EV Digest 6502
Topics covered in this issue include:
1) Re: DC Motor
by Jim Husted <[EMAIL PROTECTED]>
2) Batt resurrecting
by Eduardo Kaftanski <[EMAIL PROTECTED]>
3) RE: Batt resurrecting
by Cor van de Water <[EMAIL PROTECTED]>
4) Re: DC Motor (forklift type motors)
by James Massey <[EMAIL PROTECTED]>
5) Re: Batt resurrecting
by James Massey <[EMAIL PROTECTED]>
6) Photo of White Zombie at 51st Annual Portland Roadster Show
by Chip Gribben <[EMAIL PROTECTED]>
7) Re: DC Motor (forklift type motors)
by Jim Husted <[EMAIL PROTECTED]>
8) Re: [EV] RE: Batt resurrecting
by Eduardo Kaftanski <[EMAIL PROTECTED]>
9) RE: Should I buy 2 more batteries
by Jeff Shanab <[EMAIL PROTECTED]>
10) Re: Freedom EV Questions
by Lee Hart <[EMAIL PROTECTED]>
11) High Current / Low Voltage Drive
by "Bruce" <[EMAIL PROTECTED]>
12) Re: DC Motor (forklift type motors)
by James Massey <[EMAIL PROTECTED]>
13) Re: Compressed air as battery?
by Jeff Shanab <[EMAIL PROTECTED]>
14) Re: newbie - dc motor speed/hp/current/volts characteristics for racing!
by Ian Hooper <[EMAIL PROTECTED]>
15) Re: EV's, Ewoody and safety
by Jeff Shanab <[EMAIL PROTECTED]>
16) Re: High Current / Low Voltage Drive
by Lee Hart <[EMAIL PROTECTED]>
17) Re: High Current / Low Voltage Drive
by Ian Hooper <[EMAIL PROTECTED]>
18) Re: EV's, Ewoody and safety,
by "Michael Perry" <[EMAIL PROTECTED]>
19) Re: EV's, Ewoody and safety,
by "Michael Perry" <[EMAIL PROTECTED]>
20) Re: PFC 20 thermal compensation
by Ralph Merwin <[EMAIL PROTECTED]>
21) Re: Compressed air as battery?
by "Michael Perry" <[EMAIL PROTECTED]>
--- Begin Message ---
--- Rod Hower <[EMAIL PROTECTED]> wrote:
> If you want a really good high voltage DC motor with
> upgrades that will help on an EV, have Jim Husted
> modify it! He's learning new tricks all the time
> thanks to the abuse that EV racers like John Wayland
> and Bill Dube give their motors.
> Like John says, we break things so you don't have
> to!
> Rod
Hey Rod
I just posted to this thread when I saw this come in.
Just wanted to confirm what you said about those GE's.
I also had to reply to the above statement. I still
pray before EVery race. You know John's broken every
other things he's got a hold of except for my motor
and the Zilla.
I think that kind of irks him though, you notice he
keeps adding batteries, LMAO!!! I wont even get into
last years field weakening fiasco. Thanks for the
kind words, after 24 year building slow EV's
(forklifts) it's a fun thing to work on fast ones!
Have a great weekend, I know I'm glad it's Friday!
Cya
Jim Husted
Hi-Torque Electric
____________________________________________________________________________________
8:00? 8:25? 8:40? Find a flick in no time
with the Yahoo! Search movie showtime shortcut.
http://tools.search.yahoo.com/shortcuts/#news
--- End Message ---
--- Begin Message ---
I know I am probably loosing my time, but I have a couple of nearly dead
17ah UPS AGMs. One is now at around 11volts and the other is around 7!
I hooked up the reaaaally bad one to a small 12 volt power supply and something
interesting is happening...
It started taking in 100miliamps at 14 volts. Then, over the last hour
amps are slowly going up and volts are going down. Its now at 350mamps and
10.6 volts and volts are slowly going up again...
Is that normal? Or just a sign of a very broken batt? (I just need them
to test the controller and contactors)
--
Eduardo K. |
http://www.carfun.cl | I'm white and nerdy
http://e.nn.cl | Weird Al
http://ev.nn.cl |
--- End Message ---
--- Begin Message ---
This batt is showing signs of life, it may come back.
Continue charging, then test capacity and recharge,
if capacity keeps growing with every cycle it is still healty
and was just very empty.
I always test old batts to see if they comme back.
Some have an enormous high impedance and are finished,
others come back strong.
Success!
Cor van de Water
Systems Architect
Proxim Wireless Corporation http://www.proxim.com
Email: [EMAIL PROTECTED] Private: http://www.cvandewater.com
Skype: cor_van_de_water IM: [EMAIL PROTECTED]
Tel: +1 408 542 5225 VoIP: +31 20 3987567 FWD# 25925
Fax: +1 408 731 3675 eFAX: +31-87-784-1130
Second Life: www.secondlife.com/?u=3b42cb3f4ae249319edb487991c30acb
-----Original Message-----
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On
Behalf Of Eduardo Kaftanski
Sent: Friday, March 02, 2007 4:05 PM
To: ev@listproc.sjsu.edu
Subject: Batt resurrecting
I know I am probably loosing my time, but I have a couple of nearly dead
17ah UPS AGMs. One is now at around 11volts and the other is around 7!
