Re: [EVDL] Slow due to 96V pack?

2017-09-16 Thread Lee Hart via EV 
From: paul dove via EV 
>Great then explain (96-72) x .08 = 300 amps.

That should be (96v-72v) / .08ohms = 300 amps. This is just Ohms law. 96v is 
the unloaded battery pack voltage. 72v is the pack voltage under load. 0.08 
ohms is the ESR. So with a load of 300a, the pack voltage drops from 96v to 
72v. Do you agree with that part?

> How will the controller going to see 24 volts?

It doesn't; it sees 72v. 24v is dropped across the internal resistance of the 
battery pack. This voltage drop, and the internal resistance is what makes the 
current 300a.

>> The PWM only controls the output voltage by switching it on and off.
>> The duty cycle then sets the average voltage the motor sees.

Not quite. The motor is an inductive load. It actually sees the full on/off 
voltage switching. The motor voltage is going from (in this case) about 1v to 
73v at the switching frequency of the controller.

The average motor voltage will surprise you. It is *not* the average of the 
PWM. The motor has back EMF; i.e. it *generates* a voltage proportional to its 
RPM and current. So the average motor voltage is a complex function of PWM, 
current, and RPM.

Note that there is a great big filter capacitor bank across the input of the 
controller. Even though the switches inside the controller are switching 
on/off, the capacitors filter this into a more-or-less constant battery voltage 
and current. A voltmeter at the input of the controller does indeed show 72v 
under these conditions. It is this low voltage that is causing the Zilla 
controller to say "whoops; back off the current; we're overloading the 
batteries".

>> It may have a low voltage cutoff circuit but that just shuts down the output 
>> in the event the battery falls below 72volts thus the controller would 
>> not be working if the voltage was 96-72 = 24volts.

(Again, 96-72=24v is the voltage drop across the ESR; not the controller input 
voltage).

But as Roger said, this just results in an on/off oscillation. As soon as the 
load is removed, the battery voltage pops right back up to 96v. The controller 
comes right back on. So there is a rapid on/off switching, exactly like PWM. 
Controller designers know this; and explicitly design their controllers to work 
predictably under these conditions. They limit current when you reach the 
low-voltage threshold so the battery simply *stays* at the low-voltage 
threshold.

>> And yes hooking batteries straight up you would have no control over the 
>> current but I still don't believe lead acid would put out 1200 amps.

I can only say from direct personal experience that they certainly will. Many 
EV drag racers who have won trophies will confirm it. Millions of hard-to-start 
diesel engines also pull 1000a from their lead-acid batteries every time they 
start.

Paul, at some point, I think you will have an "Aha!" moment, and realize that 
what we're saying is really how it works. Or, you will go out and do some 
actual testing and see it for yourself. It's easy to fool yourself; but very 
hard to fool the actual devices. :-)

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Re: [EVDL] Slow due to 96V pack?

2017-09-16 Thread paul dove via EV 
Great then explain (96-72) x .08 = 300 amps. How will the controller going to 
see 24 volts

Sent from my iPhone

> On Sep 14, 2017, at 4:54 PM, Cor van de Water via EV <ev@lists.evdl.org> 
> wrote:
> 
> Paul,
> It seems you have difficulty grasping some concepts presented here,
> you would do well by studying them further before commenting.
> Maybe you just read too casually or fast that you missed what was being 
> explained to you.
> 
> You have the right to not believe what anyone says.
> Wise people listen to wise advise is all I want to offer.
> Cor.
> 
> -Original Message-
> From: EV [mailto:ev-boun...@lists.evdl.org] On Behalf Of paul dove via EV
> Sent: Thursday, September 14, 2017 11:10 AM
> To: Roger Stockton; Electric Vehicle Discussion List
> Cc: paul dove
> Subject: Re: [EVDL] Slow due to 96V pack?
> 
> There is no voltage adjustment on input voltage in any motor controller I 
> ever used.
> The PWM only controls the output voltage by switching it on and off. The duty 
> cycle then sets the average voltage the motor sees.
> It may have a low voltage cutoff circuit but that just shuts down the output 
> in the event the battery falls below 72volts thus the controller would 
> not be working if the voltage was 96-72 = 24volts.
> And yes hooking batteries straight up you would have no control over the 
> current but I still don't believe lead acid would put out 1200 amps.
> 
>  From: Roger Stockton <rstock...@delta-q.com>
> To: Electric Vehicle Discussion List <ev@lists.evdl.org>
> Cc: paul dove <dov...@bellsouth.net>
> Sent: Thursday, September 14, 2017 12:19 PM
> Subject: RE: [EVDL] Slow due to 96V pack?
> 
> paul dove wrote:
> 
>> That made no sense to me but a DC motor controller takes the input 
>> voltage to power mosfets or igbts which switch the power on and off 
>> with a pwm signal to get the desired output to drive a motor. It has 
>> no knowledge of the battery impedance.
> 
> The controller does not have, or need, knowledge the battery impedance; this 
> is simply Ohms Law at work.
> 
> The controller PWMs the power from the battery, and the duty cycle of the PWM 
> can be varied to limit whatever parameter the controller logic cares about at 
> any given time: input voltage, input current, output voltage, or output 
> current.
> 
> Since the battery has a finite, non-zero internal impedance, its terminal 
> voltage will sag as current is drawn from it.  If the motor controller 
> enforces a minimum input (battery) voltage (as does the controller in 
> question), then its logic will vary/limit the PWM duty cycle to prevent the 
> voltage at the input of the controller from falling below the target level.
> 
> Since the controller logic will limit/vary the input current to prevent the 
> input voltage from falling below the threshold, then the maximum voltage 
> difference across the battery internal resistance is the open circuit battery 
> voltage minus the minimum input voltage limit of the controller: 96V - 72V = 
> 24V, in this example.
> 
> The controller does not know what the internal impedance of the battery is, 
> but Ohms Law still applies to limit the maximum current from the battery to 
> *whatever* value results in 24V drop across the internal resistance: 24V / 
> 0.08 ohms = 300A in this example.
> 
> *IF* the sophisticated controller were replaced with a simple contactor 
> controller, then if the contactor controller allowed the entire 96V battery 
> to be connected directly to a stalled motor (~0 ohms), the voltage drop 
> across the battery internal resistance would ~approach~ 96V - 0V = 96V, and 
> the peak current into the motor would approach 96V / 0.08 ohms = 1200A.
> 
> Hope this helps,
> 
> Roger.
> 
> 
> 
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Re: [EVDL] Slow due to 96V pack?

