EV Digest 5069
Topics covered in this issue include:
1) RE: I want to build a PWM DC motor controller
by "Roger Stockton" <[EMAIL PROTECTED]>
2) Re: Geo Metro EV on a budget
by "jerryd" <[EMAIL PROTECTED]>
3) Re: Thermal runaway
by "David Roden" <[EMAIL PROTECTED]>
4) Re: Fw: Geo Metro EV on a budget
by Bill & Nancy <[EMAIL PROTECTED]>
5) RE: I want to build a PWM DC motor controller
by "Roger Stockton" <[EMAIL PROTECTED]>
6) Re: I want to build a PWM DC motor controller
by Stefan Peters <[EMAIL PROTECTED]>
7) Re: Geo Metro EV on a budget
by Stefan Peters <[EMAIL PROTECTED]>
8) RE: False alarm! RE: battery advice.
by "Roger Stockton" <[EMAIL PROTECTED]>
9) Re: Breaking in ADC Motor
by Rush <[EMAIL PROTECTED]>
10) Seating Brushes was Breaking in ADC Motor
by Jim Husted <[EMAIL PROTECTED]>
11) Re: I want to build a PWM DC motor controller
by Stefan Peters <[EMAIL PROTECTED]>
12) RE: I want to build a PWM DC motor controller
by Lee Hart <[EMAIL PROTECTED]>
13) Re: Neg supply for E-meter
by Rush <[EMAIL PROTECTED]>
14) Budget EV - motor mount and coupler
by "Glenn Meader" <[EMAIL PROTECTED]>
15) Budget EV - contactor controllers
by "Glenn Meader" <[EMAIL PROTECTED]>
16) Low vs High voltage, was: Re: Fw: Geo Metro EV on a budget
by James Massey <[EMAIL PROTECTED]>
17) Re: Thermal runaway
by "[EMAIL PROTECTED]" <[EMAIL PROTECTED]>
--- Begin Message ---
Cory Cross [mailto:[EMAIL PROTECTED] wrote:
> A similar thing happens with battery wiring and the controller
> capacitors. At high frequencies, a smoother current wave is
> seen in the wiring. When the controller turns on, the current
> ramps up (because current cannot change instantly in an inductor
> -- the wiring). When it turns off, the current keeps coming,
> boosting up the voltage on the capacitors, which is then drawn
> down next time the controller turns on.
While true, bear in mind that the inductance of the battery wiring is
(usually) *very* small, and so the ripple current they see is quite
small compared to the average value.
> I suppose you could use enough capacitance to solve the
> problem on the battery end, but you'll need to add more
> inductance or resistance to the motor. Being that more
> resistance is bad, you'll have to add quite an inductor that
> can take full motor current -- probably will be larger
> than the motor itself!
This is exactly the approach I am taking with my EV1 SCR controller. It
is simply impractical to add enough bus caps to absorb the required
ripple current at its low (<300Hz) switching frequency, so I am also
adding a largish inductor to the motor loop. The inductor does not
actually end up needing to be particularly large (much smaller than the
motor to double or triple the motor loop inductance, since the motor
inductance is on the order of 100uH at modest currents).
Cheers,
Roger.
--- End Message ---
--- Begin Message ---
Hi Lawrence and All,
----- Original Message Follows -----
From: "Lawrence Rhodes" <[EMAIL PROTECTED]>
To: "Electric Vehicle Discussion List"
<[email protected]>
Subject: Re: Geo Metro EV on a budget
Date: Fri, 6 Jan 2006 02:31:19 -0800
>An Altrax 300 amp controller is 500 dollars.
While one could go that way, he wanted on that was
under $1,000 so rather than an anemic E controller that
costs too much, for low powered EV's, a contactor controller
would be much better especially as he has friends in the
Forklift business. These are very heavy duty contactors as
designed to use for decades so by far more reliable,
powerful at 800 amps vs a 300 amp Altrax which wouldn't be
able to get out of it's own way.
Batteries are
>700. Adapter plate is 600.
Use 2 box sections to mount the motor and a make a
coupler with the clutch plate center brings this to about
$60. Why spend more?
Motor free. DC/DC not needed
>if you use an 80 dollar Trojan 12v Deep cycle.
Meters and
>wiring lets say 200 dollars. This would make a low cost
>low performing but reliable and useable EV. Around 2000
>dollars if you had a free motor.
Or a much better preforming one for under $1,000.
With a 3-5 speed contactor controller you won't notice the
smoothness difference between the CC and the EC as after
starting up, it's basicly ditigal, either on or off anyway
whether CC or EC. I only use 2 speeds in mine, starting
resistor and full power and it works fine. And he will have
transmission speeds if he needs more than a 3-5 speed one.
This style system has worked excellently for 100 yrs
so why spend more for less power with an EController? As
many Citi-car people have found out by switching to EC's,
they can't get out of their own way so switch back to CC or
buy really big controllers for much more money. Let's be
pratical and stop pricing EV'ers out of the market because
some of us are hung up on EC's..
