# Mapping Battery Performance: An Intro to Ragone Plots



## Battery Guy (May 22, 2010)

[Message from the OP: Separate threads have been created for all Ragone Plot updates. At present, there are AA Ragone Plot and 18650 Ragone Plot threads that I am actively updating. Please refer to those threads for the most recently updated plots. I will not be updating the plots in this thread, although I will be answering general questions in this thread as they come up. Cheers- Battery Guy]

I have been inspired by the work of many CPF members to bring information to the masses. The Herculean efforts of LuxLuthor, Silverfox and others are extremely valuable for the amateur (and pseudo-pro) torch aficionados.

So I have been looking for a way that I can contribute something to the CPF in a field that I know something about: batteries. In searching the CPF archives I was surprised that there has been very little talk about Ragone plots. Ragone plots are used as a way to perform “apples to apples” comparisons between batteries of different chemistries, shapes, sizes and weights.

Much of the data in the battery shootout tests that I have seen on CPF is presented in constant capacity and/or constant resistance discharge curves. Discharge curves are great, and provide a lot of data, but you need to look a many curves plotted on several plots in order to compare large numbers of cells. In addition, the results make it difficult to assess how different cell voltages might affect performance.

Enter the Ragone plot. A typical Ragone plot shows discharge energy (Wh or mWh) versus discharge power. An example Ragone plot for three different AA cells is shown in the plot below:







The data on this Ragone plot was collected on a Maccor cell tester using constant power discharge and measuring the discharge energy to a 0.8V cut-off. Each curve represents the results of 6-8 discharge tests.

You will also notice diagonal lines labeled with different times (1.8 minutes, 6 minutes, etc…). These lines represent run time. Finally, note that the data is plotted on a log-log scale, so relatively small differences in the curves can correspond to big performance differences.

Here are a few examples for how you can use the data on a Ragone plot:

Example 1: Let’s say that you have an 8AA flashlight with a 24W bulb and you want to find the appropriate battery. This configuration would give you 3W per cell (doesn’t matter what series/parallel arrangement of cells you use). Going to the Ragone plot, you can quickly see that at 3W, you will get ~6 minutes from the Energizer MAX alkaline, ~30 minutes from the e2 Energizer Lithium and ~1 hour from the Energizer 2450 mAh NiMH.

Example 2: Let’s say that you want to have a run time of at least 20 minutes. Following the 20 minute diagonal line, you can see that the maximum power levels per cell will be ~2.1W for the alkaline, ~3.5W for the lithium and ~8W for the NiMH.

By studying Ragone plots, you can start to understand why there is so much variability in battery performance tests at high power. If you are testing a particular cell at power levels that are near the plateau portion of the curve (e.g. ~9W for the NiMH cell in the above plot), then it is apparent that a small shift in the position of that plot on the graph will have a huge impact on measured performance. Therefore, it is advisable to select cells that operate on the vertical portion of the Ragone curve to minimize cell-to-cell performance variability.

If you search for Ragone plots on the web, you will find that most of them actually show the relationship between specific energy/specific power (Wh/kg versus W/kg) or energy density/power density (Wh/l versus W/l). By normalizing performance to battery weight or volume, you can make real comparisons between cells of different sizes, shapes and weights.

For the time being, I am going to focus on the creation of a AA-size Ragone plot. Since all AA cells are the same size and shape, and since not too many of us care about the weight of the cells, I will leave the axes as energy versus power.

So far, I have tested and plotted data for the following cells:

Energizer MAX alkaline
Duracell Ultra alkaline
Duracell PowerPix alkaline (NiOOH cathode)
Energizer e2 Ultimate Lithium
Energizer e2 Advanced Lithium
Energizer 2450 mAh NiMH






A couple of the cells are being tested at lower power levels, and I will add those results next week. I am also in the process of testing Duracell 2000 mAh pre-charged (which I believe are made by Sanyo and identical to Eneloops).

All of the above cells were purchased from Target and tested within a few days. Since I have been focusing on higher power testing, all cells were tabbed with spot-welded nickel tab stock to minimize contact resistance issues. 

If you have a favorite cell that you want added, please let me know. Right now, I would prefer to test newly purchased cells only, but in the future it might be nice to look at how the performance of certain popular rechargeable cells changes with use.

Comments, criticism, suggestions all welcome. Please let me know if you find this all to be mundane and find no value in it. Last thing I want is to spend a lot of time doing something that the CPF finds no value in.

Cheers Everyone,
Battery Guy


----------



## Mr Happy (May 22, 2010)

That's a fascinating way of presenting a lot of information in a compact form.

So it looks like the e2 Advanced Lithium has a very measurably lower performance than the e2 Ultimate variety. The maximum power output of the Advanced is about the same as an alkaline cell, but the capacity at lower power outputs is much better than alkaline. Whereas the Ultimate has higher maximum power output and over twice the capacity at moderate power outputs.

How many data points do you need to plot a reasonable curve? About 5 or so?

If we do not have a true constant power discharge tester, is it reasonable to use average power computed from the duration of a constant resistance discharge, say?


----------



## SilverFox (May 22, 2010)

Hello Battery Guy,

Excellent work.

I have traditionally used Ragone plots to compare various chemistries when designing a battery pack, and then turned to discharge graphs with respect to time for a particular chemistry and matching cells. 

It seems that the Ragone plot may be useful for that as well.

Tom


----------



## gswitter (May 22, 2010)

Excellent data! Thank you.

I'm curious to see how the Duracell pre-charged cells compare. Keep in mind, there are two different cells repackaged as Duracell pre-charged - the "Made in Japan" cells are Eneloops, and the "Made in China" cells are presumably Rayovac Hybrids. I think lots of us would be curious to see how the two compare, especially considering the Rayovacs (when not re-badged as Duracells) can be had for a quarter the price.

Other AA cells I'd be curious to see evaluated:


Sanyo 2700 mAh NiMH
Powergenics NiZn _-not sure if they're the same or similar to the Duracell Powerpix Zn-Ni cells you already tested_
Elite 1700 NiMH
AW 14500 protected Li-ion _-I'm particularly interested in how these compare to Eneloops_

And would it be possible to get a few more numerical labels on the horizontal and vertical scales?


