EV Digest 3944
Topics covered in this issue include:
1) Re: High current draw from floodies, was RE: Motor Amps, Battery Amps ?
by Dave Cover <[EMAIL PROTECTED]>
2) Re: kWh/mile challenge
by "Joe Smalley" <[EMAIL PROTECTED]>
3) Re: Motor Amps, Battery Amps ?
by "Steve Clunn" <[EMAIL PROTECTED]>
4) Re: Motor Amps, Battery Amps ?
by "Rich Rudman" <[EMAIL PROTECTED]>
5) Re: Motor Amps, Battery Amps ?
by "Rich Rudman" <[EMAIL PROTECTED]>
6) DC clamp meter recomendation
by TiM M <[EMAIL PROTECTED]>
7) Re: DC clamp meter recomendation
by James Massey <[EMAIL PROTECTED]>
8) Test Message Please Ignore
by "Mike Chancey" <[EMAIL PROTECTED]>
9) Re: DC clamp meter recomendation
by Rod Hower <[EMAIL PROTECTED]>
10) Re: DC clamp meter recomendation
by Lee Hart <[EMAIL PROTECTED]>
11) Re: DC clamp meter recomendation
by Lee Hart <[EMAIL PROTECTED]>
12) Re: DC clamp meter recomendation
by "Joe Strubhar" <[EMAIL PROTECTED]>
13) Re: DC clamp meter recomendation
by [EMAIL PROTECTED]
14) Re: DC clamp meter recomendation
by Neon John <[EMAIL PROTECTED]>
15) Re: DC clamp meter recomendation
by "Philippe Borges" <[EMAIL PROTECTED]>
16) REV C/D Rudman reg.(Mark I) voltage control
by "Lawrence Rhodes" <[EMAIL PROTECTED]>
17) dc motor control for electric vehicles
by "Jacqui Bunner" <[EMAIL PROTECTED]>
18) Re: DC clamp meter recomendation
by Eric Poulsen <[EMAIL PROTECTED]>
19) article: Look Ma, No Hands
by Paul Wujek <[EMAIL PROTECTED]>
20) Re: DC clamp meter recomendation
by Martin K <[EMAIL PROTECTED]>
21) Re: dc motor control for electric vehicles
by "Philippe Borges" <[EMAIL PROTECTED]>
22) Make your own fuse.
by "Lawrence Rhodes" <[EMAIL PROTECTED]>
23) Re: dc motor control for electric vehicles
by "Jacqui Bunner" <[EMAIL PROTECTED]>
24) hubbell safety interlock plug
by Roger <[EMAIL PROTECTED]>
25) Re: DC clamp meter recomendation
by Seth Allen <[EMAIL PROTECTED]>
26) Re: DC clamp meter recomendation
by James Massey <[EMAIL PROTECTED]>
27) Re: Make your own fuse.
by James Massey <[EMAIL PROTECTED]>
28) Re: dc motor control for electric vehicles
by "Philippe Borges" <[EMAIL PROTECTED]>
--- Begin Message ---
Lee
Excellent response! That's what makes this list so great and gives me hope of
getting an EV on the
road. Kudos to all you guys (East Coasters, Left Coasters, Canadians,
Europeans, Australians,
etc.) who've been at it for decades so I can jump in this late in the game.
It's taken at least
three major gas crunches to get me to head down the electric highway. I
remember waiting in long
lines in the early 70's to get my $2 ration of gasoline. Now that same two
bucks barely buys a
gallon of gas. Why didn't I get started back then? Hopefully I'll have that EV
grin in 2005. And I
will share!
Dave Cover
--- Lee Hart <[EMAIL PROTECTED]> wrote:
> Date: Thu, 02 Dec 2004 23:02:45 -0800
> From: Lee Hart <[EMAIL PROTECTED]>
> To: [EMAIL PROTECTED]
> Subject: Re: Fwd: Re: High current draw from floodies, was RE: Motor Amps,
> Battery Amps ?
>
> Dave Cover wrote:
> > Newbie question: Whats the difference between a reversed cell and
> > a dead cell? Is a reversed cell salvagable?
>
> Most types of batteries use two different metals for their two
> electrodes; carbon-zinc, nickel-cadmium, nickel-iron, etc. The
> electrolyte is just a current carrier; it does not participate in the
> chemical reactions.
>
> The lead-acid cell is unique in that *both* plates are lead, and the
> acid electrolyte is the second electrode. Therefore, you can charge a
> lead-acid battery with either polarity, and it still works. One of the
> plates winds up at the same potential as the electrolyte, and the other
> will be 2v away from it.
>
> But as a practical matter, the "+" and "-" plates in all modern
> lead-acid batteries are built differently to optimize them for their
> intended polarity. Like left and right shoes, you get far better results
> if you use them the right way! :-)
>
> When the cells are manufactured, they are given a "forming" charge which
> establishes this polarity. Henceforth, "+" must always be about 2v more
> positive than "-" or you destroy this formation.
