EV Digest 3983
Topics covered in this issue include:
1) Re: Motors in series? Torque vs. power?
by "Michael Hills" <[EMAIL PROTECTED]>
2) Hybrid truck musings
by Jeff Shanab <[EMAIL PROTECTED]>
3) Re: 1500W ceramic heater options at Target
by Dave Cover <[EMAIL PROTECTED]>
4) RE: Hybrid truck musings
by "J Sullivan" <[EMAIL PROTECTED]>
5) Re: Sparrow article in the Akron Beacon Journal - the text!
by Rod Hower <[EMAIL PROTECTED]>
6) Re: Switching from PbSO4
by Chris Zach <[EMAIL PROTECTED]>
7) Re: Switching from PbSO4
by Derrick J Brashear <[EMAIL PROTECTED]>
8) Tracking down shorts from battery pack to ground
by W Bryan Andrews <[EMAIL PROTECTED]>
9) Re: The Amazing Little Hawkers.
by Chris Zach <[EMAIL PROTECTED]>
10) Re: Hybrid truck musings
by "Ryan Stotts" <[EMAIL PROTECTED]>
11) Re: Motors in series? Torque vs. power?
by jerry dycus <[EMAIL PROTECTED]>
12) Re: Tracking down shorts from battery pack to ground
by "Tom Shay" <[EMAIL PROTECTED]>
13) Re: Ideal motor RPM?
by [EMAIL PROTECTED]
14) Re: The Amazing Little Hawkers.
by "David Roden (Akron OH USA)" <[EMAIL PROTECTED]>
15) Re: More EV ideas
by Tim Clevenger <[EMAIL PROTECTED]>
16) re: NEDRA Wicked Watts February 4-6, 2005!
by Tim Clevenger <[EMAIL PROTECTED]>
17) Re: Trying to avoid battricide...SOC stuff
by Lee Hart <[EMAIL PROTECTED]>
18) Re: 1500W ceramic heater options at Target
by Lee Hart <[EMAIL PROTECTED]>
19) Re: Tracking down shorts from battery pack to ground
by Lee Hart <[EMAIL PROTECTED]>
20) Re: Tracking down shorts from battery pack to ground
by "Joe Smalley" <[EMAIL PROTECTED]>
21) Re: Tracking down shorts from battery pack to ground
by "Joe Smalley" <[EMAIL PROTECTED]>
22) Re: Motors in series? Torque vs. power?
by "Joe Smalley" <[EMAIL PROTECTED]>
23) Re: Motors in series? Torque vs. power?
by Otmar <[EMAIL PROTECTED]>
--- Begin Message ---
I'm not well known here, and since I'm in digest mode, someone may have
already answered, but I'll see if I can explain this clearly. The general
answer to your questions is: It's all about the gearing.
If you've got twice the torque at half the RPM, you've got the same amount
of power, but you have it earlier in the race (assuming that the gear ratio
is the same). At zero RPM, the power at the wheels is 0 in both cases, but
one has twice the torque so it gets to 1 RPM sooner. At 1 RPM, the dual
motor setup has twice the power, so not only did it get to 1 RPM sooner, but
when it got there it is accelerating twice as fast (ignoring the fact that
it probably has bigger heavier tires to get all this extra power to the
pavement). It is of course using much more energy out of the batteries, but
at low speeds, the power being used isn't very high yet so this isn't a
limiting factor. You could make the single motor car get off the line just
as fast if you lower its gear ratio enough, allowing it to spin up faster
and produce the same amount of power at the same vehicle speed. However,
then you'd need either a multispeed transmission (those tend to break, take
time to shift, and aren't much lighter than having a second motor), or else
dramatically increase the top speed RPM (but most racers have already maxed
this out as much as possible). Series parallel switching has been compared
to an electronic two speed transmission because it accomplishes the same
thing: more torque at low speed without having to increase the battery
voltage or max RPM to get good high speed performance. Note: the above is
mainly describing what's happening when you're limited by the maximum motor
current from the controller. Once you're going a few miles an hour, other
limits such as battery current limit, battery voltage, etc. start comming
into play and the picture gets much more complicated.
Gearing is also the answer to your questions about ICE torque vs. power.
With an imaginary ideal transmission that could convert all the power at any
RPM to the same amount of power at any other RPM, then the racers could just
run the engine at its peak power RPM and the torque curve would be
irrelevant. In reality, CVTs have not been widely used for racing (I assume
because they're not strong enough), and even those have a minimum low gear
ratio. From a standing start, the engine will have to operate at some RPM
other than its peak horsepower for some significant amount of time. I'm no
expert on engine tuning, but from what I've heard, if you tune an engine to
have more torqe at a lower RPM, it has less torque at high RPMs, so the peak
horsepower isn't as high. However, if this isn't taken to too much of an
extreme, it can potentially still accelerate faster for two reasons. 1) The
power of the high torque engine is higher for more of the RPM range even
though there is one small RPM range where the other has more horsepower. 2)
Getting more horsepower to the wheels early in the race is important. If
you gain 1 mph now, and your opponent gains 1.01 mph a second later, you're
still ahead and he may not catch up until after the finish line.