----------



## Battery Guy (May 22, 2010)

gswitter said:


> Excellent data! Thank you.
> 
> I'm curious to see how the Duracell pre-charged cells compare. Keep in mind, there are two different cells repackaged as Duracell pre-charged - the "Made in Japan" cells are Eneloops, and the "Made in China" cells are presumably Rayovac Hybrids. I think lots of us would be curious to see how the two compare, especially considering the Rayovacs (when not re-badged as Duracells) can be had for a quarter the price.



The Duracell pre-charged that are on test this weekend have a "Made in Japan" label, so I assume they are Sanyo Eneloop cells. I did not know that Duracell was also sourcing from China, so I will keep on the lookout for those. Any idea where I can buy the Chinese pre-charged Duracells?



gswitter said:


> Other AA cells I'd be curious to see evaluated:
> 
> 
> Sanyo 2700 mAh NiMH
> ...



I have already ordered Powergenics, as I am also curious about those. The Powergenics cells have the same chemistry as the Duracell Powerpix (zinc anode, NiOOH cathode, KOH electrolyte), but the construction is different. The Powerpix cells have a bobbin construction the same as all standard alkaline cells, whereas the Powergenics cells are spiral-wound like all NiMH cells. The spiral-wound construction increases electrode surface area (which decreases current density on the electrodes), reduces diffusion distance of ions, and therefore results in higher power capability.



gswitter said:


> AW 14500 protected Li-ion _-I'm particularly interested in how these compare to Eneloops_



Not familiar with these, but they would be a great addition. Where can I buy them?



gswitter said:


> And would it be possible to get a few more numerical labels on the horizontal and vertical scales?



I know, I know. I made these plots on Excel and I am having a tough time getting more labels. If I cannot do it automatically, I will add the labels manually and group them with the plot. That will work well as long as nobody wants me to rescale the axes.

Cheers,
Battery Guy


----------



## Battery Guy (May 22, 2010)

Mr Happy said:


> So it looks like the e2 Advanced Lithium has a very measurably lower performance than the e2 Ultimate variety. The maximum power output of the Advanced is about the same as an alkaline cell, but the capacity at lower power outputs is much better than alkaline. Whereas the Ultimate has higher maximum power output and over twice the capacity at moderate power outputs.



Agreed. What you cannot see from the posted plot is that at lower discharge power levels the Advanced Lithium is identical to the Ultimate Lithium. My guess is that both the Advanced and Ultimate use the same electrodes, but the Ultimate uses a lower resistance (and more expensive) separator. Hence the lower price for the Advanced versus the Ultimate.



Mr Happy said:


> How many data points do you need to plot a reasonable curve? About 5 or so?



I like to get somewhere between 5 and 8 points. The hard part is selecting the power levels before the test. Most of the data needs to be in the range where the curve begins to plateau in order to get nice, smooth plots. 



Mr Happy said:


> If we do not have a true constant power discharge tester, is it reasonable to use average power computed from the duration of a constant resistance discharge, say?



Unfortunately, the hard answer is "no". That being said, you can make exceptions if you stay within the same cell chemistry. For example, most of Silverfox's data on alkaline cells could be plotted as log capacity versus log current. This would be a valid way of representing that massive amount of test data on one plot.

Cheers,
Battery Guy


----------



## Battery Guy (May 22, 2010)

SilverFox said:


> Hello Battery Guy,
> 
> Excellent work.



Thanks, but I have a long way to go to catch up to you!



SilverFox said:


> I have traditionally used Ragone plots to compare various chemistries when designing a battery pack, and then turned to discharge graphs with respect to time for a particular chemistry and matching cells.
> 
> It seems that the Ragone plot may be useful for that as well.
> 
> Tom



Agreed. A lot of the constant current discharge data that you have posted on CPF could be plotted in a similar way (log Ah vs log A), and it would be very useful as long as you compare cells within the same chemistry family (i.e. same operating voltage). 

Cheers,
Battery Guy


----------



## Battery Guy (May 22, 2010)

gswitter said:


> And would it be possible to get a few more numerical labels on the horizontal and vertical scales?



Done! Excellent suggestion.

Cheers,
Battery Guy


----------



## Burgess (May 22, 2010)

to Battery_Guy --


Good Work ! ! !


:wow::goodjob::thanks:


Oh, and by the way . . . .

Welcome to CandlePowerForums !


:welcome:
_


----------



## 45/70 (May 22, 2010)

Interesting plots, Battery Guy. Information overload is always welcome here.  There are many types of cells I'd like to see graphed in this manner, but I'll let the general populace be your guide, as most members likely aren't interested in NiCd, or carbon zinc cells, for example.

Keep up the good work! :thumbsup:

Dave


----------



## Battery Guy (May 22, 2010)

45/70 said:


> ... as most members likely aren't interested in NiCd, or carbon zinc cells, for example.



Well, I for one am still interested in NiCd for high power applications, so let me know if there is a specific cell you want tested.

With respect to carbon-zinc, I actually have some test data on Eveready SHD (Super Heavy Duty) cells that I can add to the AA Master Ragone Plot. However, since I am focusing on higher power drains, I am afraid you won't see a lot of data on these Ragone plots for carbon-zinc. 

Cheers,
Battery Guy


----------



## Mr Happy (May 22, 2010)

Just for fun, I have correlated the performance data I have measured for NiZn rechargeable cells and computed a predicted Ragone plot for such a cell:






As and when you get to actually measure one of these cells, it will be interesting to see how closely my prediction matches your results.


----------



## Battery Guy (May 22, 2010)

Mr Happy said:


> Just for fun, I have correlated the performance data I have measured for NiZn rechargeable cells and computed a predicted Ragone plot



whoa, that is much higher power capability than I expected from that cell. Pretty impressive actually. I suspect that your estimated numbers will be very close to the actual constant power measurements since the NiZn cells have relatively flat discharge curves. Also, I notice that the total energy that you measured is around 2.25Wh, which is pretty close to the rated value for these cells.

