14500 battery that can discharge @ 25C?

[jasonck08]

So I've been trying to hunt down some 14500 cells that can be discharged faster then the 2C standard for LiCO cells.

I've found a factory that sells LifePo4, LiMn (IMR) and LiCo cells.

They have IMR 14500's @ ~600mAH and LiCo's at ~800mAH.

The rep I was talking to was saying that they recommend the LiCo cells for higher drain applications which struck my funny, as I thought generally speaking IMR cells can discharge at a much higher rate. The rep sent me discharge curves that claimed to show a 14500 LiCO cell discharging at 5C, 10C, 20C and 25C! I've been under the impression that most LiCo cells shouldn't be discharged at much over 2C.

Is this even possible coming from a high capacity LiCo cell. I'm very confused and skeptical about the specs and information that has been provided thus far.

Feedback?

 

[csshih]

let's see some AW cell figures.

AW16340:750 mAH
AWIMR16340:550 mAH

AW14500: 750mAH

AW18650: 2200mAH/2600mAH
AWIMR18650: 1600mAH

I wonder how much that factory overrates, and, I'm also suspicious on their LiCOO2/LiMnO2 data. :thinking: 25C is definitely unlikely with LiCoO2 cells. Mind posting the graphs?

 

[VidPro]

i have pulled 4C from a 14500, but it wasnt for long. anything over 4C would just cause so much heat (it seems) that it wouldnt work in a flashlight like that without popping.
I pulled 4C ONLY because there wasnt crud for "C" to begin with so multiples of Cs on a discharge was easy.

25C yes would be entierly possible to have fat plates, and be built like a RC li-poly inside , but 25C AND high capacity, would only work if it was built wrong and didnt last cycles. (something will have to give)
Still would have the issue of containd in a light , the heat could cause it to fail quick.
but not all 25C testing is for the purpose of 25C Operation, if it "tests" at 25C, even shortly, might work ok at 5C say.

you can test any battery at 25C load but without the VOLTAGE it had with that load, it doesnt tell you anything now does it.
Hey i tested this with a 20 amp load . . . and . .? . . it turned red and glowed

so really what purpose would be a light that lasted less than 4 minutes?

 

[ampdude]

Discharge at 25C? Isn't that pretty much like a dead short?

 

[jasonck08]

So it turns out that the 14500 cells are actually not LiCo cells after all.

And they are not IMR, or LifePo4's either.

After some research it appears the chemistry is:

Li(NiCoMn)O2 (aka lithium NCM)(lithium nickel cobalt manganese oxide) 3.7V

 

[csshih]

hmm.. interesting.

Wikipedia says it doesn't last long cycle wise.

 

[jasonck08]

hmm.. interesting.

Wikipedia says it doesn't last long cycle wise.

They rate it at 500 cycles... same as most LiCO cells. Anyone else know anything about this Li-on chemistry?

From Wikipedia:

In 2008, Imara Corporation[54] began promoting the first materials-agnostic technology applied on an NMC material. This technology has the effect of lowering impedance and extending cycle life. These high power-capable cells have a higher energy density, relative to other high power cells in the market.[55] Imara ceased operations in December 2009 due to a lack of funding.[56]
Sony and Sanyo use NMC and NCA blended with LMO (spinel) for high-powered applications. NMC has a significant safety advantage over cobalt oxide and 50% greater energy density than FePO4, but suffers from a poor cycle life.
Nissan Motor has nearly completed development of a lithium-ion battery using a lithium nickel manganese cobalt oxide cathode (NMC). The new system will reportedly offer almost double the capacity of Nissan/AESC's current manganese spinel cell.[57]

The bolded statements seem semi-contradictory.

Maybe they are referring to poor cycle life as compared to LifePo4's. LifePo4 cells are commenly rated @ 2000 cycles while LiCo cells are rated @ 500

 

[Juggernaut]

Obviously these things can only withstand very short burst / or sag heavily under load. Because even if it's Capacity was only 300 mah at 25C it could supposedly drop 7.5A! That would mean you could slap a SST-90 in a AA cell light and nearly power it to it's maximum output! Last I checked if such technologies existed to run a single AA flashlights at 1,500 lumens, even if for a few minuets manufactures would have already used this by now.

Just my 2 cents.

 

[jasonck08]

Well based on the discharge curves they sent me @ 25C the capacity is only 10% less then the capacity at 5C. So far these batteries seem too good to be true, but I may need to pick a few up to test out. If anyone else is interested in testing a couple, let me know.

 

[divine]

I bought some cheapie LifePO4 14500's a while back. I have no idea how well they perform though, since I have nothing that will draw much power from them.

 

[Mr Happy]

OK, so you have to be realistic about what you are asking for here.

It is not discharge rate you are interested in as such, but internal resistance.

Let's suppose you have a 600 mAh cell and you want to discharge it at 25C: that is 25 x 0.6 = 15 A.

Now, I have here for example a 600 mAh capacity LiFePO4 cell in the 14500 size. I measure its internal resistance between 0.16 ohms and over 0.2 ohms depending on state of charge. Let's take the best of those figures and assume 0.16 ohms.

If I discharge this cell at 15 A, the internal voltage drop will be 15 x 0.16 = 2.4 V. The output voltage will therefore be about 3.3 V − 2.4 V = 0.9 V. More interestingly, the internal power dissipation will be 15 x 2.4 = 36 W. That cell is going to start glowing like a red hot coal!

