Peukert, break-in and other LiFePO4 fuzzy data

classic Classic list List threaded Threaded
15 messages Options
Reply | Threaded
Open this post in threaded view
|

Peukert, break-in and other LiFePO4 fuzzy data

Mark Hanson-2

Hi Folk's,
 
Does anyone know what the Peukert exponent is for LiFePO4 (specifically CALB-130) batteries is?  My inquring LinkPro battery monitor would like to know, default is 1.25.  No exponent is 1.00 (which is where I set it presently).
 
Also is there a break-in period on Lithium batteries like lead, be jentle for 10 cycles no more than 1/2 discharge?
 
Is there a good info page on the web etc on Lithium LiFePO4 *characteristics*?  The manufacturer's data sheet is pretty skimpy.
 
Have a renewable energy day,
Mark      
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://lists.sjsu.edu/mailman/private/ev/attachments/20120504/2acf8c30/attachment.html 
_______________________________________________
| Moratorium on drag racing discussion is in effect.
| Please take those discussions elsewhere.  Thanks.
|
| REPLYING: address your message to [hidden email] only.
| Multiple-address or CCed messages may be rejected.
| UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
| OTHER HELP: http://evdl.org/help/
| CONFIGURE: http://lists.sjsu.edu/mailman/listinfo/ev
Reply | Threaded
Open this post in threaded view
|

Re: Peukert, break-in and other LiFePO4 fuzzy data

Bill Dube
Short answer: LiFePO4 cells don't have a Peukert effect that you
would care about in normal use in an EV. Under normal dischare over
minutes and hours, you lose no A-hr capacity whatsoever in LiFePO4.

Longer answer:

The chemistry (diffusion of reactants, etc.) in a lead-acid works on
the scale of minutes and hours, while that chemical reaction type
time constant is on the order of seconds in LiFePO4. If you discharge
the pack in seconds, you get Puekert-like effects in LiFePO4.

No break-in after the very first cycle in LiFePO4.

Bill D.


At 01:31 PM 5/4/2012, you wrote:

>Hi Folk's,
>
>Does anyone know what the Peukert exponent is for LiFePO4
>(specifically CALB-130) batteries is?  My inquring LinkPro battery
>monitor would like to know, default is 1.25.  No exponent is 1.00
>(which is where I set it presently).
>
>Also is there a break-in period on Lithium batteries like lead, be
>jentle for 10 cycles no more than 1/2 discharge?
>
>Is there a good info page on the web etc on Lithium LiFePO4
>*characteristics*?  The manufacturer's data sheet is pretty skimpy.
>
>Have a renewable energy day,
>Mark
>-------------- next part --------------
>An HTML attachment was scrubbed...
>URL:
>http://lists.sjsu.edu/mailman/private/ev/attachments/20120504/2acf8c30/attachment.html 
>
>_______________________________________________
>| Moratorium on drag racing discussion is in effect.
>| Please take those discussions elsewhere.  Thanks.
>|
>| REPLYING: address your message to [hidden email] only.
>| Multiple-address or CCed messages may be rejected.
>| UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
>| OTHER HELP: http://evdl.org/help/
>| CONFIGURE: http://lists.sjsu.edu/mailman/listinfo/ev

_______________________________________________
| Moratorium on drag racing discussion is in effect.
| Please take those discussions elsewhere.  Thanks.
|
| REPLYING: address your message to [hidden email] only.
| Multiple-address or CCed messages may be rejected.
| UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
| OTHER HELP: http://evdl.org/help/
| CONFIGURE: http://lists.sjsu.edu/mailman/listinfo/ev
Reply | Threaded
Open this post in threaded view
|

Re: Peukert, break-in and other LiFePO4 fuzzy data

Cruisin
In reply to this post by Mark Hanson-2
Hey Mark, the reason the manufacturers web sit is fuzzy is that those who buy their products dont hold them accountable. Have you called them and complained and then posted here their response. Who is your dealer for the batteries? What is his answer? Post it here.
Reply | Threaded
Open this post in threaded view
|

Re: Peukert, break-in and other LiFePO4 fuzzy data

Derek Barger-2
In reply to this post by Mark Hanson-2
Hi Mark,
I asked this question about Peurkert years ago to the engineers at
A123 Systems. The answer I received is 1.1 so CALB will be around that
number.

