----------- board, x and y hazards
| |
_| |_
========== =========== case
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--- Begin Message ---
Calling Roger Stockton:
Back in 1999(!) you wrote:
"My goal is to derive a new model based on the standard DC motor
equations, but taking into account torque lost to the cooling fan, etc.
which will be reasonably accurate for both series and PM motors, which
would be available to you for use in your EV calculator, should you
desire (unless someone else points out useful equations in the meantime
and saves me the effort 8^)."
This was in the context of a short exchange with Uwe about his
calculator's accuracy in calculating motor behavior at various voltages.
I'm sure you remember :-) The post can be found at:
http://www.crest.org/discussion/ev/199903/msg01120.html
My question is: did you manage to come up with such a model?
I ask because I'm trying to do some calcs for a *fan-cooled* ADC FB4001, but
can't find the values for the parameters Uwe's calculator requires. His
calculator has a page to calc the parameters, but I can't get that to work
(even for motors he *does* have parameters for--i.e., it doesn't even seem
to calculate properly when I give it the correct answer for other motors).
So either I need values for the "a, b, c, d, n and k" parameters, or
I need a reliable way of deriving them, or I need a model
that can be made to work given info from the curves provided by ADC.
I don't mind writing some software, but I don't have the EE/Math background
to derive the equations myself (for instance, I'm stymied by the fact
that the standard motor equation seems to be linear,
but the ADC rpm vs. torque curves aren't).
Any help you (or anyone) can provide is most welcome...
--Steve
--- End Message ---
--- Begin Message ---
Hi Folk's,
I hooked up my 14 batteries in my E-Porsche 914 in 3 seperate strings per
the Saft manual and noticed at final charge that a couple strings had pee'd
electrolyte (an ounce or two) on the ground from the rear of the car. I
then decided to put plastic hose clamps on them to keep them from dumping
electolyte but was worried about hydrogen gas escaping.
1. Can final charge gas escape from the orange tops or is the only route
out the fill hose?
2. Should I clamp the low exit end of the pee exit tube when not doing a
fill operation?
3. I noticed at final charge 3 batteries at 7.6V instead of 8.5V on the
battery scanner. Is this normal? I noticed that these 3 had 00' date codes
instead of 01' but they were supposed to be all new. The voltage settles
out on all 14 to 7.00V after the charger is removed though.
See ya at the Wind Expo June 3-7 in LA, Cal
Have a renewable energy day,
Mark
_________________________________________________________________
Like the way Microsoft Office Outlook works? Youll love Windows Live
Hotmail.
http://imagine-windowslive.com/hotmail/?locale=en-us&ocid=TXT_TAGHM_migration_HM_mini_outlook_0507
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Was it here that I read a statistic something like, it takes more
electricity to refine a gallon of gas than it takes to propel an EV
the equivalent number of miles down the road? If that's true, that's
a statistic I'd like to throw around - gets you around the whole dirty
electricity arguement.
Good luck, have fun on the radio show...
They way I figure it, if my 15mpg car made 19 lbs of CO2 for each gallon of
gasoline then the ICE I had made 0.8 lbs CO2 per mile.
My EV that gets ~333 Wh/Mi would only make 0.33 lbs CO2 per mile (electricity
produced from Natural Gas here in Anchorage)
To me that looks like a 2-1/2 times cleaner Carbon footprint.
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I'm afraid you lost me on that one????
I did state that the broken belts did NOT break due to excessive
torque. We have never broken a belt with too much power! Not even
close! The belts broke because of debris. Mine broke because a tree
branch got caught in it. ANY size belt will break when debris is caught
in the teeth. Kevlar synchronous belts, will not stretch, so foreign
objects caught in the teeth will break it. Has nothing to do with
torque or power.
Just make sure you have a good belt guard!
Ken
-----Original Message-----
From: [EMAIL PROTECTED]
To: ev@listproc.sjsu.edu
Sent: Tue, 8 May 2007 9:18 PM
Subject: RE: More Tweety (NmG) fun...
Now I am concerned that my 8mm 30mm wide 950mm long primary belt is too
small......what are the sprocket sizes you are using? I have 38 groves
on the motor and 64 on the jack shaft for a primary ~1.7:1 primary ratio
for the belt and 16 teeth on the jack shaft to 45 on the wheel for
~2.8:1 secondary ratio for the chain and an overall ratio of ~4.75:1.