2017-09-14 Thread Lee Hart via EV 
From: paul dove via EV 
>There is no voltage adjustment on input voltage in any motor controller I ever 
>used.

Interesting. What motor controllers have you used?

Every controller I've used *has* had a low-voltage cutout. That includes 
everything from the venerable GE EV1, Curtis, Sevcon, Zilla, DCP, etc. If the 
controller is sold for a specific battery voltage, the threshold is usually 
fixed by internal resistors. When there is a range of voltages, then there is 
and adjustable low-battery threshold.

When you think about it, it makes sense. Without such a threshold, users would 
run the pack totally utterly dead, and destroy their pack! That causes customer 
complaints and warranty problems that the controller manufacturers don't want!

--
Excellence does not require perfection. -- Henry James
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Re: [EVDL] Slow due to 96V pack?

2017-09-14 Thread Bill Dube via EV 

On 9/9 I wrote:

>>> I seem to recall that the minimum input voltage for a Zilla is 72 
volts.
Might be sagging the pack to 72 volts and that is that is simply amps it 
puts out at that voltage.

>>>

Seems pretty straightforward. You just have to read the posts in the thread.

All PWM controllers have _some_ lower voltage limit.
The internal logic circuitry and the gate drivers have a power supply 
that has a lower threshold of operation, if nothing else.


The controller in question was indeed a Zilla. The pack was indeed 96 
volts of lead-acid batteries. This leaves ~24 volts of headroom voltage 
sag above the cut off.


>>>

You also mentioned that you couldn't imagine a lead-acid battery putting 
out more than 900 amps.


There are many high-performance lead-acid AGM's that will easily put out 
more than 1000 amps. A single 78 gram BolderTech cell will put out 1000 
amps. An Optima battery has 900 _cold_ cranking amps, and will put out 
far more than 1000 amps when loaded to half/voltage.




I believe Mark Twain said:

"It is better to remain silent and be thought a fool than to speak and 
remove all doubt."


Bill D.



On 9/14/2017 4:03 PM, paul dove via EV wrote:

I agree but that is not what was claimed.

Sent from my iPhone


On Sep 14, 2017, at 4:57 PM, EVDL Administrator via EV  
wrote:


On 14 Sep 2017 at 18:10, paul dove via EV wrote:

There is no voltage adjustment on input voltage in any motor controller I ever
used.

EVERY controller I've ever used has had some kind of undervoltage limit,
though in many cases it wasn't easily adjustable.

David Roden - Akron, Ohio, USA
EVDL Administrator


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Re: [EVDL] Slow due to 96V pack?

2017-09-14 Thread Cor van de Water via EV 
Re: programmable low voltage limit on controller:
I am not too familiar with the Zilla and/or its capability to set a
minimum pack voltage to protect batteries from too deep discharge,
but my controller is very configurable and has input battery high and
low limits, which will simply disable the controller
when the input is outside that range. I ran into these limits when I
converted from lead-acid to Lithium and increased pack
voltage. In rather discharged state, the car ran. Once I charged the
pack, it disabled the controller until I reprogrammed the
high battery input voltage limit (and also upped the low input voltage
limit to protect the pack from deep discharge,
I rather have a slowing down/crawling EV that needs a charge or a tow
than ruining an expensive Lithium pack.

My truck has the "Dolphin" inverter/charger that was used in the factory
conversion of US Electricars in 1994 where
a few hundred sedans and trucks were converted with Hughes 50kW
induction motor bolted to a manual transmission
that was then locked in fixed (reduction) gear so the motor could spin
from 0 - 9k RPM pushing the trucks from 0 - 72MPH
and the sedans from 0 - 90MPH I believe.
The battery box was very well done and contained two individual strings
of 26 lead-acid (Hawker) batteries for a nominal
312V pack (300V for the sedan). The truck has enough space to fit 2
complete Leaf packs in the box
and the controller has components (Electrolytic Capacitors) of 450V
working voltage, so with 90% derating the controller
is rated for 405V, so it is well suited to be run from a Leaf pack, also
because the Dolphin can be field-configured to use
different limits.

BTW, configurable input limits was not the original mentioned problem,
that was something that appeared later in the thread.
The original issue that was suspected is the fixed Low Voltage limit on
the Zilla of 72V which might cause the Zilla to fade out
when attempting to draw more current from the GC batteries, so it is
self-limiting to about 200-300A depending
on the resistance in the circuit, either a high resistance connection or
the GC battery internal resistance.

It seems that a 96V GC pack and a Zilla are not a successful combination
in terms of getting adequate power to the motor.
Either "stiffer" pack is needed or higher voltage or a controller that
allows lower voltage on hard pulls.

Hope this clarifies,
Cor.

-Original Message-
From: EV [mailto:ev-boun...@lists.evdl.org] On Behalf Of paul dove via
EV
Sent: Thursday, September 14, 2017 3:04 PM
To: Electric Vehicle Discussion List
Cc: paul dove
Subject: Re: [EVDL] Slow due to 96V pack?

I agree but that is not what was claimed.

Sent from my iPhone

> On Sep 14, 2017, at 4:57 PM, EVDL Administrator via EV
<ev@lists.evdl.org> wrote:
> 
>> On 14 Sep 2017 at 18:10, paul dove via EV wrote:
>> 
>> There is no voltage adjustment on input voltage in any motor 
>> controller I ever used.
> 
> EVERY controller I've ever used has had some kind of undervoltage 
> limit, though in many cases it wasn't easily adjustable.
> 
> David Roden - Akron, Ohio, USA
> EVDL Administrator
> 
> = = = = = = = = = = = = = = = = = = = = = = = = = = = = = EVDL 
> Information: http://www.evdl.org/help/ = = = = = = = = = = = = = = = =

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Re: [EVDL] Slow due to 96V pack?

