EV Digest 6767
Topics covered in this issue include:
1) Re: BMS EV dash(Battery Management System (Was: 1-Wire Expertise)
by Jeff Shanab <[EMAIL PROTECTED]>
2) Vehicle efficiency, wh/mile
by Ian Hooper <[EMAIL PROTECTED]>
3) Re: Vehicle efficiency, wh/mile
by "Peter VanDerWal" <[EMAIL PROTECTED]>
4) Re: OT: Magnetic fields (Re: magnetic field in EV car?)
by "TrotFox Greyfoot" <[EMAIL PROTECTED]>
5) Re: Vehicle efficiency, wh/mile
by "Roland Wiench" <[EMAIL PROTECTED]>
6) Sepex regen
by tt2tjw <[EMAIL PROTECTED]>
7) Re: magnetic field in EV car?
by "Patrick Robin" <[EMAIL PROTECTED]>
8) Re: Vehicle efficiency, wh/mile
by [EMAIL PROTECTED]
9) Re: Sepex regen
by "George Swartz" <[EMAIL PROTECTED]>
10) Re: magnetic field in EV car?
by "George Swartz" <[EMAIL PROTECTED]>
11) RE: EMF in EVs
by JS <[EMAIL PROTECTED]>
12) Re: BMS (Battery Management System)
by Steve <[EMAIL PROTECTED]>
13) Re: Sepex regen
by tt2tjw <[EMAIL PROTECTED]>
14) Re: BMS (Battery Management System)
by "Timothy Balcer" <[EMAIL PROTECTED]>
15) Re: Sepex regen
by "George Swartz" <[EMAIL PROTECTED]>
16) RE: Contactor Controller Page
by "childreypa" <[EMAIL PROTECTED]>
17) How does a 48v motor handle higher voltages?
by "childreypa" <[EMAIL PROTECTED]>
18) Noodling Lithium prices and batteries
by "Timothy Balcer" <[EMAIL PROTECTED]>
19) Re: Vehicle efficiency, wh/mile - cruise control
by Tehben Dean <[EMAIL PROTECTED]>
20) Re: Sepex regen
by tt2tjw <[EMAIL PROTECTED]>
21) RE: Contactor Controller Page
by "Myles Twete" <[EMAIL PROTECTED]>
22) Re: EMF in EVs (and how to mitigate it)
by "(-Phil-)" <[EMAIL PROTECTED]>
--- Begin Message ---
You've seen thru my cunning plan.
Being a true software geek, having one monolithic device that does all,
rubs us the wrong way. Instead, each autonomous part comes together to
create the whole through standardized interfaces.
The display can work with any number of different manufacturer's device
that implements the interface.
The BMS communicates it's info
If you want GPS, it will talk to the display/storage unit via USB probably.
Maps,video,mute on phone.mp3,ODBII....no problem.
google DashPC, I think it may be a good thing to build on.
--- End Message ---
--- Begin Message ---
Hi all,
I was just curious if many people on the list have measured their
EV's efficiency i.e average watt-hours per mile?
I've heard figures around 300wh/mile thrown around, but that seems
like a fair bit of energy to me.. Could that be based on people using
the C20 capacity of lead acid to calculate the pack's energy?
-Ian
--- End Message ---
--- Begin Message ---
Actually it's usually measured, not estimated. Devices like E-meters give
a reading on watt-hr consumed, divide it by the miles driven and bingo,
WH/Mile.
Just a note: this is WH/mile from the batteries. Measured from the outlet
it's even more.
Most of the production EVs (from roughly 7-10 years ago) had measured wall
to road efficiency of 500-1000 WH/mile.
Just out of curiousity what makes you think 300wh/mile is high?
> I was just curious if many people on the list have measured their
> EV's efficiency i.e average watt-hours per mile?
>
> I've heard figures around 300wh/mile thrown around, but that seems
> like a fair bit of energy to me.. Could that be based on people using
> the C20 capacity of lead acid to calculate the pack's energy?
>
--
If you send email to me, or the EVDL, that has > 4 lines of legalistic
junk at the end; then you are specifically authorizing me to do whatever I
wish with the message. By posting the message you agree that your long
legalistic signature is void.
--- End Message ---
--- Begin Message ---
Just a note of mud-type clarity...
Field reversal is indeed what allows operation of a DC motor. What
you miss here is that:
1) We're talking about field reversal relative to the armature. The
armature is rotating which causes the field to reverse. Thus, the
field reversal is only relative to the armature, not the stator (field
magnet.) So you may say that there's a slightly pulsing field as the
various armature coils energize and de-energize but it's not a truly
alternating field from the perspective of anything outside the motor
housing.