I hooked up the reaaaally bad one to a small 12 volt power supply and
something interesting is happening...
It started taking in 100miliamps at 14 volts. Then, over the last hour amps
are slowly going up and volts are going down. Its now at 350mamps and
10.6 volts and volts are slowly going up again...
Is that normal? Or just a sign of a very broken batt? (I just need them to
test the controller and contactors)
--
Eduardo K. |
http://www.carfun.cl | I'm white and nerdy
http://e.nn.cl | Weird Al
http://ev.nn.cl |
--- End Message ---
--- Begin Message ---
At 05:01 PM 2/03/07 -0500, Patrick Andrews wrote:
What is the most common motor used for Ev's. What would this motor be
used for other than Ev's. I am asking because I am in the process of
building my project car and I would like to know the best setup possibly
used or from another piece of machinery. would a electric crain/ pallet
jack motor work? I am sorry for the newbie questions. Thanks to everyone
I feel like I am going to EV school opening my email everyday.
G'day Patrick, and All
The most common motor for EVs is a DC motor - the most common DC motor is..
well .. (diameters) 6.7", 7.2", 8", 9", 11" (manufacturers) Advanced DC,
Netgain, Prestolite, General Electric... you get the idea?
In general, 6.7" and 7.2" sized motors are for very light vehicles, or
modest power level vehicles. 8" motors for light vehicles (Geo Metro/Suzuki
Swift, etc), 9" for pickups. Smaller motors into bigger vehicles is done,
but the results are less than impressive (lesser acceleration and
hill-climb ability than the original ICE). Twin motor arrangements allow
essentially for more power in a smaller space, small rotors can rev higher
so develop more horsepower at lower amperages (Since amps make the torque,
and horsepower is a function of torque x RPM, if you can rev 20% higher for
the same amps you can develop 20% more horsepower - but the voltage is 20%
higher - no free lunches).
Big motors handle higher amperages - more horsepower is available from
higher amperages than higher RPM in conventional designs. A particular 6.7"
motor has a redline that may be 7500RPM, where a particular 9" may be
5500RPM - but the 9" can take 3x the current, so deliver more than 2.5x the
horsepower, and do it for longer as it takes longer to get hot (more mass)
and sheds heat better (more surface area). This is a bit generalised, but
you get the idea.
Forklift traction motors have been quite successfully used for on-road EVs,
but most people get an "electric car" motor. The down side to using a
forklift type motor (from a forklift, electric tug/truck, etc) are that
they are designed for a fork (etc) and so:
1) Heavier for its' size
2) Typically optimised for lower speeds (often full series field for double
the magnetic field strength, twice the torque/half the revs or just more
field turns - maybe 22 as opposed to say 14 for a similar on-road motor)
3) Often not cooled (totally enclosed, non-ventilated) or marginally cooled
(vents, but no fans)
4) Often have unusual output shafts
5) Internal design has no consideration for higher voltages (short
distances between parts)
6) Older motors may be lower temperature insulation.
So what can you do about it?
1) The weight you may just have to put up with, although it may be possible
to replace a cast iron end plate with an aluminium one (one of my motors I
made a bell-housing adapter plate that is also a new drive-end plate,
replacing a cast-iron one).
2) Modify the field connections - I am modifying a pair of motors this
weekend from having the fields connected all four in series to being 2
paralleled with 2, which will halve the torque but double the RPM/volt
characteristic of the motors. To hedge the bet on this I'm bringing all
four ends out onto therminals, so the fields can be connected either way,
or switched 'on the fly' to have higher initial torque then dropped into
parallel with a contactor after getting moving.
3) The motors I am modifying have vents, but no fans. The owner of the
motors will make a new band that is around the brushes, and add a blower
port, blowing the motors with a car heater fan.
4) The output shafts are splined one end and a helical gear the other. the
splines we are making use of by using them as the coupling between the two
motors. The gear end is a little more complex. The theory at this point is:
pull the bearing off, clean up the end of the shaft and the gear. Shrink
fit a sleeve over the gear, fill the remaining spaces in between the gear
teeth with Devcon compound, then machine the outside of the sleeve to take
a new, bigger bearing in the place the original was. A paricular selected
bearing means we are adding an approximately 3mm thick sleeve. The end
plate of the motor needs to be machined out by 3mm as well (there is enough
thickness in the bearing housing to do this). The sleeve outside the
bearing point will be made a few "thou" smaller than the bearing fit, fo
ease bearing installation and removal. My bearings-and-sprockets man
reccomends using a 'sit' bush instead of a taperlock bush to mount the
flywheel adaptor, as it should handle the torque better with no key. The
flywheel adaptor will be a pulley (or sprocket), machined to suit. A plate
mounts to the face of the pulley that carries the clutch spigot bush, and
has machined into it the step(s) for the flywheel. It may be necessary to
drill a new set of holes to mount the flywheel so that the bolts miss the
locking ring and go securely into the pulley. this may end up in the
friction plate area, reducing the available friction area, but this is a
lower-performance conversion, so clutch slip should not be an issue.
