EV Digest 6806
Topics covered in this issue include:
1) Re: Low cost battery materials
by Lee Hart <[EMAIL PROTECTED]>
2) Re: Low cost battery materials
by Lee Hart <[EMAIL PROTECTED]>
3) Re: desulfating.... 2 at a time?
by Lee Hart <[EMAIL PROTECTED]>
4) Re: Triangle wave generator
by "(-Phil-)" <[EMAIL PROTECTED]>
5) Re: EV digest 6805
by Chip Gribben <[EMAIL PROTECTED]>
6) Re: Best Conversion Vehicle
by "Peter VanDerWal" <[EMAIL PROTECTED]>
7) Re: Using Audio Capacitors for Dragsters
by "Peter Gabrielsson" <[EMAIL PROTECTED]>
8) Re: Reality check, Re: Permanent magnet motor question
by "Peter VanDerWal" <[EMAIL PROTECTED]>
9) Re: Reality check, Re: Permanent magnet motor question
by Victor Tikhonov <[EMAIL PROTECTED]>
10) Re: Reality check, Re: Permanent magnet motor question
by [EMAIL PROTECTED]
11) Re: Triangle wave generator
by tt2tjw <[EMAIL PROTECTED]>
12) Re: Triangle wave generator
by tt2tjw <[EMAIL PROTECTED]>
13) RE: Reality check, Re: Permanent magnet motor question
by "Claudio Natoli" <[EMAIL PROTECTED]>
14) Re: How regen works
by tt2tjw <[EMAIL PROTECTED]>
15) Re: How regen works
by "(-Phil-)" <[EMAIL PROTECTED]>
16) RE: Best paint for Battery racks
by "midiguy732" <[EMAIL PROTECTED]>
17) Re: Best Conversion Vehicle
by "Mark Ward" <[EMAIL PROTECTED]>
18) Ni-Cad Final Taper
by "Mark Hanson" <[EMAIL PROTECTED]>
19) Re: Building a Variable Voltage, High Current Batt Charger
by Steven Ciciora <[EMAIL PROTECTED]>
--- Begin Message ---
GWMobile wrote:
Interesting idea about recovering the cost through the gold investment
however I was thinking of perhaps cheaper cathodes and anodes.
Most batteries make the plates out of the base metal that forms their
electrodes. They have an excess of metal so it won't use up all its
plate material even if run completely dead or seriously overcharged.
If you make the plates out of some other metal, you'll have to pick one
that won't enter into the electrochemical reaction itself. For example,
I worked with silver-zinc batteries. To minimize the amount of silver,
the plates were made of silver-plated stainless steel. When you totally
discharged the battery, all the silver was used up and there was a
sudden drop in voltage as the steel took over the (and it became a
steel-zinc battery).
There have been some lead-acid batteries with materials other than lead
for the supporting plate. Fiberglass and carbon fiber are two that come
to mind.
--
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 ---
Phil Marino wrote:
When I was a kid, I made a battery from a potato.
The potato just provides the electrolyte (basically water). It does not
enter into the reaction; whatever two metals you poke into it (like a
copper penny and a steel nail) are the actual working electrodes.
To make a good battery, you need to find ways to a) make the plates have
as large a surface area as possible, b) position them as close as
possible without actually touching, and c) put some ionic conductive
liquid between them that can carry the ions across and circulate without
adding resistance.
For instance, a penny is a terrible shape; you barely get 1 square inch
of area. Pound the same amount of copper out into extremely thin foil,
and you can get 100 times the area.
The iron nail is likewise a terrible shape. Unfortunately, iron won't
form to as thin a foil as copper. But you can powder the iron into
filings, and sinter it (pressure weld it back together) to form a
sponge-like mass.
Now put pieces of tissue paper between these two plates, so they are
spaced very close. Put it in an electrolyte that is a good conductor but
won't corrode either copper or iron (like lye = potassium hydroxide).
Now you have a usable battery! But, it's no longer simple to make.
--
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 ---
Mike Willmon wrote:
If flooded batteries have built up enough sulphate on the plates,
will it cause it not to come up to its normal charge voltage? I have
been typically equalizing once a month but when this last equalize
came due the pack never reached its regulation voltage. All the
batteries averaged pretty close to a 7.02V but would not go over.
