Controller power output at different motor rpms

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Controller power output at different motor rpms

Tom H
Hello to everyone,
I am still puzzled by the observation that the power (Kilowatts) controllers accept from the batteries and put out to the motor depends on motor rpms.  Does anyone have an explanation for this?  

System: '87 Nissan pickup using 120 Volts (Trojan 105) and a NetGain Impulse 9" motor.
 
I do not have meters on the output of the controller but I do monitor the power input (volts x amps) to the controller.  [If you assume a 95% efficiency on the controllers you can estimate the actual power output by multiplying the numbers by 0.95]  

I now have standard test I run. I drive at 25 mph in third gear (about 2000rpm on the motor) and in second gear (3000 rpm). I push the throttle to max and monitor the amps and voltage going into the controller.  I find that each controller has a maximum power level it will accept for each rpm, and they are different.  All five of the controllers I have tried (Curtis and 4 Kelly's) maintain the same relative relationships as power increases with rpms.  There are many hills around here so I can always find one where the speed of the truck just matches the maximum power put out by the controller.  If the hill is too steep and I slow down (motor rpms drop) the power going to the controller (and thus the power it puts out) also drops even at maximum throttle.  

Here is what I found at 2000 rpm:
KDH12500A – accepts no more than 80 amps =  9.6 KW  (@ 120 volts nominal)
KDH14650B – accepts no more than 120 amps  14.4 KW
Curtis 1221C -                 150amps              18  KW
KDH12600B -                   180 amps             21.6 KW
KDH12800B -                   200 amps             24 KW

Here are the data at 3000 rpm

KDH12500A – accepts only 120 amps               14.4 KW  
KDH14650B – accepts only 150 amps                18 KW
Curtis 1221C -                       180amps           18  KW
KDH12600B -                        220 amps           26.4 KW
KDH12800B -                        >220 amps      limited by batteries

Hope this information will also prove to be useful to others wanting to chose a controller.
Tom (soundboats) in Olympia WA
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Re: Controller power output at different motor rpms

Jeff Major


--- On Tue, 3/10/09, soundboats <[hidden email]> wrote:

> I am still puzzled by the observation that the power
> (Kilowatts) controllers
> accept from the batteries and put out to the motor depends
> on motor rpms.
> Does anyone have an explanation for this?  
>

Hi Tom,

I'll give it a shot.  The higher motor speed requires a higher motor voltage.  The controller limits the motor current.  The motor power is the product.  The current limit (motor current) remains the same for the 2 cases.  The gear selection requiring higher motor RPM and motor voltage then gives more power (Vm * Im) than the slower RPM gear selection.

Sound logical?

Jeff M



     

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Re: Controller power output at different motor rpms

Tom H
Jeff,
Thanks for answering, but I was told something different.  The last time I posted a question on this, the response that I had was that the controller limits the voltage and not the current.  At low power the controller puts out the maximum amps but at a lower voltage to get the lower power.  This reverses what goes in - constant voltage but variable current.   At one time I did manage to put a volt meter on the output of the controller and found that the voltage does vary with speed.  Unfortunately at that time I did not have an ammeter on the motor side, just the battery side.  I found that the controller (Curtis) was putting out 70 volts at 3000 rpm and about 45 at 2000.  

If this is the case what I don't understand is why there is a such a big difference between the controllers.  If the motor requires 70 volts to run at 3000 rpm wouldn't all of the controllers put out 70 volts at that rpm?  For example, the KDH12500A accepted 14.4 KW at 3000 rpm.  At 70 volts that is a current of 200 amps.  This is well below the amount it should be putting for short times.  The Curtis was putting only 257 amps of its rated 400 at 3000 rpm.  

Tom
Jeff Major wrote

--- On Tue, 3/10/09, soundboats <thru461@ecy.wa.gov> wrote:

> I am still puzzled by the observation that the power
> (Kilowatts) controllers
> accept from the batteries and put out to the motor depends
> on motor rpms.
> Does anyone have an explanation for this?  
>

Hi Tom,

I'll give it a shot.  The higher motor speed requires a higher motor voltage.  The controller limits the motor current.  The motor power is the product.  The current limit (motor current) remains the same for the 2 cases.  The gear selection requiring higher motor RPM and motor voltage then gives more power (Vm * Im) than the slower RPM gear selection.

Sound logical?

Jeff M



     

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Re: Controller power output at different motor rpms

Jeff Major

Hi Tom,

Actually the only thing the controller really limits is the duration of the on-pulse.  But the on-pulse time/period, or duty cycle is related to the output voltage from the controller, or motor voltage.  However, the controller senses motor current and uses that value to adjust the duty cycle (and therfore motor voltage) to control the motor current.

You have been looking at battery current.  Sounds like you know that motor current is higher than battery current except when the controller is full on, 100% duty cycle.  Or when at 0%.  Then the currents are the same.

So, I guess I don't see anything disturbing about your story.  The motor RPM is not just dependent on the voltage, but also the load.  Sounds like you know your EV pretty well.  Putting 5 differnet controllers in it.  But it does not sound like you are fully instrumented.  In your previous list, you used 120V for all the battery power calculations.  We know that is an approximation, right?  To really see what's going on, you need Im, Ib, Vb and RPM.  Motor temperature might be wise also with those hills.