My motorcycle weights about 750# with the rider. I have an L91-4003
6.7" ADC motor and Zilla 1k. I thought I did the belt size calculations
correctly, but based on this I'm not sure.
-----Original Message-----
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On
Behalf Of [EMAIL PROTECTED]
Sent: Tuesday, May 08, 2007 5:29 PM
To: ev@listproc.sjsu.edu
Subject: Re: More Tweety (NmG) fun...
We have already broken two belts, however, not due to excessive torque.
Heidi broke the first one and I broke the second one. They broke due to
debris.
No, the car is never driven off road. This took place on "clean" paved
roads.
Myers sent us an upgraded belt guard that fully encloses the belt.
That appears to be a fix.
The belt is a Gates Polly Chain 8mm Pitch, 200 teeth, 36mm wide, 62.99
in long. It is the same as used on big Harley Davidson motorcycles
except for the length.
Our Zilla is not turned up all the way. All this fun is taking place
with less than 375 Amps. The stock setting is 300 Amps. I have bumped
it up to 375.
Just enough for a quick easy burnout. It just doesn't take much to
really move this little thing.
Ken
In a message dated 5/8/2007 5:50:30 PM Central Daylight Time,
[EMAIL PROTECTED] writes:
What size belt is being used in this application?
-----Original Message-----
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On
Behalf Of Mark Dutko
Sent: Tuesday, May 08, 2007 3:17 PM
To: ev@listproc.sjsu.edu
Subject: Re: More Tweety (NmG) fun...
With the Zilla at max you can easily snap the belt, my friend has gone
through three and several fuses.
Mark
On May 8, 2007, at 2:58 PM, [EMAIL PROTECTED] wrote:
Actually, it has a kevlar belt, and the zilla is turned up just a bit
:)
Ken
-----Original Message-----
From: [EMAIL PROTECTED]
To: ev@listproc.sjsu.edu
Sent: Tue, 8 May 2007 2:28 PM
Subject: Re: More Tweety (NmG) fun...
Put a kevlar belt on and turn the zilla up, then you will see fast.
My friends Jelly Bean Sparrow was faster than my Cooper S at redline.
************************************** See what's free at
http://www.aol.com.
________________________________________________________________________
AOL now offers free email to everyone. Find out more about what's free
from AOL at AOL.com.
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At 09:41 AM 5/8/2007, you wrote:
they said its ONLY $25,000 over the cost of the Mini, i.e. double
the price of the car. (Interesting HT says 1500 cycles on the
batteries. A123 says "several thousand" cycles for the M1 cells, but
show only 1000 cycles at 10C discharge, is HT using M1 cells?)
Read the A123 M1 chart carefully. Notice that at 1000
cycles, there is just 5% capacity loss (95% remaining.) If you rate
them at the more typical 50% capacity remaining, like most other
battery manufacturers do, the you get 10,000 cycles.
The cycle life is really more a function of temperature than
it is it of discharge rate, by the way. What happens is that the
cells run warmer on the bench as you increase the current during the
cycle life test.
Bill Dube'
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A couple of point on AC motors: You cannot go to bypass in an AC system to
overcome semiconductor voltage drop. You can rewind a three phase AC motor
for any voltage you want. Its not that difficult.
On Tue, 8 May 2007 08:09:38 -0600, Dale Ulan wrote
> > Precisely, it's easier and cheaper to build controllers with higher
> > voltage than it is with higher current, plus you don't need huge
> ...
>
> In the AC world (mostly occupied by industrial VFD's but also
> AC traction systems) you also have systems in a few
> voltage categories. You have the 208V/230V drives,
> which use a 330 to 400V DC bus voltage, and the higher
> voltage stuff (480V and 600V). All of these will use
> IGBT's and not MOSFETs.
>
> The kicker with IGBT's is they have a substantially constant
> voltage drop (typically 2 to 3 volts). So the lower the current
> (and higher the supply voltage) the less loss you get in a
> controller using IGBT's. Also, current levels under 300A or so
> are relatively easy (?) to deal with, as the current levels
> exceed maybe 400A or so, things start to get really wierd.
> Or basically, on an AC VFD, things are fairly straightforward
> below around 60kW when running a 400V bus voltage.
>
> Running low voltage, high current systems would typically
> use massive numbers of MOSFET's which are a pain in the
> bottom to hook all together. In this case, a higher voltage,
> lower current system is easier for the controller manufacturer
> to put together.