Now it seems like the max voltage they get up to is slowly going
down. How can I get them back up to an equalize voltage?
As the batteries age, their end-of charge voltage gradually falls, their
end-of charge current gradually rises, and their amphour capacity slowly
drops. Barring abuse, this is normal, inevitable, and not reversible.
If your charger blindly tries to bring old batteries up to the same
voltage or current as new ones, it will charge too long, and so
overcharge them.
So, the best charging algorithms for old batteries are ones that count
amphours, or look for the voltage to stop rising or for the current to
stop falling.
The change in characteristics with age are not due to "sulfation". They
are due to the slow changes in the shape and size of the active material
crystals, antimony migration, impurities being selectively deposited on
the surfaces of the plates, from active material that has fallen off the
plates and drifted to the bottom of the case, and from the warping and
grid corrosion that slowly progresses from many charge/discharge cycles.
--
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 ---
Watchdogs mainly protect from software exceptions.
A properly designed support circuit makes the electrical environment
non-hostile. Electric cars are not as hostile as say an ICE with a 50kv
spark dancing around! You can install a separate supply for the MCU in an
EV that's gavlanically isolated. That stops most of the problems.
Most controllers on the market are now MCU based. There's a reason. To me
designing with Op-Amps is much more difficult! You still have all the
analog drive issues in the output stage, PLUS in the front end as well!
If you use a driver IC, they can be scaled up with the MOSFETs as well.
More drivers, maybe even one per FET if need be. There are plenty to
choose from. There are even some "power modules" on the market that take
TTL in and do their own driving. Both IGBT and MOSFET. You can Drive them
directly from an optoisolator output that comes off your micro. Not as
cheap, but much more tolerant and robust for a first design.
I'm not suggesting someone go build a controller without having extensive
electronics experience. It's not a simple do-it-yourself project, but it's
far from impossible!
I think a collection of us could work together on an open design, and that
would be a fantastic project!
-Phil
----- Original Message -----
From: "Lee Hart" <[EMAIL PROTECTED]>
To: <ev@listproc.sjsu.edu>
Sent: Tuesday, May 22, 2007 7:38 PM
Subject: Re: Triangle wave generator
(-Phil-) wrote:
Most microcontrollers have watchdogs.
Yes; and some of them actually work! But most are a band-aid; they only
matter *after* something has gone wrong.
You have to know a lot about the micro, what triggers its watchdog, and
what sorts of thing can defeat it. Usually, it works by resetting the
micro if the software fails to do something every so often. But reset
won't work if the chip is damaged, is latched up from noise, if its clock
oscillator has stopped, etc.
Lockups just don't happen unless you subject them to electrically
hostile environments.
And an electric car is one of the most hostile environments there is!
(provided you don't have buggy software, that is!)
Software bugs are a fact of life. *Every* program has bugs. One-off
programs written by amateurs or beginners are especially likely to have
them.
Best advice is to use an off-the-shelf MOSFET driver chip.
You'll find that off-the-shelf driver chips don't have sufficient gate
drive for the very large MOSFETs or IGBTs. They are made mainly for much
smaller mass-produced controllers.
When you start out, build a test bed with a small motor and a
current-limited supply. Run the MCU off a totally separate power supply.
Then get your software right. Once that's done, you can
scale up the design by adding more MOSFETs in parallel. Remember
to make sure your gate drive circuitry is up to the task. MOSFET
gates have high relative capacitance, so to switch them fast enough
to not be a problem, sometimes that involves several peak amps!
(don't switch TOO fast though!)
Good advice! PS: you'll find that even a small controller needs several
amps of gate drive. A large controller needs 10's of amps of peak gate
drive current.
--
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 ---
Like I mentioned, try powder coating.
It takes a bit more prep. The parts should be sandblasted first. But
once it's done, its the first and only time you'll need to finish
them unless you get bored of the color.
If you do black, the powder coating shops will put the pieces in with
their run of other black parts. Mine went in with some elevator parts
that were being powder coated that day.
The owners of the shop were really cool and gave me a tour of the
place and told me that battery acid would have absolutely no ill
affects on the powder coating. After 8 years they are right. Nada.
Not even a blemish on the racks. No corrosion, no rust. Nothing.
Grease and oil wipes right off too.
If you are doing a show car powder coating is perfect. But I think
its the best way to go to prevent battery corrosion on your racks.
