EV HP

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EV HP

Richard Acuti
I haven't been following this thread from the beginning but I saw the
comment about max draw from 12, and 6v batteries (500 amps on a 12v will
kill it quick)

I'm running 8v floodeds and a Curtis 1221B controller. I've never managed to
hit 400 amps draw. I've hit 300 for a few seconds a few times but when I
hill-climb, sometimes I pull 200-240 amps for as long as 1-4 minutes.

Is this too much for 8v batteries? I have 3,000 miles on them so far and
haven't noticed any problems. Well....'cept for that one that blew up
recently and that was my fault. A loose cable seemed to be the culprit. :(

Rich

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Re: EV HP

Roland Wiench
Hello Richard,

This depends where your amp meter shunt is place in the circuit.  If its
install between the main battery and controller, you are reading battery
ampere.  If it place between the controller and motor, then its motor
amperes.

Motor ampere may be much higher than the battery ampere in some controllers.
I have both meters in my EV, and my motor ampere will read about 110 amps
while the battery ampere is about 50 amps at about 30 mph.   At 50 miles per
hour the motor ampere is about 250 amps while the battery amps is at 180
amps.

I find it is more important to monitor the motor ampere which is a large
meter next to the tachometer.  Check the normal running ampere of the motor.
My motor is spec for 199 amps continuous, so I tried to keep the motor
ampere at 200 amps or lower.

Roland




----- Original Message -----
From: "Richard Acuti" <[hidden email]>
To: <[hidden email]>
Sent: Tuesday, August 14, 2007 5:20 AM
Subject: [EVDL] EV HP


> I haven't been following this thread from the beginning but I saw the
> comment about max draw from 12, and 6v batteries (500 amps on a 12v will
> kill it quick)
>
> I'm running 8v floodeds and a Curtis 1221B controller. I've never managed
> to
> hit 400 amps draw. I've hit 300 for a few seconds a few times but when I
> hill-climb, sometimes I pull 200-240 amps for as long as 1-4 minutes.
>
> Is this too much for 8v batteries? I have 3,000 miles on them so far and
> haven't noticed any problems. Well....'cept for that one that blew up
> recently and that was my fault. A loose cable seemed to be the culprit. :(
>
> Rich
>
> _________________________________________________________________
> More photos, more messages, more storage-get 2GB with Windows Live
> Hotmail.
> http://imagine-windowslive.com/hotmail/?locale=en-us&ocid=TXT_TAGHM_migration_HM_mini_2G_0507
>
> > _______________________________________________
> For subscription options, see
> http://lists.sjsu.edu/mailman/listinfo/ev 

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Re: EV HP

Lee Hart
In reply to this post by Richard Acuti
Richard Acuti wrote:
> I saw the comment about max draw from 12, and 6v batteries (500 amps
> on a 12v will kill it quick)... I'm running 8v floodeds and a Curtis
> 1221B controller. I've never managed to hit 400 amps draw. I've hit
> 300 for a few seconds a few times but when I hill-climb, sometimes
> I pull 200-240 amps for as long as 1-4 minutes. Is this too much for
> 8v batteries?

There is no current above which life suddenly falls. Instead, the
situation is that battery life shortens as average current increases.

I'd use this for a rule of thumb for flooded or gel lead-acid batteries:

1. Keep the *average* current below the 20-hour amphour capacity.
    For example:
        - 220 amps for a 6v 220 amphour golf cart battery
        - 175 amps for an 8v 175 amphour golf cart battery
        - 100 amps for a 12v 100ah deep-cycle battery

2. Keep the *peak* current times the seconds you draw it below
    5 times the battery's 20-hour amphour capacity. For example:
        - for a 6v 220ah golf cart battery:
                220 amps for 5 seconds
                440 amps for 2.5 seconds
                880 amps for 1.25 seconds
        - for an 8v 175ah golf cart battery:
                175 amps for 5 seconds
                350 amps for 2.5 seconds
                700 amps for 1.25 seconds
        - for a 12v 100ah golf cart battery:
                100 amps for 5 seconds
                200 amps for 2.5 seconds
                400 amps for 1.25 seconds

If you exceed these rates, you are accepting a shorter battery life as a
consequence. How much shorter depends on how much you exceed these limits.

For AGMs, you can push these limits harder. Depending on the type,
anywhere from 2 to 5 times harder. In part this is because of their
lower internal resistance. But it is also because their basic life
expectancy is perhaps half as much, so you can do more "damage" from
high currents before it becomes the dominant factor in their life.
--
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

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Re: EV HP

Richard Acuti
In reply to this post by Richard Acuti
Ooooh..good point Roland. I should have mentioned that.