>
> -Dale
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--- Begin Message ---
On 5/9/07, Mark Hanson <[EMAIL PROTECTED]> wrote:
Hi Folk's,
I hooked up my 14 batteries in my E-Porsche 914 in 3 seperate strings per
the Saft manual and noticed at final charge that a couple strings had pee'd
electrolyte (an ounce or two) on the ground from the rear of the car.
This normally shouldn't happen. Did you follow the correct procedure
for the maintenance charge before adding water?
1. Can final charge gas escape from the orange tops or is the only route
out the fill hose?
You're meant to leave the exit pipe unblocked for gas and a tiny bit
of condensate to escape. You could put a catch container there if you
are worried about it.
3. I noticed at final charge 3 batteries at 7.6V instead of 8.5V on the
battery scanner. Is this normal? I noticed that these 3 had 00' date codes
instead of 01' but they were supposed to be all new. The voltage settles
out on all 14 to 7.00V after the charger is removed though.
There is a manufacturing difference between 00 and the following
years, at least for the STM5-100 modules. That could account for it,
or they could in fact be used. Worth keeping an eye on anyway.
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On 5/9/07, Steve O <[EMAIL PROTECTED]> wrote:
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Yes, I heard this on the radio this morning.
It was quite clearly suggesting that all electric cars are "unsafe".
There is something very strange about this story and the "research"
that has been done:
[..]
Electric cars are seen as green and are exempt from the Congestion
Charge in London and road tax. But Government research has found that
the G-Wiz failed the sort of crash tests which conventional family
cars and 4X4s must pass to be allowed on the road.
At present, mini-cars are classified as quadricycles - a category
designed for unconventional vehicles not intended for mainstream road
use, such as four-wheeled motorbikes and some small delivery vehicles.
Vehicles in the category have four wheels and their unladen mass
(excluding batteries if it is an electric vehicle) cannot exceed
400kg. The maximum power is 15 kilowatts.
When the Department for Transport ran crash tests on a Reva G-Wiz
electric vehicle, it passed the European requirement for quadricycles.
However, a spokesman said, "When it was subjected to the same impact
test expected of normal cars, serious safety concerns were
highlighted."
[..]
I believe that the G-Wiz is a quadricycle, it passes the safety tests
for quadricycles according to that article.. So what exactly is the
story here?
Does a rickshaw or a motorcycle pass car crash tests either? No,
don't be silly!
http://www.thisislondon.co.uk/news/article-23395549-details/G-Wiz%20alert%20as%20the%20electric%20car%20fails%20safety%20tests/article.do
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On 5/9/07, Deanne Mott <[EMAIL PROTECTED]> wrote:
Was it here that I read a statistic something like, it takes more
electricity to refine a gallon of gas than it takes to propel an EV
the equivalent number of miles down the road? If that's true, that's
a statistic I'd like to throw around - gets you around the whole dirty
electricity arguement.
Good luck, have fun on the radio show...
Yep. here is a quote from evnut:
"To extract one gallon of gasoline (or equivalent distillate): 9.66 kWh
To refine that gallon: 2.73 kWh additional energy.
Total: 12.39 kWh per gallon.
Roughly one-third of the energy content of a gallon of gasoline
produced from California wells is input from natural gas. Less than
2/3's is net energy (probably a lot less!).
So I can get 24 miles in my ICE on a gallon of gasoline, or I can get
41 miles (at 300wh/mile) in my RAV4EV just using the energy to refine
that gallon. Alternatively - energy use (electricity and natural gas)
state wide goes DOWN if a mile in a RAV4EV is substituted for a mile
in an ICE!"
So in other words, add the carbon from the refining process to it and
you get a lot bigger margin.
Link: http://evnut.com/emissions.htm
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What happens if you parallel a string of 12V AGMs and a string of 12V
floodies?
Here's why I'm asking, all comments welcome!
This is for my Jeep CJ. I'm contemplating a Warp 9, a Zilla 1K and a string
of 12V AGMs to keep the weight in the 2800 lbs ball park (number of
batteries and voltage to be determined). Most days I only drive 10 miles,
but I'd like some guts. I don't live far from Joliet where the FVEAA guys
go racing, so that is a distinct possibility.
But on occasion, I may want to go farther than a relatively lightweight
string of 12V will take me. The back end of my fiberglass Jeep body looks
amazingly like a large battery box to begin with, and I've got a forklift at
my disposal, so physically, dropping a palette of additional batteries into
the back (with framework and box for safety), and a few additional up front
for balance, wouldn't be too tough.