5) whilst the motor is apart, it can be cleaned up inside and painted with
epoxy resin or glyptal 'varnish', extra pieces of Aramid paper can be
placed behind terminals, etc,. The motors I am working on today have only a
short distance between the brush holders and the brush insulator/mounting
ring mounting rivets, so they will be painted over to reduce any flash risk.
6) an older, larger motor costs less than a new, smaller motor, so you can
afford a larger motor that is not working so hard, so doesn't get so hot -
but don't abuse it!
Essentially it comes down to that you buy the motor you want, when you want
it (a new 'EV' motor) with warranty and stated performance levels, or you
go looking for a motor that will do the job, but may nned some work (but
cheap enough that you can do a lot of work and still be way ahead over the
cost of a new motor). In the case of the owner of the motors that I'm
working on today he bought a forklift and pulled all the electrical gear
off it - twin motors, contactors, controller, potbox. But they need more
work to use them, rather than 'just hook up' of buying new stuff. You can
save thousands by being careful, finding things that do the job but need
some extra work to use. If you are not in a hurry and have some cheap
storage space you can haunt your local scrap dealers, pick up a lot of the
bits you can use for scrap value or not much more, prepare them ahead of
time (overhaul and prepare a motor, for example).
Hope this helps
Regards
[Technik] James
--- End Message ---
--- Begin Message ---
At 09:04 PM 2/03/07 -0300, Eduardo K. wrote:
I know I am probably loosing my time, but I have a couple of nearly dead
17ah UPS AGMs. One is now at around 11volts and the other is around 7!
I hooked up the reaaaally bad one to a small 12 volt power supply and
something
interesting is happening...
It started taking in 100miliamps at 14 volts. Then, over the last hour
amps are slowly going up and volts are going down. Its now at 350mamps and
10.6 volts and volts are slowly going up again...
Is that normal? Or just a sign of a very broken batt? (I just need them
to test the controller and contactors)
G'day Eduardo
Very dead. High internal resistance initially so high power supply voltage.
As the cells take some charge the resistance falls and the current goes up,
but at 10.6 volts you are into the territory of 'flat' rather than 'dead'
battery voltage, so the current should be a lot higher.
Play with them, learn from them but don't expect to get too many amps or
amp-hours from them.
Hope this helps
Regards
[Technik] James
--- End Message ---
--- Begin Message ---
Hi everyone!
Just put up a picture of the White Zombie at the Portland Roadster
Show on the NEDRA website
http://www.nedra.com
You can see people checking out the White Zombie videos on the Plasma
Boy TV.
The show runs through this weekend.
Chip Gribben
NEDRA Webmaster
http://www.nedra.com
--- End Message ---
--- Begin Message ---
Hey Massey
Awesome post, you're become quite the little motor
weasle aren't you, show off hehe! Couple of years
we'll have to do us a little Aussie vs. US build off,
loser pays airfare. I'll be watching you, hehe! Hey
want a job, LMAO!
I thought that this would make a good FAQ's page, so I
was wondering if I could put my name on it and cut and
paste it to my site, LMAO! What.. that's like two
days worth of chicken pecking for me. Okay I'll let
you have credit, ROF!
Another comment to Patrick. You need to advance the
brush timing on lift motors for use with higher
voltages to prevent arcing. Hey Jmaes you seem quick
on the keys tell the man about brush timing 8^P
Had fun, have a great weekend all!
Cya
Jim Husted
Hi-Torque Motor Dork
____________________________________________________________________________________
Now that's room service! Choose from over 150,000 hotels
in 45,000 destinations on Yahoo! Travel to find your fit.
http://farechase.yahoo.com/promo-generic-14795097
--- End Message ---
--- Begin Message ---
On Fri, Mar 02, 2007 at 04:39:51PM -0800, Cor van de Water wrote:
> This batt is showing signs of life, it may come back.
after a couple of hours its still on 10 volts while charging and
less than 7 when off the charger. dead, i think.
i'll move on to the next battery. i only need 4 good ones and I have
20 to play with :)
--
Eduardo K. |
http://www.carfun.cl | I'm white and nerdy
http://e.nn.cl | Weird Al
http://ev.nn.cl |
--- End Message ---
--- Begin Message ---
I will answer my own post, Yes and no. They have a 18month free
replacement warantee. I stopped by the exide place and he is going to
meet me their tomarrow and get me some batteries to replace three or 4
of them.
18 month free replacment , ya exide!
--- End Message ---
--- Begin Message ---
From: Todd Martin
> A few questions have been nagging at me as I've watched the Freedom
> EV discussions. Maybe Jerry can help with answers.
>
> 1st How did you get a Solectria Sunrise? I think there were only about
> 5 made total.
The Sunrise and the Freedom are two unrelated projects, being done by different
people. Jerry Dycus is building the Freedom. I'm leading a group of people
building the Sunrise.
> 2nd, what does Azure Dynamics think of your project?