Another thought: a car optimized for 1/4 mile drags may be slower
accelerating from 30-60. In that case, a car with a high peak power can be
downshifted to take advantage of that high peak power as long as that power
band isn't too narrow. The higher low end torque may still be preferable
for most people though because they will be able to accelerate faster
without downshifting.
From: [EMAIL PROTECTED]
Message-ID: <[EMAIL PROTECTED]>
Date: Tue, 28 Dec 2004 04:34:12 EST
Subject: Re: Motors in series? Torque vs. power?
To: [email protected]
Read some good responses from some knowledgeable-sounding folks. Let me
respond to this answer to my question at the top:
>1) if you are getting "twice the torque"
>then what are you giving up (power perhaps)?
>1) The power is the same either way. You get twice the torque at 1/2
>the RPM (roughly speaking, in an ideal series wound motor you would
>get 4 times the torque at 1/4 the RPM
Okay, that was my suspicion, basically. "There is no free lunch" so to
speak, so the power is the same.
But if the power is the same, then what's the difference? I have two
identical cars, except that one has two motors in series, and the other
only has one
motor. I have two identical drivers, and they are both on the drag strip.
I
say "go!" and they both floor the accelerator at the exact same time. At
this
point, one car is making "twice the torque at half the RMP" and one car is
making "single the torque at full RMP" but both are making the exact same
power.
Is there a difference? Which car wins?
If you say that one car (the two motors in series car) "pulls harder," then
doesn't that translate into more power at the wheels? Well, no, because we
have just said that power is identical. Both cars have exactly the same
power.
So the question becomes, is all power created equal, or not? Is some power
"better" or "more powerful" than other power? When I am measuring power at
the
rear wheels on both of these cars, is it possible to say "yeah, they are
both
the same power, but that car is still pulling harder than this one, and
will
win?"
If you tell me there is no difference in power or pulling ability between
the
cars, and both will cross the finish line the exact same time, then I will
ask "then why bother setting up two motors in series in the first place?"
If these are perceived as stupid questions, please forgive me. I'm not
trying to be difficult - I just want to learn. I actually have a fairly
good
college physics background and what not - that's why I'm asking the
questions. In
fact, a little bit of knowlege is a dangerous thing, they say. Perhaps if
I
had no physics knowledge at all I wouldn't be asking anything. But to me,
power was always power, and was always "created equal" if you know what I
mean.
Thanks.
--- End Message ---
--- Begin Message ---
How's this for an idea.
change the transmission to a 4x4 or use an add on transfercase
(depending on year and make)
forget the front axle, just put the motor where the front driveline was.
Now just put it in 4x4 and use EV controller
or even better, run ICE as FWD and then you can disconnect it from use
from inside the cab
--- End Message ---
--- Begin Message ---
--- Patrick Maston <[EMAIL PROTECTED]> wrote:
> For a bench test I set them up in my original
> heater box with 120V AC to the cores and 12V DC to the fan motor.
> I installed the heater
> box in the car, but have yet to get it hooked up to the 120V DC power
Ok, dumb question from a non EE. You have a heater core (big resisitor meant to
get hot) and it
works the same on AC or DC? Voltage is voltage?
It makes sense, but I always think things work differently on AC vs DC.
Dave Cover
--- End Message ---
--- Begin Message ---
If you use and Atlas 2 transfer case with twin stick shifter this would be
more than possible, the Atlas should shift on the fly and twin stick
shifters will allow you to shift the front and rear outputs separately.
-----Original Message-----
From: Jeff Shanab [mailto:[EMAIL PROTECTED]
Sent: Tuesday, December 28, 2004 7:54 PM
To: EVlist
Subject: Hybrid truck musings
How's this for an idea.
change the transmission to a 4x4 or use an add on transfercase
(depending on year and make)
forget the front axle, just put the motor where the front driveline was.
Now just put it in 4x4 and use EV controller
or even better, run ICE as FWD and then you can disconnect it from use
from inside the cab
--- End Message ---
--- Begin Message ---
David Roden let me know it requires registration,
so here's the text of the article.
Thanks David for the alert, I thought it would be
a direct link.
The electric-vehicle revolution is still coming, say
its advocates...
The electric-vehicle revolution is still coming, say
its advocates at Myers Motors in Tallmadge.
Albeit, a bit more slowly than initially thought.
The fledgling custom-vehicle builder, which hoped to
begin production this fall at its South Avenue plant,
is continuing tests and designs, and plans to crank up
production of a reliable electric vehicle by summer.
``We're hoping to have our own design vehicle out on
the road by June or July,'' said owner Dana Myers.