So what happens if I have a string of AGM's permanently installed, and drop
a palette of 12V floodies in, in parallel, when I need more range? I'd
think under acceleration, the floodies would sag further and I'd be mostly
drawing from the AGM's. At cruise, the floodies would tend to top off the
AGM's again?
Marty
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Steve,
RPM = Ks * Eg / Flux
where Ks = machine constant (including units
conversion), Eg = generated voltage.
Torque = Kt * Ia * Flux
where Kt = machine constant (including units
conversion), Ia = armature current.
Although equations appear linear, the Flux is not a
linear function of current for the series motor due to
saturation, so the Torque vs RPM characteristic is
curved.
Jeff
--- Steve Peterson <[EMAIL PROTECTED]>
wrote:
>snip<
> to derive the equations myself (for instance, I'm
> stymied by the fact
> that the standard motor equation seems to be
> linear,
> but the ADC rpm vs. torque curves aren't).
>
> Any help you (or anyone) can provide is most
> welcome...
>
> --Steve
>
>
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--- Begin Message ---
Bill, what chart are you reading?
http://www.a123systems.com/images/charts/lifeCycleHighLow.gif
clearly has the line going under 80% at 1000 cycles for 10C discharge.
I've never seen a cycle life chart that goes to 50% capacity, not sure
where you get this.
Regardless, hybrid technologies gives a 1500 cycle life for the car, are
they using M1 cells?
Jack Murray
Bill Dube wrote:
At 09:41 AM 5/8/2007, you wrote:
they said its ONLY $25,000 over the cost of the Mini, i.e. double the
price of the car. (Interesting HT says 1500 cycles on the batteries.
A123 says "several thousand" cycles for the M1 cells, but show only
1000 cycles at 10C discharge, is HT using M1 cells?)
Read the A123 M1 chart carefully. Notice that at 1000 cycles,
there is just 5% capacity loss (95% remaining.) If you rate them at the
more typical 50% capacity remaining, like most other battery
manufacturers do, the you get 10,000 cycles.
The cycle life is really more a function of temperature than it
is it of discharge rate, by the way. What happens is that the cells run
warmer on the bench as you increase the current during the cycle life test.
Bill Dube'
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Thanks, Jeff...
Your explanation makes sense, but leaves me with a new question:
If Torque is proportional to Flux, and Flux varies with the current, why
is the ADC torque vs. amps curve darned near linear while the rpm vs
torque curves have a "deep" bend in them?
--Steve
On Wed, 2007-05-09 at 07:15 -0700, Jeff Major wrote:
> Steve,
>
> RPM = Ks * Eg / Flux
>
> where Ks = machine constant (including units
> conversion), Eg = generated voltage.
>
> Torque = Kt * Ia * Flux
>
> where Kt = machine constant (including units
> conversion), Ia = armature current.
>
> Although equations appear linear, the Flux is not a
> linear function of current for the series motor due to
> saturation, so the Torque vs RPM characteristic is
> curved.
>
> Jeff
>
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It seems month of May is an EV focus for another
magazine. Popular Science had a couple article in the
May issue that may be enjoyable to the EV list. One is
on the Tesla another on the GM-Volt as well as a
popularity and abilities of the Smartfortwo coming to
US in 2008.
Three ev article on ev's in the same month. This is an
EV year. I got a kick out of the 1968 cover article
listed on the back page. It talk of hybrids that would
electric hook up like private vehicles like trolley
cars for distance driving.
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--- Begin Message ---
No.. I wasn't referring to Thundersky cells, which are not LiFePO4,
they are standard chemistry.
Here is the link: http://tinyurl.com/226qwo
On 5/9/07, Ian Hooper <[EMAIL PROTECTED]> wrote:
Valence Saphions are Lithium batteries including BMS designed for EV
use. Great idea, but overpriced: http://www.valence.com
The 54c/Wh cells mentioned was probably referring to ThunderSky
(http://www.thunder-sky.com), but there's a real shortage of easy-to-
use BMSs available for EV-sized lithiums. Definitely a big hole in
the market there for some entrepreneurial soul to fill. Hmm... *gears
turning*..
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Didn't someone buy up the schematics for many adapter plates & is going to
go into the business? That might be the place to go. Maybe the Reverend
did. Lawrence Rhodes.....