>
> When you run a lead-acid cell totally dead (0v), all the acid gets
> converted into lead sulfate. This leaves nothing but water as the
> electrolyte. Water is a poor conductor, so you basically have a
> resistor. A single lead-acid cell all by itself can't normally be run
> this dead, unless you leave a load connected for weeks. Its resistance
> gets so high that the current it delivers becomes negligible.
>
> But if you do leave it dead for days, the lead sulfate gradually
> crystalizes, and cracks free from the plates. Now it is no longer
> electrically connected; and you can't recharge it. The battery is
> "sulfated". This is why you don't want to leave a lead-acid battery
> deeply discharged for very long; the longer it sits that way, the harder
> it will be to recharge, and the less amphour capacity you will be able
> to get in the future.
>
> When you run many lead-acid cells in series, it is far easier to run a
> cell completely dead. It is possible for one cell to go completely dead
> while there is still charge left in the rest. As you keep drawing
> current from the battery, the dead cell's voltage is first forced to
> zero (dead). If you keep discharging the already-dead 0v cell, it
> *reverses* to -2v. You are now "forming" the cell with a reversed
> polarity -- it is actually charging in the wrong direction. This is
> called "reversing" the cell.
>
> Once a cell is reversed, it *stays* reversed. It will act like a normal
> lead-acid battery, but with the "+" and "-" terminals reversed. But, its
> amphour capacity, internal resistance, and life are all considerably
> less than normal.
>
> To fix this, you need to re-reverse its charge -- run it completely dead
> again, and then recharge it in the normal direction. This will take a
> *lot* of charging! In effect, you have to give it a new "forming"
> charge, which takes many more amphours than any normal charge. And when
> you are done, what you have is a battery with seriously reduced amphour
> capacity and life.
> --
> "Never doubt that the work of a small group of thoughtful, committed
> citizens can change the world. Indeed, it's the only thing that ever
> has!" -- Margaret Mead
> --
> Lee A. Hart 814 8th Ave N Sartell MN 56377 leeahart_at_earthlink.net
>
>
--- End Message ---
--- Begin Message ---
Some quick ideas:
To make things fair, use a kWh meter instead of an emeter. It is older and
does not have any of the fancy stuff on it.
Check the calibration after installation to prevent tweaked shunts from
biasing the results. Using an existing shunt makes it easier to install and
remove the kWh meter. The output needs to be calibrated for the shunt being
used since it will not be precisely 50 mV/500A.
Run the meter from a portable battery so isolation is not an issue.
Keep a text file of the serial output as proof of which stoplights were
green and to verify STOP signs were observed. This can also be used to prove
how long it took to drive the route.
Joe Smalley
Rural Kitsap County WA
Fiesta 48 volts
NEDRA 48 volt street conversion record holder
[EMAIL PROTECTED]
----- Original Message -----
From: "Richard Furniss" <[EMAIL PROTECTED]>
To: "EV List" <[EMAIL PROTECTED]>
Sent: Friday, December 03, 2004 6:02 PM
Subject: kWh/mile challenge
> Hi everyone,
>
> At our monthly EV meeting everybody talks about how well or poorly
> their EV's are doing on range. Some members claim to have great range and
> efficiency but they can't prove it without damaging there battery pack and
> having there car towed when it runs out of suds. So I put out a challenge
to
> the other club members to backup there claim with hard numbers on
efficiency
> because range is just how much lead you have on board and how efficiently
> you use it.
>
> So a special custom made award (that means homemade) will go to the
club
> member that has the most efficient on-road EV, and it will be passed
around
> to the member that can top the present holder of the award.
>
> What would be a fair way to set-up this competition ?
>
> What we came up with so far is the same e-meter and shunt set to some
> generic battery settings and correct nominal voltage settings, and
everybody
> will drive the same 10 mile route as many times or as often as the want.
>
> If anybody has any suggestions on a easy, fair, FUN way of doing this
> competition we would welcome them.
>
>
>
>
> Richard Furniss
> http://lasvegasev.com
> Las Vegas, NV
> Board Member, www.lveva.org
> Las Vegas Electric Vehicle Association
>
--- End Message ---
--- Begin Message ---
>
> I have noticed that the motor seems to get hot -- in opinion too hot.
> Even after a shorter (~6 mile drive), the motor shaft and both casing
> ends are too hot to touch. I'll try to get an actual temp. reading from
> my multimeter (which has a temp. probe)...
>
6 miles and to hot to touch , its sounds like the motor , even after 30
miles I can still put my hand on mine.
> motor. I thought at first that it might be due to the motor still being
> relatively new, but now that I've got 468.4 EV miles on the Jeep (I keep
> a good log), I can't imagine that being the case.
was the motor new when you got it. ? I hope you keep posting what you find
so we can all learn , . did you do any kind of brake in on the motor. ?
steve clunn
--- End Message ---
--- Begin Message ---
Yea Nick DO NOT try the contactor across the pack trick, it will wreck aLOT
of things you can't afford to.
This is clearly not a well thought out recomendation...
Leave that kind of stunt to us racers and Hydroplane drivers...