2017-09-14 Thread Gail Lucas via EV 

David,

You are SO right on that. I melted a wrench trying to remove a battery 
from one of my 48 Volt Citicars. That caused a lot of smoke from the 
contactor section but fortunately I had a great mechanic who was able to 
put things back together. I also destroyed a Curtis controller by 
allowing a wrench to contact the frame and a battery, I think its called 
letting the smoke out.


Gail


On 9/14/2017 2:52 PM, EVDL Administrator via EV wrote:

There's a good reason that you tape up your wrenches when you work around
golf car batteries.

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Re: [EVDL] Slow due to 96V pack?

2017-09-14 Thread paul dove via EV 
I agree but that is not what was claimed.

Sent from my iPhone

> On Sep 14, 2017, at 4:57 PM, EVDL Administrator via EV  
> wrote:
> 
>> On 14 Sep 2017 at 18:10, paul dove via EV wrote:
>> 
>> There is no voltage adjustment on input voltage in any motor controller I 
>> ever
>> used.
> 
> EVERY controller I've ever used has had some kind of undervoltage limit, 
> though in many cases it wasn't easily adjustable.
> 
> David Roden - Akron, Ohio, USA
> EVDL Administrator
> 
> = = = = = = = = = = = = = = = = = = = = = = = = = = = = =
> EVDL Information: http://www.evdl.org/help/
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> Note: mail sent to "evpost" and "etpost" addresses will not 
> reach me.  To send a private message, please obtain my 
> email address from the webpage http://www.evdl.org/help/ .
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Re: [EVDL] Slow due to 96V pack?

2017-09-14 Thread EVDL Administrator via EV 
On 14 Sep 2017 at 18:10, paul dove via EV wrote:

> There is no voltage adjustment on input voltage in any motor controller I ever
> used.

EVERY controller I've ever used has had some kind of undervoltage limit, 
though in many cases it wasn't easily adjustable.

David Roden - Akron, Ohio, USA
EVDL Administrator

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Re: [EVDL] Slow due to 96V pack?

2017-09-14 Thread Cor van de Water via EV 
Paul,
It seems you have difficulty grasping some concepts presented here,
you would do well by studying them further before commenting.
Maybe you just read too casually or fast that you missed what was being 
explained to you.

You have the right to not believe what anyone says.
Wise people listen to wise advise is all I want to offer.
Cor.

-Original Message-
From: EV [mailto:ev-boun...@lists.evdl.org] On Behalf Of paul dove via EV
Sent: Thursday, September 14, 2017 11:10 AM
To: Roger Stockton; Electric Vehicle Discussion List
Cc: paul dove
Subject: Re: [EVDL] Slow due to 96V pack?

There is no voltage adjustment on input voltage in any motor controller I ever 
used.
The PWM only controls the output voltage by switching it on and off. The duty 
cycle then sets the average voltage the motor sees.
It may have a low voltage cutoff circuit but that just shuts down the output in 
the event the battery falls below 72volts thus the controller would not be 
working if the voltage was 96-72 = 24volts.
And yes hooking batteries straight up you would have no control over the 
current but I still don't believe lead acid would put out 1200 amps.

  From: Roger Stockton <rstock...@delta-q.com>
 To: Electric Vehicle Discussion List <ev@lists.evdl.org>
Cc: paul dove <dov...@bellsouth.net>
 Sent: Thursday, September 14, 2017 12:19 PM
 Subject: RE: [EVDL] Slow due to 96V pack?
   
paul dove wrote:

> That made no sense to me but a DC motor controller takes the input 
> voltage to power mosfets or igbts which switch the power on and off 
> with a pwm signal to get the desired output to drive a motor. It has 
> no knowledge of the battery impedance.

The controller does not have, or need, knowledge the battery impedance; this is 
simply Ohms Law at work.

The controller PWMs the power from the battery, and the duty cycle of the PWM 
can be varied to limit whatever parameter the controller logic cares about at 
any given time: input voltage, input current, output voltage, or output current.

Since the battery has a finite, non-zero internal impedance, its terminal 
voltage will sag as current is drawn from it.  If the motor controller enforces 
a minimum input (battery) voltage (as does the controller in question), then 
its logic will vary/limit the PWM duty cycle to prevent the voltage at the 
input of the controller from falling below the target level.

Since the controller logic will limit/vary the input current to prevent the 
input voltage from falling below the threshold, then the maximum voltage 
difference across the battery internal resistance is the open circuit battery 
voltage minus the minimum input voltage limit of the controller: 96V - 72V = 
24V, in this example.

The controller does not know what the internal impedance of the battery is, but 
Ohms Law still applies to limit the maximum current from the battery to 
*whatever* value results in 24V drop across the internal resistance: 24V / 0.08 
ohms = 300A in this example.

*IF* the sophisticated controller were replaced with a simple contactor 
controller, then if the contactor controller allowed the entire 96V battery to 
be connected directly to a stalled motor (~0 ohms), the voltage drop across the 
battery internal resistance would ~approach~ 96V - 0V = 96V, and the peak 
current into the motor would approach 96V / 0.08 ohms = 1200A.

Hope this helps,

Roger.


   
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Re: [EVDL] Slow due to 96V pack?

2017-09-14 Thread EVDL Administrator via EV 
On 14 Sep 2017 at 17:19, Roger Stockton via EV wrote:

> *IF* the sophisticated controller were replaced with a simple contactor
> controller, then if the contactor controller allowed the entire 96V battery to
> be connected directly to a stalled motor (~0 ohms), the voltage drop across
> the battery internal resistance would ~approach~ 96V - 0V = 96V, and the peak
> current into the motor would approach 96V / 0.08 ohms = 1200A.

Quite so.  The Comuta-Vans had 72 volts of 105-minute golf car batteries, a 
contactor controller, and awg 1/0 wiring.  In the early 1980s, a DOE test of 
one recorded peak currents of over 1300 amps. The testers did not seem to 
consider that a good thing.

There's a good reason that you tape up your wrenches when you work around 
golf car batteries.