2) As has already been stated, the outside of the motor is encased in
a sheet of shielding steel. This is actually not just there to
protect people and equipment. Any magnetic field that gets outside
the motor is lost energy. The outer case of the motor acts as a part
of the magnet circuit in the motor. Tying the fields together this
way increases the efficiency of the motor and greatly reduces the
emitted field, DC or not.
Of course, I could be completely wrong... In which case the 17T
magnet we're having built for work will likely cause me great deals of
harm as discussed by Mr. Dube. It's scheduled for delivery in '09...
which is likely sooner than I'll start on my EV conversion. { : ]
I'll let you know how both of those projects go.
Trot, the electronically-minded, fox...
On 5/12/07, Tehben Dean <[EMAIL PROTECTED]> wrote:
<<snip>>
DC motors spin because the current is constantly reversed or alternated.
This is something from Wikipedia on how a DC motor works:
"When the armature becomes horizontally aligned, the commutator
reverses the direction of current through the coil, reversing the
magnetic field. The process then repeats."
That sound like an alternating field to me.
<<snip>>
--
| /\_/\ TrotFox \ Always remember,
| ( o o ) AKA Landon Solomon \ "There is a
| >\_/< [EMAIL PROTECTED] \ third alternative."
--- End Message ---
--- Begin Message ---
Hello Ian,
The wh usage will depend on vehicle weight, gear ratios, type of tires,
tires PSI, road conditions, grades, and speed. It is normal for my EV to
average 3.4 wh/mile with a low in the 1.0's and high as 10.0's.
I normally let my E-meter set on AH to see how much energy I using, as you
do with a gas tank.
One way I found that can reduce the AH or wh usage is if everything else is
perfect, is the amount of pressure you maintain on the accelerator. For
example, to accelerate my EV up to a certain speed, I just press the
accelerator just to that point which will maintain that speed, not push it
to the floor and then when you get to the speed you want, then let up on the
accelerator at that point.
I found it is best to press the accelerator just enough to get up to that
speed. Lets say my motor ampere is reading 200 amps at that time while I am
acceleration. When I get up to 30 mph, I could still hold the accelerator
at that point, which will still be 200 amps, or I can ever so slightly
reduce the pressure dropping the motor amperes to about 175 amps or even as
low as 100 amps which at times will still maintain the same speed on a
street that looks dead level which is rare in my area, but it is wavy.
My EV can do this, because it has a long coast down without any power. If I
see that I cannot make a stop light 4 or 5 blocks ahead of me, I just let up
on the accelerator all the way, and the EV keeps going, like I am still
applying power to it.
Also, if your streets are either going up or down like a roller coaster, but
ever so slightly, you can take advantage of this by letting up some on the
down run. I use to maintain the same pressure on the accelerator and use
about 200 motor ampere or is about 50 battery ampere on this roller coaster
streets which is easy to do with out thinking.
In driving a EV, try to reduce the pressure on the accelerator at the end of
your acceleration or on very slightly roller coaster street and see what
happens, but you have to think about it.
Roland
----- Original Message -----
From: "Ian Hooper" <[EMAIL PROTECTED]>
To: <ev@listproc.sjsu.edu>
Sent: Sunday, May 13, 2007 3:32 AM
Subject: Vehicle efficiency, wh/mile
> Hi all,
>
> I was just curious if many people on the list have measured their
> EV's efficiency i.e average watt-hours per mile?
>
> I've heard figures around 300wh/mile thrown around, but that seems
> like a fair bit of energy to me.. Could that be based on people using
> the C20 capacity of lead acid to calculate the pack's energy?
>
> -Ian
>
>
--- End Message ---
--- Begin Message ---
Does anyone know why it might be neccessary to chop the regen current on
a sepex motor?
Below is my understanding, do other people think this is correct?
I can see that the regen current/volts must be limited to avoid cooking
the batteries.
It seems to me that at high rpm this can be achieved by varying the
field current until max field current is reached (which for my motor is
about 1500 rpm or about 15mph). As the rpm drops below this level one
way to limit the regen current would be to open the main contactor,
presumably this is not something one would want to do on a regular basis
and so the regen current is chopped.
If my understanding is correct the brake chopper only needs to work
below 1500rpm, though it could also be used at higher rpm. At higher rpm
which method is better, varying the field current or chopping the regen
current?
--- End Message ---
--- Begin Message ---
> Bill I have a question. Are you talking about magnetic fields as in a
> an electromagnet when you refer to "DC magnetic fields"?
>
> There is a difference, isn't there, between electromagnets which are
> static magnetic fields that attract ferrous materials and
> electromagnetic fields caused by rotating motors (DC and AC) and
> inverters PWM controllers etc. which do not attract ferrous materials?