Any idea how the self-discharge rate on the Powergenix compares to the Eneloop cells? It should be at least equivalent, if not better, but it would be great to see data.

I should get my Powergenix cells on test on Monday or Tuesday, and will have the plot added to the master AA Ragone plot by the end of next week.

Cheers,
Battery Guy


----------



## Battery Guy (May 22, 2010)

45/70 said:


> ... as most members likely aren't interested in NiCd, or carbon zinc cells, for example.



Data for Eveready Super Heavy Duty (SHD) has been added to the Master Ragone plot:






Cheers,
Battery Guy


----------



## Mr Happy (May 22, 2010)

Battery Guy said:


> whoa, that is much higher power capability than I expected from that cell


Yes, it does seem like quite a high number. The high power portion of my curve is the least certain part of it and may be a little optimistic compared to actual cell performance.

I generated the curve by constructing a model of the cell and then running simulated constant power discharges on that model.

As to the maximum power output, here are some figures. During the first third of the discharge the cell holds an EMF of over 1.7 V and has an internal resistance of about 30 milliohms. If we match the cell with a 30 milliohm load the expected discharge current would be 1.7/0.06 = 28 A. That current would deliver a power into the load of about 28^2 x 0.03 = 24 W.

The uncertainty is that I don't have a practical way to short out a cell and see if it really can deliver 28 A into a load. I would need a DC clamp meter that I don't have.

Even if the maximum figures are a bit optimistic, there is no doubt that these cells pack quite a punch.


----------



## Mr Happy (May 22, 2010)

Battery Guy said:


> Any idea how the self-discharge rate on the Powergenix compares to the Eneloop cells? It should be at least equivalent, if not better, but it would be great to see data.


Self-discharge seems to be very low. I have some cells that came off the charger a week or so ago at 1.83 V. I measured them just now and found them reading 1.81 V. I might leave them a bit longer before I do a discharge test, but the indications are good that they are holding their charge.


----------



## 45/70 (May 22, 2010)

Battery Guy said:


> Data for Eveready Super Heavy Duty (SHD) has been added to the Master Ragone plot:



Heh, cool!

What I meant was that some of the cells I'd like to see plotted, are more just out of curiosity than actually needing to know. NiCd cells are a bit different, as I still much prefer using them over NiMH's for tool packs and such. They are much sturdier under abusive conditions encountered in such devices, and while their per charge performance may lack in runtime, they actually seem to have more "oomph" and last a lot longer in the long run than NiMH cell packs. Still, my interest in seeing a plot, is mostly just out of curiosity.

I suppose the most interesting sizes in NiCd, to me anyway, would be "A" and 5/4 "A" (*Edit:* I meant 4/3 "A", I had "AAA" sizes on my mind for some reason), or similar. If you happen to run into any of those, that'd be cool. Again, no big deal, as I said, I don't want to request types that most here probably aren't interested in.



Mr Happy said:


> Just for fun, I have correlated the performance data I have measured for NiZn rechargeable cells and computed a predicted Ragone plot for such a cell:



Cool Mr H! :thumbsup:

Dave


----------



## gswitter (May 23, 2010)

Battery Guy said:


> The Duracell pre-charged that are on test this weekend have a "Made in Japan" label, so I assume they are Sanyo Eneloop cells. I did not know that Duracell was also sourcing from China, so I will keep on the lookout for those. Any idea where I can buy the Chinese pre-charged Duracells?


Until recently, the Chinese cells were much more common around here than the Japanese. The last time I was in Costco (two months ago), they had crates of the Chinese, and just a single pack of the Japanese. My local RiteAid pharmacy had equal amounts of both a couple weeks ago. I was in the local Office Depot a week ago, and all they had was the Chinese cells. And in my local Target tonight, all the AA's were Japanese and the AAA were equal amounts of each.

In general, you can identify the different cells by the ring of shrink wrap around the button (Japanese are white, Chinese are black), but I don't know if this is always true. The individual cells will be labeled "Made in..." in either case.



Battery Guy said:


> Not familiar with these, but they would be a great addition. Where can I buy them?


You can get the AW 14500 protected Li-ions direct from AW or domestically (quicker shipping) from Lighthound.

Thanks for adding the extra labels to the graph. I'd be curious to see NiCd results as well


----------



## Battery Guy (May 23, 2010)

Greetings Everyone,

I have PowerGenix NiZn AA cells arriving tomorrow (Monday), and Duracell pre-charged (made in Japan) cells on test now. I also have the following cells on order (by popular demand):

Elite 1700mAh NiMH
Sanyo 2700mAh NiMH
Sanyo 2500mAh NiMH
Duracell 2650mAh NiMH
AW 900mAh lithium-ion
Sanyo NiCd (various high rate and standard)

This should keep me busy for a few weeks.

Now, we need to discuss charging protocols for the NiMH and NiCd cells. My preference is to use the "old standby" charge protocol of C/10 for 15 hours. Although this method is slow, it pretty much insures that the cells reach 100% SOC. This rate is also essentially the same as that printed on the Duracell pre-charged cells (200mA for 16 hours). Given that I will be testing a wide range of NiCd and NiMH cells, does anyone see a problem with the C/10 for 15 hour charge protocol?

Also, there is the issue of "break-in". I recommend that I cycle the cells until I do not see any significant improvement in capacity. Specifically, I propose that the cells be cycled with a C/4 discharge rate and a charge protocol similar to above, until two consecutive discharge cycles have a difference of <2% in capacity. Once that happens, I will start the high power testing. Sound reasonable?

For the Powergenix NiZn, I will use a similar break-in protocol, but using the charge profile on the AA Powergenix spec sheet (CC 0.75A to 1.9V, CC 1.9V to 0.075A).

It is going to take me awhile to get this data, so be patient. I hope to add one or two cells to the Master Ragone plot each week.

Cheers,
Battery Guy


----------



## 45/70 (May 23, 2010)

Battery Guy said:


> It is going to take me awhile to get this data......