Chip
On May 23, 2007, at 12:57 AM, Electric Vehicle Discussion List wrote:
From: Lee Hart <[EMAIL PROTECTED]>
Date: May 22, 2007 10:42:48 PM EDT
To: ev@listproc.sjsu.edu
Subject: Re: Best paint for Battery racks
Michael Barkley wrote:
Do you recall what particular product you used in
this test?
At the time we tested the bedliner material, it was
some that NAPA was selling in gallon containers. Now
they along with others have the bedliner material in a
spray can, which is much easier to use. Put at least
two coats of it on the area or item, you want to
protect.
I'm sure this was a good expedient solution. But, do you actually
know what that bedliner material is? Sulfuric battery acid can be
very hard on materials. It might be worth contacting the
manufacturer to find out if it really will withstand battery acid
for any length of time.
--- End Message ---
--- Begin Message ---
914's and VW Ghia's make very efficeint EVs, however, both of these
vehicles are aprrox 30 years old and getting parts can be expensive.
While there is no "BEST" vehicle for a conversion, there are some general
guidelines. All of which can be ignored for a number of reasons.
1. The vehicle should have readily available spare parts. This generally
means a fairly common vehicle that is only 10-15 years old.
2. Should have a fair amount of useable space to put batteries in.
3. Should have a GVWR that is at least high enough for the vehicles
projected finished weight.
4. (IMHO the most important) it should be in good condition. There is no
sense in starting out with a junker, that you got for free, if you have to
put $3,000 into fixing it up BEFORE you convert it. Unless you like the
idea of driving a junker EV.
There are plenty of good vehicles that meet the first three criteria and
cost less than $1,000. Sell of some of the excess parts (ICE, Radiator,
Gas tank, etc.) and you might recover all or more than you paid for the
vehicle.
>
> I have been lurking for awhile and I too am considering an electric
> vehicle. If the 914 is not the best convert then what is? I am not
> a mechanic, so a kit sounds good to me!!!! Dan Whitley
>
>
>
>
> I used to own a 914 and they are great fun however there is one
> serious consideration to think about with them.
>
> Remember unless the goal is a science experiment you probably want a
> USEABLE electric car in the end. That means some storage space and
> maybe more than two seats.
>
> Alfter all is said and done you want a car that is functional. The
> only saving grace for a gas powered 914 which has NO back or space at
> all behind the front seats is the front and rear trunk (because the
> engine is right behind the seats so you have both a big front and
> back trunk)
> but when you add batteries in those trunks you no longer have that
> space.
>
> If you want an electric go cart for fun then a 914 is a great
> electric car.
>
> If you want a functional car that you can even put a few grocery bags
> in then an electric 914 is useless.
>
> It will have NO storage space. And only one other seat.
>
> It will seriously have NO Storage space. People really don't
> understand it until they use one for a while. There are NO nooks and
> crannies behind the seat - just a sheer firewall.
> Something to keep in mind.
>
> You would hate to spend all the time and money to make an electric
> only to realize you don't have a very day to day functional vehicle
> when you are finished.
>
> You won't save gas or the environement if it is a car you really
> won't drive.
>
> On Tue, 22 May 2007 11:05 am, Michael Wendell wrote:
>
>>
>>
>>> I was just looking at the www.electroautomotive.com site
>>>
>>
>> that link is http://www.electroauto.com
>>
>>
>>> ...and their AC kit is around 15k with batteries. After all
>>> the talk of what's available I'm begining to think that is a
>>> bargain. If you are a miser it will go 150 miles on the flat.
>>>
>>
>> i'm a lurker, still in the dreaming stage with this, but i didn't
>> realize
>> their kits had that kind of range. i'm hoping to have the time to
>> seriously
>> begin tinkering this fall.
>>
>> the 914 seems to be a somewhat popular conversion, and electro's
>> kit may
>> have something to do with that.
>>
>> while i like the 914, i've been wondering if the boxster might be a
>> better,
>> more modern equivalent. what does the list think, too heavy? i've
>> seen beat
>> up boxsters selling for reasonable prices on ebay, and i'd imagine
>> that
>> parting out the ICE equipment would yield a nice payback.
>>
>> thanks, i'll go back to lurking.
>>
>> m.