----- Original Message -----
From: "Nick Viera" <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
Sent: Friday, December 03, 2004 5:00 PM
Subject: RE: Motor Amps, Battery Amps ?
> Hi,
>
> > use your main contactors to connect the battery
> > directly to your motor.
>
> Isn't this how contactors get welded "on"? It seems to me that if my
> motor is pulling too much current they could weld together when making
> the circuit, if I'm using my normal pack voltage, that is. Or am I
> wrong?
>
> Thanks,
> -Nick
> 1988 Jeep Cherokee 4x4 EV
> http://Go.DriveEV.com/
>
> ----------------------------------------------
> On Fri, 2004-12-03 at 07:46, Markus L wrote:
> > Nick,
> >
> > this is just a thought from a novice on the following statement
> > you made:
> >
> > > I absolutely CANNOT start in 4th gear (not even in 3rd). I
> > > floor it and
> > > I might just barely inch forward on flat surface. Sometimes the motor
> > > goes into a stall condition (I'm putting in power but not
> > > moving). Still
> > > no yellow LED.
> >
> > What if you bypass (for testing) your controller and use your
> > main contactors to connect the battery directly to your motor.
> > Now try to start in 3rd or 4th gear. To be safe you may
> > try this first with only part of your pack connected. In a sense
> > you would emulate a contactor controller and see if your
> > batteries can deliver the current that your motor demands.
> >
> > You could possibly built a cheapo resistor in there that
> > a second contactor would bypass to make smoother starts.
> >
> > Markus
> >
>
--- End Message ---
--- Begin Message ---
----- Original Message -----
From: "Nick Viera" <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
Sent: Friday, December 03, 2004 5:45 PM
Subject: Re: Motor Amps, Battery Amps ?
> Hi,
>
> > How hot does the motor get??
>
> I have noticed that the motor seems to get hot -- in opinion too hot.
> Even after a shorter (~6 mile drive), the motor shaft and both casing
> ends are too hot to touch. I'll try to get an actual temp. reading from
> my multimeter (which has a temp. probe)...
>
> Now that I think about it, I have also noticed sort of a "burning
> brakes" smell coming from the motor after longer (~10+ mile) trips. This
> is especially noticeable after trips which have included hills or
> inclines, which have included me pulling up to 380 amps on the battery
> side. This smell is definitely NOT the front brakes. I've had those
> fixed and they no longer smell. The smell comes straight up from the
> motor. I thought at first that it might be due to the motor still being
> relatively new, but now that I've got 468.4 EV miles on the Jeep (I keep
> a good log), I can't imagine that being the case.
>
> > No load and a good speed should be like 25 to 50 amps...Motor amps,
> > almost nothing battery amps.
>
> I just hooked back up the Tachometer sensor (which works ok when it
> feels like it), and did a little test. With the transmission in neutral,
> the motor pulls the following currents (give or take a few amps):
>
> RPM Current drawn (battery side current)
> 1000 8 amps
> 2000 15 amps
> 3000 20 amps
> 4000 40 amps
>
I'll say 4800 watts to spin up, that's 6.43 Hoursepower to freespin....
Ok NOW we are getting somewheres......
> These are BATTERY SIDE current readings, with NO load on the motor
> except for the spinning aluminum flywheel/hub, clutch disc, and pressure
> plate. I'm guessing that this is way too much current being pulled if
> I'm supposed to see no more than 50 motor amps?
>
> I'll try to get my 400 amp shunt in the motor loop this weekend if I
> have some spare cables around here with eyelets on them... otherwise
> I'll have to order some more and wait...
>
> Last questions... If this is a motor problem, I'm assuming it could be
> repaired (at a motor shop)? Are motors like this usually expensive to
> repair?
Oh oh!
Well yea depending on the problems.
Most of us racers can do a 9" incher rebuild. Shipping is a few hunder
bucks, you can't use UPS because the motor is too heavy.
A motor rebuild shop can help, ones that do fork truck and Golf cart
rebuilds.
And once you get it out... again.... Many on this list can lead you through
testing and repair it it's simple bolt and unbolt stuff.
--- End Message ---
--- Begin Message ---
Does anyone know of a cheap DC amp clamp meter? Cheap
being in the $50 range. It seems most of the cheap amp
clamps I've seen are AC only, the DC ones I've found
are in the $180 and up range. I'm looking for a way to
verify my shunt and meter readings without breaking
the bank.
Thanks,
TiM
__________________________________
Do you Yahoo!?
Yahoo! Mail - 250MB free storage. Do more. Manage less.
http://info.mail.yahoo.com/mail_250
--- End Message ---
--- Begin Message ---
At 11:33 PM 3/12/04 -0800, you wrote:
<snip> I'm looking for a way to
verify my shunt and meter readings without breaking
the bank.
Thanks,
TiM
Hi Tim
Unless you are using a contactor controller, the fast pulsing of an
electronic controller will give cheap digital meters problems. The method
described below will still give uncertain readings with a non-true RMS
digital meter.