Regards,

Jeff M

--- On Tue, 3/10/09, soundboats <[hidden email]> wrote:

> Jeff,
> Thanks for answering, but I was told something different.
> The last time I
> posted a question on this, the response that I had was that
> the controller
> limits the voltage and not the current.  At low power the
> controller puts
> out the maximum amps but at a lower voltage to get the
> lower power.  This
> reverses what goes in - constant voltage but variable
> current.   At one time
> I did manage to put a volt meter on the output of the
> controller and found
> that the voltage does vary with speed.  Unfortunately at
> that time I did not
> have an ammeter on the motor side, just the battery side.
> I found that the
> controller (Curtis) was putting out 70 volts at 3000 rpm
> and about 45 at
> 2000.  
>
> If this is the case what I don't understand is why
> there is a such a big
> difference between the controllers.  If the motor requires
> 70 volts to run
> at 3000 rpm wouldn't all of the controllers put out 70
> volts at that rpm?
> For example, the KDH12500A accepted 14.4 KW at 3000 rpm.
> At 70 volts that
> is a current of 200 amps.  This is well below the amount it
> should be
> putting for short times.  The Curtis was putting only 257
> amps of its rated
> 400 at 3000 rpm.  
>
> Tom
>
> Jeff Major wrote:
> >
> > --- On Tue, 3/10/09, soundboats
> <[hidden email]> wrote:
> >
> >> I am still puzzled by the observation that the
> power
> >> (Kilowatts) controllers
> >> accept from the batteries and put out to the motor
> depends
> >> on motor rpms.
> >> Does anyone have an explanation for this?  
> >>
> >
> > Hi Tom,
> >
> > I'll give it a shot.  The higher motor speed
> requires a higher motor
> > voltage.  The controller limits the motor current.
> The motor power is the
> > product.  The current limit (motor current) remains
> the same for the 2
> > cases.  The gear selection requiring higher motor RPM
> and motor voltage
> > then gives more power (Vm * Im) than the slower RPM
> gear selection.
> >
> > Sound logical?
> >
> > Jeff M



     

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Re: Controller power output at different motor rpms

Tom H
Thanks Jeff,
I did not plan to put 5 controllers into the EV.  It just came about that way.  I started with the Curtis and was not satisfied with its performance.  I couldn't go up some hills around here and was wondering why I could go up the hills if I was moving, but could not start from a standstill.  I next tried the KDH12600B but that blew out after 2 months even though I had good performance.  I think it didn't like the 160 volts the Zivan charger puts out during the degassing cycle.  Kelly folks sent me the KDH12500A by mistake but I got a chance to try it.  I upgraded to the KDH12800B but two blew out (the first one within a week, and the second in 2 days) before I asked Kelly to send me the KDH14650B. [this time however I put a second contactor on the B- side to isolate the controller during the charging cycle.]  

So, now I am back to the Curtis, poking along and having to be careful not to get stuck on hills with stoplights since the power output of the 14650B is about 20% lower than the Curtis at any given rpm.  

And, yes my numbers are just estimates.  I was looking for ballpark numbers to help me explain what is going on.  My first belief was that the controllers would be able to put out 100% of its duty cycle when I stepped on the throttle to get going.  I guess that is not the case.  The controllers don't put out their maximum rated power (amps rated X battery pack voltage) until the motors are spinning at 4000-5000 rpm.  So I need a controller with a much higher rating (800 amps instead of 400 amps) to start on hills.

Tom
Jeff Major wrote
Hi Tom,

Actually the only thing the controller really limits is the duration of the on-pulse.  But the on-pulse time/period, or duty cycle is related to the output voltage from the controller, or motor voltage.  However, the controller senses motor current and uses that value to adjust the duty cycle (and therfore motor voltage) to control the motor current.

You have been looking at battery current.  Sounds like you know that motor current is higher than battery current except when the controller is full on, 100% duty cycle.  Or when at 0%.  Then the currents are the same.

So, I guess I don't see anything disturbing about your story.  The motor RPM is not just dependent on the voltage, but also the load.  Sounds like you know your EV pretty well.  Putting 5 differnet controllers in it.  But it does not sound like you are fully instrumented.  In your previous list, you used 120V for all the battery power calculations.  We know that is an approximation, right?  To really see what's going on, you need Im, Ib, Vb and RPM.  Motor temperature might be wise also with those hills.

Regards,

Jeff M

--- On Tue, 3/10/09, soundboats <thru461@ecy.wa.gov> wrote:

> Jeff,
> Thanks for answering, but I was told something different.
> The last time I
> posted a question on this, the response that I had was that
> the controller
> limits the voltage and not the current.  At low power the
> controller puts
> out the maximum amps but at a lower voltage to get the
> lower power.  This
> reverses what goes in - constant voltage but variable
> current.   At one time
> I did manage to put a volt meter on the output of the
> controller and found
> that the voltage does vary with speed.  Unfortunately at
> that time I did not
> have an ammeter on the motor side, just the battery side.
> I found that the
> controller (Curtis) was putting out 70 volts at 3000 rpm
> and about 45 at
> 2000.  
>
> If this is the case what I don't understand is why
> there is a such a big
> difference between the controllers.  If the motor requires
> 70 volts to run
> at 3000 rpm wouldn't all of the controllers put out 70
> volts at that rpm?
> For example, the KDH12500A accepted 14.4 KW at 3000 rpm.
> At 70 volts that
> is a current of 200 amps.  This is well below the amount it
> should be
> putting for short times.  The Curtis was putting only 257
> amps of its rated
> 400 at 3000 rpm.  
>
> Tom
>
> Jeff Major wrote:
> >
> > --- On Tue, 3/10/09, soundboats
> <thru461@ecy.wa.gov> wrote:
> >
> >> I am still puzzled by the observation that the
> power
> >> (Kilowatts) controllers
> >> accept from the batteries and put out to the motor
> depends
> >> on motor rpms.
> >> Does anyone have an explanation for this?  
> >>
> >
> > Hi Tom,
> >
> > I'll give it a shot.  The higher motor speed
> requires a higher motor
> > voltage.  The controller limits the motor current.
> The motor power is the
> > product.  The current limit (motor current) remains
> the same for the 2
> > cases.  The gear selection requiring higher motor RPM
> and motor voltage
> > then gives more power (Vm * Im) than the slower RPM
> gear selection.
> >
> > Sound logical?
> >
> > Jeff M



     

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Re: Controller power output at different motor rpms

Cor van de Water
What you need is a lower first gear. That will get you started on hills.



