# What happened A123 system what is replacement of high C -Rate Battery?



## onegreenev (May 18, 2012)

CALB CA cells would be a good replacement. No muss no fuss and not Li Po cells to deal with. LiFePO4 is the best. Kokam is not available to the DIY guys. Unless they happen to sponsor you. Good luck with that.


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## Genius Pooh (Dec 23, 2011)

onegreenev said:


> CALB CA cells would be a good replacement. No muss no fuss and not Li Po cells to deal with. LiFePO4 is the best. Kokam is not available to the DIY guys. Unless they happen to sponsor you. Good luck with that.


 
Are you sure? It's C rate is just 0.3....

I need big C rate.. 

GWL winston??? mark 20c at 5 sec.. and 3c for 15 minutes..

Hmm... It's ideal is 0.5c also..

Ah I miss A123

and how about headway? their continous is 10c 

I don't understand why they make bigger pack hmm


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## Elithion (Oct 6, 2009)

Genius Pooh said:


> what is replacement of high C -Rate Battery?


Actually, for high power applications (such as hybrid cars), the 20 Ah A123 pouch cells is only slightly better that average. So no great loss there. The M1 26650 small cylindrical cell, on the other side, is still a very good cell for power applications, after all these years.

Far better cells for power applications are: 


EiG F007 7 Ah cell
Dow Kokam 4, 4.5 and 5 Ah super high power cells
Enerdel 16 Ah HEV cell

This chart rates cells according to short discharge time (shorter = more efficient in power applications), based on an extensive analysis we performed.










As you see, prismatic cells (such as CALB) are nowhere near good enough for power applications: they have a short discharge time that is 10 times the one for the EiG cell. What they are good for is energy applications: EVs.
There are more considerations than short discharge time, such as energy density. Still, this chart should get you started.

Caveat emptor: you are responsible for your choice of cells, and this report is not to be taken as a recommendation.


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## Genius Pooh (Dec 23, 2011)

Elithion said:


> Actually, for high power applications (such as hybrid cars), the 20 Ah A123 pouch cells is only slightly better that average. So no great loss there. The M1 26650 small cylindrical cell, on the other side, is still a very good cell for power applications, after all these years.
> 
> Far better cells for power applications are:
> 
> ...


It's quiet impressive WOW!!

Where do you get it??

CALB SE 's spec was very low but in this graph It's quite good...

Ah where I can find Kokam or above power cells...

And Still A 123 system A20 pouch looking good ...hmm.


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## MN Driver (Sep 29, 2009)

Elithion said:


> This chart rates cells according to short discharge time (shorter = more efficient in power applications), based on an extensive analysis we performed.
> [Chart]


What is the criteria for quantifying the number of seconds?
It appears the CALB CA series has far less voltage sag, which would mean less cell heating and theoretically a high discharge current capability as long as there aren't any hot spots internally at some extreme discharge rate.


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## Elithion (Oct 6, 2009)

MN Driver said:


> What is the [criterion] for quantifying the number of seconds?.


ShortDischargeTime  = capacity [Ah] * resistance [Ω] / voltage [V] * 3600 [s/h]




MN Driver said:


> It appears the CALB CA series has far less voltage sag...


... compared to what?



MN Driver said:


> ... less voltage sag, which would mean less cell heating...


Exactly!

efficiency [%] = 100 * (1 – short_discharge_time  / actual_discharge_time  )

For the complete report, please write me directly. (I cannot publish it until after it is published by the Battery Power Magazine, in December.)


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## MN Driver (Sep 29, 2009)

"... compared to what?"
To the CALB SE cells they replaced.

Thanks for your comparison charts and the information on how you determined the figures.


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## GerhardRP (Nov 17, 2009)

Elithion said:


> ShortDischargeTime  = capacity [Ah] * resistance [Ω] / voltage [V] * 3600 [s/h]




Equals the *theoretical *time to fully discharge into a short circuit.
Don't try this at home ...or in the lab for that matter.
I think your formulation has merit.
Gerhard
edit: PS maybe rename this "shorted discharge time" G.


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## Elithion (Oct 6, 2009)

MN Driver said:


> "... compared to what?"
> To the CALB SE cells they replaced.


The CALB specs for the CA cells have too poor a resolution to be useful for this analysis. Still it appears that the CA cells may have a short discharge time that is about 12 % better than the SE cells. Nice, but not extremely different.


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## GeoMetric (Aug 13, 2010)

Elithion said:


> Actually, for high power applications (such as hybrid cars), the 20 Ah A123 pouch cells is only slightly better that average. So no great loss there. The M1 26650 small cylindrical cell, on the other side, is still a very good cell for power applications, after all these years.
> 
> Far better cells for power applications are:
> 
> ...


Awesome data chart. I would love to see all cells listed by Amps and C-ratings.


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## Elithion (Oct 6, 2009)

GeoMetric said:


> I would love to see all cells listed by Amps and C-ratings.


One of the beauties of short discharge time is that it is a characteristic of cell technology; so its value is to a great extent independent of the size of the cell! 
When we determine that the short discharge time of a CALB SE cell is 135 s, that is true for the 40 Ah, the 100 Ah, the 200 Ah cells, etc.