So far, they don't seem to care. They acquired the name as a consequence of
buying Solectria's AC motor drive business, but had no interest in the car
itself. At some point, I expect we will either change the name, or purchase it
from them.
> 3rd, How the heck can you duplicate the high-tech body that they developed?
> They spent millions figuring out how to make that composite body and I
> don't understand how an individual could duplicate that effort.
Solectria wanted to sell the Sunrise design to one of the auto companies. So,
they designed it to be mass produced by the sort of expensive molding processes
that they already use for things like Saturn body parts.
This is obviously impractical for low-volume production. But, there *are* ways
to make high-performance composites in low volumes with simple tools by home
builders. Burt Rutan and others in the Experimental Aircraft Association have
pioneered these techniques. We are adapting the Sunrise design to use them.
--
Lee Hart
--- End Message ---
--- Begin Message ---
It seems that fewer cells would simplify battery management. If taken to
the extreme, a single cell battery pack would be the simplest. Two volts
total and you would never have to worry about equalization.
But it might be hard to find a 2 volt cell that could deliver ten thousand
amps. And controllers capable of handling that current won't be common
either...
A not quite so extreme solution could be 4 cells. Still the pack would have
to be able to provide thousands of amps, but this might be possible with
lead-acid cells weighing hundreds of pounds each. For the controller you
could go with a contactor setup. Two volts all parallel with a resistor for
starting, then two volts no resistor, four volts series/parallel and finally
all eight volts in series.
The battery cables and contactors would have to be sized larger to carry the
increased current, but this sounds possible. How about the motor? Where
would you get a motor rated for 8 volts and thousands of amps? Maybe you
could rewind a regular motor with thick wire and less turns? What about
the commutator? The low voltage might keep the arcing down, but the
voltage losses could be more than desirable. Perhaps a brushless motor
would help?
What other challenges might one face in going against the accepted method
and using lower voltages?
Bruce
--- End Message ---
--- Begin Message ---
At 05:26 PM 2/03/07 -0800, Jim wrote:
Hey Massey
Awesome post, you're become quite the little motor
weasle aren't you, show off hehe! Couple of years
we'll have to do us a little Aussie vs. US build off,
loser pays airfare. I'll be watching you, hehe! Hey
want a job, LMAO!
Hey, if I can ever afford it I'll come over there and we can build up a
bunch of The Worlds' Best Motors (tm) :^)
I thought that this would make a good FAQ's page, so I
was wondering if I could put my name on it and cut and
paste it to my site, LMAO! What.. that's like two
days worth of chicken pecking for me. Okay I'll let
you have credit, ROF!
About time you updated that excuse of a web page! :^) Feel free to steal
it, Jim, heck a lot of it I learned from you anyway!
Another comment to Patrick. You need to advance the
brush timing on lift motors for use with higher
voltages to prevent arcing. Hey Jmaes you seem quick
on the keys tell the man about brush timing 8^P
Had fun, have a great weekend all!
Cya
Jim Husted
Hi-Torque Motor Dork
Me? HA! Like I sent to Don a couple of days ago:
==================
Follows is a saved message from years ago regarding advancing brushes
--
To: ev@listproc.sjsu.edu
Subject: Re: Timing efficiency
> >Rich Rudman wrote:
> >
> >The correct answer is minimal arcing at the loads and RPM you expect to
> >spend most of your time at.
> > LIGHT street use is 5 to 10 Deg advance.
> > Heavy street is 10+ Deg
> > Racing 10 to 15, and tune for best ET.
> > Anything with regen or plug braking is neutral or 0 Deg.
> > On some Avdc there are other bolt hole sets in the motor case. You
> >simple unbolt the brush end cap, rotate to the advanced hole set, take
> >out the burried Setscrews if they are there, and install the 4 long
> >screws back into the Advanced holes. Done.
> >
Martin Klingensmith wrote:
>
> Hi Rich - I'd like to ask a question with a possibly obvious answer:
> When you say "advance" the brushes, is this in the opposite direction as
> the normal shaft rotation?
> --
Yes and yes!!
It trades low end torque for high end torque. If you have more
than you
need down low, and it's a slug up high, then do it!!
--
====================
The only other thing he may need to know if using twin motors is like some
motor dork told me:
====================
Date: Tue, 27 Feb 2007 06:37:55 -0800 (PST)
From: Jim Husted <[EMAIL PROTECTED]>
Subject: Re: Numbers on Motor
To: James Massey <[EMAIL PROTECTED]>
Hey James
I've see studs mounting out the plate face and it's
actually fairly common on motors.
Anyway I'll get to you more when I have
time, I got a snowy mountain to drive over today lol.
BTW the advancement degrees will be different for CCW
vs. CW so you'll need to tach them to find equal RPM's
before you drill out the new mount holes.
Cya
Jim
====================
But to add a bit (alright a lot) more explanation as to the reason why:
Forklift type motors are just as likely to need to run backwards as
forwards, plus may have plug braking (making the motor dump energy mostly
back to itself) so the brushes are in an "average" position of forward to
backwards. This is termed 'neutral' timing. It should be a position where
if you draw a line along the center line of the field pole shoe (The metal
bit in the middle of the field winding) this center line is also of the
brush where it sits on the commutator bars. It may not be perfectly there,
depending on the windings, but within a degree or so.