HTH's,
Jerry Dycus
This is realistic on a
>budget. I'll ask Bill what his bill was. Minus the 3k he
>paid for the Glider with 8inch motor of course. Bill could
>you respond to the list on the cost of your ev minus the VW
>with the motor? Thanks....
>Lawrence Rhodes
>Bassoon/Contrabassoon
>Reedmaker
>Book 4/5 doubler
>Electric Vehicle & Solar Power Advocate
>415-821-3519
>[EMAIL PROTECTED]
>
--- End Message ---
--- Begin Message ---
On 7 Jan 2006 at 12:30, Bob Bath wrote:
> Is that
> why I'm seeing darker (greyish) electrolyte at higher
> currents after a long charge?
I'm not an electrochemist, but I think the greyish stuff is shed crystalline
lead sulfate. Some of this is a perfectly normal product of cycling; I've
seen it in batteries at 4-6 months of use. Usually most of it precipitates
out, but when you gas the battery vigorously (as you apparently have), it's
stirred up and turns the electrolyte greyish.
David Roden - Akron, Ohio, USA
EV List Assistant Administrator
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--- End Message ---
--- Begin Message ---
Your recommendation is to run 90 amps or less on a 120 volt system, so
running 150 amps or less on a 72 volt system would be equal?
Bill
Lawrence Rhodes wrote:
Sorry. 120v system. That's the problem with low voltage systems. High
amp draw at speed. However if you keep your speed down low voltage
systems can be quite useful. The 72vdc system would also draw less
amps. LR.........
----- Original Message ----- From: "jmygann" <[EMAIL PROTECTED]>
To: "Lawrence Rhodes" <[email protected]>
Sent: Saturday, January 07, 2006 6:54 AM
Subject: Re: Fw: Geo Metro EV on a budget
"90 amps or less" With how many volts ?
--- In [EMAIL PROTECTED], "Lawrence Rhodes" <[EMAIL PROTECTED]>
wrote:
Pretty good for 48vdc but notice on the flats I'd be drawing
90amps or less.
Less volts more amps to do the same work. Ohm's Law. Lawrence
Rhodes.....
----- Original Message ----- From: "jmygann" <[EMAIL PROTECTED]>
To: "Lawrence Rhodes" <[EMAIL PROTECTED]>
Sent: Friday, January 06, 2006 12:32 PM
Subject: Re: Fw: Geo Metro EV on a budget
> So I got the Metro going ....
>
>
> APPROX. - 43mph ....4th gear 210amps on the flat.....48 volts
>
> Is this in the ball park ??
>
> Only have a digital multi meter. 53.4 volts starting (is that a
full
> charge ?)
>
>
>
>
--- End Message ---
--- Begin Message ---
Stefan Peters [mailto:[EMAIL PROTECTED] wrote:
> I am hoping for a solution that doesn't require more hardware. I'm
> already at over half the cost of a Curtis (but one third the
> cost of a Curtis and a BMS combined, and this is one-off costs :D ).
The retail cost of a Curtis, or the parts cost? Remember, you are
considering only your parts cost; the retail cost of a Curtis is
*significantly* greater than its parts cost. If part of your motivation
is to develop something that hobbiests can build themselves at a lower
cost than an off-the-shelf controller, you should consider if it would
not in fact be significantly cheaper for the hobbiest to build a single
PWM controller instead.
> Actually, it's an attempt to be one step up from a contactor
> controller, one step *sidewise* from a curtis. It's my effort
> to create a modern equivalent of a contactor controller with
> it's own unique set of advantages. In other words, simple
> (build/modify and fix it yourself), inexpensive, and
> completely upgradeable/scalable so you only need to buy
> what you need, when you need it.
Could you give a paragraph or two summary/overview of how your system is
expected to work?
You refer to it as an attempt to create a modern contactor controller,
yet it sounds significantly more complex, more expensive, and less
accessible to the home builder (believe it or not, many hobbiests do not
have the ability or desire to program their own micros).
I do think that the goal of a "modern" contactor controller has a lot of
potential, but I'm not sure that this is really what you are headed for.
A (good) contactor controller re-arranges the battery pack into
different voltages, while ensuring that all batteries are used at each
voltage level (so that all are discharged equally). This system works
well for lowish voltage packs since controller cost/complexity increases
with the number of voltage steps and the step size must remain small
enough not to result in jerky vehicle operation. The remaining
weaknesses are that the first speed step typically requires the use of a
large current limiting resistor (which means that the operator must not
operate the vehicle in the lowest speed step for long periods as this is
inefficient and will overheat the resistor), and that there is nothing
to prevent the operator from mashing the throttle and applying full pack
voltage to a stalled motor (resulting in "unlimited" current and
eventually some sort of carnage), and finally, since there are fixed
voltage steps the operator will sometimes have to continuously switch
between two adjacent steps (manual PWMing) to maintain their desired
speed.