Myers came up with the idea to build an electric
vehicle as part of a process to change his family
business, S.D. Myers, which was founded by his father
to service and repair large electric transformers. A
large part of the transformer business was sold in the
summer to a General Electric subsidiary, GE Energy.
The new company he created, Myers Motors, is still
building the three-wheel Sparrow electric vehicle,
using parts for 78 vehicles it acquired after buying
out former California-based Sparrow-builder Corbin
Motors this year. Most of the production is still in
California. The Sparrow, which can hit 70 mph, is
classified as a motorcycle, not a car.
``It's a good learning curve,'' Myers said. ``We're
trying to make them run more reliably.''
Myers Motors' engineers are doing a good job of
working out problem areas in the Sparrow and applying
it to the concept vehicle the company wants to make,
he said. Although the concept vehicle probably will be
electric, the company has a prototype that uses a
Harley-Davidson motorcycle engine.
``We have a reliable vehicle,'' Myers said. ``We think
we have most of the problems solved.''
But to make sure that it will work the way customers
need it to, they need to put a lot more miles on it,
he said. And with winter here, ``now we can test in
the snow,'' he said.
Myers Motors has two or three prototype vehicles it is
looking at making, said Rob Dobson, the firm's
operations and customer support manager.
``The longer we work on it, the more we want to start
from the ground up,'' he said, instead of focusing on
the Sparrow. Myers Motors still may continue building
the Sparrow in addition to its own designed vehicle,
he said.
``It keeps getting to be a bigger and bigger
project,'' Dobson said.
--- Rod Hower <[EMAIL PROTECTED]> wrote:
>
http://www.ohio.com/mld/ohio/2004/12/26/business/10496545.htm
>
>
--- End Message ---
--- Begin Message ---
Hm. That's interesting. I just sent them a message asking if the battery
can handle the following:
Cruise discharge at 60 amps constant
Standard charge rate of 18 amps constant
Accel discharge of 140 amps for 2-5 minutes (to climb hills)
Floor it discharge of 200amps for 30 seconds
Braking regen charge rate of 50 amps for 30 seconds
Max Brake-it regen charge rate of 150 amps for 10 seconds
If it can handle the above it would be worth a lot to me. Hm Assuming a
normal 21ah battery costs $50, 666% of that is $333, and 56% of that is
$186.48 per battery giving a pack cost of 25 to be either $4,662 (wow!)
or $9,300 (more expensive but still less than 5 Hakwer packs)
Hm.
Chris
Derrick J Brashear wrote:
On Mon, 27 Dec 2004, Doug Hartley wrote:
1) Valence makes Lithium Ion batteries packaged in PbSO4 AGM battery
style plastic cases with the cell/battery management electronics
built-in:
http://www.valence.com/ucharge.asp
Apparently, you can charge them like lead acid.
So I'd assume 56% of 666% of a lead acid battery price, but of course I
don't see prices on the site.
--- End Message ---
--- Begin Message ---
On Tue, 28 Dec 2004, Chris Zach wrote:
If it can handle the above it would be worth a lot to me. Hm Assuming a
normal 21ah battery costs $50, 666% of that is $333, and 56% of that is
$186.48 per battery giving a pack cost of 25 to be either $4,662 (wow!) or
$9,300 (more expensive but still less than 5 Hakwer packs)
A $5k pack would actually be in range to save for. (I don't have it laying
around, but it's not out of question)
A $10k pack would be like 1/4 of my remaining mortgage.
--- End Message ---
--- Begin Message ---
First of all, I wanted to thank everyone who's answered my newbie
questions in the past. Here's the latest:
It's winter in the midwest .. pretty consistent below-freezing weather
and my garage is unheated. My rabbit had at first become temperamental
about charging, and now flat out refuses to.
The charger's GFI trips every time I try to plug it in.
I've taken the wires that lead from the charger to the battery
pack and sure enough, they read as they should.. somewhere in the
100-something volt range.
So, I believe the implication is that my battery pack is somehow
shorting to ground. The proper procedure here is (I think) to
run around the battery pack and measure the voltage to ground.
Lowest voltage being the culprit.
So, I find a spot between two batteries (on a fusible link) that
reads less than 1V to the chassis. The rest going away from it
increment by 6v. Seems sane enough. So I remove the connectors on
the far ends of the batteries connected to the fusible link, thus taking
them out of the circuit. (The intention was to bridge the gap
eventually with a jumper cable and 'prove' that this was the short.)
The GFI still trips. Is this right?! If the short to ground
was anywhere on those two batteries, shouldn't the circuit
be so wide open that the GFI can't trip?
Could I have.. two shorts to ground?! What am I doing wrong here?
Is it just because my garage is built wrong and collects water?
Thanks!
WB
--- End Message ---
--- Begin Message ---
That is not *simultaneously*, and you previously wrote that you observed
the voltages during the *bulk* phase. If you log the module voltages of
a *healthy* pack, you will observe that they remain quite well clustered
until you swtich to constant voltage. During constant voltage, you will
observe that the module voltages not only vary more significantly, but
they also move around; i.e. a module that is high one moment may be the
lowest in the string a few moments later.