Cor van de Water
Director HW & Systems Architecture Group
Proxim Wireless Corporation http://www.proxim.com
Email: [hidden email]    Private: http://www.cvandewater.com
Skype: cor_van_de_water     IM: [hidden email]
Tel: +1 408 383 7626        VoIP: +31 20 3987567 FWD# 25925
Tel: +91 (040)23117400 x203 XoIP: +31877841130

Please consider the environment before printing this e-mail.
-----Original Message-----
From: [hidden email] [mailto:[hidden email]] On
Behalf Of soundboats
Sent: Wednesday, March 11, 2009 3:11 AM
To: [hidden email]
Subject: Re: [EVDL] Controller power output at different motor rpms


Thanks Jeff,
I did not plan to put 5 controllers into the EV.  It just came about
that
way.  I started with the Curtis and was not satisfied with its
performance.
I couldn't go up some hills around here and was wondering why I could go
up
the hills if I was moving, but could not start from a standstill.  I
next
tried the KDH12600B but that blew out after 2 months even though I had
good
performance.  I think it didn't like the 160 volts the Zivan charger
puts
out during the degassing cycle.  Kelly folks sent me the KDH12500A by
mistake but I got a chance to try it.  I upgraded to the KDH12800B but
two
blew out (the first one within a week, and the second in 2 days) before
I
asked Kelly to send me the KDH14650B. [this time however I put a second
contactor on the B- side to isolate the controller during the charging
cycle.]  

So, now I am back to the Curtis, poking along and having to be careful
not
to get stuck on hills with stoplights since the power output of the
14650B
is about 20% lower than the Curtis at any given rpm.  

And, yes my numbers are just estimates.  I was looking for ballpark
numbers
to help me explain what is going on.  My first belief was that the
controllers would be able to put out 100% of its duty cycle when I
stepped
on the throttle to get going.  I guess that is not the case.  The
controllers don't put out their maximum rated power (amps rated X
battery
pack voltage) until the motors are spinning at 4000-5000 rpm.  So I need
a
controller with a much higher rating (800 amps instead of 400 amps) to
start
on hills.

Tom

Jeff Major wrote:
>
>
> Hi Tom,
>
> Actually the only thing the controller really limits is the duration
of
> the on-pulse.  But the on-pulse time/period, or duty cycle is related
to
> the output voltage from the controller, or motor voltage.  However,
the
> controller senses motor current and uses that value to adjust the duty
> cycle (and therfore motor voltage) to control the motor current.
>
> You have been looking at battery current.  Sounds like you know that
motor
> current is higher than battery current except when the controller is
full
> on, 100% duty cycle.  Or when at 0%.  Then the currents are the same.
>
> So, I guess I don't see anything disturbing about your story.  The
motor
> RPM is not just dependent on the voltage, but also the load.  Sounds
like
> you know your EV pretty well.  Putting 5 differnet controllers in it.
But
> it does not sound like you are fully instrumented.  In your previous
list,
> you used 120V for all the battery power calculations.  We know that is
an
> approximation, right?  To really see what's going on, you need Im, Ib,
Vb

> and RPM.  Motor temperature might be wise also with those hills.
>
> Regards,
>
> Jeff M
>
> --- On Tue, 3/10/09, soundboats <[hidden email]> wrote:
>
>> Jeff,
>> Thanks for answering, but I was told something different.
>> The last time I
>> posted a question on this, the response that I had was that
>> the controller
>> limits the voltage and not the current.  At low power the
>> controller puts
>> out the maximum amps but at a lower voltage to get the
>> lower power.  This
>> reverses what goes in - constant voltage but variable
>> current.   At one time
>> I did manage to put a volt meter on the output of the
>> controller and found
>> that the voltage does vary with speed.  Unfortunately at
>> that time I did not
>> have an ammeter on the motor side, just the battery side.
>> I found that the
>> controller (Curtis) was putting out 70 volts at 3000 rpm
>> and about 45 at
>> 2000.  
>>
>> If this is the case what I don't understand is why
>> there is a such a big
>> difference between the controllers.  If the motor requires
>> 70 volts to run
>> at 3000 rpm wouldn't all of the controllers put out 70
>> volts at that rpm?
>> For example, the KDH12500A accepted 14.4 KW at 3000 rpm.
>> At 70 volts that
>> is a current of 200 amps.  This is well below the amount it
>> should be
>> putting for short times.  The Curtis was putting only 257
>> amps of its rated
>> 400 at 3000 rpm.  
>>
>> Tom
>>
>> Jeff Major wrote:
>> >
>> > --- On Tue, 3/10/09, soundboats
>> <[hidden email]> wrote:
>> >
>> >> I am still puzzled by the observation that the
>> power
>> >> (Kilowatts) controllers
>> >> accept from the batteries and put out to the motor
>> depends
>> >> on motor rpms.
>> >> Does anyone have an explanation for this?  
>> >>
>> >
>> > Hi Tom,
>> >
>> > I'll give it a shot.  The higher motor speed
>> requires a higher motor
>> > voltage.  The controller limits the motor current.
>> The motor power is the
>> > product.  The current limit (motor current) remains
>> the same for the 2
>> > cases.  The gear selection requiring higher motor RPM
>> and motor voltage
>> > then gives more power (Vm * Im) than the slower RPM
>> gear selection.
>> >
>> > Sound logical?
>> >
>> > Jeff M
>
>
>
>      
>
> _______________________________________________
> General EVDL support: http://evdl.org/help/
> Usage guidelines: http://evdl.org/help/index.html#conv
> Archives: http://evdl.org/archive/
> Subscription options: http://lists.sjsu.edu/mailman/listinfo/ev
>
>
>