You are correct. The fields I was talking about in this thread I started
are purely of the time varying kind. IE remove the DC component.
A permanent magnet only has a static field unless you start to move or
rotate the magnet with respect to something else subjected to it (a
measuring device in this case)
A wire with a steady DC current also only produces a DC/Static magnetic
field. But when you start to pulse or vary the current, the field is not
static anymore and produces electro-magnetic waves (waves with both an
electric and magnetic component)
Meters like the tri-field only measure time varying magnetic fields. If
you subject it to a non moving magnet, they register nothting. If you
start to move or rotate that magnet, the do measure the resulting
electromagnetic field. The company that makes the tri-field does have
other meters to measure DC magnetic fields but this is not the topic of
this thread.
The big difference between static and non static magnetic fields is that
the later can induce electric current in conductors.
Whe measuring electromagnietic field from motors you are measuring many
different time varying magnetic fields depending on the kind of motors.
There are:
1) rotating magnets for permanent magnet motors
2) Time varying fields in the coils of wires that makup the AC motors
3) Repetitive buidup and colpase of magnetic fields in DC motors with
brushes that swith the current from one coil to the other as the shaft
rotates.
So as you can see there are plenty of time varying fields in motors and
they are the subject of the thread I sarted. I was only and strictly
asking about measurements of those fields but you seem to understand that
very well.
All of the other DC field that were brought up in this duscussion were not
brought up by me and have nothing to do with the thread: Earth's field and
other DC fields no mattter how large. They all have one thing in common.
They do not induce currents in conductors.
Also, I clearly mentioned that I was mostly refering to ELF fields, not
RF, not micro-wave and not light waves or above.
Thank you for actually reading my posts Tehben
Patrick Robin
--
Patrick Robin
http://atelierrobin.net
--- End Message ---
--- Begin Message ---
Roland> One way I found that can reduce the AH or wh usage is if
Roland> everything else is perfect, is the amount of pressure you
Roland> maintain on the accelerator. For example, to accelerate my EV up
Roland> to a certain speed, I just press the accelerator just to that
Roland> point which will maintain that speed, not push it to the floor
Roland> and then when you get to the speed you want, then let up on the
Roland> accelerator at that point.
Seems like cruise control would be very helpful in an EV.
--
Skip Montanaro - [EMAIL PROTECTED] - http://www.webfast.com/~skip/
--- End Message ---
--- Begin Message ---
You need both. The chopper is probably a "shunt" boost chopper which is in
parallel with the motor and is used when the motor back emf is less than the
battery voltage. The chopper boosts the lower motor voltage up to the
battery voltage. Regen braking is strong and effective down to low speed,
like 3 mph or so. At high speeds, if you used a chopper, it would have to
be in a series configuration with the batteries, assuming you were stuck
with full field. It is easy to use field control in the sepex motor for
regen above base speed.
On Sun, 13 May 2007 15:45:35 +0100, tt2tjw wrote
> Does anyone know why it might be neccessary to chop the regen
> current on a sepex motor?
>
> Below is my understanding, do other people think this is correct?
>
> I can see that the regen current/volts must be limited to avoid
> cooking the batteries.
>
> It seems to me that at high rpm this can be achieved by varying the
> field current until max field current is reached (which for my motor
> is about 1500 rpm or about 15mph). As the rpm drops below this
> level one way to limit the regen current would be to open the main
> contactor, presumably this is not something one would want to do on
> a regular basis and so the regen current is chopped.
>
> If my understanding is correct the brake chopper only needs to work
> below 1500rpm, though it could also be used at higher rpm. At higher
> rpm which method is better, varying the field current or chopping
> the regen current?
--- End Message ---
--- Begin Message ---
I have worked on EV controllers, dc-dc converters, and battery chargers that
use air core inductors as part of high frequency circuits, such as motor
smoothing, isolating inductor, di/dt suppression, commutation energy
storage, etc. Sometimes, gapped iron core inductors are used which also
have stray fields. To make it more dangerous, fiberglass enclosures are
sometimes used for this equipment since high voltages are present, and these
enclosures offer no magnetic shielding. This equipment in close proximity to
passengers in an EV does emit ELF worth worrying about.
One of the biggest concerns is with pace makers and the possibility of ELF
causing a heart attack. Years ago, on a newly designed trolley bus
controller just put into service, I got a report that a bus passenger
sitting in the back seat, next to the controller compartment had a heart
attack and was rushed to the hospital. These reports are usually garbled
when first received. The passenger was actually sitting in the front of the
bus, had indigestion, and asked to get off the bus at an unscheduled stop.
On Sun, 13 May 2007 10:48:49 -0400 (EDT), Patrick Robin wrote
> > Bill I have a question. Are you talking about magnetic fields as in a
> > an electromagnet when you refer to "DC magnetic fields"?
