Lithium Ion Categories

LuxLuthor

LuxLuthor

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After many questions and confusion over various Lithium Ion battery types discussed in this 18650 thread, I thought it would be useful to try and give a breakdown of the various categories of Lithium Ions. There are more details that could be given, but this is meant to just be a "handy" guide.

Edit: I recently did a "Safe Chemistry" 18650 Shootout here

Source References:



Three structural parts inside the battery can & top:

  • 1) When we talk about various Lithium chemistry batteries, most of the differences relate to the structure & metal alloy used in the positive cathode.

  • 2) Since 1996, the negative anode made of graphite (carbon) has been well optimized.

  • 3) The electrolyte is a Lithium salt solution, and may be a source of further improvements in the future.

Two major categories of Lithium batteries:

  • 1) Lithium Primary (non-rechargeable) batteries which contain pure Lithium metal which is volatile in water/oxygen.

  • 2) Lithium Secondary (Li-Ion or LiPo -rechargeable) batteries which contain Lithium as an cathode alloy or salt. They have no memory or self-discharge issues.
Four major categories of Secondary Li-Ion cell cathode metals:


  • a) "Unsafe" Lithium Cobalt Oxide (Layered Structure) is the original Lithium Ion rechargeable cell, first made by Sony in 1991. It is what most people recognize as Li-Ion, and is now made by many companies such as Sony, Sanyo, Pila, Panasonic, AW (sales link), etc.
Lithium Cobalt is a more volatile cathode material with a higher resistance to the flow of ions, resulting in heat buildup.

It is best to use cells with separate built in protection circuit (AW & Pila), or pack with circuit board ("PCB") & balance tap leads going to each cell (or at least to groups of cells).
This protection PCB resolves most of the safety concerns & issues.


  • Limited charge/discharge loads without heating up (fire/explosion) are generally 1-2C (5 Amp discharge & 2 Amp charge in protected 18650 cell)

  • Higher stored capacity. 18650 size has ~2200mAh

  • Higher 3.6/3.7V nominal voltage, charges up to 4.2V

  • Begins losing function (voltage drops) in 2-3 years after manufacture due to Lithium crystalizing onto Lithium Cobalt Oxide cathode layers, thereby increasing internal cell resistance.

  • Useful rule of thumb for checking the voltage to determine charge capacity left in a Li-Cobalt cell.

    These readings should be taken where cell has rested at least 15 mins after charge, not under any load.
4.2V Full 100%
4.1V About 90%
4.0V About 80%
3.9V About 60%
3.8V About 40%
3.7V About 20%

3.6V Empty
<3.5V Overdischarged
<3.0V Cell damage
occurs (increasingly based on duration and how much lower voltage goes.)



  • b) "Safe" Lithium Manganese (Spinel Structure) developed in 1996, with increased cathode surface area using a complex 3-dimensional cross-lattice "spinel" structure. Only made by: Emoli. Found in specific Ridgid or "Ryobi One+ Lithium" tool packs.

  • Has much higher discharge rate of 10-15C (for 18650 cells that's 15-20 Amps output). It should be charged at 1-2C (1.5 to 3.0 Amps).

  • Moderate stored capacity. 18650 size has ~1300mAh

  • Higher 3.7/3.8V nominal, charging up to 4.2V

  • Begins losing function (voltage drops) several years after manufacture due to Lithium crystalizing onto Lithium Manganese Oxide cathode.
.
  • c) "Safe" Lithium Nickel Cobalt Manganese cathode. This is close to the previous category, but this combination gives a bit more capacity but a bit less output rate. This is the Sony V (or VT in 26700 size), Sanyo, or Konion is another licensed brand made in Germany. Found in specific Makita, Ryobi, Bosch tool packs.

  • Has higher discharge rate of 5-7C (for 18650 cells that's ~10 Amps output). It should be charged at 1-2C (1.6 to 3.0 Amps).

  • Moderate high stored capacity. 18650 size has ~1400mAh

  • Higher 3.7V nominal, charging up to 4.1V (charging higher reduces cycle life from 800 to 300 cycles)

  • Begins losing function (voltage drops) several years after manufacture due to Lithium crystalizing onto Lithium Nickel Cobalt Manganese Oxide cathode.
.
  • d) "Safe" Lithium Iron Phosphate cathode. This has a huge leap forward in discharge rates, but with a lower capacity & voltage. It needs a separate charging setup. Saphion is one of the original brands, with other Chinese/Hong Kong versions springing up (including some from CPF member: AW). There is a "Nano" Lithium Iron Phospate made by the A123 Systems company which seems to have the highest quality and performance.