----- Original Message -----
From: <[EMAIL PROTECTED]>
To: <ev@listproc.sjsu.edu>
Sent: Tuesday, May 08, 2007 4:11 PM
Subject: Re: Can anyone recommend a machinist in Los Angeles?
> I would ck with reverend gadget.He makes a really nice adapter but i
> don't Know if he has the time. He is in culver city. Sincerely Larry Cronk
72
> Datsun Elec tk
>
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Bill,
What I was referring to when I mentioned the 5% per year capacity loss
was a time varying amount, due to the volatile nature of the chemistry
leading to an inevitable, 5% per year loss even if you treat the cells
perfectly.
However, that is true of -standard- lithium chemistry. As far as I
know, no one has released a time varying capacity decay rate for
LiFePO4 chemistries, of any kind.
On 5/9/07, Bill Dube <[EMAIL PROTECTED]> wrote:
At 09:41 AM 5/8/2007, you wrote:
>they said its ONLY $25,000 over the cost of the Mini, i.e. double
>the price of the car. (Interesting HT says 1500 cycles on the
>batteries. A123 says "several thousand" cycles for the M1 cells, but
>show only 1000 cycles at 10C discharge, is HT using M1 cells?)
Read the A123 M1 chart carefully. Notice that at 1000
cycles, there is just 5% capacity loss (95% remaining.) If you rate
them at the more typical 50% capacity remaining, like most other
battery manufacturers do, the you get 10,000 cycles.
The cycle life is really more a function of temperature than
it is it of discharge rate, by the way. What happens is that the
cells run warmer on the bench as you increase the current during the
cycle life test.
Bill Dube'
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Hi Steve,
Good question.
The plots you refer to are amps vs torque and RPM vs
torque. So this makes it a combination of the two
basic equations. Plus the fact that the torque in the
equation is the *electromagnetic torque* and not the
output torque. The plots use output torque which
accounts for losses (friction, windage and core).
These losses are significant at light loads on the
series motor where RPM is high. This tends to
straighten out the amp vs torque curve, but it still
bends down somewhat at light loads.
Also, the Eg in the equation is the generated voltage
or back EMF and not the applied voltage. So one has
to account for the resistance and brush drop. These
are low at light loads so affect the RPM vs torque in
the opposite manner.
Hopes that helps.
Jeff
--- Steve Peterson <[EMAIL PROTECTED]>
wrote:
> Thanks, Jeff...
>
> Your explanation makes sense, but leaves me with a
> new question:
>
> If Torque is proportional to Flux, and Flux varies
> with the current, why
> is the ADC torque vs. amps curve darned near linear
> while the rpm vs
> torque curves have a "deep" bend in them?
>
> --Steve
>
> On Wed, 2007-05-09 at 07:15 -0700, Jeff Major wrote:
> > Steve,
> >
> > RPM = Ks * Eg / Flux
> >
> > where Ks = machine constant (including units
> > conversion), Eg = generated voltage.
> >
> > Torque = Kt * Ia * Flux
> >
> > where Kt = machine constant (including units
> > conversion), Ia = armature current.
> >
> > Although equations appear linear, the Flux is not
> a
> > linear function of current for the series motor
> due to
> > saturation, so the Torque vs RPM characteristic is
> > curved.
> >
> > Jeff
> >
>
>
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Too much field weakening could lead to arcing, especially for higher voltages.
This is a reason a sepex motor should have interpoles, or adjustable brush
angle.
If the field suddenly goes to zero, the motor will try to spin very fast as the
field dies, and may overspeed.
----- Original Message ----
From: Steve Condie <[EMAIL PROTECTED]>
To: EV List <ev@listproc.sjsu.edu>
Sent: Wednesday, May 9, 2007 8:20:17 AM
Subject: Field weakening basics
...
I think this also implies that while the motor will spin faster with the field
weakened, available torque will be less. Yes? What's not clear to me is if
there's any **other** adverse consequence of field weakening on a regular basis
as opposed to short term for a burst of speed. To put it into a "real world"
situation, most current road going (and certainly freeway-capable) vehicles are
designed with higher voltage systems because higher voltage will allow a motor
to spin faster (among other things. It also allows the delivery of more watts
with less current and thus smaller wires - but I digress.) Could the same RPM
range be accomplished with a lower voltage-based system by going without FW
during the first half of the motor speed range, then shifting to FW - and
keeping it activated - all the while the motor is in its upper RPM range? Is
there a hidden downside? Losses through the FW circuit, perhaps?