David Roden - Akron, Ohio, USA
EVDL Administrator

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Re: [EVDL] Slow due to 96V pack?

2017-09-14 Thread paul dove via EV 
There is no voltage adjustment on input voltage in any motor controller I ever 
used.
The PWM only controls the output voltage by switching it on and off. The duty 
cycle then sets the average voltage the motor sees.
It may have a low voltage cutoff circuit but that just shuts down the output in 
the event the battery falls below 72volts thus the controller would not be 
working if the voltage was 96-72 = 24volts.
And yes hooking batteries straight up you would have no control over the 
current but I still don't believe lead acid would put out 1200 amps.

  From: Roger Stockton <rstock...@delta-q.com>
 To: Electric Vehicle Discussion List <ev@lists.evdl.org> 
Cc: paul dove <dov...@bellsouth.net>
 Sent: Thursday, September 14, 2017 12:19 PM
 Subject: RE: [EVDL] Slow due to 96V pack?
   
paul dove wrote:

> That made no sense to me but a DC motor controller takes the input voltage
> to power mosfets or igbts which switch the power on and off with a pwm
> signal to get the desired output to drive a motor. It has no knowledge of
> the battery impedance.

The controller does not have, or need, knowledge the battery impedance; this is 
simply Ohms Law at work.

The controller PWMs the power from the battery, and the duty cycle of the PWM 
can be varied to limit whatever parameter the controller logic cares about at 
any given time: input voltage, input current, output voltage, or output current.

Since the battery has a finite, non-zero internal impedance, its terminal 
voltage will sag as current is drawn from it.  If the motor controller enforces 
a minimum input (battery) voltage (as does the controller in question), then 
its logic will vary/limit the PWM duty cycle to prevent the voltage at the 
input of the controller from falling below the target level.

Since the controller logic will limit/vary the input current to prevent the 
input voltage from falling below the threshold, then the maximum voltage 
difference across the battery internal resistance is the open circuit battery 
voltage minus the minimum input voltage limit of the controller: 96V - 72V = 
24V, in this example.

The controller does not know what the internal impedance of the battery is, but 
Ohms Law still applies to limit the maximum current from the battery to 
*whatever* value results in 24V drop across the internal resistance: 24V / 0.08 
ohms = 300A in this example.

*IF* the sophisticated controller were replaced with a simple contactor 
controller, then if the contactor controller allowed the entire 96V battery to 
be connected directly to a stalled motor (~0 ohms), the voltage drop across the 
battery internal resistance would ~approach~ 96V - 0V = 96V, and the peak 
current into the motor would approach 96V / 0.08 ohms = 1200A.

Hope this helps,

Roger.


   
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Re: [EVDL] Slow due to 96V pack?

2017-09-14 Thread paul dove via EV 
I believe that is on the hairball not the controller.
You have three battery settings on the hairball:

 BA is the Battery Amp limit. • LBV is the Low Battery Voltage limit. The 
controller will automatically reduce current so as notto run below this. • LBVI 
is the Low Battery Voltage Indicator. The battery light on the dash will 
lightbelow this level.

  From: Roger Stockton <rstock...@delta-q.com>
 To: Electric Vehicle Discussion List <ev@lists.evdl.org> 
Cc: paul dove <dov...@bellsouth.net>
 Sent: Thursday, September 14, 2017 2:09 PM
 Subject: RE: [EVDL] Slow due to 96V pack?
   
paul dove wrote:

> There is no voltage adjustment on input voltage in any motor controller I
> ever used.

This discussion specifically concerns a vehicle using a Zilla motor controller; 
from the Z1K specsheet:

"Other features include programmable motor voltage and current limits, 
programmable battery voltage and current limits, adjustable low battery voltage 
protection and an additional low battery indicator output."

> It may have a low voltage cutoff circuit but that just shuts down the
> output in the event the battery falls below 72volts thus the
> controller would not be working if the voltage was 96-72 = 24volts.

Even this simple case would achieve the *same* behaviour: the controller would 
PWM "willy-nilly" until the input voltage sagged below the minimum input 
threshold, then it go to 0% duty.  As soon as it went to 0% duty, the load on 
the battery would decrease, and the input voltage would rise slightly above the 
minimum threshold, and the controller would resume PWMing.

Resuming the load would sag the input voltage below the threshold again, and 
the cycle would repeat such that the input voltage is regulated in a sawtooth 
manner at the minimum voltage.

Cheers,

Roger.




   
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Re: [EVDL] Slow due to 96V pack?

2017-09-14 Thread Roger Stockton via EV 
paul dove wrote:

> There is no voltage adjustment on input voltage in any motor controller I
> ever used.

This discussion specifically concerns a vehicle using a Zilla motor controller; 
from the Z1K specsheet:

"Other features include programmable motor voltage and current limits, 
programmable battery voltage and current limits, adjustable low battery voltage 
protection and an additional low battery indicator output."

> It may have a low voltage cutoff circuit but that just shuts down the
> output in the event the battery falls below 72volts thus the
> controller would not be working if the voltage was 96-72 = 24volts.

Even this simple case would achieve the *same* behaviour: the controller would 
PWM "willy-nilly" until the input voltage sagged below the minimum input 
threshold, then it go to 0% duty.  As soon as it went to 0% duty, the load on 
the battery would decrease, and the input voltage would rise slightly above the 
minimum threshold, and the controller would resume PWMing.

Resuming the load would sag the input voltage below the threshold again, and 
the cycle would repeat such that the input voltage is regulated in a sawtooth 
manner at the minimum voltage.

Cheers,

Roger.


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Re: [EVDL] Slow due to 96V pack?

2017-09-14 Thread Roger Stockton via EV 
paul dove wrote:

> That made no sense to me but a DC motor controller takes the input voltage
> to power mosfets or igbts which switch the power on and off with a pwm
> signal to get the desired output to drive a motor. It has no knowledge of
> the battery impedance.

The controller does not have, or need, knowledge the battery impedance; this is 
simply Ohms Law at work.