DUH! That's quite an undertaking there BG! :thumbsup:

The "standard charge" referred to on the labels of nickel based cells, is in fact a reference to the IEC 61951 evaluation "standard" used to determine the cell's capacity that is printed on the side of the cell. So, yes that would be the way to go about it.  A lot of folks believe that the "standard charge" is a reference as to how the cell is supposed to be charged normally, which it is not, except when determining the cell's capacity per IEC standards.


As for NiZn, I don't know any other way to go about it. They're so new you're going to have to go by what the manufacturer suggests, unless someone else knows another way that is more proper.



> This should keep me busy for a few weeks.


Ya, I'll bet! Nice job BG!

Dave


----------



## Mr Happy (May 23, 2010)

I have not observed any noticeable requirement for breaking in or conditioning the NiZn cells. As far as I can tell you just take them out of the packaging, charge them up, and start using them.

If I were seeking a simple way to describe them, I would say they are like lithium ion cells with lower voltage. They arrive from the factory with a 50% charge, they charge up to a fixed voltage, and they appear to hold their charge once charged.


----------



## Battery Guy (May 24, 2010)

Update: Complete results for Duracell Ultra, Duracell Powerpix and Energizer e2 Advanced Lithium have been added to the Master AA Ragone plot. I also have also added the first of the data sets for the Duracell Pre-charged NiMH (made in Japan) AA cell. Nothing too interesting about those yet because I am still testing at low power levels.

I received PowerGenix cells today and will get them on test tomorrow. Really looking forward to seeing those results.

However, I am having a problem finding the Elite 1700 mAh NiMH cells, and Sanyo high-rate NiCd cells. Both tnrbatteries.com and batterystore.com are back-ordered. If you know where I can purchase these, please post the supplier.

Cheers,
Battery Guy


----------



## Bullzeyebill (May 24, 2010)

http://www.cheapbatterypacks.com/index.asp?sid=402263& 

click on loose cells.


----------



## Mr Happy (May 24, 2010)

Battery Guy said:


> However, I am having a problem finding the Elite 1700 mAh NiMH cells, and Sanyo high-rate NiCd cells. Both tnrbatteries.com and batterystore.com are back-ordered. If you know where I can purchase these, please post the supplier.


Radical RC lists both, but I have never dealt with that vendor.


----------



## Bullzeyebill (May 24, 2010)

Mr Happy said:


> Radical RC lists both, but I have never dealt with that vendor.


 I do not understand. You asked who had them in stock, and I gave you a name. I have used this supplier, and others have too, here on CPF.

Bill


----------



## Mr Happy (May 24, 2010)

Bullzeyebill said:


> I do not understand. You asked who had them in stock, and I gave you a name. I have used this supplier, and others have too, here on CPF.


On the contrary, it's me who does not understand. 

Battery Guy asked a question, then both you and I posted possible answers at the same time. Now Battery Guy has two alternatives to consider.

It was not me that asked who had them in stock.


----------



## Battery Guy (May 24, 2010)

Found the Elite 1700mAh cells at cheapbatterypacks.com (thanks Bullzeyebill :thumbsup. Mike at cheapbatterypacks.com was quick to respond to my email confirming that they have these cells in stock.

Thanks again.
Battery Guy


----------



## Bullzeyebill (May 24, 2010)

Mr Happy said:


> On the contrary, it's me who does not understand.
> 
> Battery Guy asked a question, then both you and I posted possible answers at the same time. Now Battery Guy has two alternatives to consider.
> 
> It was not me that asked who had them in stock.



Whoops, I miss posted. Post was meant for Battery Guy and not you.

Bill


----------



## bshanahan14rulz (May 24, 2010)

Battery Guy,

Would there be an easy way to make a constant power load to use for battery testing? Perhaps something based off of the Joule thief? 
http://www.emanator.demon.co.uk/bigclive/joule.htm


----------



## Battery Guy (May 25, 2010)

bshanahan14rulz said:


> Battery Guy,
> 
> Would there be an easy way to make a constant power load to use for battery testing? Perhaps something based off of the Joule thief?
> http://www.emanator.demon.co.uk/bigclive/joule.htm



I'm not an electrical engineer, so I honestly don't know if it would be easy or hard to make an inexpensive constant power load. However, after reading the linked website on the Joule Thief, it seems to me that it is almost the opposite of a constant power load. 

A constant power load will raise the current draw as the cell voltage drops. It seems that the Joule Thief draws a vanishingly small current from the cell as the cell approaches 0% SOC, so that every last drop of capacity can be used.

I could be very mistaken. Hopefully one of the EE guys will chime in here. I think that it would be great to have a cheap, easy way of doing constant power discharge. The only way I have ever seen someone do it without using expensive test equipment is to set up a power supply and write a Labview program, but that is obviously not very easy.

Cheers,
Battery Guy


----------



## VidPro (May 25, 2010)

Battery Guy said:


> I'm not an electrical engineer,
> . . .
> A constant power load will raise the current draw as the cell voltage drops.
> 
> Battery Guy


 
well you got question #22 on the test correct  
I think your almost there.

When you state that providing information would be usefull FOR . . . .
any testing that simulates actual use , can be as effective as the elusive to reality CC discharge mode.

as long as we known the method used the rest is good comparisons still.
if you really want to know how well//long a battery will run that Incan bulb say , mabey of different wattages, then testing for that is data.

the cool thing about using Crasy methods to test with, is other *points of reality* occur, making the testing even more interesting????

Like Test SERIES ni-mhy on a bulb, which ones survive Reverse charge??? 
again that is where cruddy cells that are mismatched or have poor self discharge will really shine a light on things.
the great self discharge testing people are doing too.

I just say there is more to testing than always comes out of a machine, and we have VERY excellent machine testing already.
i would sooo like to see testing that Breaks the "standard" rules (also), and shows that not everything is about watts Too.

The standard is great, and a good way to confirm what the manufactures show, that they can sell batteries 
weird tests that are "different" that people are providing data from confirm what the USERS show, they can Buy & USE Batteries 

crasy stuff like how many Actual flash pictures a camera actually did , using robotic camera flashing, is all cool usefull data.
How many minutes a battery actually lasted in a flashlight, and how well they SURVIVED various aspects of TIME , is still usefull data.


