# Choosing 2200mah, 2600mah, or 2900mah AW 18650



## mckeand13 (Nov 4, 2011)

I'm just thinking of entering the 18650 game. I have two parts to my question:

1) There are different capacities for the same cell. 2200, 2600, 2900. It almost seems too simple to just say bigger is better and choose the 2900 as it will give me the most capacity. Is there a reason to choose one capacity over another? Do they have different current handling capabilities?

2)I'm planning on running these in my Fenix PD31 and a bored 6P with an M61. Which cell makes the mose sense for these lights? I'm definitely looking for capacity as a top priority.

Thanks.


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## bshanahan14rulz (Nov 4, 2011)

They should all work fine for that setup. A cell's maximum safe current discharge is based on its capacity, i.e. 2xCapacity (divided by 1 hour, which mathematically does nothing). 2200 cell can only safely put out 4.4A. 2900 can only safely put out 5.8A. I doubt that the M61 would draw 4.4A, but perhaps someone here will post up the actual current draw of the M61. However, you do gain runtime, which means less frequent charging/checking voltages.


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## moldyoldy (Nov 4, 2011)

as always, the choice is not quite that simple. Capacity is only one factor. Chemistry is a major consideration. Does the cell have a protruding + contact? I know very little about the lights you mentioned.

ie: I have the AW 2900 and AW 2200 protected 18650 cells and the AW 2200 unprotected 18650 cell. The AW 2900 mah cell is made from the Panasonic LiNiCoO2 NNP cells. The AW 2200 mah cell evidently is a fairly normal LiCO. There are some threads on the subject of the Panasonic cell. the chemistry is safer. Although the AW 2900 mah cell is missing a button on the + terminal like the 2200mah cell, the 2900 mah cell still fits in the ZL SC600. By comparison, the AW 2200 mah unprotected cell needs a small magnet disc on top to make contact in the ZL SC600. Keep in mind that the protection PCBs are normally added to an existing cell from the actual manufacturer of the cell. 

AW brands are still recommended. My experience with other brands purchased from known CPF dealers has varied widely. I stick with AW cells now.


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## moderator007 (Nov 4, 2011)

To me the top three choices would have to be Callie's Kustoms 3100mah or Redilast 3100mah and the AW 2900 mah. They all use quality panasonic cells rewrapped with their label and a pcb added.


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## bshanahan14rulz (Nov 4, 2011)

AW 2600 is a sanyo, IIRC, as is the 2200. I'd go with a 2900.

Point is, pick something besides the StartFire brands. 

What moldyoldy posted is a very important aspect too: the positive nub. You know that nub on the end of regular batteries? 18650 does not have that, unless it is added by the rewrapper when they add the protection circuit. Might want to double-check to see if your light requires this or not. M61 has a spring, so it will be fine. I don't know what the + connection on the PD31 looks like.

The 3100mAh needs a special charger, but if you're willing to get that, then those will have a few minutes more runtime than even the 2900s.


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## jasonck08 (Nov 4, 2011)

mckeand13 said:


> 1) There are different capacities for the same cell. 2200, 2600, 2900. It almost seems too simple to just say bigger is better and choose the 2900 as it will give me the most capacity. Is there a reason to choose one capacity over another? Do they have different current handling capabilities?



More capacity = more runtime and higher safe discharge rate (2C).



bshanahan14rulz said:


> AW 2600 is a sanyo, IIRC, as is the 2200. I'd go with a 2900.



No they are not sanyo based cells.



bshanahan14rulz said:


> The 3100mAh needs a special charger, but if you're willing to get that, then those will have a few minutes more runtime than even the 2900s.



No special charger required. The 3100's have a normal 4.20v charge voltage. The only cells you need a special charger for is the 2800 and 3000mAh cells from Sanyo, Samsung, or LG. These have 4.3 or 4.35v charge voltages.


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## mckeand13 (Nov 5, 2011)

Thanks for the replies. 

I think the Callie's Kustoms 3100 will be my first choice and the AW 2900 2nd choice. I have emailed Callie's to get the cell diameter before I order so I can verify that it will fit my lights.


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## Morelite (Nov 5, 2011)

mckeand13 said:


> Thanks for the replies.
> 
> I think the Callie's Kustoms 3100 will be my first choice and the AW 2900 2nd choice. I have emailed Callie's to get the cell diameter before I order so I can verify that it will fit my lights.


The CK cells are 18.8mm x 68.85mm. I can't use them in most of my lights so I use the Redilast 3100's. The Redilast are still oversized but only 18.5mm at the widest but they are also 69mm long.


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## Battery Guy (Nov 6, 2011)

jasonck08 said:


> More capacity = more runtime and higher safe discharge rate (2C).