The advantage of a contactor controller is simplicity (easy for a
hobbiest to build, repair, and maintain) and low cost. The challenge
for a modern contactor controller is that pack voltages for on-road EVs
tend to be highish, which can significantly increase the cost of a
contactor controller until it has little if any advantage over a PWM
controller.
I think the rectactor style contactor controller may have the most
promise for "modernisation", as it requires the fewest switches and so
could have the lowest cost for higher voltage packs. I think an
appropriate task for a micro in a modern contactor controller would be
to act as an interface/referee between the throttle pedal and the
contactors. That is, use a typical 5K pot (or similar) for the
throttle, and let the micro open/close the appropriate switches (be they
contactors or FETs, etc). This way the micro can prevent the user from
overheating the starting resistor (if present), and it can automatically
PWM (however fast or slow is appropriate for the switches) between fixed
voltage steps as required, and it can enforce a throttle ramp such that
mashing the throttle results in some sort of controlled sequence through
the voltage steps. Finally, it might even monitor a shunt so that it
could enforce motor current limiting.
Anyway, I look forward to better understanding your scheme! ;^>
Cheers,
Roger.
--- End Message ---
--- Begin Message ---
Cory Cross wrote:
The increase in loss for something that doesn't maintain constant
current is 1 over the duty cycle. 90% modulation would only be 10%
(1.1x loss) worse. Stepped DC would have a lower voltage swing,
resulting in less loss.
You mean the step size for the voltage swing with stepped DC? It should
always be +- 6, 8, 12 or 18V. It can maintain a constant current, that
is what I meant by "stepped DC". I'll start with that code first, then -
since it offers the highest potential payback.
You could PWM only one battery of the substring and get the best of
stepped & PWM.
I'm not sure what you mean by "PAM".
Must be too old a term for ya: Pulse Amplitude Modulation. It was used
for a bit (not in motor control though) before higher speed silicon
became common. Still is the basis of Ethernet, though. I have gotten
alot of warnings about attempting to PWM individual batteries with this
setup (unless they are all synchronized).
There'll still be some times when it isn't perfect, but you are
aware, so that is fine. Perfect is the enemy of good, so, continue!
However, it would be simpler if you used only the "subnet switch" (to
do series/parallel shifting of the batteries), and a rheostat+field
weakening setup for fine-adjustments of the speed. Dirt cheap and
proven, but that isn't what you are going for ;).
I'm going for the "drive it into the ground without any pampering, just
like a ICE". Which is how so many people treat their cars. I have seen
quite a few of those simple examples, but they seem to need even more of
the usual battery babying. Plus you are very limited in motor selection.
But for the tech inclined, they do work well.
Why complicate it with MOSFETs and diodes? The system I mentioned
above would be a great product/project, I don't see anything like it
offered as a package.
True, but I'm not making a product, and I'm not just building my car. If
so, I would be tempted to do it that way. I'm trying to give more
(system durability, ease of use, and another way of doing it cheap)
possibilities to the community.
You could use the rheostat to bypass current around the field
coils, weakening the field, though you would need a 4-terminal series
motor. Most car ones appear to be 4-terminal.
So no, I can't use field weakening with an old pump motor (cheap and
durable), or a PM brushed motor (good scrounging possibilities). Problem
is, that is what I have!
Plus you would loose the durability possibilities which are unmatched at
this time (unless you want to spend close to $2000 or more). No
reversing, no over-discharges, not being stranded when a battery fails,
and the ability to replace individual batteries without hurting the
others - even mix and match different ones, like 8 Trojan 6V and 4 US
12V. And it's all automatic.
--- End Message ---
--- Begin Message ---
jerryd wrote:
Let's be
pratical and stop pricing EV'ers out of the market because
some of us are hung up on EC's..
HTH's,
Jerry Dycus
Hear, hear!
Though hopefully you can get some of the automation benefits of a
monolithic EC at the price of a DIY 5 speed contactor controller someday ;)
--- End Message ---
--- Begin Message ---
Bob Bath [mailto:[EMAIL PROTECTED] wrote:
> But this is what happens: at 173V, limit LED and timer
> go on for awhile, then go off!
What is happening is that you have the limit set for 173V and are able
to force the batteries to reach this level, but the voltage is higher
than they want and so they are overheating because the current does not
taper off as it should. As they heat up, they draw more current until
the charger is once again in current limit; at this point the charger is
forced to lower its output voltage to maintain the current at this
(maximum) level, and so the limit LED and timer go off as the charger
returns to bulk mode. If left this way it will continue grossly
overcharging your batteries until a maximum charge duration timer shuts
things down. If I recall Bill Dube's report correctly, the PFCxx does
not have such a timer and you must use an external timer on the AC input
to ensure the charger does not continue charging forever should
something unexpected (such as thermal runaway or a shorted cell or two,
etc.) occur.
> Is there a way for a damaged battery
> to have normal SGs, and low voltages, but still be
> acting like a resistor?