> >
> > There is a difference, isn't there, between electromagnets which are
> > static magnetic fields that attract ferrous materials and
> > electromagnetic fields caused by rotating motors (DC and AC) and
> > inverters PWM controllers etc. which do not attract ferrous materials?
>
> You are correct. The fields I was talking about in this thread I started
> are purely of the time varying kind. IE remove the DC component.
>
> A permanent magnet only has a static field unless you start to move
> or rotate the magnet with respect to something else subjected to it
> (a measuring device in this case)
>
> A wire with a steady DC current also only produces a DC/Static magnetic
> field. But when you start to pulse or vary the current, the field is
> not static anymore and produces electro-magnetic waves (waves with
> both an electric and magnetic component)
>
> Meters like the tri-field only measure time varying magnetic fields.
> If you subject it to a non moving magnet, they register nothting. If
> you start to move or rotate that magnet, the do measure the
> resulting electromagnetic field. The company that makes the tri-
> field does have other meters to measure DC magnetic fields but this
> is not the topic of this thread.
>
> The big difference between static and non static magnetic fields is that
> the later can induce electric current in conductors.
>
> Whe measuring electromagnietic field from motors you are measuring many
> different time varying magnetic fields depending on the kind of motors.
> There are:
>
> 1) rotating magnets for permanent magnet motors
> 2) Time varying fields in the coils of wires that makup the AC motors
> 3) Repetitive buidup and colpase of magnetic fields in DC motors with
> brushes that swith the current from one coil to the other as the
> shaft rotates.
>
> So as you can see there are plenty of time varying fields in motors and
> they are the subject of the thread I sarted. I was only and strictly
> asking about measurements of those fields but you seem to understand
> that very well.
>
> All of the other DC field that were brought up in this duscussion
> were not brought up by me and have nothing to do with the thread:
> Earth's field and other DC fields no mattter how large. They all
> have one thing in common. They do not induce currents in conductors.
>
> Also, I clearly mentioned that I was mostly refering to ELF fields, not
> RF, not micro-wave and not light waves or above.
>
> Thank you for actually reading my posts Tehben
>
> Patrick Robin
>
> --
> Patrick Robin
> http://atelierrobin.net
--- End Message ---
--- Begin Message ---
Everything old is new again:
About 1959 I was involved in a bio-magnetic research project.
We found an obscure research project IIRC by Thompson about 1906.
He studied workers around large transformers in the power industry,
and found no effects.
EV's were popular in that time frame.
John in Sylmar, CA
PV EV
--- End Message ---
--- Begin Message ---
> Instead of the time and care needed to wire that up and the ensuing
> rats nest, I think it would be nice to try the single chip wireless
> solutions(zigbee).
I've never played with zigbee, someone should try them inside a running
EV environment to see how reliable they are. But more to the point,
we should think about these things in a "building block" context.
Design the battery module as a standalone monitor (possibly
controller), without designing in a specific communications block.
Then we can design alternate communications blocks (IR/zigbee/wilbee/
bluetooth/CAN/etc.). Each user could then select the version suitable
for their needs.
> It may take a lot of development, but once complete
> the individual unit costs would be pretty low. The Programming is
> where a lot of the cost would be on developing something like this, >
but I can donate that to the cause.
I can help. I just started a website to chronical my own conversion,
I can provide space on it to organize such a project. If it gets
serious we should consider sourceforge.
> But I don't think just monitoring is suffient, it needs to do more.
Agreed, again, think about modularity, ie. building block approach.
GPS systems, milage computers, etc. should be able to act as standalone
modules that can communicate with other systems if present.
> can any of you ee/computer guys come up with some
> thing that a combines a BMS with speed, rpms, wind
> direction, slope, altitude and watts
> consumed/consuming/projected all based on route
> programed in a GPS system so we have a comprehensive
> EV info center on just one screen...while dreaming
> make it bluetooth compatable so we can use our phone
> and mp3 player too
see above.
> > > An open source project is a worthy goal, but too
> > often people use the name to mean, "I want somebody else to
> > develop it for me for free." I'm not sure how to inspire a group
> > of people to work together on such a project.
Starting is the first point. The first things to be done will be those
of interest to people that are actually willing to do some work. There
is also a great need for "domain experts", ie. people with knowledge of
motors, batteries, bms, etc. They have just as great a role to play as
the EEs.
> If I build it, I will open-source it. Hurray if
> others want to build them
> using my code! If more DIY EV'ers had a BMS, we'd
> save a lot of batteries!