My shut is 'tween the pack and the controller. But now you've given me the
great idea to get another one to measure motor amps.

I have the ADC L91-4003 which is rated for 130 amps continuous, 150 amps for
1 hour, 500 amps peak.

I think my particular application rides this motor hard, but within it's
limits. I'm at 128 volts. When I'm on flat road, I draw 80-100 (battery)
amps at 55 mph, 120-140 (battery amps) at 65 mph. When I hill-climb, I pull
200-240 amps for 1-4 minutes at the longest.

When I build the next E-Beetle, I guess I should really step it up to an 8"
ADC huh?

Rich

>Message: 15
>Date: Tue, 14 Aug 2007 06:38:46 -0600
>From: "Roland Wiench" <[hidden email]>
>Subject: Re: [EVDL] EV HP
>To: "Electric Vehicle Discussion List" <[hidden email]>
>Message-ID: <[hidden email]>
>Content-Type: text/plain; charset="iso-8859-1"

Hello Richard,

This depends where your amp meter shunt is place in the circuit.  If its
install between the main battery and controller, you are reading battery
ampere.  If it place between the controller and motor, then its motor
amperes.

Motor ampere may be much higher than the battery ampere in some controllers.
I have both meters in my EV, and my motor ampere will read about 110 amps
while the battery ampere is about 50 amps at about 30 mph.   At 50 miles per
hour the motor ampere is about 250 amps while the battery amps is at 180
amps.

I find it is more important to monitor the motor ampere which is a large
meter next to the tachometer.  Check the normal running ampere of the motor.
My motor is spec for 199 amps continuous, so I tried to keep the motor
ampere at 200 amps or lower.

Roland

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Re: EV HP

Tom Jones-5
In reply to this post by Lee Hart
Just a sanity check here. How could motor current exceed the battery
current? Since everything comes from the battery!

My rash assumption is that the PWM of the controller is causing a falsely
high motor current reading. Any other opinions?
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Re: EV HP

Richard Acuti
In reply to this post by Richard Acuti
Wow. Thanks Lee.

In block #2, when I exceed 175 amps, I definitely exceed it for longer than
that.  Luckily I don't have to draw more than 175 amps too often. On the way
home today I tried to time how long the periods are than I draw 200 amps or
more. It's kind of hard without an assistant but I think I was
overestimating when I said 1-4 minutes. It's more like 1-2. Less if I'm
driving faster and use my momentum to hop over some of these hills. The
trade off is that I draw more "averaged" amps.: Instead of 80-100 @ 55 mph,
I'm doing 65 mph and pulling 120-160 amps

Based on how hard I hammer my pack, I pulled the arbitrary number of a
10,000 mile life cycle out of my butt for these batteries when I first
bought them. I'm at 3,000 now. It'll be interesting to see what happens.

I get 65-70 mph now with a 128v pack. If I switch to 6v batts at 96v total,
I wonder how much top speed I'll lose.

Rich A.


>Message: 23
>Date: Tue, 14 Aug 2007 12:19:27 -0500
>From: Lee Hart <[hidden email]>
>Subject: Re: [EVDL] EV HP
>To: Electric Vehicle Discussion List <[hidden email]>
>Message-ID: <[hidden email]>
>Content-Type: text/plain; charset=ISO-8859-1; format=flowed

Richard Acuti wrote:
>I saw the comment about max draw from 12, and 6v batteries (500 amps
>on a 12v will kill it quick)... I'm running 8v floodeds and a Curtis
>1221B controller. I've never managed to hit 400 amps draw. I've hit
>300 for a few seconds a few times but when I hill-climb, sometimes
>I pull 200-240 amps for as long as 1-4 minutes. Is this too much for
>8v batteries?

There is no current above which life suddenly falls. Instead, the
situation is that battery life shortens as average current increases.

I'd use this for a rule of thumb for flooded or gel lead-acid batteries:

1. Keep the *average* current below the 20-hour amphour capacity.
    For example:
        - 220 amps for a 6v 220 amphour golf cart battery
        - 175 amps for an 8v 175 amphour golf cart battery
        - 100 amps for a 12v 100ah deep-cycle battery

2. Keep the *peak* current times the seconds you draw it below
    5 times the battery's 20-hour amphour capacity. For example:
        - for a 6v 220ah golf cart battery:
                220 amps for 5 seconds
                440 amps for 2.5 seconds
                880 amps for 1.25 seconds
        - for an 8v 175ah golf cart battery:
                175 amps for 5 seconds
                350 amps for 2.5 seconds
                700 amps for 1.25 seconds
        - for a 12v 100ah golf cart battery:
                100 amps for 5 seconds
                200 amps for 2.5 seconds
                400 amps for 1.25 seconds

If you exceed these rates, you are accepting a shorter battery life as a
consequence. How much shorter depends on how much you exceed these limits.