*nod* That is indeed possible.
If your pack of 50 new Hawkers exhibited significantly differing
voltages while in the initial constant current bulk phase, then they may
not yet have been balanced (despite what your testing suggested), or
there may be an issue with the design of the pack wiring impacting the
division of the voltage and/or current through the modules. A healthy,
reasonably well-balanced pack will not exhibit significantly differing
module voltages before the end of bulk.
Actually I did a quick spot-check when the pack was new before bolting
it up, and they all did have pretty much the same voltages under charge
at particular points in time. When I dropped the pack after a year
though they were all dry and in various states of unhappiness.
Your experience suggests that you typically cycle your pack shallowly
and that your packs have died prematurely as a result of having been
vented...
*nod* That's actually probably the cream of the crust; most of my
driving is shallow discharge, thus every time it would fly up to 375
volts, then sit there roasting then of course the 50 minute "finish
charge" at 390 volts and .1 amps. Quite possible that contributed to the
roasting.
I am happy to read what you write, but must, unfortunately, wait for you
to write it ;^>
Drat. Sorry about that, thought I mentioned it before. My apologies.
No; Hawker specifies constant current to 14.7V/module: 367.5V. 375V is
15V/module. 375V may indeed be a bad idea, but it is not something
Hawker recommends as part of their IUI algorithm.
I'll have to look around; somewhere in my life I picked up the 375 volts
even though I also saw the 14.7 volt numbers.
I would be concerned that this is too much current at too high a voltage
for too long, and will contribute to excessive venting and premature
failure of your pack.
Hm. How so? Should I back off on the bulk charging voltages?
If you were charging at Hawker's C/3 min rate, about 17.3A for your 52Ah
pack, then the bulk phase would take about 38min, and so Hawker's IUI
algorithm would recommend spending a *maximum* of 19 minutes in the
final constant current phase where the voltage is allowed to peak at
15.6V/module. 50min is too long, in my opinion. 2.5A is 0.05C for a
52Ah battery, however, since you cannot ensure that the current will
divide equally between your two parallel strings, this is an unsafe
level of current to allow the batteries to see at these elevated
voltages (i.e. > 14.7V/module); just my opinion, but I would not go
much, if any, higher than the 0.05C value for one of your 26Ah strings:
1.3A.
*nod* The Dolphin seems to have a linear ramp-down once the pack voltage
goes above 350 or so. At 390 volts it's typically under 1 amp total so
it's around .5 amps per string. Is that too much, or too long?
I wish you all the best with your pack and look forward to hearing how
it fares.
Thank you. I think that installing the LED battery monitor in the spring
is going to tell me a lot more facts about what is happening in the
pack. I will finally be able to see for all batteries at the same time*
when they drop below 11.0 volts, when they come to 14.7 volts, and when
they start whacking into the 15.6 volt limit. If I'm on bulk charge and
I see some of the lights going green or yellow I know I have a problem.
I'll also feel more comfortable cranking the MC up to it's full power
knowing that if I see 350 volts on the E-meter and green lights
everywhere I need to adjust my setpoints down.
Thanks for the thoughts. This is a learning experience, no doubt.
Chris
* (well, the time will be slightly different since the speed of light
dictates that the LEDs closer to my eye will appear to me to come on
before the LEDs further away from my eyes, but I think that will be a
minimal source of error)
Cheers,
Roger.
--- End Message ---
--- Begin Message ---
Here's a good pic of a 4x4 S-10 frame, motor, and running gear:
http://www.free-image-host.org/images/616336865s10_chassi2.jpg
I'd have the ICE power the front wheels and the electric power the back.
--- End Message ---
--- Begin Message ---
Hi Sam and All,
--- [EMAIL PROTECTED] wrote:
> Was reading a post the other day from... I believe
> Jerry Dycus but could be
> wrong... and he said that if you put two electric
> motors in series, you'd get
> twice the torque because the current has to series
> through both of them.
Yes, it was me. I said it as it's a way to reduce
peak amps needed so to get faster pickup without
straining the batts.
And as so many have said so well, I'll try to
explain it another way.
With the two motors in series, you get twice the
torque up to 1/2 the rpm, then you need to increase
the voltage or switch them to parallel to keep on
accelerating.
But comparing DC series motor torque, hp to an
ICE's isn't fair as the series puts out 5x the rated
hp and 9x the torque as it gets up to speed.
Torque is turning force.
So lets say you have 2 - 36vdc, 125-150 amp,
3,000rpm motors.
Add to that 72vdc pack of T125's for 720 lbs and
another 780 lbs of car, like a kit car or custom made.
T125's can put out 800 amps with their lower purkeut
and higher cap.
Most of the EV's here are conversions that carry
much excess weight so need even more batts and
overload them more.