The controller PWMs the power from the battery, and the duty cycle of the PWM 
can be varied to limit whatever parameter the controller logic cares about at 
any given time: input voltage, input current, output voltage, or output current.

Since the battery has a finite, non-zero internal impedance, its terminal 
voltage will sag as current is drawn from it.  If the motor controller enforces 
a minimum input (battery) voltage (as does the controller in question), then 
its logic will vary/limit the PWM duty cycle to prevent the voltage at the 
input of the controller from falling below the target level.

Since the controller logic will limit/vary the input current to prevent the 
input voltage from falling below the threshold, then the maximum voltage 
difference across the battery internal resistance is the open circuit battery 
voltage minus the minimum input voltage limit of the controller: 96V - 72V = 
24V, in this example.

The controller does not know what the internal impedance of the battery is, but 
Ohms Law still applies to limit the maximum current from the battery to 
*whatever* value results in 24V drop across the internal resistance: 24V / 0.08 
ohms = 300A in this example.

*IF* the sophisticated controller were replaced with a simple contactor 
controller, then if the contactor controller allowed the entire 96V battery to 
be connected directly to a stalled motor (~0 ohms), the voltage drop across the 
battery internal resistance would ~approach~ 96V - 0V = 96V, and the peak 
current into the motor would approach 96V / 0.08 ohms = 1200A.

Hope this helps,

Roger.

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Re: [EVDL] Slow due to 96V pack?

2017-09-14 Thread paul dove via EV 
That made no sense to me but a DC motor controller takes the input voltage to 
power mosfets or igbts which switch the power on and off with a pwm signal to 
get the desired output to drive a motor. It has no knowledge of the battery 
impedance.

Sent from my iPhone

> On Sep 13, 2017, at 6:09 PM, Roger Stockton via EV  wrote:
> 
> paul dove wrote:
> 
>> You said:Here's my guess: A 6v golf cart battery has an internal
>> resistance of about 5 milliohms (0.005 ohms). A 96v pack has 16 of them;
>> so the resistance is 0.005 x 16 = 0.08 ohms. Let's say the Zilla limits
>> voltage to 72v (i.e. it won't pull the pack below 72v). Then the most
>> current you can get is I = V/R = (96v-72v) / 0.08 ohms) = 300 amps.
>> **It is either going to be 96v/0.08, 72v/0.08, or somewhere in between.
>> The voltage won't be 24/0.08 at any time.So, somewhere between 1200 and
>> 900 amps.
> 
> You are (almost) correct only if you *short* the battery terminals, so that 
> the voltage on the load side of the internal resistance is 0V.
> 
> This is *not* the case with a controller that enforces a low voltage cutoff, 
> such as the 72V value in the example:
> 
> 
> 0.08 ohm
>Internal R 
> +---/\/\/\/\--oo--+
> | |
>   --+-- ideal / 72V 
>---  96V   \ minimum load
>   - battery   / voltage
>-+-\
> | |
> +-oo--+ 
> 
> The controller effectively regulates the voltage on the load side of the 
> battery internal resistance such that the voltage difference across the 
> internal resistance will indeed be approximately as Lee states.  And the 
> maximum battery current that *this* load can draw will be on the order of 
> (96-72)/0.08=300A.
> 
> Cheers,
> 
> Roger.
> 
> 
> 
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Re: [EVDL] Slow due to 96V pack?

2017-09-13 Thread Roger Stockton via EV 
paul dove wrote:

> You said:Here's my guess: A 6v golf cart battery has an internal
> resistance of about 5 milliohms (0.005 ohms). A 96v pack has 16 of them;
> so the resistance is 0.005 x 16 = 0.08 ohms. Let's say the Zilla limits
> voltage to 72v (i.e. it won't pull the pack below 72v). Then the most
> current you can get is I = V/R = (96v-72v) / 0.08 ohms) = 300 amps.
> **It is either going to be 96v/0.08, 72v/0.08, or somewhere in between.
> The voltage won't be 24/0.08 at any time.So, somewhere between 1200 and
> 900 amps.

You are (almost) correct only if you *short* the battery terminals, so that the 
voltage on the load side of the internal resistance is 0V.

This is *not* the case with a controller that enforces a low voltage cutoff, 
such as the 72V value in the example:


 0.08 ohm
Internal R 
 +---/\/\/\/\--oo--+
 | |
   --+-- ideal / 72V 
---  96V   \ minimum load
   - battery   / voltage
-+-\
 | |
 +-oo--+ 

The controller effectively regulates the voltage on the load side of the 
battery internal resistance such that the voltage difference across the 
internal resistance will indeed be approximately as Lee states.  And the 
maximum battery current that *this* load can draw will be on the order of 
(96-72)/0.08=300A.

Cheers,

Roger.



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Re: [EVDL] Slow due to 96V pack?

2017-09-13 Thread paul dove via EV 
Lee,
You said:Here's my guess: A 6v golf cart battery has an internal resistance of 
about 5 milliohms (0.005 ohms). A 96v pack has 16 of them; so the resistance is 
0.005 x 16 = 0.08 ohms. Let's say the Zilla limits voltage to 72v (i.e. it 
won't pull the pack below 72v). Then the most current you can get is I = V/R = 
(96v-72v) / 0.08 ohms) = 300 amps.
**It is either going to be 96v/0.08, 72v/0.08, or somewhere in between. The 
voltage won't be 24/0.08 at any time.So, somewhere between 1200 and 900 amps.

In practice, the resistance of the pack is a bit higher due to the wire and 
connectors. So a 200a max current is probably the most you can draw from the 
golf cart batteries before their voltage under load falls to 72v.
**obviously something else is going on since you don't see 1200 Amps.

Now, if you had a different kind of batteries with less internal resistance, or 
a controller that would cheerfully pull the battery voltage even lower, you'd 
have a lot more current, and peppier performance.

For example, my old ComutaVan had a 72v pack of golf cart batteries, and a 
contactor controller. It would cheerfully pull 1000a from the batteries, and 
spin the tires if you "floored it" from a dead stop. I tried a Curtis 1221 400a 
controller; and it was *worse* than the contactor controller for accelleration, 
because it never came anywhere near 400a due to voltage sag.
**Exactly, the controller is influencing the current which is what I said. I 
ould be surprised if you could get a sustained 900 amps out of a lead battery 
but I will have to take your word since I've never tried it.