GPL or BSD license? http://en.wikipedia.org/wiki/Free_software_license
this is a serious point that needs to be settled before a project
should be started. It can be a huge point of conflict down the road
that breaks a project.
Common tools for both mechanical and electrical CAD need to be accepted
by *all* participants. Otherwise things quickly descend into a "tower
of babel" situation.
I have been involved in several open source projects in the past,
experience dictates that there needs to be a "project head" who
has power to make final decisions. This "project head" can be an
individual or committee, but has to have final authority to keep
things from falling into chaos. Some things have no "best answer",
but to make progress decisions need to be made (good or bad).
Different working groups are needed:
CAD/CAM tools
web-site organization.
documentation
???
and individual project groups:
motor controller
charger
bms
gps/route/milage
networking/project cohesion(?)
???
thought?
---
Steve
____________________________________________________________________________________
Don't pick lemons.
See all the new 2007 cars at Yahoo! Autos.
http://autos.yahoo.com/new_cars.html
--- End Message ---
--- Begin Message ---
Thanks for your help George, I think I partially understand it now
I originally stupidly thought that at low rpm there was too high a
voltage, in actual fact there is too little volts to charge the battery.
I am still a little confused though, how does the chopper boost the voltage?
I can have a guess based on what I can see in the controller;
This is how the controller is set up:
the IGBT driving the armature is a half bridge
C1 is connected to +ve battery
E1/C2 is connected to one of the armature terminals
E2 is connected to the other armature terminal and to the -ve battery
terminal
there are the usual free wheel diodes between E2 and E1/C2 and between
E1/C2 and C1
As far as I can see:
when the battery is driving the motor the low side is turned off and
the high side is chopping (up to 1500rpm, thereafter the high side is
full on)
in high rpm regen both the high and the low side are turned off
in low rpm regen the high side is off and I think the low side must chop.
In low rpm regen when the low side is on the current will flow though
the low side IGBT and back through the armature.
Does this somehow increase the voltage in the armature untill it is
large enough to charge the battery?
What would happen if the low side didn't chop?
George Swartz wrote:
You need both. The chopper is probably a "shunt" boost chopper which is in
parallel with the motor and is used when the motor back emf is less than the
battery voltage. The chopper boosts the lower motor voltage up to the
battery voltage. Regen braking is strong and effective down to low speed,
like 3 mph or so. At high speeds, if you used a chopper, it would have to
be in a series configuration with the batteries, assuming you were stuck
with full field. It is easy to use field control in the sepex motor for
regen above base speed.
On Sun, 13 May 2007 15:45:35 +0100, tt2tjw wrote
Does anyone know why it might be neccessary to chop the regen
current on a sepex motor?
Below is my understanding, do other people think this is correct?
I can see that the regen current/volts must be limited to avoid
cooking the batteries.
It seems to me that at high rpm this can be achieved by varying the
field current until max field current is reached (which for my motor
is about 1500 rpm or about 15mph). As the rpm drops below this
level one way to limit the regen current would be to open the main
contactor, presumably this is not something one would want to do on
a regular basis and so the regen current is chopped.
If my understanding is correct the brake chopper only needs to work
below 1500rpm, though it could also be used at higher rpm. At higher
rpm which method is better, varying the field current or chopping
the regen current?
--- End Message ---
--- Begin Message ---
Steve,
You're absolutely right about the functional part of the Open Source
equation.. in this case not just Open Source (code) but Open
Development in general. However almost every Open Source success is
defined by a small group of evangelists who make something really
great and share it, after which people start hopping 'on the
bandwagon' because the solution scratched a particular itch. Linux
overall, and the Apache web server are two great examples.
I would suggest that the best way to do this is to gather a small core
of interested parties, building resources, and seeing if 'they come'.
:) Over time you can enlist the aid of experts on specific items that
might need some noodling, but generally it is enthusiasts that drive
these sorts of projects.
Also, given the nature of this animal I see no trouble in using the
GPL, and great advantages since people won't be tempted just to rip
things off wholesale, refer to the OpenEV site as authoritative, but
having changed some things to be inferior for profit purposes, thus
damaging the rep of the project. With the GPL people are free to sell
everything but they have to make the plans and source code available
to end users, in adfinitum. That protects them, the end users and the
OpenEV site.
I've registered OpenEV.org as well, and I think this could be
fantastic! The rough spots are only where the rubber meets the road in
IP, hence why you have to be REALLY clear with respect to how the
stuff is lisenced. Since you are also dealing with patentable
concepts, everything needs to be completely open to avoid someone
patenting things out from under you... your site would be prior art
and thus invalidate the patent claim (someone pls correct me if I am
incorrect here). Etc etc.
--Timothy
--- End Message ---
--- Begin Message ---
In PWM boost, the low side IGBT turns on and builds up armature current.