But if you go the right, lightweight way with say
a GT-40 body and a bug or porshe chassis or better a
full composite unibody with a low frontal area, CD
then you can get both very good acceration, range
with GC batts.
At 1500 lbs, Cd of .25, frontal area of 14sq', a
72 vdc pack would get you about 100+ usable miles at
60 mph and around 130 miles at 50mph.
Lets look at how to get the acceleration.
First is low drag and weight. Being 1/2 the
weight, 1/2 the drag of most conversions mean much
less power is needed.
Then use the 2 motors from above and a contactor
controller for high amps.
Starting would be at 36vdc, 1,000 amps thru 2
motors in series. That's about 100ft-lbs each and
since the batts are in parallel at 36vdc, they only
see 500 amps each, a breeze with these batts.
Next, at 1,000rpm about, hit the batts to series
for 72vdc and the amps surge again to about 800 amps,
160ftlbs until about 2,000 rpms where you parallel the
motors, again it hits 800 amps, driving you forward to
about 4,000rpms, then hit field weakening to
6,000rpm's.
This sould get you about 10sec from 0-60mph.
Anyone want to run it thru the calculator?
So if you design it as an EV you can get good
power and range from GC batts. If you convert an ICE
you may end up with a slow lead mine at a high costs.
Where as the above EV setup including batts,
charger, motors, controller can be had for under $1500
if some surplus.
And can be put in many light, more aero cars like
the Ghia, Fastback MR2's, early RX-7's, ect at some
lost in range from higher weight.
While there is no free lunch, it can be cheap!!
Doing this way will cost you about $.06-.12/mile
total!! That's cheaper than buying gas alone!!!
HTh's,
jerry dycus
>
> Certainly I agree that the current has to series
> through both, since it is a
> series connection. In fact, I don't *disagree* with
> anything he said because
> I don't know enough to agree or disagree. My
> question is this: As Greenspan
> said the other month before Congress, "the free
> lunch has yet to be invented."
> There is no free lunch, and my studies in physics
> has taught me this. What
> are you giving up to get "twice the torque?"
__________________________________
Do you Yahoo!?
Yahoo! Mail - You care about security. So do we.
http://promotions.yahoo.com/new_mail
--- End Message ---
--- Begin Message ---
So you have a cold unheated garage which you say collects water.
Water probably condenses on and penetrates everything and makes
a jillion leakage current paths to ground. I think
you need to move the Rabbit to a dry location and get everything
clean and dry.
----- Original Message -----
From: "W Bryan Andrews" <[EMAIL PROTECTED]>
To: <[email protected]>
Sent: Tuesday, December 28, 2004 5:51 PM
Subject: Tracking down shorts from battery pack to ground
First of all, I wanted to thank everyone who's answered my newbie
questions in the past. Here's the latest:
It's winter in the midwest .. pretty consistent below-freezing weather
and my garage is unheated. My rabbit had at first become temperamental
about charging, and now flat out refuses to.
The charger's GFI trips every time I try to plug it in.
I've taken the wires that lead from the charger to the battery
pack and sure enough, they read as they should.. somewhere in the
100-something volt range.
So, I believe the implication is that my battery pack is somehow
shorting to ground. The proper procedure here is (I think) to
run around the battery pack and measure the voltage to ground.
Lowest voltage being the culprit.
So, I find a spot between two batteries (on a fusible link) that
reads less than 1V to the chassis. The rest going away from it
increment by 6v. Seems sane enough. So I remove the connectors on
the far ends of the batteries connected to the fusible link, thus taking
them out of the circuit. (The intention was to bridge the gap
eventually with a jumper cable and 'prove' that this was the short.)
The GFI still trips. Is this right?! If the short to ground
was anywhere on those two batteries, shouldn't the circuit
be so wide open that the GFI can't trip?
Could I have.. two shorts to ground?! What am I doing wrong here?
Is it just because my garage is built wrong and collects water?
Thanks!
WB
--- End Message ---
--- Begin Message ---
<< Used the following formula to calculated the motor RPM for a given speed:
...or give your calculator a break and plug some numbers into this calculator:
http://www.4qd.co.uk/faq/roadspd.html
Also useful: http://www.4qd.co.uk/faq/current.html
--- End Message ---
--- Begin Message ---
On 28 Dec 2004 at 20:58, Chris Zach wrote:
> > I would be concerned that this is too much current at too high a voltage
> > for too long, and will contribute to excessive venting and premature
> > failure of your pack.
>
> Hm. How so? Should I back off on the bulk charging voltages?
Christopher, reread the thread to date! You've missed an important point.
Within reason, you can pretty much whack AGMs with any voltage and
current you want during the bulk phase. In fact, if you watch out for excessive
heat, you can even pump in UNreasonable amounts of current - in the
hundreds of amps.