When you power a series motor, it sets up a magnetic field around the field
poles, and around the commutator. These fields are fighting each other and
make the motor spin. When the motor is doing no work, the brushes in
neutral timing are sitting on a spot of the commutator that has no voltage
between the bars - as you move away from one brush towards the next there
is an increase in the voltage between the bars that is greater and greater
until halfway to the next brush, then the steps get smaller and smaller
until the spot where the brush is. Once past the brush the polarity
reverses and happens all over again. (Most of the motor voltage is here,
around the commutator, with only a few % across the field).
When you pull power out of the motor, the fields push each other 'back' a
little or a lot, depending on how much work, so that the center of the
magnetic fields is no longer in line with the pole shoes. So if you do
nothing with the brushes, they are sitting on commutator bars that want to
have a voltage difference between them. Whilst the brush is on top of them,
current is flowing between the windings across the face of the brush. When
one bar comes clear of the brush you get a flash of arc that is a
percentage of the overall voltage. On low voltage forklifts, this is a low
voltage so not a problem. The higher the volts on the motor, the higher
this flash voltage is. Too high and the arc becomes self-sustaining and
ends up carrying all the way around the commutator.
So you move the brushes back to a point where there is minimal voltage
between the commutator bars under the brushes. This is a moving point - the
more amps, the more volts and the further it moves, so ideally is to use
moveable brush gear with a controller that maps RPM/amps and moves the
brushes to keep the brushes on top of the zero voltage difference point.
IIRC one or more of the racers is planning something along these lines.
Some motors designed for higher voltages have interpole windings - skinny
field windings that are in circuit (in series with the rest of the field
windings) for one direction and not in circuit in the other direction (in a
forklift).
Other motors are compound or shunt wound, but they are not common for
traction motors as they are usually used for constant speed applications.
Think that covers it, Jim?
Regards
[Technik] James
--- End Message ---
--- Begin Message ---
I have have done the math and I know the air car idea is not very
efficient but what if the compressed air half was cheap and all you did
was use it in an expansion motor under light load, like maybe a
multistage turbine with integral PM alternator (on air bearings of
course). This may be the path to the smallest,highest rpm PM generator
we could tow behind us or have on board.
I think for large quantities of various gases, a compressor is not used.
The air is refrigerated until it is a liquid then allowed to sublime off
a little the re-chilled to liquefy which allows them to seperate the
gases. Before we discount it with the energy used to compress the freon,
Refridgeration in these temperatures and on this scale is also not the
typical freon vapor compression cycle. Usually ammonia compression cycle.
So we buy essitially rent/exchange buy a scuba tank of air when we need
range extension. (Last I heard it was $35-$50) to refill at the local
dive shop, we used it to refill our 3000psi paintball tanks.
I once heard that the 10Kpsi pressurized hydrogen could do as much work
as the gas itself, but that may have just been talk.
--- End Message ---
--- Begin Message ---
On 03/03/2007, at 5:42 AM, Scott Littledike wrote:
Thankyou for your quick and helpful replies, i think i am
understanding more now..
so, the hp will increase with the motor speed - until your
batteries/supply reaches its limit of voltage¤t. As you
increase the speed of the motor, and therefore the voltage draw,
the current available from the batteries will decrease, this being
the limiting factor to the power and rpm available (assuming you
are battery limited not motor limited)?
Sort of.. electrical power is equal to voltage x current, and there
will be a limit to the amount of power a battery can deliver, though
it will deliver this (possibly limited by the controller) from 0 rpm.
As the motor rpm increases, it's effective resistance does increase
which will actually reduce the amount of current which flows from the
batteries. Hmm, it's a long story I guess..
so the top speed/gearing of the motor to wheel will depend on your
batteries and the voltage (& therefore speed) they can provide? I
guess this has to be found experimentally as it would depend on the
battery type? the acceleration of your vehicle will depend on the
amps you can pull from your batteries, again - battery specific?
The voltage of the pack and the maximum current they are able to
deliver are what determines the power your battery can deliver. Yep,
your acceleration will depend on the current you can pull from the
battery - but multiplied by voltage, a 12V pack which can deliver
1000 amps has the same peak power as a 120V pack which can only
deliver 100 amps.
Ian - you mention that ADC motors arent made for high speed, but my
knowledge of motors on the market that might be suitable is
basically none lol! I would be interested to learn about
alternatives if you can think of any?
Well, it's worth having a read of that "DC Motor" conversation going
on right now too! Generally the series wound DC motors (like the
ADCs) are the most economical option, for the power. They are pretty
good. Probably your best bet is to just get a big one of these and
compensate for the low top speed by having loads of torque :)
The highest power density motors are brushless DC (BLDC), they
usually have much higher top speed than commutated (brushed) motors,
but are far more expensive. AC induction motors are another option,
though ones designed for EVs are pretty expensive. The Tesla Roadster
uses a 250hp AC induction motor, out of interest.