Shunts are exceptionally hard to damage without it being visible. If you
have a shunt in place, inspect it for damage. Make certain that the sense
wires are correctly connected, typically a shunt has a block each end and
thin bars between. On the blocks there should be a small wire and a big
wire seperately connected to the block each side. Look at the writing on
the sides of the block, it may be 50mV or 75mV, and on the other block will
be the amps that this is, for an EV anything from 300A to 1000A.
You now know what the shunt should provide at a given current, conversely
you know that at a given mV there has to be a certain current flow. So,
with a true RMS voltmeter that has a mV range, you can verify your current.
Alternatively another meter connected in paralell off the shunt to compare
to the normal meter can be used.
For example, for arguments sake, your shunt may be 75mV/450A, and your
meter would be scaled 450A, but in small writing at the bottom of the meter
somewhere, there should be 75mV. Your shunt will generate 0.1667mV per amp,
so if you are using a true RMS voltmeter to read the millivolts generated,
a value can be compared to the meter reading. eg, 350A on the meter, 58.3mV
and you don't have a meter problem. Don't forget to use twisted wire out to
your meter or controller 'noise' will affect your reading.
Alternatively uou may have another meter designed to run off a shunt that
you have 'acquired' that has an invalid scale - for the purpose of the
exercise that doesn't matter. Put a second set of sense wires to the second
meter - the increased burden on the shunt is negligible, but don't paralell
two moving pointer type meters or you will be adding an inaccuracy.
Compare the meter readings - another example, the other meter may be 50mV
50Amp, so using the example above if your system is 75mV 450A, you need to
make the test at less than 300A, since that is 50mV, full scale on your
comparison instrument. So to continue the example, you are driving at an
indicated 250A on your normal meter, indicating 42amps on the comparison
meter, again you don't have an instrument problem. Of course if there is a
difference, you will need to do more tests to determine what meter is right.
Safety note: Don't forget that there may be traction voltage on the shunt,
confirm your isolation before playing with it, make certain that the
terminals on the comparison meter are covered or otherwise safe. Although
on the shunt and asociated wiring there is only one side of the traction
voltage, if you have a fault you don't know about you could end up dead.
Take care, be safe and have fun.
Regards
James Massey (instrument technician amongst all the other things people
need me to be).
Launceston, Tasmania, Australia
--- End Message ---
--- Begin Message ---
Please ignore this folks. I am testing a Hotmail address.
Thanks,
Mike Chancey
_________________________________________________________________
Don�t just search. Find. Check out the new MSN Search!
http://search.msn.click-url.com/go/onm00200636ave/direct/01/
--- End Message ---
--- Begin Message ---
These only go up to 200A at the moment, but keep an
eye on this web site,
http://www.allegromicro.com/sf/0754/
They told me there's plans to go up to 1000Amps.
Most likely for this version they'll use a large
bus bar with the hall sensor integrated somehow.
I've used the 100A version and they work very well
and are ISOLATED!
The ACS752 has a 50kHz bandwidth, so it works quite
well as a current sensor on my BLDC motor control.
They gave me pricing of $2.50 in 10k volumes.
Even the low quanity prices at www.newark.com
are less than $9 for 1 piece.
Rod
--- TiM M <[EMAIL PROTECTED]> wrote:
> Does anyone know of a cheap DC amp clamp meter?
> Cheap
> being in the $50 range. It seems most of the cheap
> amp
> clamps I've seen are AC only, the DC ones I've found
> are in the $180 and up range. I'm looking for a way
> to
> verify my shunt and meter readings without breaking
> the bank.
>
> Thanks,
>
> TiM
>
>
>
> __________________________________
> Do you Yahoo!?
> Yahoo! Mail - 250MB free storage. Do more. Manage
> less.
> http://info.mail.yahoo.com/mail_250
>
>
--- End Message ---
--- Begin Message ---
TiM M wrote:
>
> Does anyone know of a cheap DC amp clamp meter? Cheap
> being in the $50 range. It seems most of the cheap amp
> clamps I've seen are AC only, the DC ones I've found
> are in the $180 and up range. I'm looking for a way to
> verify my shunt and meter readings without breaking
> the bank.
Cheap DC clamp-on ammeters are easy to find. They start as low as a few
dollars for the analog versions. Basically, just a magnet on a moving
pointer. The magnet moves in response to the magnetic field generated by
the DC curren in the wire. In this kind, the meter itself clamps onto
the wire. But accuracy is poor -- 5% to 20%.
Better ones use a hall-effect device to sense the magnetic field. This
allows a remote meter "head", which can be analog or digital. Accuracy
is better -- 1% to 10%. These go for $20-$100.
Truly accurate (1% or better) non-contact ones get very expensive. They
usually use some precision balanced magnetic field sensor. They run
$100-$1000.
Now you see why most people use a shunt. It can achieve better than 1%
accuracy for a much lower price. The penalty is that you must insert the
wire.
--
"Never doubt that the work of a small group of thoughtful, committed
citizens can change the world. Indeed, it's the only thing that ever
has!" -- Margaret Mead
--
Lee A. Hart 814 8th Ave N Sartell MN 56377 leeahart_at_earthlink.net
--- End Message ---
--- Begin Message ---
James Massey wrote...