----------



## Battery Guy (May 25, 2010)

VidPro said:


> When you state that providing information would be usefull FOR . . . .
> any testing that simulates actual use , can be as effective as the elusive to reality CC discharge mode.
> 
> as long as we known the method used the rest is good comparisons still.
> ...



Ragone plots are not, by any means, the ultimate test. However, they are a powerful tool that enables you to compare a large number of cells with various chemistries in a manner that is meaningful and relatively easy to interpret. Ragone plots are usually the first thing I turn to when evaluating new batteries for a device. Once I have down-selected to a few best bet choices, then device specific testing is usually necessary.

That being said, it is very rare that cell performance in a device varies substantially from the Ragone plot. There are a couple of situations where the Ragone plot might mislead you, like comparing high voltage/low capacity cells to low voltage/high capacity cells in a resistance load, or looking at a device that has a high current intermittent pulse discharge. But for most applications and battery comparisons, a Ragone plot will get you really darn close.

You are correct that Ragone plots will tell you nothing about other important parameters like cycle life, self-discharge, robustness to overdischarge or overcharge, etc... However, these tests are something that you would typically run after you have down-selected to a few different cells, and even then the tests would probably be tailored to be specific to the device you are using the cells in.



VidPro said:


> I just say there is more to testing than always comes out of a machine, and we have VERY excellent machine testing already.
> i would sooo like to see testing that Breaks the "standard" rules (also), and shows that not everything is about watts Too.
> 
> The standard is great, and a good way to confirm what the manufactures show, that they can sell batteries
> ...



I think that we agree. The Ragone plot is the first step to evaluate performance for a particular application. After that, a wide range of application specific tests may be appropriate depending on what performance parameters are important to you.

Cheers,
Battery Guy


----------



## VidPro (May 25, 2010)

yes Very cool, thanks for the data.
i did not mean/imply to debate your testing/graphing in any way , is cool. i was just saying that charging and testing methods dont HAVE TO be some standard. ( you were discussing how you will accomplish such grand tasks, and however you do, it is still data.) and sometimes when you use the same mabey even Lame methods that users use , it is more usefull data. Because that is what we do for real.

all the CBA tests have already shown have the wattage shown under the specific load, the voltage droop under that load, and total actual capacity in watts. so i have always MIND Graphed  that data out of the present graphs.


----------



## Battery Guy (May 27, 2010)

*Update*

Not sure if I will have a chance to pull data tomorrow, so this might be it for the weekend:







New additions include partial plots for PowerGenix, Duracell LSD and Eneloop.

The PowerGenix cells are doing really well, as you can see. I should have a complete data set up to 16W discharge by tomorrow. 

I also started the following cells on test today:

AW 14500 lithium-ion cell
Sanyo High Rate 1650 mAh NiMH
Sanyo 2500 mAh NiMH
Sanyo 2700 mAh NiMH

Elite 1700 mAh NiMH are on order but I have not received them yet.

Hopefully I can post more data tomorrow. Otherwise, don't expect anything new until after Memorial Day.

Cheers,
Battery Guy


----------



## 45/70 (May 27, 2010)

This Ragone graph is really becoming useful, as well as interesting comparing all the cells you're putting up BG. :thumbsup:

I often reference SilverFox's thread to compare cells. One thing I never pay much attention to, but I know most people do, is the table at the beginning of the thread. The table lists the performance of the cells ranked by Watt Hours, and also gives the capacity and duration, all of this for a discharge rate of 1 Amp. It's a great comparison, but is actually only a narrow view of cell performance. I really only reference the individual graphs, as they show, with some interpretation, a much more comprehensive view of each cell's performance.

With the Ragone graph you're putting together, all the information is right there. No need to jump back and forth, and little, if any interpretation is necessary. 

Keep up the fine job!

Dave


----------



## FlashPilot (May 28, 2010)

*Re: Update*

At first, I thought I was looking at aircraft performance graphs from a pilot's operating handbook... the format looks similar. Thanks for all your hard work and excellent presentation.


----------



## gswitter (May 28, 2010)

The PowerGenix NiZn plot is interesting. The capacity barely declines at all below 9W.

It's also interesting to see where the E2 Ultimate and Duracell Pre-Charged graphs cross. I guess I expected the lithiums to hold up a little better.


----------



## 45/70 (May 28, 2010)

gswitter said:


> The PowerGenix NiZn plot is interesting. The capacity barely declines at all below 9W.



It's also revealing that in devices that run ~5 Watts (*Edit: per cell*) or less, that the NiZn really don't offer any advantage over LSD NiMH. Still, the higher voltage they provide will make a big difference as far as voltage sensitive devices are concerned, which is my primary interest in the NiZn chemistry. And of course, they don't appear to be slouches either!

As for the Ultimate Lithium's, I find it interesting that in something like a 1/2 watt glove box light, you'd really be just as well off using the Advanced Lithium's. I'll probably be changing a few applications I have over to the Advanced. Might as well save a few bucks. 

Dave


----------



## Battery Guy (May 28, 2010)

*Update*

Greetings Everyone

Here's the update for today. Expect the next update after the long weekend.






New data for:
Duracell LSD
Eneloop
PowerGenix

In addition, I added a partial data set for the AW protected lithium-ion AA cell. I plan on testing this cell with the protection by-passed after I am finished with the present testing. I have high hopes for these AW cells.

Also, I changed the format of the plot a bit. I added more diagonal discharge lines to make it easier to interpolate between times. I also added small diamonds to the curves to indicate the actual measurement points used to make up the curves. I also changed the color scheme.

A couple things to note:

1.) You will probably notice that the PowerGenix curve looks a bit funky at the high power. I attribute this to the fact that these cells get REALLY HOT at high discharge power. I happened to be present during the 13W discharge test, and I could not pick up the cell when the test finished. So I think that the self-heating of the cell at these discharge rates helps to improve the power capability of the cell. Also, I noticed that the cell I was testing showed signs of leakage (in the form of discoloration around the vent at the positive end of the cell) after the 16W discharge was complete. As I did not inspect the cell between 13W and 16W discharge, I can only say that it must have occurred at some point after the 13W discharge. The discoloration was minor, and I only noticed it because I was looking for it. No evidence of actual liquid electrolyte or salt crystals were observed. 