As for the lithiums, I have seen them, but it says on the site that
they only have a 70A continuous discharge rate (i assume i use the
continuous rate and not he pulsed)? so if i was pulling 500 -
1000amps across the run, i would need to arrange 36 cells in
series, put in parallel with another 10 or so rows? - 360 cells
(expensive!) then i could draw 700A constantly? my calculations
(quite crude!) say that to complete 1 mile using 80hp i need about
4Ah of capacity, and to complete 2 miles i need about 7Ah.. Do you
think the SVR batteries will be upto the job, they are 14Ah and
according to the EVparts site, can handle 900A for 10 seconds?
Basically I don't think you'll find a battery with higher power
density than those A123 lithiums! Power density is the power a
battery can deliver, divided by its weight, i.e 3.3V @ 70A = 231W in
a 0.07kg package, which is 3300W/kg. So 360 of them would weigh 25kg
and deliver over 80kW! Though I agree they are rather expensive.
Those SVR-14s do look like a pretty good option for you, for the
money. 10 of them (120V pack) would weigh something like 50kgs, and
you should be able to pull ~30kW from them.
Two caveats with lead acid batteries - firstly you get 'voltage sag'
when discharging at high current rates, which means their voltage
drops under load (by as much as half). Also, their capacity drops
severely with high discharge rates. 14 amp hour is a 20-hour
discharge rating, it's usually a bit over half e.g 8-9Ah at a 1-hour
discharge rate. At a 5-minute rate, you might only get 4Ah out of them!
However, all that aside, I think your component choices are pretty
good. 10x SVR-14s are well matched to deliver as much power as an L91
can handle, just make sure your motor controller is rated to 400 amps
or more (Curtis 1231C maybe?) - I guarantee you'd have "traction
issues" (read: burnouts) with these in a motorbike :)
-Ian
----
Hi there,
I am trying to design a high speed electric motorcycle (100mph+)
with a 1 -
2 mile range, for several reasons - personal learning and
interest, to
generate more interest of EV's here in the UK, and for possible
competition
use later on.
For example, lets say i use a single ADC L91. Lets presume (for
simplicity)
that my batterys have 800A current limited by the controller (from my
understanding, controllers vary the current but not voltage). I
understand
that motors deliver peak hp at 0rpm?
No, power is torque multiplied by speed (or voltage multiplied by
current). Current is related to torque and voltage to speed. Series
wound DC Motors naturally produce a high torque at 0 RPM (and low
speeds). So from standstill, the voltage at the motor will be low
(a few volts), and the current high (as high as the controller limit
allows) - this is a small amount of power. Since the voltage at the
battery will be in the 120V area, the current drawn from it will be
small at this stage (i.e. matching the power delivered to the motor,
plus losses).
So the motor will produce peak hp at 0rpm, with maximum current
draw.. will
the hp (& therefore current draw) then reduce as motor speed
increases?
No, see above.
where you want hp most.. so why no need for a transmission? How do
you get
more hp at high rpm..
Provide more voltage.
Just a few extra comments:
- More hp at high rpm: Could also look at a better motor, the ADC
ones aren't really designed for high rpms. Or just use a lower gear
ratio with a bigger motor.
- Controllers do actually vary the voltage, which effectively varies
the current (if you consider the motor to be more or less a resistive
load..)
- 1-2 mile range @ 100mph is an unusual case because that's basically
draining the whole battery in about 1 minute, which is a 60C
discharge rate (as in 1/60th of an hour). Not many batteries can
handle this sort of load - in fact I can only think of one which
comes close:
http://www.a123systems.com/html/products/cells.html
They are pretty expensive (~US$10ea), but 35 of these would give you
a 120 volt pack weighing a little over 5 pounds and able to deliver
around 12kW! (for 1 minute or so..)
Make sure you have life insurance ;)
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Federal crash testing is actually federal crash testing standards.
I looked into them at one time and they are actually voluntary. A car
manufacturer must be able to show a reasonable effort was made to
protect public safety if there was an accident. As crash simulation
software has advanced, physically crash testing is done less and less.
Usually after you have simulated it 100's of times to a small margin of
error.
One of the interesting ones is 3000lb impact to inside of door must not
open door.
It is a smorgesborg, you pick what tests you want with airbag taking up
to 10 tries at $14K each to get passed sometimes. This is because the
air bag must hit the dummy in the chest not the face. Of course very few
of us drive with the steering column at the angle that passed the test
:-(. It is an awkward position.
I have a break down of crash testing costs from a facility in northern
CA somewhere around here....
--- End Message ---
--- Begin Message ---
From: Bruce
> it might be hard to find a 2 volt cell that could deliver ten thousand
> amps.
They actually make cells that big. They are used in power plants, submarines,
and various very high capacity fixed battery backup systems.
> controllers capable of handling that current won't be common either...
Not common; but they exist. The real problem isn't the current; it's finding
one for low voltage. A 48v 10,000 amp controller is big, but straightforward. A
10,000 amp 2v controller is quite another thing!