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This a perfect example of how far battey technology is ahead of fuel cell
technology in cost, efficiency, performance & convienience. Lawrence
Rhodes....
----- Original Message -----
From: "Paul Wujek" <[EMAIL PROTECTED]>
To: "EV List" <ev@listproc.sjsu.edu>
Sent: Tuesday, May 08, 2007 8:05 PM
Subject: article: Driving Michelin's Zero-Pollution Car
> An article about a car Michelin is developing in Switzerland, it is
> example technology for manufacturers:
>
>
http://www.businessweek.com/innovate/content/may2007/id20070508_055560.htm?campaign_id=rss_autos
>
> --
>
> Paul Wujek ([EMAIL PROTECTED])
>
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A couple of point on AC motors: You cannot go to bypass in an AC system to
overcome semiconductor voltage drop.
Exactly right, so the semiconductor voltage drop needs to be considered.
IGBT's drop 2 to 3 volts so a higher bus voltage = lower losses.
You can rewind a three phase AC motor
for any voltage you want. Its not that difficult.
True, too. IGBT's normally come in 600V (or 1200V or 2400V) ratings, so
it makes sense to maximize bus voltage (400V is good for a 600V IGBT)
to minimize power loss in the drive system. Since power loss is current
times voltage, if the voltage loss is constant (two IGBT's times, say,
2.5 volts), then power loss is, too. For a 20kW output at 100Vrms,
thats 200Arms or 1000 watts of heat loss in the controller. For the
same output power but at 230Vrms, that's 67Arms or 434 watts of
heat loss in the controller. That is only considering steady-state loss
and not switching losses, which would go up with voltage - but not as
much as the conduction losses go down. At the 100V level, it makes sense
to use a pile of MOSFET's instead. To reach approximately the same amount
of loss at the 200 amp, 100 volt level that you get with the 67 amp, 230
volt
region, you would need six IRFP90N20DPBF MOSFET's in parallel for each
switch (that's a total of 36 MOSFET's). From an assembly point of
view, bussing a pile of MOSFET's is a bit of a pain in the backside, when
compared to getting a six-pack or even three half-bridge IGBT modules.
Also, those IGBT modules in the 600 volt level are pretty inexpensive
thanks to the industrial drive market.
-Dale
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Yup, that helps me understand how the concepts relate to the curves. Now
all I have to do is figure out how to model the curves. Many thanks.
--Steve
On Wed, 2007-05-09 at 08:32 -0700, Jeff Major wrote:
> Hi Steve,
>
> Good question.
>
> The plots you refer to are amps vs torque and RPM vs
> torque. So this makes it a combination of the two
> basic equations. Plus the fact that the torque in the
> equation is the *electromagnetic torque* and not the
> output torque. The plots use output torque which
> accounts for losses (friction, windage and core).
> These losses are significant at light loads on the
> series motor where RPM is high. This tends to
> straighten out the amp vs torque curve, but it still
> bends down somewhat at light loads.
>
> Also, the Eg in the equation is the generated voltage
> or back EMF and not the applied voltage. So one has
> to account for the resistance and brush drop. These
> are low at light loads so affect the RPM vs torque in
> the opposite manner.
>
> Hopes that helps.
>
> Jeff
>
>
>
> --- Steve Peterson <[EMAIL PROTECTED]>
> wrote:
>
> > Thanks, Jeff...
> >
> > Your explanation makes sense, but leaves me with a
> > new question:
> >
> > If Torque is proportional to Flux, and Flux varies
> > with the current, why
> > is the ADC torque vs. amps curve darned near linear
> > while the rpm vs
> > torque curves have a "deep" bend in them?
> >
> > --Steve
> >
> > On Wed, 2007-05-09 at 07:15 -0700, Jeff Major wrote:
> > > Steve,
> > >
> > > RPM = Ks * Eg / Flux
> > >
> > > where Ks = machine constant (including units
> > > conversion), Eg = generated voltage.
> > >
> > > Torque = Kt * Ia * Flux
> > >
> > > where Kt = machine constant (including units
> > > conversion), Ia = armature current.
> > >
> > > Although equations appear linear, the Flux is not
> > a
> > > linear function of current for the series motor
> > due to
> > > saturation, so the Torque vs RPM characteristic is
> > > curved.
> > >
> > > Jeff
> > >
> >
> >
>
>
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