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Re: Controller power output at different motor rpms

Dennis at e v school
In reply to this post by Tom H
Hello Jeff and Tom,    I've been reading your  posts on this subject for a
couple of days now,  and I must say your  attempts to understand what I know is
a very complex subject are applaudable.  BUT, the numbers will NEVER truly
make sense.  The Motor is an inductive  load and the relationship between Voltage
and Amperage and Power, is not  arithmetically calculable . Part of the
difficulty comes from instrumentation,  you are measuring with a meter which
displays the AVERAGE if the Voltage and  Current in Amps. But, the motor is
receiving energy in a series of pulses from  the controller, and that energy is stored
in the magnetic fields of the motor  field coil and armature coils, where it
slowly dissipates as the energy is  converted to TORQUE and some is wasted as
heat. I spent 1962 thru 1968 learning  this and other electrical stuff, but it
wasn't until i taught the DC and AC  Fundamentals course about 12 times thru
to my first 600 students in 1981 thru  1983 when I finally felt I UNDERSTOOD
what is happening. Sorry, to teach it  takes about 180 hours and 90 days and
that is beyond what we can do in this  forum. If you have an interest take a
class at a vocational or Community  College, or even a correspondence, perhaps
web based, program. But  understand your observations and questions are valid
but more complex than your  analysis.  Best wishes, contact me directly if you
need answers.  Dennis  (the Director) at: _EVtrainingCenter@aol.com_
(mailto:[hidden email])   .
 
 
In a message dated 3/10/2009 5:47:52 P.M. Eastern Daylight Time,  
[hidden email] writes:


Thanks Jeff,
I did not plan to put 5 controllers into the  EV.  It just came about that
way.  I started with the Curtis and  was not satisfied with its performance.
I couldn't go up some hills around  here and was wondering why I could go up
the hills if I was moving, but  could not start from a standstill.  I next
tried the KDH12600B but  that blew out after 2 months even though I had good
performance.  I  think it didn't like the 160 volts the Zivan charger puts
out during the  degassing cycle.  Kelly folks sent me the KDH12500A by
mistake but I  got a chance to try it.  I upgraded to the KDH12800B but two
blew out  (the first one within a week, and the second in 2 days) before I
asked  Kelly to send me the KDH14650B. [this time however I put a second
contactor  on the B- side to isolate the controller during the charging
cycle.]  

So, now I am back to the Curtis, poking along and having to be careful  not
to get stuck on hills with stoplights since the power output of the  14650B
is about 20% lower than the Curtis at any given rpm.  

And, yes my numbers are just estimates.  I was looking for  ballpark numbers
to help me explain what is going on.  My first belief  was that the
controllers would be able to put out 100% of its duty cycle  when I stepped
on the throttle to get going.  I guess that is not the  case.  The
controllers don't put out their maximum rated power (amps  rated X battery
pack voltage) until the motors are spinning at 4000-5000  rpm.  So I need a
controller with a much higher rating (800 amps  instead of 400 amps) to start
on hills.

Tom

Jeff Major  wrote:

>
>
> Hi Tom,
>
> Actually the only  thing the controller really limits is the duration of
> the  on-pulse.  But the on-pulse time/period, or duty cycle is related  to
> the output voltage from the controller, or motor voltage.   However, the
> controller senses motor current and uses that value to  adjust the duty
> cycle (and therfore motor voltage) to control the  motor current.
>
> You have been looking at battery  current.  Sounds like you know that motor
> current is higher than  battery current except when the controller is full
> on, 100% duty  cycle.  Or when at 0%.  Then the currents are the same.
>  
> So, I guess I don't see anything disturbing about your story.   The motor
> RPM is not just dependent on the voltage, but also the  load.  Sounds like
> you know your EV pretty well.  Putting 5  differnet controllers in it.  But
> it does not sound like you are  fully instrumented.  In your previous list,
> you used 120V for all  the battery power calculations.  We know that is an
>  approximation, right?  To really see what's going on, you need Im, Ib,  Vb
> and RPM.  Motor temperature might be wise also with those  hills.
>
> Regards,
>
> Jeff M
>
> ---  On Tue, 3/10/09, soundboats <[hidden email]> wrote:
>  
>> Jeff,
>> Thanks for answering, but I was told something  different.
>> The last time I
>> posted a question on this,  the response that I had was that
>> the controller
>> limits  the voltage and not the current.  At low power the
>> controller  puts
>> out the maximum amps but at a lower voltage to get  the
>> lower power.  This
>> reverses what goes in -  constant voltage but variable
>> current.   At one  time
>> I did manage to put a volt meter on the output of  the
>> controller and found
>> that the voltage does vary  with speed.  Unfortunately at
>> that time I did not
>>  have an ammeter on the motor side, just the battery side.
>> I found  that the
>> controller (Curtis) was putting out 70 volts at 3000  rpm
>> and about 45 at
>> 2000.  
>>  
>> If this is the case what I don't understand is why
>>  there is a such a big
>> difference between the controllers.  If  the motor requires
>> 70 volts to run
>> at 3000 rpm  wouldn't all of the controllers put out 70
>> volts at that rpm?  
>> For example, the KDH12500A accepted 14.4 KW at 3000 rpm.  
>> At 70 volts that
>> is a current of 200 amps.  This  is well below the amount it
>> should be
>> putting for  short times.  The Curtis was putting only 257
>> amps of its  rated
>> 400 at 3000 rpm.  
>>
>> Tom  
>>
>> Jeff Major wrote:
>> >
>> >  --- On Tue, 3/10/09, soundboats
>> <[hidden email]>  wrote:
>> >
>> >> I am still puzzled by the  observation that the
>> power
>> >> (Kilowatts)  controllers
>> >> accept from the batteries and put out to the  motor
>> depends
>> >> on motor rpms.
>>  >> Does anyone have an explanation for this?  
>> >>  
>> >
>> > Hi Tom,
>> >
>> >  I'll give it a shot.  The higher motor speed
>> requires a  higher motor
>> > voltage.  The controller limits the motor  current.
>> The motor power is the
>> > product.   The current limit (motor current) remains
>> the same for the  2
>> > cases.  The gear selection requiring higher motor  RPM
>> and motor voltage
>> > then gives more power (Vm *  Im) than the slower RPM
>> gear selection.
>> >  
>> > Sound logical?
>> >
>> > Jeff  M
>
>
>
>      
>  
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Re: Controller power output at different motor rpms

Jeff Major

Hi Dennis,

Thanks for the interest and post.  However, I disagree.  Average values which are taken on the motor and battery voltages and currents are accurate and will make sense.  I am not saying that Tom has done this correctly, in fact he has not.  And it appears that he is likely comparing non-repeatable tests.  One of the biggest sources of error with Tom's test is the battery voltage, which he assumes is 120V, regardless of current.  If he were to have used a measured battery voltage, it is likely that those calculated motor currents would have been closer to rated.  But, he should install a shunt in the motor circuit and measure it directly.

Another thing which might play into Tom's dilemma is the controller temperature.  It could be that his controller is in thermal cutback during his test.

Back to your point.  I have done similar tests in controlled conditions and it is my experience that measured average values do in fact make sense and add up.  Try it.  You'll see.  

Regards,

Jeff M

--- On Wed, 3/11/09, [hidden email] <[hidden email]> wrote:

> Hello Jeff and Tom,    I've been reading your  posts on
> this subject for a
> couple of days now,  and I must say your  attempts to
> understand what I know is
> a very complex subject are applaudable.  BUT, the numbers
> will NEVER truly
> make sense.  The Motor is an inductive  load and the
> relationship between Voltage
> and Amperage and Power, is not  arithmetically calculable .
> Part of the
> difficulty comes from instrumentation,  you are measuring
> with a meter which
> displays the AVERAGE if the Voltage and  Current in Amps.
> But, the motor is
> receiving energy in a series of pulses from  the
> controller, and that energy is stored
> in the magnetic fields of the motor  field coil and
> armature coils, where it
> slowly dissipates as the energy is  converted to TORQUE and
> some is wasted as
> heat. I spent 1962 thru 1968 learning  this and other
> electrical stuff, but it
> wasn't until i taught the DC and AC  Fundamentals
> course about 12 times thru
> to my first 600 students in 1981 thru  1983 when I finally
> felt I UNDERSTOOD
> what is happening. Sorry, to teach it  takes about 180
> hours and 90 days and
> that is beyond what we can do in this  forum. If you have
> an interest take a
> class at a vocational or Community  College, or even a
> correspondence, perhaps
> web based, program. But  understand your observations and
> questions are valid
> but more complex than your  analysis.  Best wishes, contact
> me directly if you
> need answers.  Dennis  (the Director) at:
> _EVtrainingCenter@aol.com_



     

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Re: Controller power output at different motor rpms

Jeff Major
In reply to this post by Cor van de Water


--- On Tue, 3/10/09, Cor van de Water <[hidden email]> wrote:
> What you need is a lower first gear. That will get you
> started on hills.

Yeah, Cor,

I was wondering the same thing.  In fact Tom says he was using 2nd and 3rd.  I wonder if he has even tried 1st.

Jeff M


     

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Re: Controller power output at different motor rpms

cowtown
In reply to this post by Tom H
> Back to your point.  I have done similar tests in controlled  
> conditions and it > is my experience that measured average values do  
> in fact make sense and add    > up.  Try it.  You'll see.

Don't start a disagreement with a Escalade-driving retiree from Florida!

Think more
    Talk less
       Become wise

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Re: Controller power output at different motor rpms

Tom H
In reply to this post by Tom H
Hello,
I tried to reply directly to Jeff's latest addition but the computer kept crashing on me.
I used 120 volts as an approximation, and yes it does not give an exact voltage.  I do have  volt meter attached and the voltage sag is only to about 110 volts at maximum current in the experiments for any of the controllers.  Remember I am at the lower end of the battery currents (100 - 200 amps).  This voltage sag is small enough that it does not explain the large differences between the controllers.  I used 120 volts as an average to calculate relative power of the different controllers.  to be specific the voltage from the battery pack when using the KDH12500A at maximum throttle at 2000 rpm was about 116 volts (pulling 80 amps from the battery pack) while the voltage when using the KDH12800B at max throttle at 2000 rpm was 110 volts (pulling 200 amps from the battery pack).  this still does not explain the differences for controllers with the similar ratings.