On Fri, May 4, 2012 at 1:31 PM, Mark Hanson <[hidden email]> wrote:

>
> Hi Folk's,
>
> Does anyone know what the Peukert exponent is for LiFePO4 (specifically CALB-130) batteries is?  My inquring LinkPro battery monitor would like to know, default is 1.25.  No exponent is 1.00 (which is where I set it presently).
>
> Also is there a break-in period on Lithium batteries like lead, be jentle for 10 cycles no more than 1/2 discharge?
>
> Is there a good info page on the web etc on Lithium LiFePO4 *characteristics*?  The manufacturer's data sheet is pretty skimpy.
>
> Have a renewable energy day,
> Mark
> -------------- next part --------------
> An HTML attachment was scrubbed...
> URL: http://lists.sjsu.edu/mailman/private/ev/attachments/20120504/2acf8c30/attachment.html
> _______________________________________________
> | Moratorium on drag racing discussion is in effect.
> | Please take those discussions elsewhere.  Thanks.
> |
> | REPLYING: address your message to [hidden email] only.
> | Multiple-address or CCed messages may be rejected.
> | UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
> | OTHER HELP: http://evdl.org/help/
> | CONFIGURE: http://lists.sjsu.edu/mailman/listinfo/ev



--
Derek Barger
High Tech Systems LLC
Worlds Quickest and Fastest Batteries in a 1/4Mile.

_______________________________________________
| Moratorium on drag racing discussion is in effect.
| Please take those discussions elsewhere.  Thanks.
|
| REPLYING: address your message to [hidden email] only.
| Multiple-address or CCed messages may be rejected.
| UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
| OTHER HELP: http://evdl.org/help/
| CONFIGURE: http://lists.sjsu.edu/mailman/listinfo/ev
Reply | Threaded
Open this post in threaded view
|

Re: Peukert, break-in and other LiFePO4 fuzzy data

David Nelson-5
In reply to this post by Mark Hanson-2
Like Bill said it is essentially 1.0. What little difference there is,
is less than the precision of my CycleAnalyst. I do have a 200Ah pack
with max draw of 500A and usually below 300A most of the time.

On Fri, May 4, 2012 at 12:31 PM, Mark Hanson <[hidden email]> wrote:

>
> Hi Folk's,
>
> Does anyone know what the Peukert exponent is for LiFePO4 (specifically CALB-130) batteries is?  My inquring LinkPro battery monitor would like to know, default is 1.25.  No exponent is 1.00 (which is where I set it presently).
>
> Also is there a break-in period on Lithium batteries like lead, be jentle for 10 cycles no more than 1/2 discharge?
>
> Is there a good info page on the web etc on Lithium LiFePO4 *characteristics*?  The manufacturer's data sheet is pretty skimpy.
>
> Have a renewable energy day,
> Mark
> -------------- next part --------------
> An HTML attachment was scrubbed...
> URL: http://lists.sjsu.edu/mailman/private/ev/attachments/20120504/2acf8c30/attachment.html
> _______________________________________________
> | Moratorium on drag racing discussion is in effect.
> | Please take those discussions elsewhere.  Thanks.
> |
> | REPLYING: address your message to [hidden email] only.
> | Multiple-address or CCed messages may be rejected.
> | UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
> | OTHER HELP: http://evdl.org/help/
> | CONFIGURE: http://lists.sjsu.edu/mailman/listinfo/ev



--
David D. Nelson
http://evalbum.com/1328
http://2003gizmo.blogspot.com

_______________________________________________
| Moratorium on drag racing discussion is in effect.
| Please take those discussions elsewhere.  Thanks.
|
| REPLYING: address your message to [hidden email] only.
| Multiple-address or CCed messages may be rejected.
| UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
| OTHER HELP: http://evdl.org/help/
| CONFIGURE: http://lists.sjsu.edu/mailman/listinfo/ev
Reply | Threaded
Open this post in threaded view
|

Re: Peukert, break-in and other LiFePO4 fuzzy data

Lee Hart
In reply to this post by Mark Hanson-2
  Mark Hanson wrote:
> Does anyone know what the Peukert exponent is for LiFePO4
> (specifically CALB-130) batteries is?  My inquring LinkPro battery
> monitor would like to know, default is 1.25.  No exponent is 1.00
> (which is where I set it presently).