Actually, I have to disagree with this statement. In general, as you push up the capacity of a cell, the rate at which you can extract that capacity decreases. This is the inherent trade-off between energy and power in every battery system.

Most of the 18650 cell on the market are designed for high energy applications like laptop computers, where the average discharge rate is C/3 or less. These so-called "energy" cells can be discharged at a higher rate, but cycle life will suffer and voltage sag will be large. 

Cheers,
Bg


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## jasonck08 (Nov 6, 2011)

Morelite said:


> The Redilast are still oversized but only 18.5mm at the widest but they are also 69mm long.



Latest batch is about 18.3x68.6mm. 



Battery Guy said:


> Actually, I have to disagree with this statement. In general, as you push up the capacity of a cell, the rate at which you can extract that capacity decreases. This is the inherent trade-off between energy and power in every battery system.
> 
> Most of the 18650 cell on the market are designed for high energy applications like laptop computers, where the average discharge rate is C/3 or less. These so-called "energy" cells can be discharged at a higher rate, but cycle life will suffer and voltage sag will be large.
> 
> ...



I'm fully aware that 18650's were designed for laptops, and that probably accounts what 80-90% of LiCo 18650's are used for. Most laptops have "up to 4-8hr" battery life depending on the model, specs etc. However if you were to max out the CPU and GPU on a laptop, most computer batteries could be drained in <2hrs. However, my statement was directed at mainstream ICR cells -- that more capacity in mAh, will generally equal longer runtime in ANY application. Obviously thats not ALWAYS true due to the way different driver circuits work and the vF of the LED etc. And secondly, almost all 18650 cells have a 2C max discharge rating. So a 2000mAh cell, 4A, and 3000mAh would be 6A. Thats all I was getting at.

Obviously "high-power" cells of other chemistries, IMR, IFR, etc, are a whole different beast. Some may be designed for only 2C, while others may be able to be discharged at 20-30C.


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## 45/70 (Nov 6, 2011)

I don't think BG was saying that they couldn't do it, just that high capacity cells won't last as long at high current rates. This would apply to your laptop example, as well.

Also, I don't think your 18650 cell usage estimate is correct. I doubt for example, that the entire Flashlight industry uses enough 18650 cells to supply the number of cells used in laptops in the county in Ohio where I live! I read somewhere where they gave some statistics for 18650 use, I forget, but I think it's more like 99%+ are used in laptops.

Dave


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## bshanahan14rulz (Nov 7, 2011)

^and some silly car that is powered by 18650s takes 0.9856275%


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## Helmut.G (Nov 7, 2011)

Many portable power tools also use 18650 packs, but not LiCo.


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## xul (Nov 7, 2011)

Battery Guy said:


> as you push up the capacity of a cell, the rate at which you can extract that capacity decreases.


Doesn't seem right. You have a link?


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## Battery Guy (Nov 7, 2011)

Helmut.G said:


> Many portable power tools also use 18650 packs, but not LiCo.



Actually, Sanyo's high power 18650s used in power tools used be LiCoO2. They were 1500 mAh. They have since changed to a mixed metal oxide cathode, but I believe that they are still 1500 mAh.


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## Battery Guy (Nov 7, 2011)

xul said:


> Doesn't seem right. You have a link?



I don't have a link handy xul, but it is a basic rule of cell design. For a given anode/cathode combination in a fixed volume, you design a cell to have higher power (higher rate capability) by increasing the electrode surface area (which decreases the current density on the electrodes, in mAh/cm2) and reducing the electrode thickness (which reduces the distance that the ions need to diffuse). In an 18650 cell, this means that you have longer, thinner electrodes rolled up in the can, and it also means that you have a higher fraction of separator and current collectors taking up space. This is why high power cells always have lower capacity than low power cells, for a given cell size.

A great example can be seen in 3V lithium primary cells, where two extremes can be seen. Ones made with a so-called "bobbin" construction have very high energy density, but very low power. Spiral wound cells with the same chemistry have much higher power, but lower energy density. If you search "Sanyo lithium primary catalog" in google you will find a pdf from Sanyo that has good illustrations of this.

Cheers,
BG


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## Battery Guy (Nov 7, 2011)

xul said:


> Doesn't seem right. You have a link?



xul

I found a link:

http://www.mpoweruk.com/cell_construction.htm

Scroll down to the "Electrodes (energy/power trade-offs)" section. I think that it explains things pretty well.

Now, there are exceptions to this rule. Old lithium-ion cell designs utilized relatively thick (~30 um) separators. As separator technology has gotten better, the thickness of the separators has been reduced to the 15-20 um range. A thinner separator means that you can use longer electrodes of the same thickness, so you can get more capacity while increasing the rate capability of the cell. 