  • Has very high discharge rate of 25-35C (for 18650 cells that's ~30 Amps output). Can be charged at 2-5C (2 to 6.0 Amps). Able to take significant user abuse.

  • Moderate stored capacity. 18650 size has ~1100mAh

  • Lower 3.3V nominal, charging up to 3.6V.

  • Has longest life & number of cycles, but will still fail in several years. (I don't have exact handle on this.)
 
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LuxLuthor

LuxLuthor

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I'll call this post: "LuxLuthor Tips"

While there is leeway with the 3 (current) brands of safe Lithium Ion chemistry batteries regarding charging, it is still wise to check voltages of individual cells of a pack charge setup (i.e. like from FiveMega or Modamag). This should be done periodically (? every 5-10 charges or more often if imbalances are noted) to make sure they are all getting fully charged and discharged together.

While the protection PCB circuit in "unsafe" Lithium Cobalt chemistry cells does resolve much of the concern of overcharge safety, and overdischarge cell damage, it will not balance cells.

If I were to make Lithium Ion cells into a pack (which I have done), I would always install individual cell "balance tap leads" so there is a way to keep cell voltages balanced.

It is best to not over-discharge any of the Li-Ion cells. A general guideline for the first three to give best lifespan is not discharge lower than 3.3 Volts. You can go lower....even down to 2.8V briefly, but it will do progressively more damage once you go below. With A123 type LiFePO4, it has a very flat discharge curve at 3.3V, and then suddenly craps out, so stop using immediately.

Best rule of thumb is to learn how your cells behave....so stop using a light when you notice light dimming (or cutting off if it has a PCB), and check your voltages to see where cells dropped to.
 
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Patriot

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Nicely laid out! I'll probably have to read it a couple of more times to retain the finer points but this is very helpful.


EDIT:

It looks like the Lithium Nickel might be the best compromise between capacity and discharge rate for most flashlight purposes.

Thanks Lux :thanks:
 
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LuxLuthor

LuxLuthor

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Patriot, I don't think the slight difference in capacity between Emoli & Konion/Sony-V is that significant as compared to the discharge rate Emoli advantage. I think it more comes down to the pack price.

The A123 cells in 18650 size as far as I know are only in the Black & Decker VPX packs, which I think is being phased out. Only reason I would consider those in this size was if I needed a lower voltage setup. It is extremely rare for our flashlights to need the higher A123 Amp output than Emoli or Konion delivers.
 
DM51

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Lux - excellent! I've added it to the "Threads of Interest" sticky.
 
Patriot

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Patriot, I don't think the slight difference in capacity between Emoli & Konion/Sony-V is that significant as compared to the discharge rate Emoli advantage. I think it more comes down to the pack price.


I see what you mean. For some reason my brain saw that as 2600mah instead of 1600mah. I completely agree then that the Emoli has a big advantage.

Speaking of 2600mah, doesn't LG and a couple other manufacturers now make 2600mah lithium cobalt batteries? It still seems like the these would make a lot of sense for LED applications, since capacity is important and discharge rate not as important.
 
LuxLuthor

LuxLuthor

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Thanks DM!

Patriot, yeah there are wide variations in Li-Cobalt capacities. But then there are capacity claims and real capacity. Likewise you should be selective with the quality and protection cup of protection circuits. I would have a hard time not choosing AW or Pila.
 
Holzleim

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I'm not sure if the so called LiPo (Lithium-Ion Polymer) cells belong to one of the categorires you mentioned.
These cells provide very high dischahrge rates (20-30C) and I think energy density is good as well. They are very commonly used in RC-Cars, Helicoters, ...
Wiki: http://en.wikipedia.org/wiki/Lithium-ion_polymer_battery

I used them in two in of my lights and am quite satisfied with results. If you look at my small 4W light, I'm really impressed of these small cells being able to supply 2A.

I integrated charging electronics, so all you need to refill the lamp is a 5V mini-USB plug.

Certainly are these cell not that suited for modding lights that have round dimesions optimized for standard sized cells like many here do, because the cells usually have rectangular dimesions.
 
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jayflash

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Lux, thanks much for the concise and complete listing of the various LiIon cell specifics. Very useful information!
 
LuxLuthor

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Yeah, I was mainly looking at the variety of chemistries available in 18650 size cells where there is the real diversity of chemistry types--and which gets confusing. LiPo are closest (but much less safe) to the Lithium Cobalt Ion cells.
 
R

rdh226

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Hey Lux, have you heard anything on the lithium nano titanate batteries?