  From: Lee Hart via EV <ev@lists.evdl.org>
 To: Electric Vehicle Discussion List <ev@lists.evdl.org> 
Cc: Lee Hart <leeah...@earthlink.net>
 Sent: Tuesday, September 12, 2017 7:36 PM
 Subject: Re: [EVDL] Slow due to 96V pack?
   
From: paul dove <dov...@bellsouth.net>
> Current out of a battery is not calculated based on internal resistance.

Actually, it is. The Equivalent Series Resistance (ESR) of a battery is not a 
theoretical number. It is found empirically by measuring the voltage drop 
caused by a high-current load. The voltage of a 6v golf cart battery really 
does drop by about 2.5 volts with a 500 amp load. In other words, it acts like 
an ideal 6v battery with a 0.005 ohm resistor in series. Thus, it's a 
reasonable way to estimate what you are likely to get.

> you won't get 100% efficiency out a controller.

No, of course not. But the efficiency is pretty high, and can usually be 
ignored for back-of-the-envelope estimates. That's all I was trying to do with 
my estimate.

>The battery industry uses a 100-hour rate as an index to compare batteries of 
>different types and sizes.

They do when they are trying to exaggerate the capacity of their battery. For 
EV use, the 100-hour rate is useless. Even the more common 20-hour rate is 
nowhere near the rate at which the battery will be used. What you want to look 
at is the 1-hour or Reserve Capacity rates, which are what you will get when 
discharged at high currents. For a golf cart battery, the reserve capacity is 
measured at 75 amps, and the 1-hour rate at about 100 amps.

But, I don't think these capacity numbers are what is limiting the maximum 
current in this case. My guess is that these golf cart batteries can only 
deliver 200a before their voltage sags to 72v and the controller starts 
limiting current.


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Re: [EVDL] Slow due to 96V pack?

2017-09-12 Thread Lee Hart via EV 
From: paul dove 
> Current out of a battery is not calculated based on internal resistance.

Actually, it is. The Equivalent Series Resistance (ESR) of a battery is not a 
theoretical number. It is found empirically by measuring the voltage drop 
caused by a high-current load. The voltage of a 6v golf cart battery really 
does drop by about 2.5 volts with a 500 amp load. In other words, it acts like 
an ideal 6v battery with a 0.005 ohm resistor in series. Thus, it's a 
reasonable way to estimate what you are likely to get.

> you won't get 100% efficiency out a controller.

No, of course not. But the efficiency is pretty high, and can usually be 
ignored for back-of-the-envelope estimates. That's all I was trying to do with 
my estimate.

>The battery industry uses a 100-hour rate as an index to compare batteries of 
>different types and sizes.

They do when they are trying to exaggerate the capacity of their battery. For 
EV use, the 100-hour rate is useless. Even the more common 20-hour rate is 
nowhere near the rate at which the battery will be used. What you want to look 
at is the 1-hour or Reserve Capacity rates, which are what you will get when 
discharged at high currents. For a golf cart battery, the reserve capacity is 
measured at 75 amps, and the 1-hour rate at about 100 amps.

But, I don't think these capacity numbers are what is limiting the maximum 
current in this case. My guess is that these golf cart batteries can only 
deliver 200a before their voltage sags to 72v and the controller starts 
limiting current.


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Re: [EVDL] Slow due to 96V pack?

2017-09-12 Thread paul dove via EV 
I don't think that math is right but you won't get 100% efficiency out a 
controller.
I think Curtis advertises 88%.
Current out of a battery is not calculated based on internal resistance. 
Internal resistance or Impedance of a battery can be modeled and measured but 
it doesn't act like a normal load. It's a chemical reaction and different 
chemistries will give you different currents.
If it is not due to limits on the controller and the efficiency drop then I 
would say the batteries aren't at full capacity any more.
The battery industry uses a 100-hour rate as an index to compare batteries of 
different types and sizes. The 100-hour rate is the amount of Ahs the battery 
will deliver during a 100-hour discharge. The capacity of a battery, in Ahs, is 
a dynamic number that is dependent on the discharge current. 

For example, a battery that is discharged at 10A will give you more capacity 
than a battery that is discharged at 100A. With the 100-hr rate, the battery is 
able to deliver more Ahs than with the 20-hr rate because the 100-hr rate uses 
a much lower discharge current than the 20-hr rate. Both rates are used as 
baselines. Either rate, however, will give you the same view of a battery. A 
higher capacity battery will have higher 5 and 20 hour rates than a battery 
with lower capacity.
They publish tables that you can look up to see these values.


  From: Lee Hart via EV <ev@lists.evdl.org>
 To: Electric Vehicle Discussion List <ev@lists.evdl.org> 
Cc: Lee Hart <leeah...@earthlink.net>
 Sent: Monday, September 11, 2017 11:40 PM
 Subject: Re: [EVDL] Slow due to 96V pack?
   
From: lektwik via EV <ev@lists.evdl.org>
>96V  = Slug

Not necessarily; but in this case, probably correct.

Here's my guess: A 6v golf cart battery has an internal resistance of about 5 
milliohms (0.005 ohms). A 96v pack has 16 of them; so the resistance is 0.005 x 
16 = 0.08 ohms. Let's say the Zilla limits voltage to 72v (i.e. it won't pull 
the pack below 72v). Then the most current you can get is I = V/R = (96v-72v) / 
0.08 ohms) = 300 amps.

In practice, the resistance of the pack is a bit higher due to the wire and 
connectors. So a 200a max current is probably the most you can draw from the 
golf cart batteries before their voltage under load falls to 72v.

Now, if you had a different kind of batteries with less internal resistance, or 
a controller that would cheerfully pull the battery voltage even lower, you'd 
have a lot more current, and peppier performance.

For example, my old ComutaVan had a 72v pack of golf cart batteries, and a 
contactor controller. It would cheerfully pull 1000a from the batteries, and 
spin the tires if you "floored it" from a dead stop. I tried a Curtis 1221 400a 
controller; and it was *worse* than the contactor controller for accelleration, 
because it never came anywhere near 400a due to voltage sag.