Tom

soundboats wrote
Hello to everyone,
I am still puzzled by the observation that the power (Kilowatts) controllers accept from the batteries and put out to the motor depends on motor rpms.  Does anyone have an explanation for this?  

System: '87 Nissan pickup using 120 Volts (Trojan 105) and a NetGain Impulse 9" motor.
 
I do not have meters on the output of the controller but I do monitor the power input (volts x amps) to the controller.  [If you assume a 95% efficiency on the controllers you can estimate the actual power output by multiplying the numbers by 0.95]  

I now have standard test I run. I drive at 25 mph in third gear (about 2000rpm on the motor) and in second gear (3000 rpm). I push the throttle to max and monitor the amps and voltage going into the controller.  I find that each controller has a maximum power level it will accept for each rpm, and they are different.  All five of the controllers I have tried (Curtis and 4 Kelly's) maintain the same relative relationships as power increases with rpms.  There are many hills around here so I can always find one where the speed of the truck just matches the maximum power put out by the controller.  If the hill is too steep and I slow down (motor rpms drop) the power going to the controller (and thus the power it puts out) also drops even at maximum throttle.  

Here is what I found at 2000 rpm:
KDH12500A – accepts no more than 80 amps =  9.6 KW  (@ 120 volts nominal)
KDH14650B – accepts no more than 120 amps  14.4 KW
Curtis 1221C -                 150amps              18  KW
KDH12600B -                   180 amps             21.6 KW
KDH12800B -                   200 amps             24 KW

Here are the data at 3000 rpm

KDH12500A – accepts only 120 amps               14.4 KW  
KDH14650B – accepts only 150 amps                18 KW
Curtis 1221C -                       180amps           18  KW
KDH12600B -                        220 amps           26.4 KW
KDH12800B -                        >220 amps      limited by batteries

Hope this information will also prove to be useful to others wanting to chose a controller.
Tom (soundboats) in Olympia WA
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Re: Controller power output at different motor rpms

Jeff Major

Hi Tom,

Let's look at it another way.  On flat road, full throttle acceleration all the way up to speed in a single gear, say third, does the ammeter hit the rated current?  It should start low, climb to rated current until 100% duty cycle and then go down from there.

Jeff M


--- On Wed, 3/11/09, soundboats <[hidden email]> wrote:

> Hello,
> I tried to reply directly to Jeff's latest addition but
> the computer kept
> crashing on me.
> I used 120 volts as an approximation, and yes it does not
> give an exact
> voltage.  I do have  volt meter attached and the voltage
> sag is only to
> about 110 volts at maximum current in the experiments for
> any of the
> controllers.


     

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Re: Controller power output at different motor rpms

Tom H
In reply to this post by Tom H
to answer Jeff's last question.. No.  The smaller controllers never reach their rated output.  The highest battery current I was able to achieve with the KDH12500A was about 160 amps and with the DKH14650 was 180 amps.  With the others it is difficult to say because the batteries become the limiting factor.  I found that the batteriews (Trojan 105's) will put out only about 320 amps after resting and this drops to about 220 for continuous use.  The Curtis will get to 200 but not to 320.  On flat roads I have to test in 4th gear because the speed goes too high in third before the current stabilizes.  I am not so concerned about the high end currents.  From my experience I need about 160-200 battery amps (19 - 24 KW) to get up the hills around here in Olympia.  

Tom
soundboats wrote
Hello to everyone,
I am still puzzled by the observation that the power (Kilowatts) controllers accept from the batteries and put out to the motor depends on motor rpms.  Does anyone have an explanation for this?  

System: '87 Nissan pickup using 120 Volts (Trojan 105) and a NetGain Impulse 9" motor.
 
I do not have meters on the output of the controller but I do monitor the power input (volts x amps) to the controller.  [If you assume a 95% efficiency on the controllers you can estimate the actual power output by multiplying the numbers by 0.95]  

I now have standard test I run. I drive at 25 mph in third gear (about 2000rpm on the motor) and in second gear (3000 rpm). I push the throttle to max and monitor the amps and voltage going into the controller.  I find that each controller has a maximum power level it will accept for each rpm, and they are different.  All five of the controllers I have tried (Curtis and 4 Kelly's) maintain the same relative relationships as power increases with rpms.  There are many hills around here so I can always find one where the speed of the truck just matches the maximum power put out by the controller.  If the hill is too steep and I slow down (motor rpms drop) the power going to the controller (and thus the power it puts out) also drops even at maximum throttle.  

Here is what I found at 2000 rpm:
KDH12500A – accepts no more than 80 amps =  9.6 KW  (@ 120 volts nominal)
KDH14650B – accepts no more than 120 amps  14.4 KW
Curtis 1221C -                 150amps              18  KW
KDH12600B -                   180 amps             21.6 KW
KDH12800B -                   200 amps             24 KW

Here are the data at 3000 rpm

KDH12500A – accepts only 120 amps               14.4 KW  
KDH14650B – accepts only 150 amps                18 KW
Curtis 1221C -                       180amps           18  KW
KDH12600B -                        220 amps           26.4 KW
KDH12800B -                        >220 amps      limited by batteries

Hope this information will also prove to be useful to others wanting to chose a controller.
Tom (soundboats) in Olympia WA
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Re: Controller power output at different motor rpms

Jeff Major


--- On Wed, 3/11/09, soundboats <[hidden email]> wrote:
> to answer Jeff's last question.. No.  The smaller
> controllers never reach their rated output.