It's during that last 20% of the charge that you need be concerned - and with
CURRENT more than voltage. Once a given cell is above the gassing
voltage, the more current that you give it, the more it gasses. If the gassing
is slow enough that the recombination reaction can keep up with it, all is
well. But if the current gets too high and the gassing exceeds the ability of
the recombinant reaction to turn the H2 and O2 back into water, the gas
pressure builds up. Then it has to be vented or the battery will explode.
That's the hissssssing or ticking sound you hear (or would if you could get
close enough to those buried modules). It means your battery is losing
moisture.
>
> *nod* The Dolphin seems to have a linear ramp-down once the pack voltage
> goes above 350 or so. At 390 volts it's typically under 1 amp total so
> it's around .5 amps per string. Is that too much, or too long?
>
Again you have missed a crucial point here. No, it is NOT around 0.5 amps
per string. You can't be sure that one amp from your charger is dividing
equally between the parallel strings. It's quite possible that 0.99 amps is
flowing through one string, and 0.01 amps through the other. The charger
should limit the equalization current to no more than the value that's
acceptable for ONE string.
= = = = =
Two packs, going on three. These are expensive lessons, aren't they? Been
there, done that, still learning. IMO, it sure would be nice if we could just
lease and maintain battery boxes with chargers and BMSes built into them.
That way we could pay somebody (presumably knowledgable) to ensure that
the charge algorithms were correct, that the battery was always meeting its
minimum specs, and that it was properly fixed if/when it wasn't.
--- End Message ---
--- Begin Message ---
Hi Lee,
Someone (I think it was you) mentioned the possibility of using a
controller as a DC/DC. What would be involved in powering the
vehicle solely with an AGM pack and a Zilla, and using a pack of
flooded batteries and a cheap controller (i.e. Curtis) to charge
the AGM pack?
You could limit the current draw on the floodies to that needed
to maintain freeway speeds (125-175 amps?), so there's no
net drain on the AGM pack except when accelerating, and the
AGM pack gets recharged as the vehicle slows or sits.
Could this be done with a Curtis controller, say, with a micro
controlling a potentiometer so the Curtis thinks it's controlled
by a potbox? Regs on the AGM pack could signal the micro to
turn down the juice on the Curtis as the AGM pack gets full,
and you could even program the micro for an occasional
equalizing charge.
I'd love to do a lead sled; maybe a pack of Orbitals under the
bed, and the bed full of floodies. Keep the overall vehicle
weight near that of Red Beastie, but have the acceleration
when I needed it.
Tim
--------
> Date: Tue, 28 Dec 2004 10:46:46 -0800
> From: Lee Hart <[EMAIL PROTECTED]>
> To: [email protected]
> Subject: Re: More EV ideas
>
> No, it's not a bad idea at all! It's been proposed before, and even
> tried on occasion. I just don't think we've seen any experimental
> results to say how well it works, and what surprises it holds.
>
> The key challenge is that now you have two packs. This means two
> chargers, two monitors (E-meters or equivalent), and two controllers (or
> other means to decide which pack supplies power). This gets expensive.
__________________________________
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--- Begin Message ---
If anybody here plans on bringing an EV, please let the list know. Vegas
is only a couple of hours away for me, and I'd love to attend if the EV
turnout is good. (Otherwise, I'll save up for the next Woodburn.) :-)
Thanks.
Tim
--------
> From: "Chip Gribben" <[EMAIL PROTECTED]>
> To: <[email protected]>
> Subject: NEDRA Wicked Watts February 4-6, 2005!
> Date: Tue, 28 Dec 2004 09:21:06 -0500
>
> NEDRA will kick off the 2005 season with Wicked Watts February 4-6, with our
> main event on
> Saturday, February 5. So get your EVs ready for 3 days of fun-filled racing
> at the Las Vegas
> Speedway.
>
> Brigham Young University will be there with their ultra-capacitor powered
> EV-1, Brian Hall from
> Thunderstruck Motors plans to race and many more plan to come out for this
> exciting event.
>
> Richard Furniss and the Las Vegas Chapter of the EAA will be organizing the
> event.
>
> DATES AND TIMES
> Friday, February 4 - Gates open at 8:00 am. The track will be closed in the
> evening
> Saturday, February 5 - Main Event. Gates open 8:00 am for a full day of
> racing.
> Sunday, February 6 - Gates open at 8:00 am. For those who can't get enough.
>
> For more information contact Richard Furniss at [EMAIL PROTECTED], the Las
> Vegas EVA website at
> http://www.lveva.org and the NEDRA website at http://www.nedra.com
>
> We are looking for sponsors for this race and other races for the 2005 season.
>
> Dates for the rest of the 2005 schedule including Power of DC and Woodburn
> are in the planning
> stages and will be available soon. We are looking at a possible date in July
> for Woodburn and a
> date in June for Power of DC.
>
> Chip Gribben
> NEDRA Webmaster
> http://www.nedra.com
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--- Begin Message ---
Jamie Marshall (GAMES) wrote:
> So if this lower SOC is only apparent, how does it affect lifespan?