NASA has built inverters for such low voltages using tunnel diodes and other
unusual semiconductors. Honeywell has even sold controllers for consumer
products that ran off the 60 millivolts (0.06v) that you get from a thermopile.
It used special low-voltage FETs.
Oddly enough, the present trend to sub-micron transistors for integrated
circuits automatically produces very low voltage, very high current FETs. While
odd, a 2v 10,000 amp controller is not out of the question.
>The battery cables and contactors would have to be sized larger to carry the
>increased current, but this sounds possible.
Yes; they might look like the frame rails of the vehicle :-)
> How about the motor? Where would you get a motor rated for 8 volts
> and thousands of amps?
You wouldn't want to use a commutator, as it would be bigger than the armature.
There would be brush drag and voltage drop problems as well.
So, some form of AC or brushless DC motor makes more sense. Perhaps a switched
reluctance motor?
This could also be an application for the strange homopolar motor. This is the
only true DC motor; it has no commutator and runs on pure DC. By nature, it can
only be built in low-voltage, high-current versions. 2v 10,000amp homopolar
motors have been built. They can be built in series, shunt, and sepex versions,
which allows simple speed control via field current.
>What other challenges might one face in going against the accepted method
>and using lower voltages?
The usual ones when you do anything that isn't fashionable. As Gandhi said,
"First they ignore you, then the laugh at you, then they fight you... then you
win!" :-)
--
Lee Hart
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--- Begin Message ---
On 03/03/2007, at 11:42 AM, Bruce wrote:
It seems that fewer cells would simplify battery management. If
taken to
the extreme, a single cell battery pack would be the simplest. Two
volts
total and you would never have to worry about equalization.
But it might be hard to find a 2 volt cell that could deliver ten
thousand
amps. And controllers capable of handling that current won't be
common
either...
Not so hard as you might think: http://www.thunder-sky.com/pdf/
200712715238.pdf
Tho the controller would be a problem, yeah. Obviously have to custom
build something. Some power MOSFETs can switch 100A continuous, so
you'd need a hundred of those.. I guess that's only a few grand worth.
A not quite so extreme solution could be 4 cells. Still the pack
would have
to be able to provide thousands of amps, but this might be possible
with
lead-acid cells weighing hundreds of pounds each. For the
controller you
could go with a contactor setup. Two volts all parallel with a
resistor for
starting, then two volts no resistor, four volts series/parallel
and finally
all eight volts in series.
I'd predict your contactors would weld themselves together if you
tried switching that sort of current mechanically!
A whole lot of power MOSFETs should be able to handle it, or you
might even be able to find some kind of massive industrial IGBT for
the job. This is getting close: http://au.farnell.com/jsp/
endecaSearch/partDetail.jsp?SKU=1208671
The battery cables and contactors would have to be sized larger to
carry the
increased current, but this sounds possible. How about the motor?
Where
would you get a motor rated for 8 volts and thousands of amps?
Maybe you
could rewind a regular motor with thick wire and less turns? What
about
the commutator? The low voltage might keep the arcing down, but the
voltage losses could be more than desirable. Perhaps a brushless
motor
would help?
I think all your cables/contactors/etc would need to be prohibitively
large..
How about just use a very beefy DC/DC converter to step up the
battery voltage, e.g from 8V 2000Ah to 160V 100Ah equivalence, then
you could juse use normal motors and controllers, with sensible cable
sizes etc. It'd have to be one heck of a big DC/DC converter though,
maybe too hard to build.
Interesting concept..
-Ian
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--- Begin Message ---
Very well put. "Your mileage will vary." DOT crash ratings are excellent
ratings... assuming you travel at 3MPH and/or are a crash dummy. <g>
For anecdotal evidence... a '94 Sidekick is about as unsafe a car as one can
drive, per the insurance companies. However, hit at 70+ MPH from the rear,
the car showed very little damage. The driver's seat reclined, there was a
dent in the rear (convertible) window where a tablet flew from the dash and
hit it, and the rear bumper was "scratched" when the Mercury slid under and
hit the sub-bumper.
Of course, you couldn't get the doors open (or closed once the passenger
door was kicked open) but damage was not obvious. Well, not completely, as
both rear springs were laying on the pavement... but the rig *looked)
perfectly normal, if they'd been put back under the car.
One thing I do find gratifying is that this car (Woody) was built with
strong batt containment. I've seen some rigs, a VW Beetle comes to mind,
where I would not wish to be in it in case of an accident. Batts inside the
passenger cage and/or not designed to drop away, is at best a classic death
wish. Remember, a 2 oz tablet flew off my dash hard enough to mar the soft
rear window. (These windows can be rolled or folded w/o mars.) What if this
had been 300 lbs of batts. They aren't necessarily going to remain in a
standard strap. It's something to think about when designing a car using a
glider ICE.
DOT doesn't look at this sort of damage.
----- Original Message -----
From: "Cor van de Water" <[EMAIL PROTECTED]>
To: <ev@listproc.sjsu.edu>
Sent: Thursday, March 01, 2007 5:58 PM
Subject: RE: EV's, Ewoody and safety,
> Hmmm,
>
> I find this discussion a little ridiculous, for I have seen
> very few crashes that complied to DOT specs, on the Highway.