>>
>> Michael Wendell
>> Web/Graphics Guy
>> Speedgoat Bicycles
>>
>> 724.238.7181
>> [EMAIL PROTECTED]
>>
>
>
--
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 ---
Buck-boost motor controller
battery+_______/ __________|/|____________
switch | |\| | |
( diode | _|_
motor ( _|_ / \ motor
field ( capacitor ___ \___/ armature
| | |
battery-______________|____________|______|
On 5/22/07, Lee Hart <[EMAIL PROTECTED]> wrote:
Bill Dennis wrote:
> Interesting concept, Lee. You mention a freewheel diode. Is a
> freewheel still necessary in this setup? If I'm understanding your
> description correctly, the field winding will be sending its current
> either through the armature winding, or through the MOSFET to ground,
> and the armatue will always be getting its current from either the
> battery (through the field winding) or from the capacitors. If a
> freewheel diode is necessary, then why, and where does it go?
This type of boost controller uses exactly the same parts as a buck
controller; one switch, one diode, one capacitor, and one inductor. The
boost version is arranged like this (view with a fixed width font):
_ _ _
battery+____| | | |________|\|____________
motor | |/| | |
field | diode | _|_
| _|_ / \ motor
switch / capacitor ___ \___/ armature
| | |
battery-______________|____________|______|
The "switch" can be an SCR, transistor, MOSFET, IGBT, etc. The diode is
still necessary; it acts as a freewheel diode for the field inductance,
so current can flow continuously in it whether the switch is on or off.
Note that this type of controller has an advantage over a conventional
buck converter; if the transistors fail on (their normal failure mode),
it STOPS the motor and shorts the input power source (and hopefully
blows a fuse).
But, it has the drawback that the motor voltage can't be less than the
pack voltage, i.e. you need a contactor (not shown) to turn the motor
completely off.
--
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
--
www.electric-lemon.com
--- End Message ---
--- Begin Message ---
I believe you are experiencing a common mathematical falacy.
Reducing the losses by 1/2 is NOT the same as doubling the efficiency.
Anyway you slice it, 99% is approximately 5% more efficient than 94%
> FWIW, something 99% efficient is ~5 times more efficient than 94%
> efficient (while, yes, it's only 5% in absolute difference).
>
> To illustrate difficulty, to go from 99% to 99.5% you *double
> existing 99% efficiency. Add "just" 1% and you made something
> infinitely more efficient (100%)...
>
> Victor
>
> Lee Hart wrote:
>> (-Phil-) wrote:
>>> I don't believe a contactor controller can be much [more] efficient
>>> than PWM.
>>
>> Not "much" more efficient; but a *little* more efficient. Like I said,
>> 99% vs. 94%. That's only 5% better, which isn't enough to even notice
>> without careful measurement.
>
>
--
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 ---
Peter VanDerWal wrote:
Anyway you slice it, 99% is approximately 5% more efficient than 94%
Really? How do you figure? Is it because 94+5=99? I really want to know.
So what happens if I improve already 99% efficient design and make it
yet 5% more efficient [5% improvement of that 99% gadget]?
Of course it is very doable but according to you it will have to be
to be 99+5=104% efficient then, which is nonsense.
It's percentage of percentage Peter. Unless I misunderstood you, indeed
appears like common misconception but on your part. Please re-think
or elaborate.
Victor
--- End Message ---
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--- Begin Message ---
Thanks Danny,
>Yes, the power stage includes that
> and the power transistors themselves
I forgot to add capacitor and diode across the battery, and presumably a
precharge circuit for the same.
> Second, the PIC output pin cannot put out enough current to turn on
large MOSFETs quickly
If we are talking IGBT here (with a 15v turn on) and are using purpose
designed driver IC (VLA500 from powerex ) with its own internal DC-DC
to provide floating supply to driver the gate and with the driver ICs
mounted on a purpose designed board (BG2A, powerex) which includes
capacitors, diodes and 15v power supplies for each driver then most of
the problems (except switching losses) are covered?
If so it seems too easy, I thought PWM controllers were hard?
Do you think its the case that integrated driver circuits, driver boards
and dedicated power supplies are fairly recent so although PWM
controllers used to be hard they are becoming easier?
It seems to me (with no knowledge or experience) that the physical
aspects of a PWM controller, ie. weather proofing, cooling, bus bars
etc. are much harder than the IGBT drivers.