Some manufacturers still make "budget" 18650 cells in the 2200 - 2400 mAh range that use relatively old separator technology, and these cells would not be expected to have rate capability as good as "state-of-the-art", higher capacity cells.

But the bottom line here is that increasing the capacity of a cell does not mean that it will have higher discharge current capability. In fact, the opposite is normally true.

Hope this helps to clarify.

Cheers,
BG


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## xul (Nov 8, 2011)

Thanks, I'll chew on this for awhile.


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## ExtremeX (Nov 8, 2011)

I wish I saved the link, but I saw somewhere that AW came out with some new cells, not sure what the changes were, but with all the reading ive been doing its hard to keep on top of all this stuff.

Once I thought I had a handle on things I started seeing all these new chemistrys like LiFePO, IMR / LiMN cells....

Im still trying to see what is the best AW for me, since I dont own any yet. I also have a Fenix PD31, but since its low amp draw, even my Ultrafire 3000 mah seem to do well in them. My Trustfire 2500mah Blue wrapper is my go-to cell right now. But I think I need to feed some better stuff into my MC-E and XM-L lights like my M3X, M30, XT10, XT20...


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## xul (Nov 9, 2011)

Battery Guy said:


> Hope this helps to clarify.
> 
> Cheers,
> BG


Now I understand why the graphs show [w-h]/kg and w/kg, and few batteries do well on both axes.


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## mckeand13 (Nov 12, 2011)

I purchased a 4Sevens single bay charger and a couple of Callies Kustoms 3100 18650 cells. 

Should I charge them at the 3.6V or 4.2V setting?

Thanks.


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## Battery Guy (Nov 12, 2011)

mckeand13 said:


> I purchased a 4Sevens single bay charger and a couple of Callies Kustoms 3100 18650 cells.
> 
> Should I charge them at the 3.6V or 4.2V setting?
> 
> Thanks.



Charge them on the 4.2 V setting.


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## 45/70 (Nov 12, 2011)

mckeand13 said:


> Should I charge them at the 3.6V or 4.2V setting?



The 4.2 Volt setting is for charging LiCo and LiMn cells at a 4.2 Volt CV (constant voltage). The 3.6 Volt setting is for charging LiFe (LiFePO4) cells with a 3.60 Volt CV. The charging voltage is always somewhat higher than the "nominal" voltage of a cell, which is the average voltage of the cell during actual use.

Dave


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## mcmc (Dec 3, 2011)

Just to add the IMR AW 18650 into this, which between the 2900 (or 3100) versus the IMR 18650s, would have actual longer runtime? Or is the IMR 1600 mAh really almost 1/2 of the capacity of the AW protecteds, but is able to do higher current?

The application I am asking for is a Tri-MC-E I have (Milkymod) direct drive in a Surefire L5.

I've run both IMR's and 2600's and they both seem similar in output on max. Just trying to figure out which cell to buy for stocking up going forward.

Gracias.


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## mcmc (Dec 3, 2011)

And, another question I always had, was - do the manufacturers rate the mAh of their cells, to the point that the protection circuit kicks in? Or of the "whole cell" - which would mean that the actual usable mAh is less than the rated, since you never want to run a cell flat (or even past 2.6, 2.7v for that matter).


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## yifu (Dec 4, 2011)

mcmc said:


> And, another question I always had, was - do the manufacturers rate the mAh of their cells, to the point that the protection circuit kicks in? Or of the "whole cell" - which would mean that the actual usable mAh is less than the rated, since you never want to run a cell flat (or even past 2.6, 2.7v for that matter).


All current AW cells (im not sure of the new 3100mah ones) have PCBs that kicks in at 2.5V under load as AW told me. Panasonic rates its NCR18650 and NCR18650As (used in 2900 and 3100 AW cells) up till 2.5v as shown here in the data sheet http://industrial.panasonic.com/www-data/pdf2/ACA4000/ACA4000CE240.pdf Sanyo does the same for its cells as well (sanyo cells are used in the 2600mah AW 18650)


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## 45/70 (Dec 4, 2011)

mcmc said:


> ......which between the 2900 (or 3100) versus the IMR 18650s, would have actual longer runtime?



Hi mcmc. I don't know what the current draw of your light is, but in my experience comparing Samsung ICR18650-30A 3000mAh cells (charged with a 4.30 Volt CV) with AW's IMR 1600mAh cells, at a 3A load, the runtime down to 3 Volts under load (where my light signals low battery) is reached, is about the same. Mind you I haven't used a stopwatch or anything, but the runtime is pretty close.