For AGMs, you can push these limits harder. Depending on the type,
anywhere from 2 to 5 times harder. In part this is because of their
lower internal resistance. But it is also because their basic life
expectancy is perhaps half as much, so you can do more "damage" from
high currents before it becomes the dominant factor in their life.
--
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

_________________________________________________________________
More photos, more messages, more storage—get 2GB with Windows Live Hotmail.
http://imagine-windowslive.com/hotmail/?locale=en-us&ocid=TXT_TAGHM_migration_HM_mini_2G_0507


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Re: EV HP

Marty Hewes
In reply to this post by Tom Jones-5
Nothing false about it.  Think of it this way, watts into the controller is
roughly equal to watts out, and watts = volts x amps.  The controller does
PWM because, at least at lower RPM, if you put full battery volts to the
motor you'd exceed current ratings, so the controller does PWM to cut the
RMS voltage to something below battery volts to reduce current and power.

Now since power is about equal on both sides of the controller, and voltage
is the full battery voltage on the battery side, but less on the motor side
due to the PWM, then current has to be less on the battery side for volt x
amps to be the same on both sides.

Thank heavens, or we'd all be toasting our batteries.

Think of the controller as an impedence matcher, or a DC transformer with a
variable turns ratio (if there was such a thing), and it starts to make
sense.  It's all about watts.

----- Original Message -----
From: "Tom Jones" <[hidden email]>
To: "Electric Vehicle Discussion List" <[hidden email]>
Sent: Tuesday, August 14, 2007 2:21 PM
Subject: Re: [EVDL] EV HP


> Just a sanity check here. How could motor current exceed the battery
> current? Since everything comes from the battery!
>
> My rash assumption is that the PWM of the controller is causing a falsely
> high motor current reading. Any other opinions?
> _______________________________________________
> For subscription options, see
> http://lists.sjsu.edu/mailman/listinfo/ev
>
>


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Re: EV HP

Joseph T.
"Just a sanity check here. How could motor current exceed the battery
current? Since everything comes from the battery!"

The controller will change (I'm sure this is the wrong electrical
term) the electricity to make it more suitable for whatever situation
the motor is in. A controller, for example, can draw 100 volts at 50
amps, and then "change" it to 50 volts and 100 amps. Because more amps
produce more torque in DC electric motor, it is sometimes favorable to
do this.

On 8/14/07, Marty Hewes <[hidden email]> wrote:

> Nothing false about it.  Think of it this way, watts into the controller is
> roughly equal to watts out, and watts = volts x amps.  The controller does
> PWM because, at least at lower RPM, if you put full battery volts to the
> motor you'd exceed current ratings, so the controller does PWM to cut the
> RMS voltage to something below battery volts to reduce current and power.
>
> Now since power is about equal on both sides of the controller, and voltage
> is the full battery voltage on the battery side, but less on the motor side
> due to the PWM, then current has to be less on the battery side for volt x
> amps to be the same on both sides.
>
> Thank heavens, or we'd all be toasting our batteries.
>
> Think of the controller as an impedence matcher, or a DC transformer with a
> variable turns ratio (if there was such a thing), and it starts to make
> sense.  It's all about watts.
>
> ----- Original Message -----
> From: "Tom Jones" <[hidden email]>
> To: "Electric Vehicle Discussion List" <[hidden email]>
> Sent: Tuesday, August 14, 2007 2:21 PM
> Subject: Re: [EVDL] EV HP
>
>
> > Just a sanity check here. How could motor current exceed the battery
> > current? Since everything comes from the battery!
> >
> > My rash assumption is that the PWM of the controller is causing a falsely
> > high motor current reading. Any other opinions?
> > _______________________________________________
> > For subscription options, see
> > http://lists.sjsu.edu/mailman/listinfo/ev
> >
> >
>
>
> _______________________________________________
> For subscription options, see
> http://lists.sjsu.edu/mailman/listinfo/ev
>

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Re: EV HP

Tom Jones-5
Interesting. Here is my understanding of how a typical DC motor controller
works: They use pulse width modulation (PWM)) to control the power applied
to the motor. They do this my switching the traction battery voltage on and
off, varying the percent of time it is on. This is the duty cycle at any
specific throttle setting. So, the voltage is always the full pack voltage,
disregarding small losses. What the motor sees is full pack voltage in
pulses.