> Will drawing 20 amphours 100 times from a cold battery kill it faster
> than drawing 20 amphours 100 times from a warm one?
These are hard questions, and not amenable to simple answers. It's like
asking, "If I smoke 1 pack a day for 10 years, will I die of lung
cancer? How about 2 packs a day for 5 years?" You can't get a definitive
answer. We just know that the damage from smoking is cumulative; the
more you smoke, the greater your chances for damage. And we know that
above some threshold (say, 10 packs a day for 1 year) you are almost
certain to go over the line and die far sooner.
It's the same with batteries. Every little stress causes a little
damage, and so shortens their life a little bit. When the cumulative
stress gets high enough, it dies. We can't predict exactly how much
stress it takes for any given battery; we can only make statistical
predictions and take educated guesses.
In general, lead-acid batteries are "cold blooded". The colder they get,
the worse they work. If I had to guess, I'd say discharging to 20% SOC
at 70 deg.F is equivalent to 50% SOC at 30 deg.F, or 80% SOC at 0 deg.F.
Discharging it deeper than these levels at these temperatures carries a
big risk of rapid damage to the battery.
--
"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
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--- Begin Message ---
Dave Cover wrote:
> Ok, dumb question from a non EE. You have a heater core (big
> resistor meant to get hot) and it works the same on AC or DC?
> Voltage is voltage?
That's correct. A resistor works the same on AC or DC. When you see
something specified as "120 volts AC", it means "the AC voltage that
just happens to produce the same heating effect in a resistor as 120
volts DC".
If you want to get technical, "120 volts RMS" is exactly the same as
"120 volts DC". RMS means "root-mean-square", a mathematical process
that takes into account not only the fact that it is AC, but also the
waveshape of the AC waveform.
--
"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 ---
W Bryan Andrews wrote:
> It's winter in the midwest... pretty consistent below-freezing
> weather and my garage is unheated. My rabbit had at first become
> temperamental about charging, and now flat out refuses to.
> The charger's GFI trips every time I try to plug it in.
Ground faults can be a real challenge to find. Sometimes it is a single
point that has a bit of debris, dirt, battery acid, corrosion, or
whatever to ground. Other times the entire pack has gotten wet or dirty,
leading to a large number of small ground faults.
Can you clean the tops of your batteries? You may just have accumulated
enough "gunk" to be causing ground faults. Wash them off with baking
soda, then distilled water. You may have to put a heat lamp or other
heat source on them to get them to dry out.
When the simple methods of find a single (or just a couple) ground
faults don't work, you may have to start by connecting as few
parts/batteries as possible, and add them one at a time until you get
the fault.
--
"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 ---
Disconnect the load end of the most positive and most negative batteries.
Turn on the charger.
If the GFCI trips, the problem is not in the pack. It is elsewhere in
the car.
If the GFCI holds, then add one battery at a time until the GFCI trips.
The last battery added (before the trip) produced enough fault current to
cause the problem. Clean it and see if you can add the additional batteries.
Joe Smalley
Rural Kitsap County WA
Fiesta 48 volts
NEDRA 48 volt street conversion record holder
[EMAIL PROTECTED]
----- Original Message -----
From: "Lee Hart" <[EMAIL PROTECTED]>
To: <[email protected]>
Sent: Wednesday, December 29, 2004 12:38 AM
Subject: Re: Tracking down shorts from battery pack to ground
> W Bryan Andrews wrote:
> > It's winter in the midwest... pretty consistent below-freezing
> > weather and my garage is unheated. My rabbit had at first become
> > temperamental about charging, and now flat out refuses to.
> > The charger's GFI trips every time I try to plug it in.
>
> Ground faults can be a real challenge to find. Sometimes it is a single
> point that has a bit of debris, dirt, battery acid, corrosion, or
> whatever to ground. Other times the entire pack has gotten wet or dirty,
> leading to a large number of small ground faults.
>
> Can you clean the tops of your batteries? You may just have accumulated
> enough "gunk" to be causing ground faults. Wash them off with baking
> soda, then distilled water. You may have to put a heat lamp or other
> heat source on them to get them to dry out.
>
>
> When the simple methods of find a single (or just a couple) ground
> faults don't work, you may have to start by connecting as few
> parts/batteries as possible, and add them one at a time until you get
> the fault.
> --
> "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 ---
You can make a fault current adapter for your meter. This consists of a
current transformer with multiple wraps of wire on it to measure the common
mode current in the supply wires. Wrap 10 turns of black and 10 turns of
white wire through the current transformer. Do not put the green wire
through the transformer. Feed one end of the pair from the line and connect
the load to the other end of the pair. Connect the secondary of the
transformer to a 1K resistor. Connect your AC voltmeter across the resistor
to read the fault current. As you add more batteries, the fault current will
increase until the GFCI opens. When the GFCI opens, you exceeded the
allowable fault current. As you add parts, you can measure the contribution
of each component. Once you have an inventory of the leaks, go after the big
ones first.