An excellent description of the shunt and how to use it, James.
However, one minor point I can clarify. A true-RMS meter is the correct
reading for things like motor torque and heating effects. Motor torque
and how hot something gets are both proportional to RMS current.
But for battery current, you want to use an average-reading meter.
Battery amphours, state of charge, and charge/discharge rates are all
proportional to the average current, not the true RMS current.
Almost all meters are average-reading. If it doesn't say otherwise,
that's what you have. True RMS meters are much more expensive, and are
labelled as such to brag about it.
The difference between the average and true-RMS readings are usually not
large, and can be ignored for most purposes. Thus, we almost always use
the cheaper average-reading meters in EVs.
--
"Never doubt that the work of a small group of thoughtful, committed
citizens can change the world. Indeed, it's the only thing that ever
has!" -- Margaret Mead
--
Lee A. Hart 814 8th Ave N Sartell MN 56377 leeahart_at_earthlink.net
--- End Message ---
--- Begin Message ---
Tim, I doubt that you'll find one that cheap, unless you come across a
surplus one, or a used one. Universal (UEI) makes the most reasonable one
that I know of, and it's still $150 or so.
Joseph H. Strubhar
E-Mail: [EMAIL PROTECTED]
Web: www.gremcoinc.com
----- Original Message -----
From: "TiM M" <[EMAIL PROTECTED]>
To: "EV-List-Post" <[EMAIL PROTECTED]>
Sent: Friday, December 03, 2004 11:33 PM
Subject: DC clamp meter recomendation
> Does anyone know of a cheap DC amp clamp meter? Cheap
> being in the $50 range. It seems most of the cheap amp
> clamps I've seen are AC only, the DC ones I've found
> are in the $180 and up range. I'm looking for a way to
> verify my shunt and meter readings without breaking
> the bank.
>
> Thanks,
>
> TiM
>
>
>
> __________________________________
> Do you Yahoo!?
> Yahoo! Mail - 250MB free storage. Do more. Manage less.
> http://info.mail.yahoo.com/mail_250
>
>
--- End Message ---
--- Begin Message ---
<< These only go up to 200A at the moment, but keep an
eye on this web site,
http://www.allegromicro.com/sf/0754/
They told me there's plans to go up to 1000Amps.
Most likely for this version they'll use a large
bus bar with the hall sensor integrated somehow.
I've used the 100A version and they work very well
and are ISOLATED!
The ACS752 has a 50kHz bandwidth, so it works quite
well as a current sensor on my BLDC motor control.
They gave me pricing of $2.50 in 10k volumes.
Even the low quanity prices at www.newark.com
are less than $9 for 1 piece.
Rod >>
Those are pretty neat! Of course, non-techies like me wouldn't have a 5V source
readily available (well, I do know how to wire in a dc-to-dc converter), which
is why a shunt is the simplest way to measure current. Do you have a power
supply with adjustable amperage? That sounds like the easiest way to check
accuracy, especially at low draws.
--- End Message ---
--- Begin Message ---
Some of my background is in running a federal metrology lab. Some
thoughts.
Even the best of the clamp-on meters are wildly inaccurate compared to
shunts. Residual magnetism in the magnetic circuit and stray external
fields cause the most problems. The best of the instruments I have
experience with, the F.W. Bell instrument, I consider only for rough
indications.
In our lab and in mine now, a precision shunt is the transfer standard for
current. I've never run into a shunt not having any physical damage that
was very much in error. This is mature technology and easy to do right.
You can check your shunt yourself or you can send it to a lab and have it
certified for probably less than $75. Google for "instrument calibration"
or "metrology service".
If you want to check your shunt at home, you need a decent voltmeter
capable of accurately reading millivolts and a known source of current.
The cheap voltmeters most of use to throw around in the field won't cut
it. I have a Fluke meter calibration station in my lab. I've looked at a
number of the cheap chicom-made meters. Never saw one that would do
better than 1% on volts, worse on millivolts. The higher end Flukes and
Agilent/HP instruments rarely lose calibration, even the old ones. I have
several Fluke 8600 5.5 digit instruments in my lab that are >15 years old
but have never failed calibration. I typically buy them at hamfests for
<$50. Beckmans have been OK. Everything else is little more than a
guess.
If you have a GOOD pair of meters, the way to check your shunt is simple.
Hook one meter up as an ammeter in series with the shunt and the other as
a millivolt meter across the shunt terminals. Pass as much current
through the loop as your instrument can handle and read the mv developed.
>From the current and mv you can computer the actual shunt resistance. It
will probably be dead-nuts on within the resolution of your meters.
If you don't have a current meter of sufficient accuracy, you can back
into it. Ordinary incandescent lamps make excellent constant current
sources over a wide range of applied voltage. American branded automotive
headlamps and 500 watt quartz-halogen work lamp bulbs in particular. I
have yet to test a 500 watt bulb that varied more than a watt from its
rating with precisely 120 volts across it.
500 watts at 120 volts is 4.1667 amps. Even though your meter won't have
very good absolute accuracy, it should be fine for comparisons as long as
you make the measurement the same way. That is, run the current for the
same amount of time and at the same temperature each time.