>
> The statistics on a single sample are not good enough to draw
> general conclusions from, it is indeed just a single occurrence
> and it may have been luck that it stayed together the way it did.
--- End Message ---
--- Begin Message ---
----- Original Message -----
From: "Mike Harvey" <[EMAIL PROTECTED]>
To: <ev@listproc.sjsu.edu>
Sent: Thursday, March 01, 2007 8:19 PM
Subject: Re: EV's, Ewoody and safety,
> Well hell. Let's just stop building cars right now since I doubt a one of
us
> can affords the crash testing. It's hopeless. Sounds like someone's
sleeping
> with the devil/car makers/lawyers... who owns the DOT anyway? The
> government? Yeah, eWoody or Freedom, or BugEV...make em guys. Put a big
> sticker on it and say "Drive at Your Own Risk"! Simple. End of
conversation.
>
> Sorry, I really hate defeatist attitude disguised as "practical devil's
> advocacy". If it's really that bleak, take up knitting.
>
> Mike
One can only make their best guess, but keep in mind the other factors.
There are too few numbers of EVs "out there" to consider this a statistical
universe... but many are built w/o any idea of safety.
Basically, try to keep batts tied to the supporting members and outside the
passenger compartment. In a real accident, you'll have up to 30% of your
car's weight in very dense packages... possibly flying around. You probably
don't want 60 lb packages inside your "cage"... assuming your car has a
cage. (Most converted cars do not.)
On the other hand, if securely mounted, batts may absorb much of the impact.
Granted, they'll split and spill, but can work (somewhat) like the
sand-filled crash barriers. Hopefully, not inside the compartment with you.
<vbg>
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--- Begin Message ---
David Roden writes:
>
> On 1 Mar 2007 at 7:20, Ralph Merwin wrote:
>
> > The Rudman Regs do have temperature compensation for the voltage set
> > point. It does assume that the reg is at the same temperature as the
> > battery it is monitoring. The surrounding air temperature may well
> > be different.
>
> At one time (10 years ago?) there were some shunt regs available that bolted
> to a battery post. I think these may have been designed by Mark Hanson
> (Mark please correct me if this is wrong). I don't think the old design had
> TC, but wouldn't the battery post be a better place to sense battery temp
> than the air around the battery?
Yes, the post would be better. However, the Rudman Regs don't provide an
easy way to move the temp sensor off of the PCB. Not that unsoldering the
diode and remounting it to two wires is hard, but I'm keeping to a 'no mods'
approach as much as possible.
Ralph
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--- Begin Message ---
As devil's advocate... what if your AC compressor didn't take the huge power
it takes? You've stored liquid gas (of some sort) in your tanks. This then
becomes one of the probs with using H2... to mass it at 1/2 the power of
gasoline it must be liquefied.
Anyone who's owned an airconditioner should know this prob. You expand a gas
and it cools the system. You can only recover the power of compressed gasses
as they expand, and as they expand the temps must come from somewhere...
supposedly the outside air.
Compressed gas... where do you get the outside temps but from the outside
air? Do you cover the skin of the car with heat exchangers (fins) to gather
enough heat to convert the liquid into gas? With compressed gasses, you get
back what you can absorb from the outside, plus some inherent portion in the
chamber. With H2, you can burn the gas. (Your engine will probably run
cooler than on other combustion materials.)
The only example I've found of where compressed gasses have been used
successfully was in steam engines, powered from stationary sources. In WWII,
England used a few trucks that were powered in this way. They weren't
practical, but the economy led to finding any method that could get a job
done. They were steam engines w/o the boiler, and good for short range and
slow speed, until their compressed gas cooled.
----- Original Message -----
From: "Jeff Shanab" <[EMAIL PROTECTED]>
To: "Electric Vehicle Discussion List" <ev@listproc.sjsu.edu>
Sent: Friday, March 02, 2007 6:48 PM
Subject: Re: Compressed air as battery?
> I have have done the math and I know the air car idea is not very
> efficient but what if the compressed air half was cheap and all you did
> was use it in an expansion motor under light load, like maybe a
> multistage turbine with integral PM alternator (on air bearings of
> course). This may be the path to the smallest,highest rpm PM generator
> we could tow behind us or have on board.
>
> I think for large quantities of various gases, a compressor is not used.
> The air is refrigerated until it is a liquid then allowed to sublime off
> a little the re-chilled to liquefy which allows them to seperate the
> gases. Before we discount it with the energy used to compress the freon,
> Refridgeration in these temperatures and on this scale is also not the
> typical freon vapor compression cycle. Usually ammonia compression cycle.
>
> So we buy essitially rent/exchange buy a scuba tank of air when we need
> range extension. (Last I heard it was $35-$50) to refill at the local
> dive shop, we used it to refill our 3000psi paintball tanks.
>
> I once heard that the 10Kpsi pressurized hydrogen could do as much work
> as the gas itself, but that may have just been talk.
>
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