When it turns off, the "flywheel" effect of the armature inductance causes
current to keep flowing thru a blocking diode and back into the battery.
(The current waveform is a two slope, and roughly triangular at 50% duty
cycle) This flyback current would flow up to any practical battery voltage.
At very low motor voltages, the boost becomes inefficient, but electrical
braking remains good, as energy is dissipated in the motor windings.
Sometimes, an external inductor is used to add inductance to the motor.
This is particularly true for a sepex motor since it has no series field to
add to motor inductance. The external inductor makes both the boost and run
more efficient.
The flyback diode could be the inverse parallel diode associated with the
upper IGBT, or could be an added diode?
On Sun, 13 May 2007 17:39:12 +0100, tt2tjw wrote
> Thanks for your help George, I think I partially understand it now
> I originally stupidly thought that at low rpm there was too high a
> voltage, in actual fact there is too little volts to charge the battery.
>
> I am still a little confused though, how does the chopper boost the
voltage?
>
> I can have a guess based on what I can see in the controller;
>
> This is how the controller is set up:
> the IGBT driving the armature is a half bridge
> C1 is connected to +ve battery
> E1/C2 is connected to one of the armature terminals
> E2 is connected to the other armature terminal and to the -ve
> battery terminal there are the usual free wheel diodes between E2
> and E1/C2 and between E1/C2 and C1
>
> As far as I can see:
> when the battery is driving the motor the low side is turned off
> and the high side is chopping (up to 1500rpm, thereafter the high
> side is full on) in high rpm regen both the high and the low side
> are turned off in low rpm regen the high side is off and I think the
> low side must chop.
>
> In low rpm regen when the low side is on the current will flow
> though the low side IGBT and back through the armature. Does this
> somehow increase the voltage in the armature untill it is large
> enough to charge the battery?
>
> What would happen if the low side didn't chop?
>
> George Swartz wrote:
> > You need both. The chopper is probably a "shunt" boost chopper which is
in
> > parallel with the motor and is used when the motor back emf is less than
the
> > battery voltage. The chopper boosts the lower motor voltage up to the
> > battery voltage. Regen braking is strong and effective down to low
speed,
> > like 3 mph or so. At high speeds, if you used a chopper, it would have
to
> > be in a series configuration with the batteries, assuming you were stuck
> > with full field. It is easy to use field control in the sepex motor for
> > regen above base speed.
> >
> >
> >
> >
> >
> >
> > On Sun, 13 May 2007 15:45:35 +0100, tt2tjw wrote
> >
> >> Does anyone know why it might be neccessary to chop the regen
> >> current on a sepex motor?
> >>
> >> Below is my understanding, do other people think this is correct?
> >>
> >> I can see that the regen current/volts must be limited to avoid
> >> cooking the batteries.
> >>
> >> It seems to me that at high rpm this can be achieved by varying the
> >> field current until max field current is reached (which for my motor
> >> is about 1500 rpm or about 15mph). As the rpm drops below this
> >> level one way to limit the regen current would be to open the main
> >> contactor, presumably this is not something one would want to do on
> >> a regular basis and so the regen current is chopped.
> >>
> >> If my understanding is correct the brake chopper only needs to work
> >> below 1500rpm, though it could also be used at higher rpm. At higher
> >> rpm which method is better, varying the field current or chopping
> >> the regen current?
> >>
> >
> >
> >
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--- Begin Message ---
Thank you everyone who has contributed to this. This is really great and
gives me enough information to have confidence in making my own.
Thanks
Paul
-----Original Message-----
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On
Behalf Of Lee Hart
Sent: Saturday, May 12, 2007 10:42 AM
To: ev@listproc.sjsu.edu
Subject: Re: Contactor Controller Page
Tom Gocze wrote:
> Well, it has taken a week, but we have a bunch of Contactor Controller
> stuff scanned and posted on www.hotandcold.tv.
Wow, that's some great vintage stuff you have there, Tom! Good work.
Hope to see more of it as you find time to scan those old classic books.
I just sent David Roden a pile of my controller information. He's going
to scan it and post it on the EVDL website as well. These are newer
designs, but still include some contactor and SCR controllers.
--
Ring the bells that still can ring
Forget the perfect offering
There is a crack in everything
That's how the light gets in -- Leonard Cohen
--
Lee A. Hart, 814 8th Ave N, Sartell MN 56377, leeahart_at_earthlink.net
--- End Message ---
--- Begin Message ---
I've been calling some forklift places trying to find an old motor that
I can use to get my project going. I am looking for a large forklift
motor at 48v. I mentioned that this was for an electric vehicle running
greater than 96v. The man said I couldn't do this. A 48v motor can only
handle 48v. This makes perfect sense but I know people use them in EV's.