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Re: [EVDL] Slow due to 96V pack?

2017-09-11 Thread Lee Hart via EV 
From: lektwik via EV 
>96V  = Slug

Not necessarily; but in this case, probably correct.

Here's my guess: A 6v golf cart battery has an internal resistance of about 5 
milliohms (0.005 ohms). A 96v pack has 16 of them; so the resistance is 0.005 x 
16 = 0.08 ohms. Let's say the Zilla limits voltage to 72v (i.e. it won't pull 
the pack below 72v). Then the most current you can get is I = V/R = (96v-72v) / 
0.08 ohms) = 300 amps.

In practice, the resistance of the pack is a bit higher due to the wire and 
connectors. So a 200a max current is probably the most you can draw from the 
golf cart batteries before their voltage under load falls to 72v.

Now, if you had a different kind of batteries with less internal resistance, or 
a controller that would cheerfully pull the battery voltage even lower, you'd 
have a lot more current, and peppier performance.

For example, my old ComutaVan had a 72v pack of golf cart batteries, and a 
contactor controller. It would cheerfully pull 1000a from the batteries, and 
spin the tires if you "floored it" from a dead stop. I tried a Curtis 1221 400a 
controller; and it was *worse* than the contactor controller for accelleration, 
because it never came anywhere near 400a due to voltage sag.

--
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--
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Re: [EVDL] Slow due to 96V pack?

2017-09-11 Thread lektwik via EV 
96V  = Slug


On Friday, September 8, 2017, John Lussmyer via EV 
wrote:

> I'm helping a guy with a used conversion he just bought.
> It's a S-10 with 96V of Golf Cart batteries, Zilla 1K, and a 8 or 9" motor.
> Even fully charged - it's acceleration is poor.
> I was never able to get it to draw more than 200 Amps in any gear at any
> speed.
> (Zilla limit is set to 500)
> About 18KW max.
>
> Is this likely to be just because it's such a low voltage pack?
>
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Re: [EVDL] Slow due to 96V pack?

2017-09-10 Thread Jay Summet via EV 



On 09/09/2017 10:14 PM, John Lussmyer via EV wrote:


I'm betting he has a Z1K LV - so that will limit how hi a voltage we can switch 
to when we switch to Lithium.
(also dealing with it having 2, 10A 48V chargers - one of which is dead, so you 
have to switch the other charger back and forth between pack halves.  sigh.)
This guy can't afford a bunch of upgrades immediately though.



I have a Curtis 1231c, so I had to keep my pack voltage at 120-130 volts 
when upgrading to lithium. I had to re-arrange my Leaf pack to put every 
3 modules in parallel reducing the voltage to 131.2 fully charged.


If you can fit an extra 4 GC batteries into the truck somewhere (mine 
had them under the hood up front) to raise your pack voltage to 120v 
nominal I can sell you my old Lead Acid chargers (Zivan for 240v  & 
Quick Charge for 110v) very cheaply


Jay
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Re: [EVDL] Slow due to 96V pack?

2017-09-10 Thread jerry freedomev via EV 
Hi John and All,
Since they haven't been worked they 
are going to need at least 5 cycles to waken up and likely 10 cycles to get to 
their real 
potential.
 Jerry Dycus



On Sat, 9/9/17, John Lussmyer via EV <ev@lists.evdl.org> wrote:

 Subject: Re: [EVDL] Slow due to 96V pack?
 To: "Electric Vehicle Discussion List" <ev@lists.evdl.org>
 Cc: "John Lussmyer" <cou...@casadelgato.com>
 Date: Saturday, September 9, 2017, 10:14 PM
 
 On Fri Sep 08 21:57:43 PDT 2017
 ev@lists.evdl.org
 said:
 >There is both a battery low
 voltage limit and a motor high voltage limit.
 >There is also a motor current limit and a
 battery current limit.
 >
 >You need to set all four to the appropriate
 values.
 
 yes, I know.  Just
 forgot to list those Motor values as they are set to be
 irrelevant.
 1000A and 150V.
 And I was reporting Battery Amps of course.
 
 I'm pretty sure now that
 it's just too low a voltage pack.  200 Batt amps was
 the max I could pull.
 The GC batts are
 basically unused - but are a couple years old, and have had
 battery maintainers connected for that time.
 
 I'm betting he has a Z1K
 LV - so that will limit how hi a voltage we can switch to
 when we switch to Lithium.
 (also dealing
 with it having 2, 10A 48V chargers - one of which is dead,
 so you have to switch the other charger back and forth
 between pack halves.  sigh.)
 This guy
 can't afford a bunch of upgrades immediately though.
 
 
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Re: [EVDL] Slow due to 96V pack?

2017-09-09 Thread David Nelson via EV 
On Sep 9, 2017 9:20 PM, "John Lussmyer via EV"  wrote:

On Sat Sep 09 20:58:50 PDT 2017 ev@lists.evdl.org said:
>I seem to recall that the minimum input voltage for a Zilla is 72 volts.
>Might be sagging the pack to 72 volts and that is that is simply amps it
>puts out at that voltage.

Well, as far as I could tell by the Volt meter, the pack wasn't sagging
below 90V.


Is that measured at the battery terminals or at the input to the Zilla?
Voltage might be really sagging through the cabling or a high resistance
connection.
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Re: [EVDL] Slow due to 96V pack?

2017-09-09 Thread John Lussmyer via EV 
On Sat Sep 09 20:58:50 PDT 2017 ev@lists.evdl.org said:
>I seem to recall that the minimum input voltage for a Zilla is 72 volts.
>Might be sagging the pack to 72 volts and that is that is simply amps it
>puts out at that voltage.

Well, as far as I could tell by the Volt meter, the pack wasn't sagging below 
90V.



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Re: [EVDL] Slow due to 96V pack?

2017-09-09 Thread Bill Dube via EV 

I seem to recall that the minimum input voltage for a Zilla is 72 volts.
Might be sagging the pack to 72 volts and that is that is simply amps it 
puts out at that voltage.