I'm not sure I follow. All batteries act somewhat like a resistors
(i.e. they all have internal resistance).
Have you tested the capacity of your pack, or of the suspect batteries?
My advice is if it ain't broken, don't fix it. If you do an equalise
charge on the pack or an individual suspect battery and the s.g. will
not rise higher than X, then X is the fully charged s.g. of that
battery. It may may not be the same as the other batteries, but if the
capacity is OK, don't lose sleep over it. This is a prime reason for
tracking the s.g. of your batteries over their life; you can notice
trends of a particular cell relative to its own initial values rather
than trying to compare it to some arbitrary fixed reference. Each
battery in your pack is different due to being at somewhat different
temperature from the others and from having somewhat different amounts
of water lost and added over its life, and due to initial manufacturing
differences.
Don't worry about the voltages at all. The voltages while charging tell
you very little. The voltages several hours after the end of charge
should tell you the state of charge, but you have flooded batteries so
don't rely on the voltage, trust the s.g. readings. If you see
unusually low voltages on discharge, this can help you to single out
sulphated batteries or bad connections.
Cheers,
Roger.
--- End Message ---
--- Begin Message ---
Bill,
The face of a new brush will be flat. It is seated when all of the face is in
contact with the commutator. In the beginning, since the commutator is round
and the brush face is flat, you have just a line that is contact with the
commutator. After it is seated the face has a round curve that has been ground
on it by the commutator so all of it is in contact with the commutator. Much
more surface area contact so much more elec is passed thru.
Rush
Tucson AZ
www.ironandwood.org
----- Original Message -----
From: "Bill Dennis" <[EMAIL PROTECTED]>
To: <[email protected]>
Sent: Saturday, January 07, 2006 11:27 AM
Subject: RE: Breaking in ADC Motor
> Thanks, Rush. How do I know when the brushes are "1/2 seated" and "fully
> seated"?
>
> Bill Dennis
>
--- End Message ---
--- Begin Message ---
Hey Bill, All
While running a motor untill it has licked away on the brushes enough to seat
I hear works, it has many drawbacks. First, it sounds like it takes forever to
achieve. Second, although the copper is harder than the brush it still gets
worn away just at a slower pace. For those who have had the EV's in service
for years they probably have developed at least some grooving by the brushes.
The harder the brush the more abbrasive it is to the comm., so there is a
trade off even with brush grades (brushes last longer vs. comm lasts longer).
Third, the idea of removing 24 hours of life from the bearings may not sound
like much but that equates to just shy of the Oregon / Illinios trip we'll be
taking this May. All of this can be cured in a few minutes with a brush seater
or finish grade comm. stone. A comm stone / brush seater is made up of grit of
one size and hardness or another. Just like sandpaper they are defind as
course to finish grades. When a comm. stone is appl!
ied with
preasure to the comm.(better to sand with comm. running away from stone and
not against it) grit is removed that passes under the brush and removes
material. A brush seater is really soft and will not begin to touch the comm.
They are the white ones some of you may have seen. They are subject to
breaking easy and they are consumed fast as you use them. A comm. stone is
much harder, and although even the finish grade will lick at the comm. it isn't
that abbrassive. In fact it is perfect for smoothing nick and scratches as it
seats the brushes. I use an even back and forth motion to achieve not only an
even seating but to keep the comm. evenly sanded in the proccess. Look at
starter / gen shops or other motor build shop as a source for brush seater and
or comm stones.
On lift motors rule of thumb is 60 to 80 percent seat, but for you guys seat
till the curve is edge to edge. Remove a couple of brushes to see where you
stand and repeat seating as needed. Immportan, remove a couple, as one maybe
seated while the others are not. If you can seat all four holder areas equally.
I'll be posting a how to use comm. stone (with pics) as soon as I can. I've
noticed that my free site is not only full but the ads that started to appear
were a joke. Chris Robinson is going to be helping me setup a more proper site
to help me share pics and info. So thanks Chris and sorry to all those who
have had to put up with the ad thing.
Although I had to breeze through this as I've got things to do, I hope this
is at least a temp answer / fix untill I can get a detailed posting on this
subject.
Also regardless of how you are seating, bring the car / motor outside and
blow it out real good. Do not breath the dust (yeah listen to me, lmao). Using
a vaccuum and a low preasure first air blast will catch most of the dust.
Best of luck
And you guys thought building motors was all fun and glory, lmao.
Cya
Jim Husted
Hi-Torque Electric
---------------------------------
Yahoo! DSL Something to write home about. Just $16.99/mo. or less
--- End Message ---
--- Begin Message ---
Roger Stockton wrote:
Stefan Peters [mailto:[EMAIL PROTECTED] wrote:
I am hoping for a solution that doesn't require more hardware. I'm
already at over half the cost of a Curtis (but one third the
cost of a Curtis and a BMS combined, and this is one-off costs :D ).