You can measure several bulbs, compare their current draw and pick some
that match the best. You can then run the bulbs in parallel to produce
whatever current magnitude you need. It is important to use a variac and
a voltmeter to keep the voltage across the lamps at exactly 120 volts.
Since your meter's AC function is invariably less accurate than the DC
function, run the whole loop on rectified and filtered DC. You know the
current by adding up the lamp currents. Measure the shunt voltage and
compute the resistance as above.
One of the keys to making these improvised methods produce good results is
cross-checking. For example, you could perform a calorimetry cross-check
on the lamp. This involves immersing the lamp in water inside a highly
insulated container (thermos bottle) and measuring the temperature rise
over a known time interval. The total energy input can be computed and
from that the power. this is quite easy to do at home and requires little
more than a precision temperature instrument and a large thermos. Surplus
platinum RTDs are available from the normal sources, are very accurate and
quite inexpensive.
John
On Fri, 3 Dec 2004 23:33:34 -0800 (PST), TiM M <[EMAIL PROTECTED]> wrote:
>Does anyone know of a cheap DC amp clamp meter? Cheap
>being in the $50 range. It seems most of the cheap amp
>clamps I've seen are AC only, the DC ones I've found
>are in the $180 and up range. I'm looking for a way to
>verify my shunt and meter readings without breaking
>the bank.
>
>Thanks,
>
>TiM
>
>
>
>__________________________________
>Do you Yahoo!?
>Yahoo! Mail - 250MB free storage. Do more. Manage less.
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---
John De Armond
[EMAIL PROTECTED]
http://bellsouthpwp.net/j/o/johngd/
Cleveland, Occupied TN
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Tim my recommandation would be look for it on ebay...
I bought two 500A DC high quality clamp meter for 40 euros, not even 1/4
one' s price.
Philippe
Et si le pot d'�chappement sortait au centre du volant ?
quel carburant choisiriez-vous ?
http://vehiculeselectriques.free.fr
Forum de discussion sur les v�hicules �lectriques
http://vehiculeselectriques.free.fr/Forum/index.php
--- End Message ---
--- Begin Message ---
R3 on the c's is 3.6 the D's are 9 to 10k. Works for 8v battery which is
about 10v. Should the resistance be about 2.5k for 12v on a rev. C? If not
what value to go up to 15v for 12v batteries at the R3 position.
Thanks.....Lawrence Rhodes...
--- End Message ---
--- Begin Message ---
Hello,
Does anyone have a copy of Richard Valentines application note
on "DC Motor control for Electric Vehicles", motorola, 1993??? If so,
can I get a copy?
Thanks,
michael
This is the app note referenced in Bob Brants, "how to build an electric
vehicle" book, chapter 8, app note 7.
Thanks!
--- End Message ---
--- Begin Message ---
I bought two 400ADC current transducers on Ebay for about $20 (for
both). They operate on (I think) 12V, and output -4 to 4 VDC,
corresponding to -400 to + 400 ADC. The only problem is that they're
the pass-through type (gotta put wire through the hoop, not clamp-on),
and power it, and read the current w/ a meter.
In fact, it would appear the very same person is selling two more:
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=7288&item=3856605920&rd=1
Dirt cheap if you don't mind a little wiring.
TiM M wrote:
Does anyone know of a cheap DC amp clamp meter? Cheap
being in the $50 range. It seems most of the cheap amp
clamps I've seen are AC only, the DC ones I've found
are in the $180 and up range. I'm looking for a way to
verify my shunt and meter readings without breaking
the bank.
Thanks,
TiM
__________________________________
Do you Yahoo!?
Yahoo! Mail - 250MB free storage. Do more. Manage less.
http://info.mail.yahoo.com/mail_250
--- End Message ---
--- Begin Message ---
In Antibes, France, there is a plan to use small, NEV-like, robotic
vehicles to move people around.
link:
http://www.time.com/time/europe/tga/article/0,13005,901041206-832078,00.html?cnn=yes
--
Paul Wujek ([EMAIL PROTECTED])
--- End Message ---
--- Begin Message ---
Rod Hower wrote:
These only go up to 200A at the moment, but keep an
eye on this web site,
http://www.allegromicro.com/sf/0754/
They told me there's plans to go up to 1000Amps.
Most likely for this version they'll use a large
bus bar with the hall sensor integrated somehow.
I've used the 100A version and they work very well
and are ISOLATED!
The ACS752 has a 50kHz bandwidth, so it works quite
well as a current sensor on my BLDC motor control.
They gave me pricing of $2.50 in 10k volumes.
Even the low quanity prices at www.newark.com
are less than $9 for 1 piece.
Rod
Plus they'll send you a few samples for free. I have a few of the 50A parts.