What you have to consider here, is that, in my case, at a 3A load, the IMR cells are pretty much just loafing along. For higher capacity LiCo (ICR) cells, a 3A load is relatively heavy, and more than these cells were designed to normally operate at. Sure, they can handle such a load, but the longevity of the cells life is likely affected in a negative way. In short, the IMR cells will last longer (number of cycles) at higher current rates.



> And, another question I always had, was - do the manufacturers rate the mAh of their cells, to the point that the protection circuit kicks in? Or of the "whole cell" - which would mean that the actual usable mAh is less than the rated, since you never want to run a cell flat (or even past 2.6, 2.7v for that matter).



Li-Ion cell manufacturers do not supply cells with added protection circuits. These "PCB's" are added by third parties, eg. distributors such as AW, Redilast, Callies's Kustoms etc. If you look at a manufacturer's data sheet, you will see various discharge graphs where the cell is discharged at certain current rates down to a voltage which the manufacturer deems is appropriate. This voltage may, or may not correspond to the cutoff voltage of added protection circuits. Again, Li-Ion cell manufacturers do not produce cells with added protection circuits. Whether the protection circuit cuts off at the manufacturer's recommended minimum voltage, is determined by the third parties that add these circuits.

Dave


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## mcmc (Dec 4, 2011)

yifu said:


> All current AW cells (im not sure of the new 3100mah ones) have PCBs that kicks in at 2.5V under load as AW told me. Panasonic rates its NCR18650 and NCR18650As (used in 2900 and 3100 AW cells) up till 2.5v as shown here in the data sheet http://industrial.panasonic.com/www-data/pdf2/ACA4000/ACA4000CE240.pdf Sanyo does the same for its cells as well (sanyo cells are used in the 2600mah AW 18650)



Cool - thanks for that info. So, is it safe to say that it's ok to run AW protecteds, until the cutoff circuit kicks in?


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## mcmc (Dec 4, 2011)

Thanks 45/70! Very useful info there  i'm not 100% sure of the draw of my light either (is there a way to check with just a multimeter?) but three MC-E's direct drive should be pretty up there I believe, so your datapoint of the two cells being similar runtime is helpful. Will probably just get the IMR's then, since they're like half the price!

Though, I still am not sure I get how a 2900 mAh and 1600 mAh cell can get similar runtime...does it have to do with internal resistance of the cell under higher load or something?


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## 45/70 (Dec 4, 2011)

mcmc said:


> Though, I still am not sure I get how a 2900 mAh and 1600 mAh cell can get similar runtime...does it have to do with internal resistance of the cell under higher load or something?



Yes, the internal resistance has a lot to do with it, as well as the different chemistry. For example, in my light when an AW IMR cell hits the 3 Volt level under load (and the low voltage warning begins), if I remove the cell and let it rest a bit, the open circuit voltage will usually read somewhere around 3.6 Volts. This is basically discharged for a LiMn cell. On the other hand, when a Samsung cell reaches the same point (~3 Volts under load), if I take it out, let it rest a bit and check the voltage, it will read about 3.80 Volts. This is only about half discharged for one of these cells, yet it is unable to hold voltage under a 3A load at this point.

The capacity of most Li-Ion cells is determined at a 0.2C discharge rate. This would be 320mA for the IMR cell, and 580mA for the Samsung cell. Whenever a cell is discharged at a higher rate however, the resulting capacity will be less. In addition to this, IMR cells are considerably more adept at being discharged at high rates (partly due to the lower resistance), so as I said before, at a 3A discharge rate, the IMR cell is quite happy. The Samsung cell is getting more of a workout at 3A, so doesn't hold voltage as well.

One thing to remember here, is if the light is used at a lower output (I don't know whether your L5 is setup with additional levels), thus reducing the current draw on the cell(s), the higher capacity cell's performance will improve and effectively at some point, outperform the IMR cell.

In the case of my light, for example, If when the light signals low voltage at the 3A current level with the 3000mAh Samsung cell, and I step it down to "medium", which is about 600mA, the light will continue to run for quite some time. With the IMR cell however, at the same point of discharge at the "high" level, while it will run for a bit longer at the lower level, it will be a relatively short time, as the cell is much nearer to being fully discharged than the Samsung cell.

Anyway it all boils down to the IMR cell's superior performance at higher discharge rates. At lower discharge rates, the higher capacity cell will win.

As for your Milky modded L5, I don't know how it's set up, but I would think you could measure the Amp draw at the tailcap. I'm guessing though, that it's probably not driving the three MC-E's at anywhere near max (2.5-3A/LED), but still could be drawing more than 3 Amps from the cell.

Dave


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