It's pretty low; like 1.01-1.1. I don't have any data on your CALB
130ah, but my CALB 90ah were around 1.03, and Thundersky 1.1.

You can measure it for yourself. Run two discharge tests to the same
ending voltage, at two widely separated discharge currents. Record the
discharge time for each. Use the equation in the LinkPro manual to
calculate the Peukert exponent and Peukert capacity.

> Also is there a break-in period on Lithium batteries like lead, be
> jentle for 10 cycles no more than 1/2 discharge?

There doesn't appear to be. Ones I've tested delivered max capacity on
the first cycle, and did not increase on subsequent cycles (unless it
wasn't fully charged on the first cycle ,or the temperature was higher
on later cycles, etc.)

> Is there a good info page on the web etc on Lithium LiFePO4
> *characteristics*?  The manufacturer's data sheet is pretty skimpy.


--
If you would not be forgotten
When your body's dead and rotten
Then write of great deeds worth the reading
Or do these great deeds, worth repeating.
        -- Ben Franklin, from Poor Richard's Almanac
--
Lee A. Hart, 814 8th Ave N, Sartell MN 56377, leeahart at earthlink.net

_______________________________________________
| Moratorium on drag racing discussion is in effect.
| Please take those discussions elsewhere.  Thanks.
|
| REPLYING: address your message to [hidden email] only.
| Multiple-address or CCed messages may be rejected.
| UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
| OTHER HELP: http://evdl.org/help/
| CONFIGURE: http://lists.sjsu.edu/mailman/listinfo/ev
Reply | Threaded
Open this post in threaded view
|

Re: Peukert, break-in and other LiFePO4 fuzzy data

Lee Hart
In reply to this post by Bill Dube
On 5/4/2012 3:30 PM, Bill Dube wrote:
> Short answer: LiFePO4 cells don't have a Peukert effect that you
> would care about in normal use in an EV. Under normal discharge over
> minutes and hours, you lose no A-hr capacity whatsoever in LiFePO4.

I dunno, Bill. I've tested half a dozen different lithiums, and they all
*do* have a Peukert effect. It's always present in any battery that has
an internal resistance and has a fixed cutoff voltage that you end your
discharge at.

The exponent can be pretty low. The lowest I've measured is 1.02 for
A123 cylindrical cells.

> The chemistry (diffusion of reactants, etc.) in a lead-acid works on
> the scale of minutes and hours, while that chemical reaction type
> time constant is on the order of seconds in LiFePO4. If you discharge
> the pack in seconds, you get Puekert-like effects in LiFePO4.

Here again, I'm not so sure.

I can discharge a battery with a continuous current (say 10 amps for
steady), and I get a smooth discharge voltage vs. time curve. Or, I can
discharge the same battery with a pulsed current (say 100 amps for 1
second, 0 amps for 9 seconds, so the average is the same 10 amps) and
get a completely different curve.

Each time the load switches off, the voltage jumps up, and then slowly
rises to its resting value. Each time the load switches on, the voltage
suddenly falls, then slowly ramps down. Like this (bad ASCII art).

   _________load switches off; voltage jumps up (internal resistance?)
  |  _______voltage gradually rises over time (diffusion rate?)
  | |  _____load switches on; voltage jumps down (internal resistance?)
  | | |  _____voltage gradually falls over time (diffusion rate?)
  | | | |  ____load switches off; voltage jumps up (internal resistance?)
  | | | | |

     /|
    / |
   /  |
  |    \  | cell voltage versus time with load switched on/off
  |     \ |
  |      \|

When I plot the data over a period of off-time and on-time and fit it to
a curve, I see a curve with at least 3 different time constants. There's
a very fast one (seconds), a much slower one (minutes), and a very slow
one (hours or days).