Tom Ward
Danny Miller wrote:
Yes, the power stage includes that- and the power transistors
themselves, of course.
A driver is necessary for several reasons. The 5V/0V from a PIC is
not high enough to fully turn on a MOSFET gate. 7v-10v or so is much
better.
Second, the PIC output pin cannot put out enough current to turn on
large MOSFETs quickly, the gate has too much capacitance. Higher
transition times result in much greater heat in the transistors (heat
originating from this cause is called "switching losses").
Third, to do the best job, some tuning the to driver's waveform is
sometimes needed to minimize switching losses. The sharpest square
wave from low-to-high may not be the best choice. Perfecting this
requires some detailed knowledge of transistors and usually we model
the transistor and driver in SPICE and observe the predicted behavior,
saves a lot over trial-and-error tweaking especially when you need to
test a circuit running on hundreds of amps.
Danny
tt2tjw wrote:
Danny,
by power stage do you mean busbars , cooling, mountings ?
by driver do you mean the IGBT driver? If a driver board such as BG2A
from powerex is used does that solve the "driver" problem or is the
"driver" problem more than just this?
Tom Ward
Danny Miller wrote:
You can design a lot of great features into a uC-driven motor
controller too. It's simple and easy to make them effective.
Still, a reminder- additional features are of limited use. The
primary problem is still the power stage and its driver. Having a
PWM generator 10x more advanced than an analog one won't do much to
reduce the problem. Well, advanced thermal shutdown procedures,
testing the ON-state voltage drop, and overcurrent detection can
reduce the demands on the transistors, but generally not a
remarkably high reduction, if any.
Danny
tt2tjw wrote:
Danny Miller wrote:
> It is far easier to design a system- and do it right- with a uC.
That was the impression I came to after reading many application
notes and reference designs (from IR, POWEREX, SEMIKRON, FAIRCHILD
etc) for intelligent IGBT modules, and IGBT drivers, they all seem
to be designed around a microcontroller.
Chet Fields wrote:
> it may not be a good idea as it may lock up and cause the MOSFETs
to be stuck on
the IGBT drivers I have looked at have integrated protection to
deal with this situation, I was assuming that in a mass produced
driver this function would be implemented correctly and reliably.
Danny Miller wrote:
That's pretty close to nonsense. IIRC the person claiming this
has no experience with microcontrollers.
A uC is a fine way to generate a PWM signal. It is far easier to
design a system- and do it right- with a uC. There's an awful lot
to designing an analog controller. The analog controller has a
lot more that can go wrong with it. You need a lot of inside
information on how each type of component may fail to start to
work the problems out.
It's important to understand however that being able to generate a
PWM is only a small part of the design problem for an EV
controller. The output transistors are large and expensive to
obtain and very tricky to mount where you can meet their extreme
thermal, mechanical, and electrical needs. The transistor driver,
where we take 0 to 5v or whatever PWM and turn it into a
transistor drive with the appropriate voltage level and best
waveform shape is tricky too.
Danny
Chet Fields wrote:
I had thought first of using a microcontroller, but then good
advice from the list suggested that
it may not be a good idea as it may lock up and cause the MOSFETs
to be stuck on. I don't really
know of a good way to protect from that happening except for
maybe some fuses or something.
I did think that a microcontroller like a PIC would give me alot
of flexibility though. I am a
programmer professionally so I would definitely be more in my
element instead of designing these
discrete analog circuits, although I have to admit it has been
and still looks like a lot of fun
if I can get it working.
I thought of starting with the analog and then moving later
(perhaps) into the PIC if I can come
up with the proper scheme to protect against a dangerous
situation with a lock up.
Chet
--- tt2tjw <[EMAIL PROTECTED]> wrote:
Chet,
is there any reason not to use a microcontroller with PWM outputs?
Chet Fields wrote:
I am trying to generate the triangle wave for the PWM circuit
and I am using the good ol' 741
Op
____________________________________________________________________________________
Looking for earth-friendly autos? Browse Top Cars by "Green
Rating" at Yahoo! Autos' Green Center.
http://autos.yahoo.com/green_center/
--- End Message ---
--- Begin Message ---
Lee Hart wrote:
You'll find that off-the-shelf driver chips don't have sufficient gate
drive for the very large MOSFETs or IGBTs. They are made mainly for
much smaller mass-produced controllers.