On 9/9/2017 8:14 PM, John Lussmyer via EV wrote:

On Fri Sep 08 21:57:43 PDT 2017 ev@lists.evdl.org said:

There is both a battery low voltage limit and a motor high voltage limit.
There is also a motor current limit and a battery current limit.

You need to set all four to the appropriate values.

yes, I know.  Just forgot to list those Motor values as they are set to be 
irrelevant.
1000A and 150V.
And I was reporting Battery Amps of course.

I'm pretty sure now that it's just too low a voltage pack.  200 Batt amps was 
the max I could pull.
The GC batts are basically unused - but are a couple years old, and have had 
battery maintainers connected for that time.

I'm betting he has a Z1K LV - so that will limit how hi a voltage we can switch 
to when we switch to Lithium.
(also dealing with it having 2, 10A 48V chargers - one of which is dead, so you 
have to switch the other charger back and forth between pack halves.  sigh.)
This guy can't afford a bunch of upgrades immediately though.


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Re: [EVDL] Slow due to 96V pack?

2017-09-09 Thread SLPinfo.org via EV 
John,

As someone mentioned, even at 120v you won't get great acceleration with GC
batts.  That's why we often call them "lead sleds".

Peter Flipsen Jr

On Sep 9, 2017 7:14 PM, "John Lussmyer via EV"  wrote:

> On Fri Sep 08 21:57:43 PDT 2017 ev@lists.evdl.org said:
> >There is both a battery low voltage limit and a motor high voltage limit.
> >There is also a motor current limit and a battery current limit.
> >
> >You need to set all four to the appropriate values.
>
> yes, I know.  Just forgot to list those Motor values as they are set to be
> irrelevant.
> 1000A and 150V.
> And I was reporting Battery Amps of course.
>
> I'm pretty sure now that it's just too low a voltage pack.  200 Batt amps
> was the max I could pull.
> The GC batts are basically unused - but are a couple years old, and have
> had battery maintainers connected for that time.
>
> I'm betting he has a Z1K LV - so that will limit how hi a voltage we can
> switch to when we switch to Lithium.
> (also dealing with it having 2, 10A 48V chargers - one of which is dead,
> so you have to switch the other charger back and forth between pack
> halves.  sigh.)
> This guy can't afford a bunch of upgrades immediately though.
>
>
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Re: [EVDL] Slow due to 96V pack?

2017-09-09 Thread John Lussmyer via EV 
On Fri Sep 08 21:57:43 PDT 2017 ev@lists.evdl.org said:
>There is both a battery low voltage limit and a motor high voltage limit.
>There is also a motor current limit and a battery current limit.
>
>You need to set all four to the appropriate values.

yes, I know.  Just forgot to list those Motor values as they are set to be 
irrelevant.
1000A and 150V.
And I was reporting Battery Amps of course.

I'm pretty sure now that it's just too low a voltage pack.  200 Batt amps was 
the max I could pull.
The GC batts are basically unused - but are a couple years old, and have had 
battery maintainers connected for that time.

I'm betting he has a Z1K LV - so that will limit how hi a voltage we can switch 
to when we switch to Lithium.
(also dealing with it having 2, 10A 48V chargers - one of which is dead, so you 
have to switch the other charger back and forth between pack halves.  sigh.)
This guy can't afford a bunch of upgrades immediately though.


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Re: [EVDL] Slow due to 96V pack?

2017-09-09 Thread Jay Summet via EV 
When I was driving my S-10 with 20 6v golf cart batteries (120v pack) I 
was never able to draw more than 240-300 amps from the battery pack even 
when the batteries were new. (and the acceleration wasn't great in 
anything but 1st gear from 0-20mph...)


If your friend's pack is used, 200 amps seems reasonable, especially for 
a 96v pack, which will probably have even more of a voltage sag than my 
120 volt pack.


I definitely recommend upgrading to LiIon (perhaps from a wrecked Leaf 
pack, which is what I did...)


Jay

On 09/09/2017 12:57 AM, Bill Dube via EV wrote:

There is both a battery low voltage limit and a motor high voltage limit.
There is also a motor current limit and a battery current limit.

You need to set all four to the appropriate values.

You never said if you were reading battery current or motor current. 
Makes a bit of difference. Also, it would be useful to know the battery 
voltage under load.


Bill D.

On 9/8/2017 9:51 PM, John Lussmyer via EV wrote:

I'm helping a guy with a used conversion he just bought.
It's a S-10 with 96V of Golf Cart batteries, Zilla 1K, and a 8 or 9" 
motor.

Even fully charged - it's acceleration is poor.
I was never able to get it to draw more than 200 Amps in any gear at 
any speed.

(Zilla limit is set to 500)
About 18KW max.

Is this likely to be just because it's such a low voltage pack?

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Re: [EVDL] Slow due to 96V pack?

2017-09-08 Thread Bill Dube via EV 

There is both a battery low voltage limit and a motor high voltage limit.
There is also a motor current limit and a battery current limit.

You need to set all four to the appropriate values.

You never said if you were reading battery current or motor current. 
Makes a bit of difference. Also, it would be useful to know the battery 
voltage under load.


Bill D.

On 9/8/2017 9:51 PM, John Lussmyer via EV wrote:

I'm helping a guy with a used conversion he just bought.
It's a S-10 with 96V of Golf Cart batteries, Zilla 1K, and a 8 or 9" motor.
Even fully charged - it's acceleration is poor.
I was never able to get it to draw more than 200 Amps in any gear at any speed.
(Zilla limit is set to 500)
About 18KW max.

Is this likely to be just because it's such a low voltage pack?

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[EVDL] Slow due to 96V pack?

2017-09-08 Thread John Lussmyer via EV 
I'm helping a guy with a used conversion he just bought.
It's a S-10 with 96V of Golf Cart batteries, Zilla 1K, and a 8 or 9" motor.
Even fully charged - it's acceleration is poor.
I was never able to get it to draw more than 200 Amps in any gear at any speed.
(Zilla limit is set to 500)
About 18KW max.

Is this likely to be just because it's such a low voltage pack?

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