O.K. Tom,

How about this?  Is your throttle pot adjusted correctly to give a full on signal input?  On the DC controllers, I have just worked with the lower voltage units, but am able to get full rated current, no problem.  Pretty much right on with Curtis and Sevcon units.  275, 400 and 500 amp versions.

Jeff M


     

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Re: Controller power output at different motor rpms

Jeff Major
In reply to this post by Tom H


--- On Wed, 3/11/09, soundboats <[hidden email]> wrote:

With
> the others it is difficult to say because the batteries
> become the limiting
> factor.  I found that the batteriews (Trojan 105's)
> will put out only about
> 320 amps after resting and this drops to about 220 for
> continuous use.

Tom,

I am somewhat confused about this statement.  How does the battery limit current?  Would that not be by drooping voltage?  Which you said earlier is not the case.  I used the T-125s in my eJeep and those would put out 5 or 600 amps regularly.  I suspect more.

Jeff M


     

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Re: Controller power output at different motor rpms

Tom H
In reply to this post by Tom H
Jeff,
The issue with the batteries is based on their construction.  The T105 are constructed for long life and rugged use.  As a result the recombination/dissociation chemistry is a bit slower than in many other batteries because of the position of the plates etc..Initially when the battery has not been used for a while there are more of the ions floating around so you can get an initial surge of higher current.  However after this has dissipated the output is controlled by how fast the ions can move around.  The T-125 have a different construction and thus can provide a higher continuous current.  The same is true AGM and other sealed batteries.  With the T105's it seems as if the continuous current is about 220 amps this is in the winter with the battery pack at about 45 degrees F.   I expect it will be higher in the summer when the temperature increases.

Also, I have checked the pot box with my meter.  It provide the full 5Kohm range.  I even have tried a second pot box in case there was something wrong with the first.

tom  
soundboats wrote
Hello to everyone,
I am still puzzled by the observation that the power (Kilowatts) controllers accept from the batteries and put out to the motor depends on motor rpms.  Does anyone have an explanation for this?  

System: '87 Nissan pickup using 120 Volts (Trojan 105) and a NetGain Impulse 9" motor.
 
I do not have meters on the output of the controller but I do monitor the power input (volts x amps) to the controller.  [If you assume a 95% efficiency on the controllers you can estimate the actual power output by multiplying the numbers by 0.95]  

I now have standard test I run. I drive at 25 mph in third gear (about 2000rpm on the motor) and in second gear (3000 rpm). I push the throttle to max and monitor the amps and voltage going into the controller.  I find that each controller has a maximum power level it will accept for each rpm, and they are different.  All five of the controllers I have tried (Curtis and 4 Kelly's) maintain the same relative relationships as power increases with rpms.  There are many hills around here so I can always find one where the speed of the truck just matches the maximum power put out by the controller.  If the hill is too steep and I slow down (motor rpms drop) the power going to the controller (and thus the power it puts out) also drops even at maximum throttle.  

Here is what I found at 2000 rpm:
KDH12500A – accepts no more than 80 amps =  9.6 KW  (@ 120 volts nominal)
KDH14650B – accepts no more than 120 amps  14.4 KW
Curtis 1221C -                 150amps              18  KW
KDH12600B -                   180 amps             21.6 KW
KDH12800B -                   200 amps             24 KW

Here are the data at 3000 rpm

KDH12500A – accepts only 120 amps               14.4 KW  
KDH14650B – accepts only 150 amps                18 KW
Curtis 1221C -                       180amps           18  KW
KDH12600B -                        220 amps           26.4 KW
KDH12800B -                        >220 amps      limited by batteries

Hope this information will also prove to be useful to others wanting to chose a controller.
Tom (soundboats) in Olympia WA
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Re: Controller power output at different motor rpms

Jeff Major


--- On Wed, 3/11/09, soundboats <[hidden email]> wrote:

> Jeff,
> The issue with the batteries is based on their
> construction.  The T105 are
> constructed for long life and rugged use.  As a result the
> recombination/dissociation chemistry is a bit slower than
> in many other
> batteries because of the position of the plates
> etc..Initially when the
> battery has not been used for a while there are more of the
> ions floating
> around so you can get an initial surge of higher current.
> However after
> this has dissipated the output is controlled by how fast
> the ions can move
> around.  The T-125 have a different construction and thus
> can provide a
> higher continuous current.  The same is true AGM and other
> sealed batteries.
> With the T105's it seems as if the continuous current
> is about 220 amps this
> is in the winter with the battery pack at about 45 degrees
> F.   I expect it
> will be higher in the summer when the temperature
> increases.
>

Hi Tom,

This just doesn't sound right.  Hopefully someone else can chime in with battery expertise.  Got to go now.

Regards,

Jeff M




     

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Re: Controller power output at different motor rpms

Morgan LaMoore
In reply to this post by Tom H
It's true that the T-105s can't handle as high a current as AGMs and
the like, but they won't just prevent you from pulling higher
currents.

The only way a battery has to limit its current is to sag, lowering
the output voltage. Of course, you should respect this and lower
current draw to protect the batteries, but the batteries won't protect
themselves from delivering high currents.

If your batteries aren't sagging to low voltage but you're still not
getting the current you should, the problem is the motor, controller,
or measurements.