Unfortunately C-rating is a marketing tool more than a physical value. Take for example the Headway cells: they are touted as having one of the highest C-ratings in the industry, yet their efficiency in high power applications is terrible: their short discharge time is the worst of any Li-ion cell we checked.


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## Batterypoweredtoad (Feb 5, 2008)

When you say "Short discharge time" what exactly are you saying? Is it time required to discharge the full capacity of the cell when shorted? If so that would be an interesting test to watch.


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## Elithion (Oct 6, 2009)

Batterypoweredtoad said:


> When you say "Short discharge time" what exactly are you saying? Is it time required to discharge the full capacity of the cell when shorted?


Theoretically, yes.
Of course, it cannot be achieved in practice; it can only be calculated from cell performance under normal conditions. 
It is a great tool for comparing apples to apples when working with cells and batteries, a convenient tool to calculate resistance and efficiency of a pack.


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## drgrieve (Apr 14, 2011)

Elithion said:


> Take for example the Headway cells: they are touted as having one of the highest C-ratings in the industry, yet their efficiency in high power applications is terrible: their short discharge time is the worst of any Li-ion cell we checked.


Thanks for the chart - although I'm not sure many on there sell to the DIY crowd 

In regards to the headway cells. Which one was tested? Also from how long ago? 

From other testing I've seen reported there is a significant difference between the 16ah cell and the 8ah (P or is it S) range.

Certainly better then the old Calb SE cell.

Anyway with the new Calb grey cell the point is moot I guess.


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## Batterypoweredtoad (Feb 5, 2008)

There are several examples out there of the discharge characteristics of the 8ah "power cells" from Headway. Two I can of think of are the tests from the Electrabishi and Rebirth Auto/Evnetics with the 911 dyno at EVCon. 

Electrabishi: http://visforvoltage.org/forum/8523-headway-cell-testing-preliminary-study


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## Yabert (Feb 7, 2010)

Hi Elithion

I'm also really interested to know which headway cells was tested?
On paper, EIG-F007 (7Ah) at <0.003 ohm and Headway 38120 hp (8Ah) at < 0.003 ohm should be roughly the same.

Let us know.... and by the way, thanks for all the great information you share!


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## Elithion (Oct 6, 2009)

Yabert said:


> On paper, EIG-F007 (7Ah) at <0.003 ohm and Headway 38120 hp (8Ah) at < 0.003 ohm should be roughly the same.


Hey! That's AC impedance at 1 kHz; that's not DC resistance!

There is no relation between the two. Even within the same model of cell, there is no relation between the two. See the Li-ion book, section 1.1.2 which you can read for free at Google Books.

DC resistance (at 1 C discharge, 50 % DOC, 25 °C):
* EiG F007: 1.6 mΩ
* Zhejiang Headway HW38120LS: 15.0 mΩ

Please write me directly for a copy of the soon to be published article on Short Discharge Time, which explains the methodology.


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## major (Apr 4, 2008)

Elithion said:


> Hey! That's AC impedance at 1 kHz; that's not DC resistance!
> 
> There is no relation between the two.


I'm glad to see someone else state this. I've been telling people this for years. Again, thanks for sharing info.


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## Elithion (Oct 6, 2009)

drgrieve said:


> In regards to the headway cells. Which one was tested? Also from how long ago?.


I just got my hands on a 16 AH Headway cell. The good news is that they tested better than the specs indicated, 17 % better. That places them just neck and neck with the new CALB CA cell.



drgrieve said:


> Certainly better then the old Calb SE cell.


Yes, about 10 % better.

These are not huge differences: the large prismatic cells and the Headway large cylindrical cells are all in the slow poke class of cells, with a Short Discharge Time in the 140 seconds range (a far cry from the honest to goodness high power cells with a SDT of 10 to 20 s).


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## rmay635703 (Oct 23, 2008)

I always thought Xtreme energy lead acid where vapor ware, did this change at some point?


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## Genius Pooh (Dec 23, 2011)

Elithion said:


> I just got my hands on a 16 AH Headway cell. The good news is that they tested better than the specs indicated, 17 % better. That places them just neck and neck with the new CALB CA cell.
> 
> 
> 
> ...


Wow amazing...

I thinkk you must get a prize for these works


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## IamIan (Mar 29, 2009)

Elithion said:


> ShortDischargeTime  = capacity [Ah] * resistance [Ω] / voltage [V] * 3600 [s/h]




I'm curious if you don't mind sharing a a bit of your reasoning.

#1> Why not include cell weight in the calculation?

#2> Why setup the formula to favor smaller Ah cells?


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## Elithion (Oct 6, 2009)

IamIan said:


> Why not include cell weight in the calculation?


Why should it be included? 

A battery of a given capacity and voltage, whether made out of lead acid or Li-ion, both with the same SDT, will the same performance in power application: the same resistance, the same efficiency, will generate the same heat. That's one the beauties of Short Discharge Time.



IamIan said:


> Why setup the formula to favor smaller Ah cells?