2.) The results from Duracell pre-charged LSD cell are nearly identical to the Eneloops. In fact, the curves are right on top of each other. Many of you will not be surprised by this, as the Duracell cells are frequently referred to as "Duraloops". This test data simply adds more evidence that these are indeed the same cells.

Ok, that's it for now. My Maccor is running all weekend, so I hope to have a lot more data to add by Tuesday. I also received the Elite 1700 cells today, but I won't have an test channels free until the end of next week to start them.

I have appreciated all of the feedback I am getting on these plots. Let me know if I can do anything to make these plots easier to use.

Have a great long weekend everyone.

Cheers!
Battery Guy


----------



## Battery Guy (May 28, 2010)

45/70 said:


> It's also revealing that in devices that run ~5 Watts or less, that the NiZn really don't offer any advantage over LSD NiMH. Still, the higher voltage they provide will make a big difference as far as voltage sensitive devices are concerned, which is my primary interest in the NiZn chemistry. And of course, they don't appear to be slouches either!



The PowerGenix cells really do appear to shine in at the upper end of power spectrum. These may turn out to be the cells of choice for many really high lumen output torch modifications. At present, they have the highest power capability of any cell I have tested, BUT, I have yet to test the Sanyo high rate 1650mAh or the Elite 1700mAh cell. Stay tuned!



45/70 said:


> As for the Ultimate Lithium's, I find it interesting that in something like a 1/2 watt glove box light, you'd really be just as well off using the Advanced Lithium's. I'll probably be changing a few applications I have over to the Advanced. Might as well save a few bucks.



The lower rate performance of the Advanced Lithium is identical to the Ultimate Lithium. This leads me to believe that the electrodes are identical in both cells, and that the only changes have been to the separator and/or the electrolyte. FWIW, I use the Advanced Lithium for many lower rate, constant power applications like cordless mice and cordless keyboards.

Cheers,
Battery Guy


----------



## 45/70 (May 28, 2010)

Battery Guy said:


> The PowerGenix cells really do appear to shine in at the upper end of power spectrum. These may turn out to be the cells of choice for many really high lumen output torch modifications.



Yes, of course you are correct. I want to mention that I was thinking along the lines of how _I will be using NiZn cells_ and the qualities they have that make them suitable _for my applications_. They should really be able to be put to good use in both hotwire and LED mods, I would think.

Also, I edited my previous post, as I was thinking single AA cell ~5 Watt lights. Of course, the available Watts during discharge, would be dependent on the number of cells being used.

Keep up the good work, BG! :thumbsup:

Dave


----------



## HKJ (May 29, 2010)

*Re: Update*

Very good information.




Battery Guy said:


> I have appreciated all of the feedback I am getting on these plots. Let me know if I can do anything to make these plots easier to use.



You can add some horizontal and vertical lines and with all this information I believe that it would be a good idea to make the graph as big as possible, i.e. use the maximum allowed size of 800px.
I have played with the graph to illustrate what I mean:


----------



## MichaelW (May 29, 2010)

Where those zinc-carbon, or zinc-chloride?
I though that, at the extreme, you can get 1 watt from zinc-chloride chemistry.

How about Panasonic's Evolta alkaline?


----------



## Battery Guy (May 30, 2010)

MichaelW said:


> Where those zinc-carbon, or zinc-chloride?
> I though that, at the extreme, you can get 1 watt from zinc-chloride chemistry.



These were Eveready Super Heavy Duty, so the chemistry would be defined as carbon-zinc with zinc chloride electrolyte.

As far as getting 1 Watt from a AA size carbon zinc cell, that seems a bit optimistic to me. Perhaps in a D size cell, but not a AA.



MichaelW said:


> How about Panasonic's Evolta alkaline?



I will add it to the list. I would not expect a substantial difference on this plot, but it is worth taking a look at the "Guinness World Record Longest Lasting AA Battery".

Cheers,
Battery Guy


----------



## MichaelW (May 30, 2010)

Thanks Battery Guy
Have a good Memorial Weekend.

These brick & mortar places are not around me, http://www.panasonic.com/evolta/EVOLTA_WheretoBuy.html
so I purchased mine from the panasonic direct.

Forgot to add:
http://data.energizer.com/PDFs/carbonzinc_appman.pdf


----------



## Battery Guy (May 31, 2010)

*Re: Update*



HKJ said:


> You can add some horizontal and vertical lines and with all this information I believe that it would be a good idea to make the graph as big as possible, i.e. use the maximum allowed size of 800px.



Here you go:


----------



## DaveTheDude (May 31, 2010)

*Re: Update*

After reading this entire thread, I'm compelled to declare myself unenlightened in regard to battery chemistry, etc. So, can anyone point me to a good, basis written source or tutorial I might read to start to understand this cluster of topics better? (My training is in subjects other than electrical engineering, but I'm not adverse to self-study.) Thanks.


----------



## Battery Guy (May 31, 2010)

*Re: Update*



DaveTheDude said:


> After reading this entire thread, I'm compelled to declare myself unenlightened in regard to battery chemistry, etc. So, can anyone point me to a good, basis written source or tutorial I might read to start to understand this cluster of topics better? (My training is in subjects other than electrical engineering, but I'm not adverse to self-study.) Thanks.



Hey DaveTheDude (great name!)

You can try Buchmann's website: Battery University

There is a lot of good information there.

Here is a quick bullet list of things to understand:

1. All batteries contain a fuel and an oxidizer
2. The "fuel" in a battery is always the negative electrode, and commonly referred to as the "anode".
3. The oxidizer in a battery is always the positive electrode, and commonly referred to as the "cathode"
4. The fuel/anode is usually a metal, such as cadmium, zinc, lead and lithium
5. The oxidizer/cathode is usually a metal oxide, sulfide, hydroxide, where the metal ion is in a high oxidization state such as MnO2, NiOOH, LiCoO2, FeS2.