Is it the better cooling these motors receive in a car? Advancing the
brushes? Maybe the motor has to be rewound? Maybe the life is severely
deminished? How do I answer an oldtimer who knows plenty more than me
about motors that I want to use a 48v motor in an EV?
Thanks,
Paul
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--- Begin Message ---
I was curious as to how much actual Lithium was in the Lithium
secondary batteries, and then to compare that to the spot price. That
would give some gauge as to cost per battery at baseline for just that
component, which is the restricted resource (pretty much everything
else is very common and very cheap. Iron and Phosphate, plastics).
well, the US price for lithium (carbonate) got to $5500/tonne or so
this year. So let's use that. That comes out to $2.75/lb. The amount
of lithium metal in lithium carbonate is about 11/58. So that brings
the Lithium metal cost to about $80 per lb (per 453.59 g).
Then I found a paper that clearly stated: "The amount of lithium
contained in a secondary lithium cell by weight is approximately 0.3g
per AH" That assumes of course the base voltage of 3.7.
So, a 50AH Lithium cell has ~15g of Lithium metal in it. Which comes
out to about $2.65.
I just thought that was very interesting :) Even if you tripled that
cost (buying LiFePO4 from a manufacturer) it comes out to only $7.93
Thundersky 40AH batteries are selling for $80.
So if everything else in that battery cost $30 (which is quite high),
they are still clearing quite a chunk of change. I realize...
recouping costs, R&D, and so on. I just wanted to illustrate the basic
costs.
FYI.
--T
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--- Begin Message ---
It seems like cruise control would be very easy to build into an EV
controller... its all electronic.
Wonder why its not done... or is it?
On May 13, 2007, at 6:49 AM, [EMAIL PROTECTED] wrote:
Roland> One way I found that can reduce the AH or wh usage is if
Roland> everything else is perfect, is the amount of pressure you
Roland> maintain on the accelerator. For example, to accelerate
my EV up
Roland> to a certain speed, I just press the accelerator just
to that
Roland> point which will maintain that speed, not push it to
the floor
Roland> and then when you get to the speed you want, then let
up on the
Roland> accelerator at that point.
Seems like cruise control would be very helpful in an EV.
--
Skip Montanaro - [EMAIL PROTECTED] - http://www.webfast.com/~skip/
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--- Begin Message ---
Ok thanks again George, I'm off to read about inductance then hopefully
I will understand a little better how it works and how to choose the
duty value.
George Swartz wrote:
In PWM boost, the low side IGBT turns on and builds up armature current.
When it turns off, the "flywheel" effect of the armature inductance causes
current to keep flowing thru a blocking diode and back into the battery.
(The current waveform is a two slope, and roughly triangular at 50% duty
cycle) This flyback current would flow up to any practical battery voltage.
At very low motor voltages, the boost becomes inefficient, but electrical
braking remains good, as energy is dissipated in the motor windings.
Sometimes, an external inductor is used to add inductance to the motor.
This is particularly true for a sepex motor since it has no series field to
add to motor inductance. The external inductor makes both the boost and run
more efficient.
The flyback diode could be the inverse parallel diode associated with the
upper IGBT, or could be an added diode?
On Sun, 13 May 2007 17:39:12 +0100, tt2tjw wrote
Thanks for your help George, I think I partially understand it now
I originally stupidly thought that at low rpm there was too high a
voltage, in actual fact there is too little volts to charge the battery.
I am still a little confused though, how does the chopper boost the
voltage?
I can have a guess based on what I can see in the controller;
This is how the controller is set up:
the IGBT driving the armature is a half bridge
C1 is connected to +ve battery
E1/C2 is connected to one of the armature terminals
E2 is connected to the other armature terminal and to the -ve
battery terminal there are the usual free wheel diodes between E2
and E1/C2 and between E1/C2 and C1
As far as I can see:
when the battery is driving the motor the low side is turned off
and the high side is chopping (up to 1500rpm, thereafter the high
side is full on) in high rpm regen both the high and the low side
are turned off in low rpm regen the high side is off and I think the
low side must chop.
In low rpm regen when the low side is on the current will flow
though the low side IGBT and back through the armature. Does this
somehow increase the voltage in the armature untill it is large
enough to charge the battery?
What would happen if the low side didn't chop?
George Swartz wrote:
You need both. The chopper is probably a "shunt" boost chopper which is
in
parallel with the motor and is used when the motor back emf is less than
the
battery voltage. The chopper boosts the lower motor voltage up to the
battery voltage. Regen braking is strong and effective down to low
speed,
like 3 mph or so. At high speeds, if you used a chopper, it would have
to
be in a series configuration with the batteries, assuming you were stuck
with full field. It is easy to use field control in the sepex motor for
regen above base speed.