What about
this driver data sheet
http://www.pwrx.com/pwrx/docs/vla500_01.pdf
it states 600V up to 600A and 1200V up to 1400A
this is the board with 15v power supply to go with it
http://www.pwrx.com/pwrx/app/bg2a_univ_gate.pdf
or SKHI22B + PCB is more sophisticated and more expensive.
http://www.semikron.com/internet/webcms/online/pdf/SKHI21_22_A_B_H4.pdf
http://www.semikron.com/internet/webcms/online/pdf/SKPC_22-2.pdf
--- End Message ---
--- Begin Message ---
Hello all,
Victor, iirc this isn't the first time this has come up on the EVDL. Let's see
if we can put it to bed this time :-)
> > Anyway you slice it, 99% is approximately 5% more efficient than 94%
>
> Really? How do you figure? Is it because 94+5=99? I really
> want to know.
No, it is because (99-94)/94 =~ 5%.
> So what happens if I improve already 99% efficient design and make it
> yet 5% more efficient [5% improvement of that 99% gadget]?
>
> Of course it is very doable but according to you it will have to be
> to be 99+5=104% efficient then, which is nonsense.
No, what is (potentially) possible is to reduce the losses by a further 5%. In
any case, Peter did not make the claim that a further 5% improvement was
possible at 99%, so the second sentence is a straw man.
> It's percentage of percentage Peter.
This doesn't matter. Let's look at things at the other end of the scale.
Imagine that Company A produces 20% efficient solar panels. Company B makes an
announcement that their panels are now twice the efficiency of their
competitor. The vast majority of people would assume that this meant that
Company B's panels are 40% efficient. What would you say?
Cheers,
Claudio
--- End Message ---
--- Begin Message ---
(-Phil-) wrote:
My take is that as long as you aren't going down Lombard street in San
Francisco on a fully charged AGM pack, charging current during regen
is not too much of an issue.
Oh, from reading discussions on this list I understood that it could be
a big problem
this is from EVDL, Lee Hart 21 December 2006
4. I'm not sure whether these controllers would give regen (which
isn't a
big issue to me). If this does not give regen then would there be
a need
for cooling to dissipate heat in armature and/or field if the
throttle is
dropped without applying brakes?
With a shunt or sepex motor, you have to add parts to PREVENT regen. It
will naturally be there if you don't prevent it. With a large generator
as a motor, the amount of regen is really quite excessive, so you have
to limit it for safety's sake (to avoid skidding the driven tires, or
damaging the batteries from excessive regen current). With normal motors
not intended for use as generators, you need to limit regen to prevent
motor damage from brush arcing.
--- End Message ---
--- Begin Message ---
It's my understanding that regen and plug braking are 2 different things.
If you are doing a true regen and sending the energy into the batteries, it
will not build up much heat, if you simply short the motor, then you are
plug braking, and it turns all the energy into heat.
-Phil
----- Original Message -----
From: "tt2tjw" <[EMAIL PROTECTED]>
To: <ev@listproc.sjsu.edu>
Sent: Wednesday, May 23, 2007 2:30 AM
Subject: Re: How regen works
(-Phil-) wrote:
My take is that as long as you aren't going down Lombard street in San
Francisco on a fully charged AGM pack, charging current during regen is
not too much of an issue.
Oh, from reading discussions on this list I understood that it could be a
big problem
this is from EVDL, Lee Hart 21 December 2006
4. I'm not sure whether these controllers would give regen (which
isn't a
big issue to me). If this does not give regen then would there be
a need
for cooling to dissipate heat in armature and/or field if the
throttle is
dropped without applying brakes?
With a shunt or sepex motor, you have to add parts to PREVENT regen. It
will naturally be there if you don't prevent it. With a large generator as
a motor, the amount of regen is really quite excessive, so you have to
limit it for safety's sake (to avoid skidding the driven tires, or
damaging the batteries from excessive regen current). With normal motors
not intended for use as generators, you need to limit regen to prevent
motor damage from brush arcing.
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Spray in/on bedliners typically are resin polymers with some filler, the
filler being for texture to help the prevent the load from sliding, as
well as providing a non-slip surface to some degree. The best kind in
my opinion are the ones that the filler is most shreaded tire particles
- it provides enough flex that it's very difficult to chip off.
