14500 Li-Ion - Max Safe Current Draw?

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garrybunk
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14500 Li-Ion - Max Safe Current Draw?

I've searched around, but am not coming up with an answer.  I have some Trustfire Flame 900mAh 14500's and would like to know what the recommended safe max current draw would be.  If I would build a mod with an XM-L powered by one of these, what is a safe level for high mode? 

Thanks,
Garry

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Kokopelli
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I guess twice the capacity of the cells is like the safe max current. 1.4-1.5A I would say. Other than Trustfire flames you can get IMR 14500 from bestinone.net and feed your led with higher currents. I use an IMR 18350 with my 1.5A XML 501a light and I am more than happy with the light it emits.
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Ok, from the information I did find I was guessing at twice the capacity (which appears to be about 800mAh true), but wasn't quite sure.  I'd like to drive it higher - maybe 2A, but I don't want to push it too hard.  Might have to look into those IMR's.  How hard can the IMR's be pushed? And what is their true capacity?

-Garry

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The ones at bestinone seems to have the exact capacities on them. They seem to give more than 5c with ease. 

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Kokopelli wrote:
I guess twice the capacity of the cells is like the safe max current. 1.4-1.5A I would say. Other than Trustfire flames you can get IMR 14500 from bestinone.net and feed your led with higher currents. I use an IMR 18350 with my 1.5A XML 501a light and I am more than happy with the light it emits.

Garry: Another source for AW IMR: Lighthound

Chicago X recommended these for the modified Balder SE-1 XM-L he sold me. It has very high current draw (17-18 minutes on high). As he explained, the TFs would wear out very quickly. The IMR [Really LMR] is also a safer alternative to Li-ion.

 

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Yeah, I was looking at Lighthound.  So I understand IMR's don't come protected - is that of any concern?  Do you have to watch  over-discharging more closely? 

-Garry

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garrybunk wrote:

Yeah, I was looking at Lighthound.  So I understand IMR's don't come protected - is that of any concern?  Do you have to watch  over-discharging more closely? 

-Garry

Garry:

Chicago X also mentioned the bestinone site, I chose LH for speed of deliver and AW have a great rep. As I understand it, Lithium-Manganese Rechargeables are a safer chemistry than Li-ion (the ion part is Cobalt generally) that don't vent with flame and are more tolerant of lower voltage. He built a low voltage warning into the driver of my SE-1 [Blinks then steps down]. So my reco to you is go with the IMR's and do some testing on runtime/voltage to the point you are comfortable, but you should not be as nervous as you would be with Li-ion cells. Main advantage with IMR is it tolerates the high current so the battery will last through many recharge cycles. If you go with the protected TF, the batteries will last less than 50 cycles.

Hope that helps.

Dave

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With lithium cells the usual recommendation is 0.5-0.7C so for a "900mAh" cell somewhere between 450 and 600mA.

 

IMR cells should be able to be charged at higher rates - mine get charged at 600mA usually - but unless you are in a hurry there's no real benefit. The AW page on CPF specifies a maximum of about 3C.

http://www.cpfmarketplace.com/mp/showthread.php?191277-IMR16340-IMR14500...

 

Charging tends to be when lithium cells show their evil nature. IMR cells are not explosion proof if mistreated - the cells in the much publicised light explosion were Sony's IMR cells. Sorry, I can't find it on CPF though it got a lot of publicity a couple of years back.

 

The numbers from my light tests are always to be found here.

https://spreadsheets.google.com/ccc?key=0ApkFM37n_QnRdDU5MDNzOURjYllmZHI...

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gorann wrote:

And what's the safe charging rate - 1A ? No good?

Did anybody tried it?

500 mA good? 

Gorann: I have an Xtar WP II and it was recommended to use 500 ma charge rate for 14500.

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Don wrote:

With lithium cells the usual recommendation is 0.5-0.7C so for a "900mAh" cell somewhere between 450 and 600mA.

Yikes!  I don't like hearing that!  So should I not go with a 1.4A driver?  Or will using the 1.4A driver just reduce the life of the cell?  (Which I think I'm ok with so long as it's not reduced ridiculously low - the 50 cycles BetweenRides mentioned might be ok.) 

-Garry

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garrybunk wrote:

Don wrote:

With lithium cells the usual recommendation is 0.5-0.7C so for a "900mAh" cell somewhere between 450 and 600mA.

Yikes!  I don't like hearing that!  So should I not go with a 1.4A driver?  Or will using the 1.4A driver just reduce the life of the cell?  (Which I think I'm ok with so long as it's not reduced ridiculously low - the 50 cycles BetweenRides mentioned might be ok.) 