--
If we knew what we were doing, it wouldn't be called research, would it?
        -- Albert Einstein
--
Lee A. Hart, 814 8th Ave N, Sartell MN 56377, leeahart at earthlink.net

_______________________________________________
| Moratorium on drag racing discussion is in effect.
| Please take those discussions elsewhere.  Thanks.
|
| REPLYING: address your message to [hidden email] only.
| Multiple-address or CCed messages may be rejected.
| UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
| OTHER HELP: http://evdl.org/help/
| CONFIGURE: http://lists.sjsu.edu/mailman/listinfo/ev
Reply | Threaded
Open this post in threaded view
|

Re: Peukert, break-in and other LiFePO4 fuzzy data

Lee Hart
In reply to this post by Derek Barger-2
On 5/4/2012 5:35 PM, Derek Barger wrote:
> Hi Mark,
> I asked this question about Peurkert years ago to the engineers at
> A123 Systems. The answer I received is 1.1 so CALB will be around that
> number.

I tested them at 0.1c and 1c, and got a number more like 1.02. Maybe it
gets worse at higher currents, or they were just being conservative.

BTW, 1.02 is a fantastically good Peukert value!

--
Ring the bells that still can ring
Forget your perfect offering
There is a crack in everything
That's how the light gets in.
        -- Leonard Cohen, from "Anthem"
--
Lee A. Hart, 814 8th Ave N, Sartell MN 56377, leeahart at earthlink.net

_______________________________________________
| Moratorium on drag racing discussion is in effect.
| Please take those discussions elsewhere.  Thanks.
|
| REPLYING: address your message to [hidden email] only.
| Multiple-address or CCed messages may be rejected.
| UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
| OTHER HELP: http://evdl.org/help/
| CONFIGURE: http://lists.sjsu.edu/mailman/listinfo/ev
Reply | Threaded
Open this post in threaded view
|

Re: Peukert, break-in and other LiFePO4 fuzzy data

Morgan LaMoore
On Fri, May 4, 2012 at 11:05 PM, Lee Hart <[hidden email]> wrote:
> I tested them at 0.1c and 1c, and got a number more like 1.02. Maybe it
> gets worse at higher currents, or they were just being conservative.
>
> BTW, 1.02 is a fantastically good Peukert value!

Lee,

The internal resistance of any battery will cause a decrease in
capacity with increasing current similar to the Peukert effect, but
Peukert's Law (the equation) was written for lead-acids  and is not
valid for Lithium (or alternatively, with Lithium the Peukert value is
significantly dependent on discharge current).

With Lithiums, at low currents, you will see almost zero Peukert
effect, but at very high currents (near or beyond the maximum the cell
is capable of), you will see a moderate to significant Peukert effect.

What counts as 'low current' depends on the internal resistance of the
cell compared to the cell capacity. With A123, you probably have to
measure at 10C-100C to see significant Peukert effect, while with
ThunderSky or similar cells, the Peukert effect is at least slightly
noticeable at 1C-3C.

-Morgan LaMoore

_______________________________________________
| Moratorium on drag racing discussion is in effect.
| Please take those discussions elsewhere.  Thanks.
|
| REPLYING: address your message to [hidden email] only.
| Multiple-address or CCed messages may be rejected.
| UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
| OTHER HELP: http://evdl.org/help/
| CONFIGURE: http://lists.sjsu.edu/mailman/listinfo/ev
Reply | Threaded
Open this post in threaded view
|

Re: Peukert, break-in and other LiFePO4 fuzzy data

Lee Hart
On 5/9/2012 7:22 PM, Morgan LaMoore wrote:
> The internal resistance of any battery will cause a decrease in
> capacity with increasing current similar to the Peukert effect, but
> Peukert's Law (the equation) was written for lead-acids...

Well, it was written over 100 years ago. He didn't have a lot of other
options. :-)

Peukert's equation says nothing about the type of battery. All he did
was plot the amphour capacity versus current, and wrote an equation to
fit the data.

Your comment makes me realize that we need to do the same thing for
lithiums (and other chemistries, while we are at it). Plot capacity vs.
discharge current, and see what equation fits the data.

> With Lithiums, at low currents, you will see almost zero Peukert
> effect, but at very high currents (near or beyond the maximum the cell
> is capable of), you will see a moderate to significant Peukert effect.

That happens with lead-acid as well. I think the Peukert effect is
largely an artifact of any battery that has an internal resistance, and
use a particular voltage to indicate the endpoint (point at which it is
considered "dead").