> -----Original Message-----
> From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]
On
> Behalf Of Lee Hart
> Sent: Tuesday, May 22, 2007 10:43 PM
> To: ev@listproc.sjsu.edu
> Subject: Re: Best paint for Battery racks
>
>
> I'm sure this was a good expedient solution. But, do you actually know
> what that bedliner material is? Sulfuric battery acid can be very hard
> on materials. It might be worth contacting the manufacturer to find
out
> if it really will withstand battery acid for any length of time.
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Pick something you really like and are passionate about. Some of the other
posts mentioned usefulness of the vehicle, but that is relative to your
needs, whether they be range, utility, performance, etc. Keep in mind that
converting a very common vehicle might be quick if there are already kits
available, but then you will have an EV that millions of other cars look
just like going down the street. So there is no "right" car or truck to
convert, even though some of the folks here will tell you otherwise. Some
are easier or cheaper than others to do. On that point I will agree. I
decided when I started my project 2 years ago (nearing completion now), that
I was going to have either a BMW or Saab with the features I wanted. I
could have gotten two Hondas, a Ford Taurus (free), and a 76 Beetle for less
than my 900, but I wouldn't have nearly as "lustful" a relationship as I do
now with my EV.
Finally, more than anything else you have to believe in your project, take
your time and be ready to do stuff over it doesn't work out.
Just my two cents worth
Mark Ward
95 Saab 900SE "Saabrina"
www.saabrina.blogspot.com
----- Original Message -----
From: "Dan Whitley" <[EMAIL PROTECTED]>
To: <ev@listproc.sjsu.edu>
Sent: Tuesday, May 22, 2007 5:30 PM
Subject: Best Conversion Vehicle
I have been lurking for awhile and I too am considering an electric
vehicle. If the 914 is not the best convert then what is? I am not a
mechanic, so a kit sounds good to me!!!! Dan Whitley
I used to own a 914 and they are great fun however there is one serious
consideration to think about with them.
Remember unless the goal is a science experiment you probably want a
USEABLE electric car in the end. That means some storage space and maybe
more than two seats.
Alfter all is said and done you want a car that is functional. The only
saving grace for a gas powered 914 which has NO back or space at all
behind the front seats is the front and rear trunk (because the engine is
right behind the seats so you have both a big front and back trunk)
but when you add batteries in those trunks you no longer have that space.
If you want an electric go cart for fun then a 914 is a great electric
car.
If you want a functional car that you can even put a few grocery bags in
then an electric 914 is useless.
It will have NO storage space. And only one other seat.
It will seriously have NO Storage space. People really don't understand
it until they use one for a while. There are NO nooks and crannies behind
the seat - just a sheer firewall.
Something to keep in mind.
You would hate to spend all the time and money to make an electric only
to realize you don't have a very day to day functional vehicle when you
are finished.
You won't save gas or the environement if it is a car you really won't
drive.
On Tue, 22 May 2007 11:05 am, Michael Wendell wrote:
I was just looking at the www.electroautomotive.com site
that link is http://www.electroauto.com
...and their AC kit is around 15k with batteries. After all
the talk of what's available I'm begining to think that is a
bargain. If you are a miser it will go 150 miles on the flat.
i'm a lurker, still in the dreaming stage with this, but i didn't
realize
their kits had that kind of range. i'm hoping to have the time to
seriously
begin tinkering this fall.
the 914 seems to be a somewhat popular conversion, and electro's kit may
have something to do with that.
while i like the 914, i've been wondering if the boxster might be a
better,
more modern equivalent. what does the list think, too heavy? i've seen
beat
up boxsters selling for reasonable prices on ebay, and i'd imagine that
parting out the ICE equipment would yield a nice payback.
thanks, i'll go back to lurking.
m.
Michael Wendell
Web/Graphics Guy
Speedgoat Bicycles
724.238.7181
[EMAIL PROTECTED]
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Howdy Folk's,
I was curious on my STM5-180's the manual says they will taper off charge
above 8V per battery (block is the French term). I'm trying to decide
whether or not to put more turns on the secondary of my ferro-resonant
transformer. It's tapering off at 1.66V per cell or 8.28V per battery which
may be a bit low. I think the TE-Van's were around 1.73V per cell or 8.65V
but that could be a bit high, not sure. The manual says to final taper
current at 7.5A but I think that's a bit much, I'm at C/40 4.5A and they gas
quite a bit. The new guy at Saft didn't know. Does anyone know what the
final taper voltage is typically on these flooded ni-cads?