The retail cost of a Curtis, or the parts cost? Remember, you are
considering only your parts cost; the retail cost of a Curtis is
*significantly* greater than its parts cost.
I thought the "buy it one part at a time from retailers" parts cost was
more then the retail cost of most electronic gadgets? Is that different
in this industry?
If part of your motivation
is to develop something that hobbiests can build themselves at a lower
cost than an off-the-shelf controller, you should consider if it would
not in fact be significantly cheaper for the hobbiest to build a single
PWM controller instead.
It's part of it. But you have to include the cost of a BMS in that as
well to get an equivalent exchange.
Could you give a paragraph or two summary/overview of how your system is
expected to work?
I'm still figuring that out with these posts ;)
My main idea is *Modular*. As in use-just-the-pieces-you-need. It's
supposed to work in as many different configurations as possible, with
as many different pack sizes and battery types and feature sets as
possible. I started with the contactor controller and the BatPack system
as promising starting points (each with their own set of unique
advantages that I want in my EV).
You refer to it as an attempt to create a modern contactor controller,
Modern equivalent. Maybe it's a bad comparison. I'd like to think of it
as potentially a framework.
yet it sounds significantly more complex, more expensive, and less
accessible to the home builder (believe it or not, many hobbiests do not
have the ability or desire to program their own micros).
It takes more electronic skill (and parts cost) to build a basic power
supply then to flash a micro. I did the latter before I could ever do
the former. If someone could simply download one of a couple hex files
and then "plug, click, wait, unplug" I think anybody who can use a
soldering iron and read a schematic can build one. I'm an software
engineer, so I tend to make simple things much more complex sounding
then they actually are (sorry, habit of looking at the big picture). The
schematics are very simple, very low parts count. The cost is as low as
$50 a battery if you buy the parts one at a time. 10 or more and they go
down a bit. The main controller is $30 tops. The "subnet switch" *is* a
silicon controlled contactor controller. Just use that and the Speed
Controller if you want. Best part is, you can start with as few as you
want. Need more voltage? Throw a few on there and let 'er rip. Ain't got
no money? Don't use the Power Modules yet, you can add them later if you
want. Want their benefits without the other fancy stuff? Use the
"simple" ones instead of the individual battery current sensing charge
balancing ones. You can use one Power Module with two or three batteries
as well.
I've seen Curtis schematics. Looks like greek spaghetti to me.
I do think that the goal of a "modern" contactor controller has a lot of
potential, but I'm not sure that this is really what you are headed for.
I have been trying to combine the benefits of a "BatPack" setup (vehicle
still drives fine with one or more failed/dead battery (without harming
any of them), mix and max batteries, individual replacement/upgrade of
batteries) with those of a contactor controller setup (easy to
reconfigure/upgrade, make you own customizations, buy only what you need
at the time)
I think you would want to use just the Speed Controller with a four-way
Subnet Switch, and upload the "Basic Contactor Controller" software into
the Speed Controller. Or better yet, if there was no Power Modules seen
on the bus when it turns on, it would switch to that mode automatically.
You could add the Power Modules later for finer speed control and basic
BMS capabilities. Just upload the "Power Network" software into your
Speed Controller. Don't want to buy an E-meter? Plug in a few sensors
and upload the "Power Network with SOC" into the Speed Controller, then
tell it the Ah and P of each battery (or whatever). Don't like the Speed
Controller I designed? Modify it or use someone else's.
I don't think you are seeing this as a network of modular devices. That
can be a tremendously powerful concept if you fully embrace it. It's not
"a particular EV controller split into several pieces", it's a bunch of
simple pieces that can enable you to build the control system of an EV.
Think of LEGOs
A (good) contactor controller re-arranges the battery pack into
different voltages, while ensuring that all batteries are used at each
voltage level (so that all are discharged equally).
That would always require a "matched" set of batteries, even then, you
will be throwing away perfectly good lead sometime. You virtually *have*
to replace the whole pack at once. But like I said, you can choose that
functionality if you want.
I think the rectactor style contactor controller may have the most
promise for "modernisation", as it requires the fewest switches and so
could have the lowest cost for higher voltage packs. I think an
appropriate task for a micro in a modern contactor controller would be
to act as an interface/referee between the throttle pedal and the
contactors. That is, use a typical 5K pot (or similar) for the
throttle, and let the micro open/close the appropriate switches (be they
contactors or FETs, etc). This way the micro can prevent the user from
overheating the starting resistor (if present), and it can automatically
PWM (however fast or slow is appropriate for the switches) between fixed
voltage steps as required, and it can enforce a throttle ramp such that
mashing the throttle results in some sort of controlled sequence through
the voltage steps. Finally, it might even monitor a shunt so that it
could enforce motor current limiting.
