# [EVDL] Peukert, break-in and other LiFePO4 fuzzy data



## EVDL List (Jul 27, 2007)

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 
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## EVDL List (Jul 27, 2007)

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.

--
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## EVDL List (Jul 27, 2007)

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 <[email protected]> wrot=
e:
>
> Hi Folk's,
>
> Does anyone know what the Peukert exponent is for LiFePO4 (specifically C=
ALB-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 pre=
sently).
>
> 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 *characterist=
ics*? The manufacturer's data sheet is pretty skimpy.
>
> Have a renewable energy day,
> Mark
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-- =

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

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## EVDL List (Jul 27, 2007)

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 <[email protected]> wro=
te:
>
> Hi Folk's,
>
> Does anyone know what the Peukert exponent is for LiFePO4 (specifically C=
ALB-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 pre=
sently).
>
> 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 *characterist=
ics*? The manufacturer's data sheet is pretty skimpy.
>
> Have a renewable energy day,
> Mark
> -------------- next part --------------
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-- =

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

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## EVDL List (Jul 27, 2007)

> 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
> ...


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## EVDL List (Jul 27, 2007)

> Lee Hart <[email protected]> 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.
> >
> ...


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## EVDL List (Jul 27, 2007)

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. 

--
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## EVDL List (Jul 27, 2007)

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



> tomw <[email protected]> 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
> ...


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## EVDL List (Jul 27, 2007)

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

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## EVDL List (Jul 27, 2007)

> Lee Hart <[email protected]xxx> 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
> ...


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