I haven't been able to find all that much online, viz:

http://www.newscientist.com/article.ns?id=dn7081
http://www.nextenergynews.com/news08/next-energy-news7.9.08c.html
http://www.b2i.us/profiles/investor/fullpage.asp?f=1&BzID=546&to=cp&Nav=0&LangID=1&s=236&ID=9313

(A 2MWt battery pack? Woof!)

I recall reading somewhere they're 2.3V cells rather than 3.3/3.6/3.7V, and with a little less energy
density than LiIon, but "Safe" (Type "5" in your list?), and with thousands of charge/discharge
cyles over a decade of life.

I first heard of them via the new (http://www.lightningcarcompany.co.uk/home.php) English Lightning
sports car, and the (http://www.phoenixmotorcars.com/) Phoenix fleet SUVs.

-RDH
 
LuxLuthor

LuxLuthor

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RDH, only thing I have heard on that company/technology is their focus on large utility power supply backup storage that you mentioned. Getting from a new technology like that--scaled down to a power tool size when A123, Saphion, Emoli, Sony/Konion already have a foothold will likely present a real challenge. That is why I suspect these various new Lithium battery technologies are targeting various niche uses like Power Plant backup/storage, electric cars, power tools.

This Forbes story is linked on their home site, and gives a good idea of the complexity facing Altair Nanotechnologies in this pursuit. It is interesting that they are looking at the previously "settled" performance of the graphite anion to get the fast charge capability. Hope it works out they way they intend.
 
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SR.GRINGO

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Lets say you are building an elephant with 8 cells. Would you use the emoli or the AW 18650?

I see the advantage of AW being plug and play.
 
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Lets say you are building an elephant with 8 cells. Would you use the emoli or the AW 18650?

I see the advantage of AW being plug and play.

Series or parallel?

As FM holders for the Elle-2 are series, I assume thats what you mean.

I guess that if you are using a ~4A lamp the AW may be better suited, as they have larger cappacity, and will shut down when the V becomes to low; If you need more current, like 12A for the Osram 64657 then then Emoli would be the only way to go.
 
LuxLuthor

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Yeah, as Raoul says, the 5 Amp protection circuit limit of AW (or any Li-Cobalt) cell is the determining issue for a given bulb....and if you are using 8s x 4.15V (33V), by definition you are using a high current bulb. Almost any bulb above 50W is going to need over 5A current.
 
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SR.GRINGO

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Raoul/Lux,

Thanks for clearing this up....starting to get a grasp on this. Can the Emoli's that are harvested out of the rigid pack fit into FM's battery holder for the elleII? If not, Lux will you make an emoli pack?
 
jeffosborne

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Well done, Lux Luther, one I will save & keep this documentation.

But you mentioned "balance tap leads",, which I have wanted to include on the battery packs I have assembled, but I have always tripped over one point: How do you protect that connector? PTC or fuse for each line? Perhaps I am too paranoid. I used Battery Junction's 3-cell protection PCB's for my packs, and that seems fine. But bringing those leads to a connector on the side of my battery enclosures seems like a asking for trouble. A simple short circuit and "poof!" The leads circumvent the protection PCB, right? How do you deal with that, Lux?

Thanks a bunch,
Jeff O.
 
LuxLuthor

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When I make a pack, I weld a Nickel contact strip to the batteries. The balance tap wire is first soldered to the middle of the contact strip. Tap wires need to run down either in the center space of 4 cells, or along length in gap outside two cell bodies. Ultimately I have them come down together into a shrink pigtail, and then into a JST balance connector. You need a heavier guage wire/contact end plate like shown in my battery pack signature link for the major charging current. I have enough safeguards that I am not concerned about needing a fuse.

When I make a pack, it is all cushioned with mastick and shrink wrapped to insulate. It is not as easy to set up a safe scenario with an FM battery holder, although I did make one.
 
sylathnie

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Excellent post Lux. Thanks!

My intention for balance charging my cells was to assemble a separate "charging tray" with slots for each cell. This will allow me to permanently wire the balancer into it as well as making it easy to swap out bad cells. I do loose the advantage of pack charging and balancing but I don't think I will balancing more than once every 3 or 4 charges. (Maybe longer if they don't get out of whack to quickly.)
I'm also toying with the idea of adapting it to different cell sizes but I haven't decided on a good batter retention method.
 
TorchBoy

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LiPo are closest (but much less safe) to the Lithium Cobalt Ion cells.
Nice resource. 18650s aside for a moment, I remember when lithium ion polymer took over from lithium ion in cellphones. So they're the same chemistry but with different construction? What do you make of the claim in the Wikipedia article "The advantages of Li-poly over the lithium-ion design include lower cost manufacturing and being more robust to physical damage"?
 

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