That's a very good idea, but you can't do the PWM with contactors. Why
not leave that part out of it. Then it would sound like a great "Subnet
Switch" or whatever you want to call it. Remember, you don't have to use
the Power Modules - they just are a refinement or upgrade. They are the
same (basic) chips as you would use in a simple PWM power stage, just
much lower voltage and have the ability to switch out an individual
battery from the pack. That last part is my favorite :D
But you could build such a switch, then plug it into the Speed
Controller. The speed controller is simply sending a voltage level to
it. It then decides how to switch the packs around to give the closet
result it can. If it could PWM the motor output, then it would just do
that as well to give an exact result. For the best of all worlds, when
cost isn't an issue, use the "variable output switch" with a full set of
Power Modules. They would normally stay on for minimal losses, and only
switch off when a battery went down.
I'm a firm believer of "use your resources where they work best". Since
I'm a network & software engineer with tons of experience on high
scalability projects, I figured that this would be the most appropriate
application of what I know, versus what I don't. Sounds like there are
many others (like you) that would make a much better modern contactor
controller then I could ever devise. An EE or Electrictian or even a HV
hobbiest would be much better suited for the particular part you speak
of. I would love to have others add much better pieces to the puzzle
then I can whip up. That is a big point of this and why I post so much
about it. Modular would be the main term here - use the pieces that you
need, get the system you want.
--- End Message ---
--- Begin Message ---
Danny Miller wrote:
>> Peukert's depresses the voltage based on long term current. Short
>> pulses only see voltage depression due to I*R drops.
Roger Stockton replied
>Peukert doesn't "depress" the voltage; it expresses a relationship
>between the usable capacity of a lead acid battery and the rate of
>discharge (usable capacity decreases non-linearly as the rate of
>discharge increases).
I agree. In fact, Peukert says nothing at all about voltage. It only describes
the effect of current on amphour capacity. Voltage sag due to internal
resistance is a separate effect, causing an additional reduction in energy
delivered as the load is increased.
>Pretty much anyone who has used an EV equipped with one of the older GE
>EV1 SCR controllers can verify that they got *much* less range and
>*much* shorter battery life than the same type of batteries used with a
>high-frequency MOSFET controller. The EV1 switches in the range of
>100-300Hz and has no bus capacitance at all; the inductance of our
>typical motors is insufficient to keep the motor loop current continuous
>except perhaps near full throttle (~90% duty), and so the batteries are
>discharged at close to the full motor current instead of the average
>current.
However, it's worth noting that the EV1 was designed for forklifts, not
road-going EVs. Forklift motors tend to have a lot of extra iron, and more
turns on their field windings, which increases their inductance. This decreases
the ripple current that the batteries will see.
Also, forklifts tend to have much higher capacity packs. It's not unusual to
see 1000ah (or more! battery packs in a forklift. A 100amp peak-to-peak ripple
is only 10% of a 1000ah pack, but 100% of a 100ah pack!
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--- Begin Message ---
Lee,
Would this one work - http://datasheet.astrodyne.com/PWB.pdf
Model AFC-15S, output V- 15vdc, output A - 0.66, output W - 10W, input V -
85-265vac?
sorta pricy, $39 from them.
Thanks
Rush
Tucson AZ
www.ironandwood.org
----- Original Message -----
From: "Lee Hart" <[EMAIL PROTECTED]>
To: <[email protected]>
Sent: Saturday, January 07, 2006 12:29 PM
Subject: Re: Neg supply for E-meter
> From: damon henry
>> I still have a couple more questions specific to my application. I don't
>> currently have an accesory battery, just a DC-DC converter. The negative
>> side of my DC-DC is connected to my frame. The E-meter manual states
>> that I must connect pin one to both the negative side of my traction pack
>> as well as the negative supply for the E-meter. This of course connects
>> the negative side of my traction pack to the negative side of my DC-DC
>> and my frame. This sounds bad...
>
> Correct! You can't power the E-meter directly from your 12v accessory power.
>
>>The manual offers two options...
>
> There is another option, which I prefer. Get a small switching power supply
> that can run directly off your traction pack, and which has an isolated 12v
> output to power the E-meter (and nothing else). The E-meter takes so little
> power that this can be a "wall wart" or old laptop power brick. Just make
> sure it is a SWITCHING power supply, not one with a 60hz transformer!
>
> Almost all low-power switchers have "universal" inputs and work on AC or
> DC, at anything from 90-300v. For example, I use an Astrodyne 15vdc
> 0.5amp switcher. It is rated for 90-264vac input, but actually works from
> 60-350vdc. It's a little potted "brick", and would even work underwater.
>
> The advantage of this approach is that the little switcher is more efficient
> than having to run the main DC/DC just to power a *second* DC/DC to get
> the 25ma or so the E-meter needs. The Astrodyne I use draws 4-9ma from
> my 132v propulsion pack, depending on whether the E-meter is asleep or in
> full sunlight. A normal "full-size" DC/DC would draw over 20ma even with NO
> load on its output.
> --
> Lee Hart
>
>
>
--- End Message ---
--- Begin Message ---
Was Re: Geo Metro EV on a budget
> jerryd says: Use 2 box sections to mount the motor and a make a coupler
> with the clutch plate center brings this to about $60.