Martin Klingensmith
http://infoarchive.net/
http://nnytech.net/
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--- Begin Message ---
A copy on my webpages:
http://vehiculeselectriques.free.fr/racingcontroller.html
enjoy,
Philippe
Et si le pot d'�chappement sortait au centre du volant ?
quel carburant choisiriez-vous ?
http://vehiculeselectriques.free.fr
Forum de discussion sur les v�hicules �lectriques
http://vehiculeselectriques.free.fr/Forum/index.php
----- Original Message -----
From: "Jacqui Bunner" <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
Sent: Saturday, December 04, 2004 8:08 PM
Subject: dc motor control for electric vehicles
Hello,
Does anyone have a copy of Richard Valentines application note
on "DC Motor control for Electric Vehicles", motorola, 1993??? If so,
can I get a copy?
Thanks,
michael
This is the app note referenced in Bob Brants, "how to build an electric
vehicle" book, chapter 8, app note 7.
Thanks!
--- End Message ---
--- Begin Message ---
Is there some where that lists the capacity of copper wire or strips and
their use as a fuse. This might be dangerous but a 1/16 inch thick by 1/8
inch side piece of copper aught to be a good fuse for 48v 400 amps.
--- End Message ---
--- Begin Message ---
Philippe,
Thank You Very Very Much! :o)
Have you designed a regenerative breaking application to go
along with this yet? Have you implemented this design?
Thanks,
Michael
----- Original Message -----
From: "Philippe Borges" <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
Sent: Saturday, December 04, 2004 4:06 PM
Subject: Re: dc motor control for electric vehicles
> A copy on my webpages:
>
> http://vehiculeselectriques.free.fr/racingcontroller.html
>
> enjoy,
> Philippe
>
> Et si le pot d'�chappement sortait au centre du volant ?
> quel carburant choisiriez-vous ?
> http://vehiculeselectriques.free.fr
> Forum de discussion sur les v�hicules �lectriques
> http://vehiculeselectriques.free.fr/Forum/index.php
>
>
> ----- Original Message -----
> From: "Jacqui Bunner" <[EMAIL PROTECTED]>
> To: <[EMAIL PROTECTED]>
> Sent: Saturday, December 04, 2004 8:08 PM
> Subject: dc motor control for electric vehicles
>
>
> Hello,
> Does anyone have a copy of Richard Valentines application note
> on "DC Motor control for Electric Vehicles", motorola, 1993??? If so,
> can I get a copy?
>
> Thanks,
> michael
>
> This is the app note referenced in Bob Brants, "how to build an electric
> vehicle" book, chapter 8, app note 7.
>
> Thanks!
>
>
>
--- End Message ---
--- Begin Message ---
Hi folks,
I have a Ford Courier Pickup truck converted to full electric by Jet
Industries
in 1981 (or soon thereafter)
The charging receptacle where I plug in a 110 plug has gone bad (the power
pin has worn loose and the connection is intermittent; way bad)
I could just replace it with a modern 3 pin twist-lock plug & receptacle
except
for the safety interlock. What might normally be a center ground pin has
instead been replaced with a plug-button safety switch. When the plug
is inserted,
the center pin is pressed in and allows charging, but not motion. I
believe it
is a disconnect for the main contactor.
Any suggestions where to find this? I tried the hubbell site and found
nothing
with a center safety button.
help
jolly roger
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--- Begin Message ---
They need a bipolar supply, and if they are like other LEMs, probably
need a few hundred milliamps worth for a current output. 25 mA might be
quiescent current, you will want to check the datasheet. Typically
better frequency response than Allegro parts, a more robust output, but
cost more and need a bipolar supply. Nice if you are driving noisy low
inductance motors where the response of the current transducer needs to
be fast so you can actually catch overcurrent trips.
Seth
On Dec 4, 2004, at 2:34 PM, Eric Poulsen wrote:
I bought two 400ADC current transducers on Ebay for about $20 (for
both). They operate on (I think) 12V, and output -4 to 4 VDC,
corresponding to -400 to + 400 ADC. The only problem is that they're
the pass-through type (gotta put wire through the hoop, not clamp-on),
and power it, and read the current w/ a meter.
In fact, it would appear the very same person is selling two more:
http://cgi.ebay.com/ws/eBayISAPI.dll?
ViewItem&category=7288&item=3856605920&rd=1
Dirt cheap if you don't mind a little wiring.
TiM M wrote:
Does anyone know of a cheap DC amp clamp meter? Cheap
being in the $50 range. It seems most of the cheap amp
clamps I've seen are AC only, the DC ones I've found
are in the $180 and up range. I'm looking for a way to
verify my shunt and meter readings without breaking
the bank.
Thanks,
TiM
__________________________________ Do you Yahoo!? Yahoo! Mail - 250MB
free storage. Do more. Manage less.
http://info.mail.yahoo.com/mail_250
--- End Message ---
--- Begin Message ---
At 09:52 AM 4/12/04 -0800, Lee Hart wrote:
James Massey wrote...
An excellent description of the shunt and how to use it, James.
Thank you.
However, one minor point I can clarify. <snip>
The difference between the average and true-RMS readings are usually not
large, and can be ignored for most purposes. Thus, we almost always use
the cheaper average-reading meters in EVs.