The controller will limit both the motor current and the motor
voltage. The only way you'll actually get the battery current equal to
your controller's rated current is at full throttle at a specific
speed, determined by your motor characteristics and gear ratio.

If you really think your controller isn't giving you what it should, I
recommend using a motor current meter. You could even move your
existing current meter to the motor side temporarily to test things
out, then move it back to the batteries.

-Morgan LaMoore

On Wed, Mar 11, 2009 at 3:43 PM, soundboats <[hidden email]> wrote:

>
> Jeff,
> The issue with the batteries is based on their construction.  The T105 are
> constructed for long life and rugged use.  As a result the
> recombination/dissociation chemistry is a bit slower than in many other
> batteries because of the position of the plates etc..Initially when the
> battery has not been used for a while there are more of the ions floating
> around so you can get an initial surge of higher current.  However after
> this has dissipated the output is controlled by how fast the ions can move
> around.  The T-125 have a different construction and thus can provide a
> higher continuous current.  The same is true AGM and other sealed batteries.
> With the T105's it seems as if the continuous current is about 220 amps this
> is in the winter with the battery pack at about 45 degrees F.   I expect it
> will be higher in the summer when the temperature increases.
>
> Also, I have checked the pot box with my meter.  It provide the full 5Kohm
> range.  I even have tried a second pot box in case there was something wrong
> with the first.
>
> tom
>
> soundboats wrote:
>>
>> Hello to everyone,
>> I am still puzzled by the observation that the power (Kilowatts)
>> controllers accept from the batteries and put out to the motor depends on
>> motor rpms.  Does anyone have an explanation for this?
>>
>> System: '87 Nissan pickup using 120 Volts (Trojan 105) and a NetGain
>> Impulse 9" motor.
>>
>> I do not have meters on the output of the controller but I do monitor the
>> power input (volts x amps) to the controller.  [If you assume a 95%
>> efficiency on the controllers you can estimate the actual power output by
>> multiplying the numbers by 0.95]
>>
>> I now have standard test I run. I drive at 25 mph in third gear (about
>> 2000rpm on the motor) and in second gear (3000 rpm). I push the throttle
>> to max and monitor the amps and voltage going into the controller.  I find
>> that each controller has a maximum power level it will accept for each
>> rpm, and they are different.  All five of the controllers I have tried
>> (Curtis and 4 Kelly's) maintain the same relative relationships as power
>> increases with rpms.  There are many hills around here so I can always
>> find one where the speed of the truck just matches the maximum power put
>> out by the controller.  If the hill is too steep and I slow down (motor
>> rpms drop) the power going to the controller (and thus the power it puts
>> out) also drops even at maximum throttle.
>>
>> Here is what I found at 2000 rpm:
>> KDH12500A – accepts no more than 80 amps =  9.6 KW  (@ 120 volts nominal)
>> KDH14650B – accepts no more than 120 amps  14.4 KW
>> Curtis 1221C -                 150amps              18  KW
>> KDH12600B -                   180 amps             21.6 KW
>> KDH12800B -                   200 amps             24 KW
>>
>> Here are the data at 3000 rpm
>>
>> KDH12500A – accepts only 120 amps               14.4 KW
>> KDH14650B – accepts only 150 amps                18 KW
>> Curtis 1221C -                       180amps           18  KW
>> KDH12600B -                        220 amps           26.4 KW
>> KDH12800B -                        >220 amps      limited by batteries
>>
>> Hope this information will also prove to be useful to others wanting to
>> chose a controller.
>> Tom (soundboats) in Olympia WA
>>
>>
>
> --
> View this message in context: http://www.nabble.com/Controller-power-output-at-different-motor-rpms-tp22439693p22464089.html
> Sent from the Electric Vehicle Discussion List mailing list archive at Nabble.com.
>
>
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Re: Controller power output at different motor rpms

Zeke Yewdall
In reply to this post by Tom H
On Wed, Mar 11, 2009 at 1:58 PM, soundboats <[hidden email]> wrote:

>
> [The smaller controllers never reach their rated output.  The highest
> battery current........]


Isn't the controller rated for motor current, not battery current?  So, you
are unlikely to see the rated current from the controller on the battery
side unless you somehow load the motor alot when it's at high rpm -- like
starting up a steep hill already at high speed in 4th gear???

>
>
>
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Re: Controller power output at different motor rpms

Lee Hart
In reply to this post by Tom H
soundboats wrote:

> The issue with the batteries is based on their construction.  The
> T105 are constructed for long life and rugged use.  As a result the
> recombination/dissociation chemistry is a bit slower than in many
> other batteries because of the position of the plates etc. Initially
> when the battery has not been used for a while there are more of the
> ions floating around so you can get an initial surge of higher
> current.  However after this has dissipated the output is controlled
> by how fast the ions can move around.  The T-125 have a different
> construction and thus can provide a higher continuous current.  The
> same is true AGM and other sealed batteries. With the T105's it seems
> as if the continuous current is about 220 amps this is in the winter
> with the battery pack at about 45 degrees F.   I expect it will be
> higher in the summer when the temperature increases.

This is quite different than my experience. I've found that even the
cheapest off-brand golf cart batteries will deliver 500 amps. Of course,
the voltage sags to about 5 volts.

There are times when I drove my ComutaVan at -20 deg.F. The Sam's Club
6v batteries would still deliver 200 amps continuously, while sagging to
about 5 volts.

Is it possible that your controller is cutting back the current because
the batteries are sagging below its undervoltage limit?

Or, the motor may simply not be drawing enough current, either because
the voltage is too low or the RPM is too high.

--
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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