Could you give more details on this?
What's a "box section"?
How do you make a coupler with a clutch plate center for $60? Any writeups
on this?
--- End Message ---
--- Begin Message ---
Was: Geo Metro EV on a budget
jerryd wrote:
> With a 3-5 speed contactor controller you won't notice the smoothness
> difference between the CC and the EC as after starting up...
Where do you get, or how do you make a 3-5 speed contactor controller?
Any pointers to info on this?
--- End Message ---
--- Begin Message ---
At 06:39 PM 7/01/06 +0000, jmygann wrote:
120V X 90A = 10,800 Watts
48V X 210A = 10,080 Watts
Is one moe efficient than the other ??
Hi jmygann (it would be good to have your proper name, at least a first
name) and all.
The answer to this is, it depends.
In two cars that have the same motors, same cable sizes and similar
controllers, the 120V one will be 2.5 times less inefficient
(approximately). Why? because the losses are primarily due to the amps
involved, from resistive losses. (When I say less inefficient, I am talking
about the high voltage one being maybe 75% efficient stored-energy-to-road,
and the low voltage one maybe 70%).
But, the cars won't be the same. The 48V one should be wired with
substantially heavier cables, so the cable resistance will be lower, the
motor may be different, the batteries are probably different, it is
possible to build a low-voltage car of high efficiency, also to build a
higher voltage car with lower efficiency.
So why do people build for higher voltage? Practicalities.
What do I mean by this?
Well, 120mm2 welding flex is far less flexible than 60mm2 welding flex, in
fact something like 4x the bend radius. Making low voltage/high power
motors can be a challenge, since using 'normal' design methods starts
running into fractions of a turn of winding, etc. Also a low voltage motor
NEEDs a bigger commutator and bigger brushes to take the higher amps than a
similar capacity higher voltage motor, so the motor will have more inertia
and higher cost.
But there is a trade-off between complexity and cost of heavier components,
and the complexity and cost of higher voltage components. So the practical
route points to NEV/golf car size vehicles being sub-72V, and fully on-road
car (probably requiring a minimum of 4x the power delivery of a NEV-class
vehicle) ending up with a voltage greater than 72V.
DC traction systems normally don't have battery packs greater than around
200V, but this is a moving data-point. In the 4 years or so I've been fully
into EVs, the number of 200V+ EVs has gone from only a few, to maybe 10s of
vehicles (it is hard to keep track, so I don't try). It would be
interesting to compare EVDL photo album vehicles (which can be taken as a
typical cross-section of EV enthusiasts' vehicles) by voltage rather than
manufacturer, and see how many vehicles are in what voltage range.
The choices that people make as to low vs high voltage depends more on the
guidance that the individual receives, and the depth of their pockets,
rather than efficiency considerations.
As an example, my decision processes went along the lines of:
Vehicle choice: practical small truck (but in hindsight I chose a little
too small)
System style: "techy" rather than "simple"
Battery choice: AGMs (for clean installation),
Number of batteries: 20 (for the total stored energy for projected range),
Motor choice: 2nd-hand Ex-forklift (cheap, but strong and gives me scope to
play)
Controller choice: Zilla for programmability, flexibility, safety features.
System voltage: 120V, due to cheaper Zilla than for 240V and using
ex-forklift contactors.
Charging system: "roll my own" based around Rudman Regs and a small
industrial PLC (programmable logic controller) controlling a rewound
forklift charger transformer.
So in my design I have gone expensive in some areas and cheap in others, as
suits my skills, interests and abilities. I could have built my own
controller, but then I'd have had better contactors, since my controller
would have been 'prototype' and have a higher probability of failure and
needing emergency disconnection than the Zilla. This would have upped my
costs to the point where a Zilla becomes a cheaper option. Similar if I'd
got a Cursit (Curtis) controller - I wanted to have (due in part to my
motor choice) features that are designed in to the Zilla, but would have
needed to be added on to the Curtis.
If you are chasing extreme efficiency, you'd better have deep pockets,
regardless of choice of voltage or AC vs DC, since the less the vehicle
weighs, the more efficient it is to move (accelerate) - and that means
advanced batteries.
Want extreme efficiency? Silver-wound motor, Aluminium (less mass for
conductivity than silver) buss bars, Aluminium wire, Titanium bolts, etc...
not that I've ever heard of anyone going to that extreme, although lynch
motors aparently can have silver-loaded brushes for improved efficiency.
Regards
James
--- End Message ---
--- Begin Message ---
It the charger plug doesn't have a wind-up type timer, you should install
one soon. Set it to the maximum time that you think the batteries should
continue charging. This will protect them from extreme damage if they are
unattended and they do go into thermal runaway.
When the batteries are full their terminal voltage goes down as their
temperature goes up. At the end of the charge cycle is when your batteries
are typically at the highest temperature.