Well, you would know what can be got away with. A little illustration to
show why I avoid cheap meters for anything with a high-AC (pulsing DC)
component: I was called to a site by a customer who services
printing-industry machines, complaint that the control board for a DC motor
was not putting any volts out at standby, instead of the 40V the
(interstate) service technician and the manual said. I get there, measure
with a Fluke meter, sure enough, 40V. On his cheaper (and older)
average-reading digital meter, 4V. This was on a phase-angle controlled
rectifier from 50Hz mains, so the off-time was long relative to the on
time. Once the speed-reference switching relay was replaced and we could
control the speed, as the on-time of the rectifier incresed, his meter read
closer to the Fluke I was using.
As I interpret it, the problem is in the slow sample rate of cheaper
meters, rather than the fact of not being true RMS. If a meter is true RMS
it has to have a fast sample rate, and generally will have a high Cat
rating and be safer in the event of mis-connection. It may be better to
recommend that if people want to use a cheap meter, they stick to an
analogue meter to avoid the slow sample rate problem.
So the moral of the story is: you get what you pay for!
Regards
James
--- End Message ---
--- Begin Message ---
At 01:50 PM 4/12/04 -0800, Lawrence Rhodes wrote:
Is there some where that lists the capacity of copper wire or strips and
their use as a fuse. This might be dangerous but a 1/16 inch thick by 1/8
inch side piece of copper aught to be a good fuse for 48v 400 amps.
Hi Lawrence (and all)
Good quality fuses are made with silver down the middle, in a silicon-sand
filled ceramic tube for higher rupturing capacity. These are what should be
used for higher voltage EV traction pack use.
Automotive fuses are copper or copper-composite, and we've all seen the
'splat' in an automotive fuse at 12V when they have blown. Due to the low
voltage this is not a problem.
At 48V you are starting to be in a grey area of what is needed. One of the
problems with sizing fuses is the time that they take to blow at a given
current. For example, off a HRC fuse chart that I have, your fuse size
selected will depend on the length of time the maximum load is going to be
present.
400A 0.01 second, 35A fuse
400A 1 second, 80A fuse
400A 10 seconds, 100A fuse
400A 100 seconds, 150A fuse
400A 1000 seconds, 300A fuse
A 400A fuse can carry 400A indefinately.
So without knowing what your 400A time spec is, and your average current,
the size to fuse-open the piece of copper is unknown.
What I'd reccommend if you really want to try this, is to follow the
pattern that some forklifts use, copper sheet, cut similar to:
_____ _____
| | | |
| O ========= O |
|_____| |_____|
And mounted between two studs, with the molten copper able to fall away
onto something that does not matter (I'd use ceramic or cement sheet, an
inch or more away).
The width of the middle bit is the unknown, I'd make it what you think is
too small, and if it fails, go bigger. If it doesn't fail, and doesn't heat
discolour after a maximum-normal-current trial, maybe you have it too big
to do its job.
Regards
James Massey
Launceston, Tasmania, Australia.
--- End Message ---
--- Begin Message ---
nothing yesterday, today or tomorrow :^)
Philippe
Et si le pot d'�chappement sortait au centre du volant ?
quel carburant choisiriez-vous ?
http://vehiculeselectriques.free.fr
Forum de discussion sur les v�hicules �lectriques
http://vehiculeselectriques.free.fr/Forum/index.php
----- Original Message -----
From: "Jacqui Bunner" <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
Sent: Saturday, December 04, 2004 11:03 PM
Subject: Re: dc motor control for electric vehicles
> Philippe,
> Thank You Very Very Much! :o)
> Have you designed a regenerative breaking application to go
> along with this yet? Have you implemented this design?
> Thanks,
> Michael
> ----- Original Message -----
> From: "Philippe Borges" <[EMAIL PROTECTED]>
> To: <[EMAIL PROTECTED]>
> Sent: Saturday, December 04, 2004 4:06 PM
> Subject: Re: dc motor control for electric vehicles
>
>
> > A copy on my webpages:
> >
> > http://vehiculeselectriques.free.fr/racingcontroller.html
> >
> > enjoy,
> > Philippe
> >
> > Et si le pot d'�chappement sortait au centre du volant ?
> > quel carburant choisiriez-vous ?
> > http://vehiculeselectriques.free.fr
> > Forum de discussion sur les v�hicules �lectriques
> > http://vehiculeselectriques.free.fr/Forum/index.php
> >
> >
> > ----- Original Message -----
> > From: "Jacqui Bunner" <[EMAIL PROTECTED]>
> > To: <[EMAIL PROTECTED]>
> > Sent: Saturday, December 04, 2004 8:08 PM
> > Subject: dc motor control for electric vehicles
> >
> >
> > Hello,
> > Does anyone have a copy of Richard Valentines application note
> > on "DC Motor control for Electric Vehicles", motorola, 1993??? If so,
> > can I get a copy?
> >
> > Thanks,
> > michael
> >
> > This is the app note referenced in Bob Brants, "how to build an electric
> > vehicle" book, chapter 8, app note 7.
> >
> > Thanks!
> >
> >
> >
>
--- End Message ---