See you at the June 3-7 Wind Expo in LA,
Have a renewable energy day,
Mark
_________________________________________________________________
PC Magazines 2007 editors choice for best Web mailaward-winning Windows
Live Hotmail.
http://imagine-windowslive.com/hotmail/?locale=en-us&ocid=TXT_TAGHM_migration_HM_mini_pcmag_0507
--- End Message ---
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You don't _have_ to charge A123 cells at 3A per cell,
what you described is just one way to charge them.
For the Killacycle, initially we just used (at the
track) a 6KW generator, one huge heavy variac, a
bridge rectifier, and (very important!) a volt meter
and clamp on ammeter. Our first BMS would start
flashing an LED as it started to bypass, and turned on
another LED when a warning condition was met (such as
one cell too high/low voltage, over temperature). We
would charge as fast as we dared (without tripping a
breaker or stalling the generator) until one cell
started bypassing, and then manually backed off the
charger until all cells were bypassing with no warning
LEDs lit. With a BMS, it did a very good job of
keeping each cell in ballance. We initially used the
big variac pretty much because that's what we always
did on lead batteries. After a while Bill started
taking his PFC-20 out of his wabbit and bringing it to
the track, and I'd bring my PFC-30. Now we usually
charge with the PFC-xx set at about 410V. Our current
BMS is a bit simpler. It still has two LEDs per cell.
A green one that lights when the cell is bypassing,
and a red one that lights at 3.7V. Since there is
always at least one person watching the pack while
charging, and charging only takes about 15 minutes
between runs (at the rate we have the charger set to),
we have not (yet) implemented feedback to the charger
to have the charger throttle back as the cells come up
to voltage. So we charge at high current until the
green LEDs turn on (it's amazing to see all 110 BMS
boards turn on the green LEDs, all within less than a
minute of each other), and throttle back the current
to make sure all the red LEDs are off. We stop
somewhere after the e-meter reads something above
380V, and let the BMS knock down the voltage to 374V
(3.4V per cell). We have learned that the impedance
of the cells are lowest at 3.4V. Charging above 3.4V
doesn't help us much anyway. Much above this, and the
zilla will limit max power out. Charging above 374V
doesn't give you that much more energy into the pack
(just a few percent).
What I described above works well for manual charging
at the track. If you wanted an automatic charger for
unattended charging, a lot more safty protection
methods should be implemented.
- Steven Ciciora
--- Scott Littledike <[EMAIL PROTECTED]>
wrote:
> Hi there,
>
> I was just wondering how complex it is to build a
> charger for an EV, with
> lithium batteries in mind. Taking A123 cells as an
> example, they should be
> charged at 3.6V per cell, at a maximum of 3A until
> the current drops off.
> However, if you look at a pack like bill dubes
> killacycle pack, there are 9
> batteries in parallel, and 110 rows of these!
>
> Looking at the 9 batteries in parallel, you must
> supply 3.6V at 27A to
> charge each cell at 3A.. if you have a 150V system,
> thats 27A at 150V. As if
> that wasnt difficult enough, a BMS should be used,
> which may involve
> changing the output voltage to below 150V. so, thats
> a variable voltage
> charger, 0 - 150V, at 27A!
>
> How is this normally done? An appropriate
> transformer would need a 4kVA
> rating, which would be a very large transformer? and
> even then, you would
> not be able to change voltage, unless you use a
> giant potential divider (two
> resistors in series, from +ve to gnd, with a tap
> between them).
>
> suitable variacs are expensive and very large. plus,
> there is the difficulty
> of handling such a high power supply - how do you
> rectify and smooth it etc
> - normal components cant be used.
>
> Or, do you make lots of 3.6V 27A chargers and
> connect them to each
> individual "bank"?
>
> chargers such as the PFC20 dont look very large, and
> you can simply change
> the voltage with a trimmer pot...
>
> If anyone can shed some light on how the ac voltage
> is reduced, rectified
> and smoothed, whilst being completely variable, i
> would be most grateful!
>
> Many Thanks
>
> Scott
>
>
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> Could you be the guest MSN Movies presenter? Click
> Here to Audition
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>
>
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