-Garry

 

That's charge rate - not discharge rate.

 

Conventionally it is reckoned that 2C is the highest wise discharge rate for lithium-ion cells - 1.4A should be fine. For lithium manganese cells (IMR) the usual recommendation is about 5-8C discharge rate. And 2-3C charge rate

 

The numbers from my light tests are always to be found here.

https://spreadsheets.google.com/ccc?key=0ApkFM37n_QnRdDU5MDNzOURjYllmZHI...

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Discharging them too hard is fine of itself - though in multiple cell applications this is less than a good idea - as long as you regard them as single-use devices and don't try to charge them if they don't recover to above 3V. High discharge rates (Say above 5A for an 18650, 2A for a 14500) will shorten the life/lower the capacity of a cell. In single cell usage this isn't a big deal. In multi cell lights this can become a very big deal. Series connected cells are likely to fare worse at high rates of discharge than parallel connected cells. I'd be happy enough to pull 15A from four parallel connected 18650s - up to 24A with appropriate cells. But I would pay very, very close attention to voltage matching. In practice, in parallel setups the stronger cells will hold up the weaker cells.

 

In series connected cells, Bad Things can happen as the other cells can't compensate for the weakness of one or more cells. This can lead to kaboom events or venting with flame and copious clouds of nasty gases. That said, I've pulled upwards of 4A from 4 series connected no-name RCR123 cells. This is what is normally called "incredibly stupid". Nothing bad happened other than the cells refusing to charge shortly afterwards.

 

My X2000 zoomie pulled above 8A from an 18650 after it died. It did produce some horrible smells, but no light. The smells were primarily burning fibreglass which is horrible stuff - not nasties from the cell. Which survived this (brief) abuse.

 

The numbers from my light tests are always to be found here.

https://spreadsheets.google.com/ccc?key=0ApkFM37n_QnRdDU5MDNzOURjYllmZHI...

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garrybunk wrote:

Yikes!  I don't like hearing that!  So should I not go with a 1.4A driver?  Or will using the 1.4A driver just reduce the life of the cell?  (Which I think I'm ok with so long as it's not reduced ridiculously low - the 50 cycles BetweenRides mentioned might be ok.) 

-Garry

Hi Garry,

That's the recommended charge rate, not discharge.  The 1.4A current draw would only be twice capacity, or 2C - well within published specs.

 

If you were, for example, to use this cell to power a 3.1A XM-L, you would be asking it to discharge at a 4-5C rate.  This is where you would notice the drop in useful charge cycles.

I prefer to use IMR cells for current loads much above 2C.

 

EDIT: Don beat me to it.

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Ok, thanks for the clarification.  Glad to hear I am safe at 1.4A discharge (makes the mod worth it).  I'm only planning on running a single cell.  I'll consider going IMR if I get thirsty for more power (and what flashaholic doesn't!).  .

-Garry

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I have been pulling 1.8 amps from a 14500 flame for about a year now and it's still going strong.

http://budgetlightforum.com/node/2418

I am already visualizing the duct tape over your mouth.

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E1320 wrote:

I have been pulling 1.8 amps from a 14500 flame for about a year now and it's still going strong.

http://budgetlightforum.com/node/2418

Thanks for the info, good to hear that.

-Garry

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E1320 wrote:

I have been pulling 1.8 amps from a 14500 flame for about a year now and it's still going strong.

http://budgetlightforum.com/node/2418

 

How many cycles on the cell though? I doubt it'll last 3 years. But then most lithium cells of my experience don't last much over three years anyway - they get recycled here at 75% of whatever they originally measured as. I started checking this when all of my unprotected 14500s turned out to have less than 100mAh capacity left in them. I was fortunate that I don't own any light that could handle 2x14500s or some exciting chemistry might have reared its ugly head.

 

The numbers from my light tests are always to be found here.

https://spreadsheets.google.com/ccc?key=0ApkFM37n_QnRdDU5MDNzOURjYllmZHI...

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Don wrote:

E1320 wrote:

I have been pulling 1.8 amps from a 14500 flame for about a year now and it's still going strong.

http://budgetlightforum.com/node/2418

 

How many cycles on the cell though? I doubt it'll last 3 years. But then most lithium cells of my experience don't last much over three years anyway - they get recycled here at 75% of whatever they originally measured as. I started checking this when all of my unprotected 14500s turned out to have less than 100mAh capacity left in them. I was fortunate that I don't own any light that could handle 2x14500s or some exciting chemistry might have reared its ugly head.

Less than once a week so 50 might be accurate and I don't use it on high all the time either.

I am already visualizing the duct tape over your mouth.