On Sun, 13 May 2007 15:45:35 +0100, tt2tjw wrote
Does anyone know why it might be neccessary to chop the regen
current on a sepex motor?
Below is my understanding, do other people think this is correct?
I can see that the regen current/volts must be limited to avoid
cooking the batteries.
It seems to me that at high rpm this can be achieved by varying the
field current until max field current is reached (which for my motor
is about 1500 rpm or about 15mph). As the rpm drops below this
level one way to limit the regen current would be to open the main
contactor, presumably this is not something one would want to do on
a regular basis and so the regen current is chopped.
If my understanding is correct the brake chopper only needs to work
below 1500rpm, though it could also be used at higher rpm. At higher
rpm which method is better, varying the field current or chopping
the regen current?
--- End Message ---
--- Begin Message ---
And to add more kudos to Tom for this:
The 3rd item posted on the list of contactor controller resources is a
1911-1913 Hupp-Yeats Electric Car Instruction Book!! This was on the list
of holy grail items for me and my 1911 H-Y Model 1A project. Not one of the
dozen-plus automotive libraries/archives, Hupp experts or anyplace online or
elsewhere had I ever come up with a wiring diagram, let alone an instruction
book for one of these rare electrics. And so it was with great luck,
surprise and elation that in going to Tom's page and selecting the contactor
controllers page that I end up with yet another very useful item for this
project.
Thanks again Tom.
-Myles Twete, Portland, Or.
1911 Hupp-Yeats Model 1A project: http://www.austinev.org/evalbum/1018
-----Original Message-----
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On
Behalf Of childreypa
Sent: Sunday, May 13, 2007 10:16 AM
To: ev@listproc.sjsu.edu
Subject: RE: Contactor Controller Page
Thank you everyone who has contributed to this. This is really great and
gives me enough information to have confidence in making my own.
Thanks
Paul
-----Original Message-----
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On
Behalf Of Lee Hart
Sent: Saturday, May 12, 2007 10:42 AM
To: ev@listproc.sjsu.edu
Subject: Re: Contactor Controller Page
Tom Gocze wrote:
> Well, it has taken a week, but we have a bunch of Contactor Controller
> stuff scanned and posted on www.hotandcold.tv.
Wow, that's some great vintage stuff you have there, Tom! Good work.
Hope to see more of it as you find time to scan those old classic books.
I just sent David Roden a pile of my controller information. He's going
to scan it and post it on the EVDL website as well. These are newer
designs, but still include some contactor and SCR controllers.
--
Ring the bells that still can ring
Forget the perfect offering
There is a crack in everything
That's how the light gets in -- Leonard Cohen
--
Lee A. Hart, 814 8th Ave N, Sartell MN 56377, leeahart_at_earthlink.net
--- End Message ---
--- Begin Message ---
My personal belief is that there is little harm from any low frequency EMF
(under 100khz). I don't *know* this for sure though.
A study, as old as 1959, or even worse, 1906, is not going to have large
magnetic fields much over 60hz. Now we live in a world of hundreds of kHz
high frequency switch-mode power supplies. Every computer has multiples!
Most EV motor controllers operate around 15-20khz, and we are dealing with
hundreds of amps. The battery wiring all is going to "see" this frequency
and because the wiring isn't exactly a twisted-pair, we are going to have
all kinds of large magnetic fields in this way.
Not only is it good for the controller to minimize battery inductance, it's
possibly good for the humans too!
I saw an Porsche 914 EV conversion a few years back and the front battery
wiring had been passed through the rocker boxes on either side of the
passenger compartment. One wire on each side! That turns the passenger
compartment into a huge air-core inductor! The capacitors failed in his
Curtis in short order and cooked the controller, and he didn't believe that
routing the battery wires in such a way could have caused the problem,
despite my insistence.
FYI: Whenever you run battery or motor wiring, try to keep the wires as
close as possible to each other, even twist them if possible. If they run
through the passenger compartment, run them in a metallic conduit. Whatever
you do, Don't run each wire through it's own conduit! You can end up
inducing a large eddy current in the conduits...
-Phil
----- Original Message -----
From: "JS" <[EMAIL PROTECTED]>
To: <ev@listproc.sjsu.edu>
Sent: Sunday, May 13, 2007 8:28 AM
Subject: RE: EMF in EVs
Everything old is new again:
About 1959 I was involved in a bio-magnetic research project.
We found an obscure research project IIRC by Thompson about 1906.
He studied workers around large transformers in the power industry,
and found no effects.
EV's were popular in that time frame.
John in Sylmar, CA
PV EV
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