You may know that if you put a fuel and an oxidizer together, a chemical reaction can occur to produce heat. This reaction is an oxidation-reduction reaction (redox reaction), where the fuel is losing electrons (oxidation) and the oxidizer is grabbing those electrons (reduction).

The trick to making a battery is to keep the fuel and oxidizer (anode and cathode) separated so that the electrons cannot go directly from the anode to the cathode. Instead, the electrons are forced to go through an alternate path (like the filament of your flashlight bulb) on their way from the anode to the cathode. In doing so, the chemical energy is converted into electrical work.

So, your AA battery contains a fuel and oxidizer, and these are electrically isolated from each other by a component appropriately named a separator. The separator does not allow the direct passage of electrons from one electrode to the other, but it does allow the passage of ions between the anode and cathode, and this is needed because the ions provide charge balance during discharge. Since ions must travel from one electrode to the other during discharge, an appropriate liquid electrolyte is added to provide a medium for these ions to diffuse.

Batteries are typically named after their anode, cathode and/or electrolyte. For example:

Ni-Cd: cadmium anode, NiOOH cathode, alkaline electrolyte
Ni-MH: metal hydride anode, NiOOH cathode, alkaline electrolyte
Lead-acid: lead anode, lead oxide cathode, sulfuric acid electrolyte

That, in general is how all batteries (except metal-air batteries and Nickel-Hydrogen batteries) work. 

The voltage is directly related to the chemical potential of the redox reaction.

The capacity of the cell is simply related to how much of the fuel and oxidizer you can squeeze into the battery container. 

The energy is simply the capacity multiplied by the voltage

The power is a measure of how fast you can get the energy out of the battery, which is directly related to how fast the ions can diffuse through the electrolyte, and the distance they have to diffuse.

So, the power of a battery is dependent both on the chemistry and the construction of the battery. A great example of this is the comparison of the Duracell PowerPix and the PowerGenix batteries in the Ragone plot shown earlier. Both of these cells use the same chemistry (zinc anode, NiOOH cathode, alkaline electrolyte). The only difference is the ion diffusion distance. In the Duracell, which has a bobbin construction, the distance from the center of the anode to the center of the cathode is about 5 mm. In the PowerGenix, the distance is about 1 mm. If you ever took a class on diffusion, you may remember that Fick's First law states that diffusion time is proportional to the square of the diffusion distance. So reducing the distance by a factor of five will reduce the ion transport time by a factor of 25. Less time for ion diffusion between electrodes means that you can discharge the cell faster and get more power out it.

The down side is that by reducing the electrode thickness, you have to add more separator to the cell, which means that there is less room for fuel and oxidizer. Therefore, for any given battery chemistry, there is usually a trade-off between energy and power.

I will stop there. I don't want to ramble on if this is not helpful. Check out the Battery University, and then let me know if you want more rambling. 

Cheers,
Battery Guy


----------



## Mr Happy (May 31, 2010)

*Re: Update*



Battery Guy said:


> "Batteries in a nutshell"


Hey, nice write-up.

One little comment I'd make is to use the terms "negative electrode" and "positive electrode" instead of anode and cathode. This is both easier to remember and understand, and also less ambiguous. It is less ambiguous because when you are charging a cell the electron flow reverses direction making the negative electrode the cathode and the positive electrode the anode.

I have observed that the battery manufacturers generally use positive and negative electrode in their literature rather than anode and cathode, possibly for this reason.


----------



## Battery Guy (May 31, 2010)

*Re: Update*



Mr Happy said:


> One little comment I'd make is to use the terms "negative electrode" and "positive electrode" instead of anode and cathode. This is both easier to remember and understand, and also less ambiguous. It is less ambiguous because when you are charging a cell the electron flow reverses direction making the negative electrode the cathode and the positive electrode the anode.
> 
> I have observed that the battery manufacturers generally use positive and negative electrode in their literature rather than anode and cathode, possibly for this reason.



You are 100% correct. During normal discharge, the negative electrode is the anode, and during normal charge, the negative electrode is the cathode. This is because the anode, by definition, is the electrode where oxidation occurs, and similarly the cathode is the electrode where reduction occurs.

That being said, for reasons that amount to pure laziness, much of the academic community has adopted the terms "anode" and "cathode" to be synonymous with negative and positive electrode, respectively. Technically, the negative electrode is the anode during discharge, and the cathode during discharge. However, it seem that most people now use the terminology consistent with discharge, which is negative electrode=anode and positive electrode=cathode.

Cheers,
Battery Guy


----------



## gSPIN (Jun 1, 2010)

Battery Guy said:


> In the Duracell, which has a bobbin construction, the distance from the center of the anode to the center of the cathode is about 5 mm. In the PowerPix, the distance is about 1 mm.



'Gen' in the place of 'P'(ix).





Battery Guy said:


> much of the academic community has adopted the terms "anode" and "cathode" to be synonymous with negative and positive electrode, respectively.





guess it all depends on which academy.
http://en.wikipedia.org/wiki/Cathode

"In physics or electronics, a *cathode* is an electrode that emits electrons into the device."

i'm used to the cathode being the negative electrode, like on an LED.


----------



## Mr Happy (Jun 1, 2010)

gSPIN said:


> "In physics or electronics, a *cathode* is an electrode that emits electrons into the device."http://en.wikipedia.org/wiki/File:LED,_5mm,_green_(en).svg


This is still true. You will find that when an electrochemical cell is discharging, the positive electrode is emitting electrons into the cell. (Since conventional current is flowing out of the positive electrode into the circuit, electrons are flowing from the circuit into the positive electrode and being dispersed inside the electrolyte.)


----------



## Battery Guy (Jun 1, 2010)

gSPIN said:


> 'Gen' in the place of 'P'(ix).



Nice catch. I edited that in the original post. Thanks.



gSPIN said:


> guess it all depends on which academy.



I was referring to the academic community that focusses on batteries.

But like I said, Mr. Happy is absolutely correct, and the terms "positive" and "negative" electrode are always the technically correct terms to use for the battery electrode since the anode and cathode switch depending upon whether the battery is being charged or discharged. So, during discharge, the cathode is the positive electrode and during charge the cathode is the negative electrode.

