I'm just thinking of entering the game. I have two parts to my question:
1) There are different capacities for the same cell. , , . It almost seems too simple to just say bigger is better and choose the 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.
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 and AW protected cells and the AW unprotected cell. The AW mah cell is made from the Panasonic LiNiCoO2 NNP cells. The AW 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 mah cell is missing a button on the + terminal like the mah cell, the mah cell still fits in the ZL SC600. By comparison, the AW 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.
AW is a sanyo, IIRC, as is the . I'd go with a .
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? 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 mAh needs a special charger, but if you're willing to get that, then those will have a few minutes more runtime than even the s.
1) There are different capacities for the same cell. , , . It almost seems too simple to just say bigger is better and choose the 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).
AW is a sanyo, IIRC, as is the . I'd go with a .
No they are not sanyo based cells.
The mAh needs a special charger, but if you're willing to get that, then those will have a few minutes more runtime than even the s.
No special charger required. The 's have a normal 4.20v charge voltage. The only cells you need a special charger for is the and mAh cells from Sanyo, Samsung, or LG. These have 4.3 or 4.35v charge voltages.
Thanks for the replies.
I think the Callie's Kustoms will be my first choice and the AW 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 's. The Redilast are still oversized but only 18.5mm at the widest but they are also 69mm long.
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 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
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.
????
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 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
I'm fully aware that 's were designed for laptops, and that probably accounts what 80-90% of LiCo '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 cells have a 2C max discharge rating. So a mAh cell, 4A, and mAh 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.
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 cell usage estimate is correct. I doubt for example, that the entire Flashlight industry uses enough 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 use, I forget, but I think it's more like 99%+ are used in laptops.
Dave
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 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
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" cells in the - 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