Don't forget to disconnect any DC motors. The carbon in them is known to
cause GFCI problems.
Joe Smalley
Rural Kitsap County WA
Fiesta 48 volts
NEDRA 48 volt street conversion record holder
[EMAIL PROTECTED]
----- Original Message -----
From: "Lee Hart" <[EMAIL PROTECTED]>
To: <[email protected]>
Sent: Wednesday, December 29, 2004 12:38 AM
Subject: Re: Tracking down shorts from battery pack to ground
> W Bryan Andrews wrote:
> > It's winter in the midwest... pretty consistent below-freezing
> > weather and my garage is unheated. My rabbit had at first become
> > temperamental about charging, and now flat out refuses to.
> > The charger's GFI trips every time I try to plug it in.
>
> When the simple methods of find a single (or just a couple) ground
> faults don't work, you may have to start by connecting as few
> parts/batteries as possible, and add them one at a time until you get
> the fault.
--- End Message ---
--- Begin Message ---
Comments inserted...
----- Original Message -----
From: "Lee Hart" <[EMAIL PROTECTED]>
To: <[email protected]>
Sent: Tuesday, December 28, 2004 11:36 AM
Subject: Re: Motors in series? Torque vs. power?
> Joe Smalley wrote:
> > There are four brushes alternating positive and negative around the
> > commutator. All four quadrants of the armature are in parallel.
> > The best I can imagine would be to change the polarity of two field
> > poles to make it a two pole motor and then use only one pair of
> > opposing brushes.
>
> I don't think that would work very well. There are in effect 4 armature
> coils. They are wired in a square, with a brush at each corner. Going
> around the square, the brushes are + - + -. When powered, this structure
> generates 2 north and 2 south poles. Thus, the field has to provide a
> matching 2 north and 2 south poles.
Concur.
> Off the top of my head, I think if you connected power to only the
> diagonal two + brushes (making one + and the other -), you'd have 4
> times the armature resistance. The poles on its surface would be N N S
> S. If you rewire the 4 field coils to produce the same poles (N N S S),
> it should run as a 2-pole motor, but with a badly designed pole shape
> (there would be a "hole" in the center of each N-N and S-S pole where
> the peak field strength should be), and with twice the normal winding
> resistance. So it would be a rather inefficient motor.
A four pole motor is actually four segments that produce torque. Since each
of these quadrants is consuming 1/4 of the amps and runs off the same
terminal voltage, the segments can be arranged in two stacks of two in
series rather than four in parallel. It is not like the field that can be
wired in either four in series, four in parallel or two high by two wide.
If the motor had a back EMF of one ohm per 1000 RPM, each quadrant of the
motor would have a back EMF of four ohms. By putting the quadrants in a two
by two arrangement, the back EMF would be eight ohms in parallel with eight
ohms for a back EMF of four ohms total.
Since each quadrant of the armature is drawing 1/2 the total amps instead of
1/4 the total amps, the torque would be doubled for the same current.
Overall, the motor speed would drop by a factor of four to draw the same
current.
>
> But, you *could* wire the 4 field poles in parallel, series, or
> half-parallel, half series. The stock setup (all in series) provides the
> lowest speed per volt and highest torque per amp. Half-series and
> half-parallel is equivalent to 50% field weakening, and is faster per
> volt, and less torque per amp. All fields in parallel would be
> equivalent to 25% field weakening, even faster per volt and less torque
> per amp.
>
> It's usually easier to accomplish this with an external field weakening
> resistor (far fewer connections).
Agreed. The brush rigging wiring would need to be changed as well as the
field. It takes only half the parts to do just the field.
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--- Begin Message ---
At 4:34 AM -0500 12-28-04, [EMAIL PROTECTED] wrote:
Okay, that was my suspicion, basically. "There is no free lunch" so to
speak, so the power is the same.
I agree.
But if the power is the same, then what's the difference?
.......
"then why bother setting up two motors in series in the first place?"
What everyone seems to be missing is the reason I run two motors.
I get twice the brush and commutator area.
Who cares about poles, windings and torque? Ratios make up for all of
that. It's all just electrical gearing. Amps and volts are good to
look at in some cases, but drag race power is usually limited by the
batteries, brushes and commutators.
I'm running two motors so that I still have commutators and brushes
left to get me back to the pits at the end of the 1/4 mile.
Yes, the "gear shift" of switching series parallel helps keep things
simpler since mechanical shifting is no longer required (if the
controller is large enough), but it's commutation capacity that makes
the race.
Just my 2 rupees,
--
-Otmar-
9-11 was chump change compared to the Sumatra quake, please consider
helping as you can. In the US, his fraudulency sent a drop in the
bucket.
http://www.msf.org/ is an option I chose.
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