So what you need if you are going to have any hope of such high discharge rates is an internal resistance about ten times lower. Say 0.02 ohms instead of 0.16 ohms. This is not easy to do with lithium ion cells as they are inherently limited by how fast the lithium ions can migrate in and out of the positive electrode.

The direction to look in is the technology used for power tools, such as the A123 Systems cell. This has an internal resistance in the order of 0.01 ohms for larger cells and can sustain 35C discharge rates. I do not know if this is obtainable in the 14500 size however. I suspect not, as such a cell is too small for practical uses.

 

[jasonck08]

OK, so you have to be realistic about what you are asking for here.

It is not discharge rate you are interested in as such, but internal resistance.

Let's suppose you have a 600 mAh cell and you want to discharge it at 25C: that is 25 x 0.6 = 15 A.

Now, I have here for example a 600 mAh capacity LiFePO4 cell in the 14500 size. I measure its internal resistance between 0.16 ohms and over 0.2 ohms depending on state of charge. Let's take the best of those figures and assume 0.16 ohms.

If I discharge this cell at 15 A, the internal voltage drop will be 15 x 0.16 = 2.4 V. The output voltage will therefore be about 3.3 V − 2.4 V = 0.9 V. More interestingly, the internal power dissipation will be 15 x 2.4 = 36 W. That cell is going to start glowing like a red hot coal!

So what you need if you are go have any hope of such high discharge rates is an internal resistance about ten times lower. Say 0.02 ohms instead of 0.16 ohms. This is not easy to do with lithium ion cells as they are inherently limited by how fast the lithium ions can migrate in and out of the positive electrode.

The direction to look in is the technology used for power tools, such as the A123 Systems cell. This has an internal resistance in the order of 0.01 ohms for larger cells and can sustain 35C discharge rates. I do not know if this is obtainable in the 14500 size however. I suspect not, as such a cell is too small for practical uses.

Obviously discharging at 25C for a 800mAH battery is not practical. But it is cool to find a battery that is capable of it.

Do you know of a 14500 battery that can be discharged at even 5C? This is the first one I've found. And this makes it possible to drive LED's like the SST-50, P7, MC-E at fully current for short durations.

 

[Mr Happy]

No, I don't know of such a cell (but I have not researched it). What current are you looking for specifically: 4 A, 5 A?

I do know how to achieve that easily with three AA size NiMH cells in series. With much higher capacity and longer run time too.

 

[jasonck08]

No, I don't know of such a cell (but I have not researched it). What current are you looking for specifically: 4 A, 5 A?

I do know how to achieve that easily with three AA size NiMH cells in series. With much higher capacity and longer run time too.

And much larger in size too. I'm just looking for a cell capable of being used in a 14500 pocket rocket light to fully drive an MC-E, P7 or SST-50 for a short period of time. Modes would be needed to make runtime reasonable.

 

[Juggernaut]

And much larger in size too. I'm just looking for a cell capable of being used in a 14500 pocket rocket light to fully drive an MC-E, P7 or SST-50 for a short period of time. Modes would be needed to make runtime reasonable.

Runtime! Ha, who cares about runtime, even if such a cell could ever exist "highly unlikely" do you have any idea what the heat from a SST-50 would be like in a AA cell light! You could hardly run it for minuet at a time. It would be like those 200+watt Maglite mods. The batteries run time is only like 5 minuets, but the lights / cells get so hot they can only be used for like 30 seconds at a time!

 

[jasonck08]

Of course you couldn't run it for more then a minute on full blast, but that's ok. Usually when I use a keychain light its only for short bursts.

But in reality I think its reasonable to have a small light that draws maybe 2A on high for short durations. A regular LiCo cell can not safely supply that, but these NCM cells can supply that with ease.

Also, I see another plus to these cells.

Are there any 14500 LiCo cells that can actually supply over 800mAH? These are also much safer I'm told then LiCo's so that's another plus. So if these live up to their hype they will be:

-Higher capacity
-Safer
-Able to discharge at higher currents

They seem at least worth testing out?

 

[Mr Happy]

But in reality I think its reasonable to have a small light that draws maybe 2A on high for short durations.

I don't think 2A is entirely impossible. I tested a 14500 cell here that managed a respectable showing at 1.4 A, so I suspect it would do OK at 2 A as well. The voltage is going to sag a little, but a good boost driver will take care of that.

It can for instance run an LD10 at full brightness with all modes.

 

[bulbman]

what is the name of the factory, and can the cells be bought individually or do you have to buy like 1000 minimum

 

[lightseeker2009]

And much larger in size too. I'm just looking for a cell capable of being used in a 14500 pocket rocket light to fully drive an MC-E, P7 or SST-50 for a short period of time. Modes would be needed to make runtime reasonable.

I've got a single mode MC-E drop-in I use in a Solarforce L2, obviously with a 18650. But the point I want to make is the led is drawing 1.33 amps at the tailcap. The drop-in is apparently rated at 500 lumens. So if a 14500 can do just 3C you are making it with a good reserve. Runtime will be short, but like its said, who cares about runtime lol.

 

[Chrontius]

So who's selling these NMC cells in "conventional" form factors? I'm about ready to drop a battery order, and I was planning on loading up on IMRs, but…

Hangon, this may be the new cell that AW's putting in their 2900 mAh 18650, though on second consideration, the AWs seem to lack the manganese. As I hear it, they're inherently safer than conventional LiCo, though less so than IMR, and their engineering techniques have advanced a good bit over the 2600s.