Batteries that have a very low internal resistance (in proportion to
their amphour capacity) have a very low Peukert exponent. The exponent
starts to get bigger as the currents start to cause a significant
voltage drop in the internal resistance.

Anyone looking for a subject for a master's thesis? :-)
--
Ingenuity gets you through times of no money better than money
will get you through times of no ingenuity. -- Terry Pratchett
--
Lee A. Hart, 814 8th Ave N, Sartell MN 56377, leeahart at earthlink.net

_______________________________________________
| Moratorium on drag racing discussion is in effect.
| Please take those discussions elsewhere.  Thanks.
|
| REPLYING: address your message to [hidden email] only.
| Multiple-address or CCed messages may be rejected.
| UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
| OTHER HELP: http://evdl.org/help/
| CONFIGURE: http://lists.sjsu.edu/mailman/listinfo/ev
Reply | Threaded
Open this post in threaded view
|

Re: Peukert, break-in and other LiFePO4 fuzzy data

tomw
I agree with Lee.  You can see from the manufacturer's voltage vs Ah curves that capacity of LiFePO4 cells varies with discharge current, and that is the effect Peukert described for lead acid.  I've been using 1.03, but haven't done measurements like Lee has.  It seems to predict range fairly well, but their are so many other effects on range that doesn't mean a lot.
Reply | Threaded
Open this post in threaded view
|

Re: Peukert, break-in and other LiFePO4 fuzzy data

Morgan LaMoore
Yes, capacity does vary with discharge current as expected by the Peukert
effect.

My point was that the Peukert equation or a number like '1.03' is
meaningless because how much the 'Peukert Exponent' varies with discharge
current.

I see how my comment about seeing more Peukert effect at higher currents is
easy to misunderstand. What I meant is that if you measure at quite low
currents (say 0.1C and 0.5C) you will measure a Peukert exponent of
something like 1.01-1.03, and if you go down to 0.05C, you will probably
get a value so close to 1.00 that you can't tell it apart from the noise.

However, if you measure at 1C and compare to 5C or 10C (maybe 40C for
A123), then you will get a Peukert exponent as high as 1.3 or more.

So even though you see lower capacity at higher currents as expected by the
Peukert effect, Peukert's equation is nearly useless for Lithium. Someone
needs to take a lot of data and make a new equation to fit that data.

As a rough guess, I would expect that while for a lead battery, capacity
continues to increase with decreasing discharge current (until you get low
enough that self-discharge becomes significant), with Lithium you will have
some base capacity that is decreased with increasing current.

Lead: capacity = (capacity at 1 amp) * I ^ (1-k)

That is a different way to write Peukert's equation to make it easier to
compare to other equations.

I expect that for Lithium, the equation would be something more like:

Lithium: capacity = (nominal capacity) * (1 - k1*e^(k2*I)

You can compare these by going to www.wolframalpha.com and entering:

graph y=100*x^-0.06 and y=100*(1-0.002*e^(0.02*x)) for x from 0 to 300

-Morgan LaMoore

On Thu, May 10, 2012 at 9:07 AM, tomw <[hidden email]> wrote:

> I agree with Lee.  You can see from the manufacturer's voltage vs Ah curves
> that capacity of LiFePO4 cells varies with discharge current, and that is
> the effect Peukert described for lead acid.  I've been using 1.03, but
> haven't done measurements like Lee has.  It seems to predict range fairly
> well, but their are so many other effects on range that doesn't mean a lot.
>
> --
> View this message in context:
> http://electric-vehicle-discussion-list.413529.n4.nabble.com/Peukert-break-in-and-other-LiFePO4-fuzzy-data-tp4609493p4623611.html
> Sent from the Electric Vehicle Discussion List mailing list archive at
> Nabble.com.
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://lists.sjsu.edu/mailman/private/ev/attachments/20120510/dc7b7ca8/attachment.html 
_______________________________________________
| Moratorium on drag racing discussion is in effect.
| Please take those discussions elsewhere.  Thanks.
|
| REPLYING: address your message to [hidden email] only.
| Multiple-address or CCed messages may be rejected.
| UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
| OTHER HELP: http://evdl.org/help/
| CONFIGURE: http://lists.sjsu.edu/mailman/listinfo/ev
Reply | Threaded
Open this post in threaded view
|

Re: Peukert, break-in and other LiFePO4 fuzzy data

Chris Zach
Speaking of all this, what *should* I be seeing in terms of voltage drop
on the A123 pouch cells. I did a quick hit on them last night with the
100a load tester, and voltage read in the 10.5's on a 4 cell pack.