Since the voltage in and out is the almost the same, the currents should
also be close. Now, I don't have any real world, hands on, knowledge of
these measurements. So, if anyone more knowledgeable wants to set me
straight, please do. From a simple electrical point of view, if the voltage
is the same you can't create more current. There is no amplification effect.
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Re: EV HP

rodhower
Tom,
Check this out,
http://www.4qdtec.com/pwm-01.html
It's no 'amplification effect.'
It shows where the voltage and current is going.
Hope this helps,
Rod
--- Tom Jones <[hidden email]> wrote:

> Interesting. Here is my understanding of how a
> typical DC motor controller
> works: They use pulse width modulation (PWM)) to
> control the power applied
> to the motor. They do this my switching the traction
> battery voltage on and
> off, varying the percent of time it is on. This is
> the duty cycle at any
> specific throttle setting. So, the voltage is always
> the full pack voltage,
> disregarding small losses. What the motor sees is
> full pack voltage in
> pulses.
>
> Since the voltage in and out is the almost the same,
> the currents should
> also be close. Now, I don't have any real world,
> hands on, knowledge of
> these measurements. So, if anyone more knowledgeable
> wants to set me
> straight, please do. From a simple electrical point
> of view, if the voltage
> is the same you can't create more current. There is
> no amplification effect.
> _______________________________________________
> For subscription options, see
> http://lists.sjsu.edu/mailman/listinfo/ev
>

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Re: EV HP

Zeke Yewdall
In reply to this post by Tom Jones-5
Well, I think that only works for non-inductive loads.  For a motor,
the current has to be constant.... the self inductance will adjust the
voltage to keep the current constant.  But, we give it pulsed voltage
from the battery.  What this effectively does is result in a lower
voltage at the motor, and a pulsed current from the battery (which can
be filtered with capacitors -- which try to keep voltage constant, and
pulse the current to keep it this way).  Each time the FETS or IGGT's
in the controller turn off the motor gets no voltage, and in steady
state, no current.  However, it has current flowing through it from
before, and the inductor doesn't want to let this stop.  It generates
it's own voltage, and keeps the current flowing (in a loop through the
motor and the bypass diodes in the controller).  After a while of
course, this current will stop after the inductor has lost all of it's
stored power -- but by then the controller has turned back on and put
more current in there again.  So, you can see that for say a 30% duty
cycle, the batteries at 100 volts, the motor could see 33 volts (the
average of the 100 volt pulses it's getting), but 100 amps continously
-- a third of the time coming from the battery, and 2/3rds of the time
coming from the stored energy in the inductance (which is charged by
the high voltage pulse from the batteries).  But the battery only
delivers that 100 amps when the controller is turned on -- 30% of the
time.  So it only sees 33 amps average.

This isn't the most electrically rigorous explanation, but it's
essentially what's going on I think.

Z


On 8/14/07, Tom Jones <[hidden email]> wrote:

> Interesting. Here is my understanding of how a typical DC motor controller
> works: They use pulse width modulation (PWM)) to control the power applied
> to the motor. They do this my switching the traction battery voltage on and
> off, varying the percent of time it is on. This is the duty cycle at any
> specific throttle setting. So, the voltage is always the full pack voltage,
> disregarding small losses. What the motor sees is full pack voltage in
> pulses.
>
> Since the voltage in and out is the almost the same, the currents should
> also be close. Now, I don't have any real world, hands on, knowledge of
> these measurements. So, if anyone more knowledgeable wants to set me
> straight, please do. From a simple electrical point of view, if the voltage
> is the same you can't create more current. There is no amplification effect.
> _______________________________________________
> For subscription options, see
> http://lists.sjsu.edu/mailman/listinfo/ev
>

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GM Volt will use A123 batteries

Dan Frederiksen-2
In reply to this post by rodhower
http://fastlane.gmblogs.com/archives/2007/08/eflex_update_1.html#more

I hope that means they will finally make some bigger cells.
this will probably make A123 even more conceited in the short run but
perhaps it will give them some peace so they can make the right decision
and sell at reasonable prices to everyone.

Dan

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Re: EV HP

Tom Jones-5
In reply to this post by Zeke Yewdall
Thank you all for enlightening me. I am guessing here that this also has
something to do with using series wound motors. Boy, time goes by. The last
time I had a class in motors was 1971.
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How PWM works, was Re: EV HP

James Massey
In reply to this post by rodhower
G'day All

This is simpler-laymans talk, not strictly accurate, so please no-one shoot
me for using "bad" terminology. It is in response to the question: how come
there can be more amps in the motor than coming from the batteries?