Cheers,
Battery Guy


----------



## Battery Guy (Jun 1, 2010)

*Update*

Here's the update from the tests that ran over the weekend:






New cells added:
Sanyo 2700 mAh NiMH
Sanyo 2500 mAh NiMH
Sanyo HH-AAU 1650 mAh NiMH

More data for "Duraloops", Eneloop and AW 14500 lithium-ion also added.

Updates are going to get a bit slower because I need to use some of my test stations for actual work. I will keep a few dedicated for this project, but I will really be only to do one cell at a time for awhile. I will focus on getting the high power data for the Duraloops, Eneloops and Sanyo NiMH cells first. Once those are complete, I have the Elite 1700mAh cell to put on test, then some Sanyo Ni-Cd cells, and a few Panasonic Evolta alkaline cells per request.

I know that the plot is getting a bit crowded. Given that the NiMH cells are starting to dominate the plot, I will probably start making a few different plots to separate the chemistries a bit more and make these easier to read.

As always, your suggestions and recommendations are appreciated. I hope that some of you are finding this useful.

Cheers,
Battery Guy


----------



## 45/70 (Jun 1, 2010)

*Re: Update*

Nice job again BG. :thumbsup:



Battery Guy said:


> I know that the plot is getting a bit crowded. Given that the NiMH cells are starting to dominate the plot, I will probably start making a few different plots to separate the chemistries a bit more and make these easier to read.



I hope you can figure this out better than I'm imagining. In particular, the Duracell precharged and the eneloop are on top of each other (gosh golly gee whiz, I wonder why that is? ). Seriously, it's nice to have everything on one plot, but there are limitations. Again, I hope you can figure out a good way to do it. 

The one thing I'll mention is maybe grouping cells with similar characteristics, rather than chemistries together, and different groups on different plots, as you suggested. That kills the "everything on one plot" idea though, and with three axis even that would be compromised, I suppose.

Dave


----------



## Battery Guy (Jun 1, 2010)

*Re: Update*



45/70 said:


> Nice job again BG. :thumbsup:
> I hope you can figure this out better than I'm imagining. In particular, the Duracell precharged and the eneloop are on top of each other (gosh golly gee whiz, I wonder why that is? ). Seriously, it's nice to have everything on one plot, but there are limitations. Again, I hope you can figure out a good way to do it.



Let me know if you like this better:






I need to work on the color coordination of the curves a bit (seems that Excel just starts recycling colors after 10 plots), but I think that by narrowing the range of the x-axis brings out the differences a bit better. Of course, the disadvantage is that you can no longer see the performance of the carbon-zinc cell (not that too many people on CPF are running flashlights with carbon-zinc).

Cheers,
Battery Guy


----------



## 45/70 (Jun 1, 2010)

Yeah, spreading it out some definitely helps.

As for colors etc, perhaps you could go to a numbering system? I'd still keep as many colors as possible though. Sorry, I "play" with graphics a bit, but am no expert for sure. 

Dave


----------



## Battery Guy (Jun 5, 2010)

Greetings Everyone

Updates to the AA Ragone Plot have been moved to a dedicated thread here.

Cheers,
Battery Guy


----------



## Stereodude (Jun 5, 2010)

I'm pretty sure I understand how to read these...

A few questions to make sure I'm on the right track.

1) Would an ideal battery (theoretical) have a perfectly vertical line on a Ragone plot?

2) The ideal region where you would want to use any given battery is on the vertical portions?


----------



## Battery Guy (Jun 5, 2010)

Stereodude said:


> I'm pretty sure I understand how to read these...
> 
> A few questions to make sure I'm on the right track.
> 
> 1) Would an ideal battery (theoretical) have a perfectly vertical line on a Ragone plot?



Yes, an ideal battery would be able to deliver all of its stored energy instantly, and therefore would be a vertical line on the Ragone plot.



Stereodude said:


> 2) The ideal region where you would want to use any given battery is on the vertical portions?



There are a few reasons why you would want to stay on the vertical portion. First, you are not wasting energy. Second, the plateau region of the plot is subject to the most cell-to-cell performance variability. Third, for rechargeables, the plateau portion of the curve moves down as the cell ages, so if you were pushing the absolute upper power capability of the new cell, chances are that you are going to get terrible performance as soon as the cell begins to age.

That being said, there are many people who push their cells to the limit for a particular flashlight design. For these people, they may need to operate on the upper plateau of the Ragone curve for a particular cell in order to meet their performance criteria. 

Cheers,
Battery Guy


----------



## SilverFox (Jun 19, 2010)

Hello Battery Guy,

In an effort to keep from having this drop off the page and loosing track of it, I have added it to the sticky of threads of interest in this section.

Tom


----------



## 4earthlight (Apr 4, 2013)

Would there be a way to do an ongoing Ragone plot while the battery is in service to measure its changes in performance as it ages? Thanks



Battery Guy said:


> [Message from the OP: Separate threads have been created for all Ragone Plot updates. At present, there are AA Ragone Plot and 18650 Ragone Plot threads that I am actively updating. Please refer to those threads for the most recently updated plots. I will not be updating the plots in this thread, although I will be answering general questions in this thread as they come up. Cheers- Battery Guy]
> 
> I have been inspired by the work of many CPF members to bring information to the masses. The Herculean efforts of LuxLuthor, Silverfox and others are extremely valuable for the amateur (and pseudo-pro) torch aficionados.
> 
> ...


----------



## Argonne (Oct 20, 2014)

Dear All,

Very nice intro to this area, but I was wondering on how to do the calculations for the x-axis (power), and y axis (energy). 

Thus I have a question, perhaps silly, but hope some one can help. I want to make a Ragone plot, I have energy which is in units of Joules and I convert this to energy density Joules/cm3 (thus normalized). I can convert this to Wh/cm3, (simply by using 1 kilowatt hour (kWh) = 3.6 x 106​ joules (J)). I'm however at a loss as to how to correctly calculate power density, from energy only I have no other data values. I know Power = J/s, but then the number look silly. Any idea?

2) Also how do we decide on the diagonal time lines?

Any help is welcomed.
thanks


----------