Of course this was for a few seconds, and the interconnects were *not*
screwed down snugly. Will work on that this weekend. And another 4
batteries are on the way so I can do some real testing with the
Elec-trak in a few weeks.

Mowing my lawn. ON LITHIUM!

C

_______________________________________________
| Moratorium on drag racing discussion is in effect.
| Please take those discussions elsewhere.  Thanks.
|
| REPLYING: address your message to [hidden email] only.
| Multiple-address or CCed messages may be rejected.
| UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
| OTHER HELP: http://evdl.org/help/
| CONFIGURE: http://lists.sjsu.edu/mailman/listinfo/ev
Reply | Threaded
Open this post in threaded view
|

Re: Peukert, break-in and other LiFePO4 fuzzy data

Lee Hart
In reply to this post by Morgan LaMoore
On 5/10/2012 11:17 AM, Morgan LaMoore wrote:
> Yes, capacity does vary with discharge current as expected by the Peukert
> effect.
>
> My point was that the Peukert equation or a number like '1.03' is
> meaningless because the 'Peukert Exponent' varies with discharge
> current.

It's not "meaningless"; but it only applies over a limited range.
Peukert's equation only fits the battery's actual behavior over a
limited range of discharge currents. Pick the range to match what your
EV actually draws.

For instance, if your EV draws 50a to 500a, then use these two limits to
calculate the Peukert capacity and exponent. It will match at the end
points, and be off by a little for currents in between these limits. And
it will probably be off by a *lot* for currents outside these limits.

Peukert simply found that his exponential equation was a better fit than
a linear equation.

If we get more data on actual battery behavior, we can improve on the
mathematical model. Add terms to better fit the data, to include other
effects like temperature, etc.

That's a reasonable hypothesis. Now it remains to TEST it! :-)

Someone has to do the real work. We can't just blindly accept the curves
from the manufacturers. They are too smooth and perfect; someone has
obviously "prettied them up" for publication.

--
Ingenuity gets you through times of no money better than money
will get you through times of no ingenuity. -- Terry Pratchett
--
Lee A. Hart, 814 8th Ave N, Sartell MN 56377, leeahart at earthlink.net

_______________________________________________
| Moratorium on drag racing discussion is in effect.
| Please take those discussions elsewhere.  Thanks.
|
| REPLYING: address your message to [hidden email] only.
| Multiple-address or CCed messages may be rejected.
| UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
| OTHER HELP: http://evdl.org/help/
| CONFIGURE: http://lists.sjsu.edu/mailman/listinfo/ev
Reply | Threaded
Open this post in threaded view
|

Re: Peukert, break-in and other LiFePO4 fuzzy data

Morgan LaMoore
On Thu, May 10, 2012 at 12:47 PM, Lee Hart <[hidden email]> wrote:

> ...
> It's not "meaningless"; but it only applies over a limited range.
> Peukert's equation only fits the battery's actual behavior over a
> limited range of discharge currents. Pick the range to match what your
> EV actually draws.
>
> For instance, if your EV draws 50a to 500a, then use these two limits to
> calculate the Peukert capacity and exponent. It will match at the end
> points, and be off by a little for currents in between these limits. And
> it will probably be off by a *lot* for currents outside these limits.
> ...

Good point. I was thinking you would need to go all the way down to 1A
or whatever the standby current of your EV is, but it doesn't matter
if the curve is accurate there because you use such a tiny percentage
of your energy at those discharge currents.

As you've quoted many times, the perfect is the enemy of the good.

-Morgan LaMoore

_______________________________________________
| Moratorium on drag racing discussion is in effect.
| Please take those discussions elsewhere.  Thanks.
|
| REPLYING: address your message to [hidden email] only.
| Multiple-address or CCed messages may be rejected.
| UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
| OTHER HELP: http://evdl.org/help/
| CONFIGURE: http://lists.sjsu.edu/mailman/listinfo/ev