First thing, a PWM (pulse width modulation) controller is one that varies
the on-time pulse width, be it a Curtis, Zilla, Raptor or an older design
SCR controller. A contactor controller almost always has the same amps in
the battery and motor wires.

A PWM controller has some kind of electronic switch in it that turns the
battery connection on and off. In an older SCR controller, it actually is
(on) same current in battery and in motor (off) no current from battery,
which is why SCR controllers are usually harder on batteries. (in a
transistorised controller,the controller has other components [capacitors]
that averages out the battery amps so that Nothing Bad happens).

OK, so the controller turns on, connecting the battery to the motor. Amps
starts to flow into the motor, and it is the same amps in the battery wire
as in the motor wires. A little bit of time later, the controller decides
that there is enough amps happening, so turns off the switch, so amps stops
flowing from the batteries. The current in the motor cannot 'just stop'
because it pushed up a magnetic field, and now that magnetic field starts
to fall back, keeping the amps going - this goes through the free-wheel
diodes in the controller. At some time depending on the controller design,
the controller switches back on, and amps again flow from the battery into
the motor.

If the controller has the amps coming from the battery at 10% on time, and
90% off time, the average amps from the batteries is only 10% of the amps
in the motor wires. You don't get something for nothing, the average motor
volts is only 10% that of the batteries.

Hope this is of help to someone.

Regards

[Technik] James

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Re: GM Volt will use A123 batteries

Joseph T.
In reply to this post by Dan Frederiksen-2
I think it says that GM is co-developing battery packs with A123, not
that they have already chosen A123 as their supplier.

On 8/14/07, Dan Frederiksen <[hidden email]> wrote:

> http://fastlane.gmblogs.com/archives/2007/08/eflex_update_1.html#more
>
> I hope that means they will finally make some bigger cells.
> this will probably make A123 even more conceited in the short run but
> perhaps it will give them some peace so they can make the right decision
> and sell at reasonable prices to everyone.
>
> Dan
>
> _______________________________________________
> For subscription options, see
> http://lists.sjsu.edu/mailman/listinfo/ev
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Porsche testdriving their hybrid

Dan Frederiksen-2
The porsche cayenne hybrid has now been shown in operation. from the
sound of it is much like a prius in configuration, even using crappy NIMH :)
http://www.motortrend.com/roadtests/hybrid/112_0707_porsche_cayenne_hybrid/
some more pictures:
http://www.bilzonen.dk/test-og-artikler/nyheder/autobild/2007/7/foerste-billeder-af-cayenne-hybrid?&altTemplate=articlegallery&selectedimage=4

googling for more I came across articles that if true indicated Porsche
announced this Cayenne hybrid back in 2005 already.

they indicate that it was developed in cooperation with VW and Audi
which is quite good news although not unexpected but more interestingly
they say VW will beat porsche to it and come out with a hybrid of their
Touareg in 2008

these hybrid are still only slightly more efficient gas cars and not EVs
but it's start

Dan

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Re: EV HP

Peter VanDerWal
In reply to this post by Tom Jones-5
If all the motor controller had was the switch (MOSFET or IGBT) then this
would be true.  However, the controller includes a couple other major
components,  Freewheeling diodes and input capacitors.

The freewheeling diodes keep the current flowing in the motor even when
the switch is off.  The diodes charge up (from the battery) during the
time the switch is off and discharge during the time it's on.
Because of the capacitors, the current going through the switch can be
higher than the battery current, the freewheeling diodes keep this current
flowing during the off time.

The acutal explanation is a bit longer than this and you have to
understand how the inductance of the motor effects the curent and voltage.

The whole combination -inductance, switch, capactor, diode- forms what's
commonly know known as a DC-to-DC buck converter.

> Interesting. Here is my understanding of how a typical DC motor controller
> works: They use pulse width modulation (PWM)) to control the power applied
> to the motor. They do this my switching the traction battery voltage on
> and
> off, varying the percent of time it is on. This is the duty cycle at any
> specific throttle setting. So, the voltage is always the full pack
> voltage,
> disregarding small losses. What the motor sees is full pack voltage in
> pulses.
>
> Since the voltage in and out is the almost the same, the currents should
> also be close. Now, I don't have any real world, hands on, knowledge of
> these measurements. So, if anyone more knowledgeable wants to set me
> straight, please do. From a simple electrical point of view, if the
> voltage
> is the same you can't create more current. There is no amplification
> effect.
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