The typical charger has a "trigger voltage" that it must reach to cut back
the current and switch over from constant current (CC) mode to constant
voltage (CV) mode. If the battery is WAY too hot, it will never reach the
trigger voltage. More typically, the battery will reach the trigger voltage
and while the current is tapering off, because it will heat up just enough
to drop below the trigger voltage.
When the battery drops below the trigger voltage, the charger
might return to the CC mode (depends upon the logic in the charger.) When
this happens, the battery has entered "thermal runaway". It will never
reach the trigger voltage because it is getting hotter and hotter as the
charger pumps a massive overcharge into it. A battery must go open circuit
for the cycle to stop (if you don't have a wind-up timer, or that feature
is not built into your charger.)
Bill Dube'
At 01:30 PM 1/7/2006, you wrote:
Certainly my batteries are heating up as the voltage
drops. The limit LED is not coming on. But the
batteries are performing fine, at least for now. I'm
at a huge loss as to what is going on. SGs look good;
maybe it is a battery in the back of the car that has
a cruddy cell I'm just missing. I didn't think one
cell could screw things up this significantly...
What (chemically) occurs in thermal runaway? Is that
why I'm seeing darker (greyish) electrolyte at higher
currents after a long charge?
--- Ralph Merwin <[EMAIL PROTECTED]> wrote:
>
> Bob,
>
> I recommend trying it again, and this time watch the
> current meter
> when the pack voltage starts to drop. If the
> current isn't also
> dropping, the charger is not the cause of the
> voltage drop.
>
> As a double-check, temporarily lower the charger's
> voltage setting
> and rerun the test. You should see the LIMIT LED
> come on when the
> pack reaches the voltage setting and the blue LED
> should start
> blinking, and the current should start dropping.
> This tells you
> the charger is working.
>
> Then put the voltage setting back to what you expect
> and start the
> charger. Manually monitor each battery voltage to
> see if you can
> find one or more battery voltages that are dropping.
> This might
> help find the bad battery.
>
> Ralph
>
>
> Bob Bath writes:
> >
> > I should've said "voltage threshold, thus starting
> > current cutback."
> > I do believe the potential for a bad battery. But
> > Interstate load tested the worst, and indicated
> that
> > it was fine! I'm confused!
> > Yes, I know about the voltage trimpot triggering
> the
> > timer, etc. Most of what I read indicates that
> > thermal runaway won't occur with floodies. Is
> this
> > not correct?
> >
> >
> > --- Ralph Merwin <[EMAIL PROTECTED]> wrote:
> >
> > > Bob Bath writes:
> > > >
> > > > I ramped up the current throttle to max, set
> the
> > > > voltage limit to 183V, and hit 178. Got
> WAAAAY
> > > > excited, but before the blue LED came on
> > > indicating
> > > > current limit, voltage started dropping again.
>
> > > This
> > > > is what it's been doing all along. Why is it
> > > ramping
> > > > back voltage before it hits current limit?
> Water
> > > > levels are fine.
> > >
> > > Bob,
> > >
> > > There is no indication for current limit. You
> need
> > > to watch
> > > your pack current meter to see how much current
> is
> > > flowing.
> > >
> > > The blue LED indicates that the timer is
> running.
> > > It gets
> > > triggered by voltage limit, regbus activity or
> hot
> > > reg,
> > > depending on switch settings.
> > >
> > > The LIMIT LED should come on if the pack hits
> the
> > > voltage
> > > limit set by the trim pot. The blue LED should
> > > start blinking
> > > at the same time if you have switch 1 set to ON.
>
> > > This is
> > > when the charger will start cutting back on the
> > > current.
> > >
> > > If your pack voltage peaks and then starts
> dropping
> > > before
> > > hitting the charger's voltage setting, the
> charger
> > > will continue
> > > pumping in the selected current into the pack.
> This
> > > may cause
> > > thermal run away.
> > >
> > > Maybe you need to set a lower limit, perhaps to
> > > account for a
> > > bad battery?
> > >
> > > Ralph
> > >
> > >
> >
> >
> > '92 Honda Civic sedan, 144V (video or DVD
> available)!
> > www.budget.net/~bbath/CivicWithACord.html
> > ____
> > __/__|__\ __
> > =D-------/ - - \
> > 'O'-----'O'-'
> > Would you still drive your car if the tailpipe
> came out of the steering wheel? Are you saving any
> gas for your kids?
> >
> >
> >
> > __________________________________________
> > Yahoo! DSL Something to write home about.
> > Just $16.99/mo. or less.
> > dsl.yahoo.com
> >
>
>
'92 Honda Civic sedan, 144V (video or DVD available)!
www.budget.net/~bbath/CivicWithACord.html
____
__/__|__\ __
=D-------/ - - \
'O'-----'O'-'
Would you still drive your car if the tailpipe came out of the steering
wheel? Are you saving any gas for your kids?
__________________________________________
Yahoo! DSL Something to write home about.
Just $16.99/mo. or less.
dsl.yahoo.com
--- End Message ---