On the contrary, Short discharge time is totally independent of capacity.
Give me a 1 Ah, 3 V cell, or a 100 Ah, 3 V battery made out of 100 of those cells in parallel, or a 1 Ah. 300 V battery made out of 100 of those cells in series, and they all have the same SDT. 

The capacity is one of the terms in the formula precisely because we want to eliminate the dependency of SDT on capacitance.


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## IamIan (Mar 29, 2009)

Elithion said:


> Why should it be included?
> 
> A battery of a given capacity and voltage, whether made out of lead acid or Li-ion, both with the same SDT, will the same performance in power application: the same resistance, the same efficiency, will generate the same heat. That's one the beauties of Short Discharge Time.


Exactly why I would think it should be included.

A heavier cell that has the same SDT will give a BEV using it inferior acceleration , top speed , etc ... compared to a lighter cell that has the same SDT.

If it were a stationary application then weight is far less important.



Elithion said:


> On the contrary, Short discharge time is totally independent of capacity.
> Give me a 1 Ah, 3 V cell, or a 100 Ah, 3 V battery made out of 100 of those cells in parallel, or a 1 Ah. 300 V battery made out of 100 of those cells in series, and they all have the same SDT.
> 
> The capacity is one of the terms in the formula precisely because we want to eliminate the dependency of SDT on capacitance.


It can't be independent of capacity as long as capacity is a variable in the equation.

As written the equation favors small Ah capacity cells with a better SDT rating than larger Ah cells.

For example:
If Cell A has the same V , Ohms of resistance as cell B ... but if Cell A is 5 Ah and Cell B is 10 Ah ... as long as that formula rates lower numbers as being better ... it is going to rate the smaller Ah cell with a better SDT... thus my question about why favor the smaller Ah cell?

- - - - - 
Add:
It occurred to me that as long as this preference for smaller Ah is to the same scale as preference for lower Ohms ... the SDT would give the same number for testing cells of higher ohms if the Ah were equally smaller ... ie 2x the ohms and 1/2 the Ah would give the same SDT rating for the cells ... but 2x the ohms will not be equally performing... and will give less power under a given load and the same voltage.


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## PStechPaul (May 1, 2012)

Excellent information. I'll have to read up on the methods for testing the short discharge time. I just today received my order of 4 3600 mAh 18650 Li-Ion cells and 8 3000 mAh AA NiMH cells from "recyclepowers" Singapore.

http://www.ebay.com/itm/150974934354
http://www.ebay.com/itm/400371084253

The NiMH read 1.26 volts and the Li-Ion read 3.91-3.93 V. I plan to do some testing on these and I'd like to be able to use the results to compare to the chart of short discharge time, but of course I won't short them! My idea is to use my BMS to discharge the cells to their minimum of 2.75 volts at the 3.6A 1C rate. At the same time, I can determine the internal resistance by comparing the open cell voltage to that under load, so it will be 
(V(open)-V(load))/I(load). 

I'm not sure if the IR value will stay fairly constant or increase as the energy is drained. But if it is fairly constant, then the short discharge time would be determined by the Ah/A or Ah(V(cell)/IR). If these cells are truly 3.6 Ah and the internal resistance is such that they allow a 10C discharge of 36A at 0.9*3.7 = 3.33V then the IR = 0.37/36 = 10 mOhms, and power dissipation of the cell is 0.37*36 = 13.3W, which is probably a bit higher than what is safe for any more than about 10 seconds. The short discharge time would be based on 3.7V/0.01 ohms = 370 amps and 3.6Ah/370 = 0.01 hr or 36 seconds. 

Please let me know if this seems to be a reasonable approach to determining the short discharge time. I also need to determine the true Ah or Wh of these batteries, which will require a full charge and then a constant discharge of 1C over a period of up to 1 hour or until cell voltage under load drops to 2.75V.


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## lorraine (Feb 11, 2009)

Hi Davide,
Thanks for your good job, but could you tell me which model of Headway-HW cyl(LiFePO4) cell you tested for this report, 38120S(3.2V10AH), or 38120HP(3.2V8AH)? 

----------------------------------------------------
Lorraine
Headway Group
email: [email protected]
skype: lorainy0
MSN: [email protected]


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## Elithion (Oct 6, 2009)

40152S, 15 ah


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## lorraine (Feb 11, 2009)

Thanks for your information. But for high C-rate, the* best choice* is *HEADWAY 38120HP* cell(3.2V8AH)!
We welcome our customers to publish their different test reporte here. Anyone want our 38120HP specification, can send email to me: [email protected]

----------------------------------------------------
Lorraine
Headway Group
email: [email protected]
skype: lorainy0
MSN: [email protected]


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## Elithion (Oct 6, 2009)

lorraine said:


> for high C-rate, the* best choice* is *HEADWAY 38120HP* cell(3.2V8AH)!


Do you mean best among all Headway cells? Sure.


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## lorraine (Feb 11, 2009)

haha... 
Sorry for the misunderstanding here in my words. 
I mean for High-C rate among Headway cells, 38120HP is the best choice. As you know you hadn't told us in your report which Headway cell type before,right?

Hope someone can know my meaning under such language environment here.


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