LiFePo4 safe for super high drain?

[nasa779]

i have a few lifepo4's i was thinking about using in my 9p with a EO-9 drop in....

is that safe for rechargables to be drained that fast?

(20 min runtime on primaries)

 

[45/70]

It all depends on the cell's rating. Some LiFePO4 cells can be discharged at very high rates (A123's for example), others like some of the smaller RCR2 and RCR123's from China are limited to a 1C discharge rate. The best thing is to check the manufacturer's specs for that particular cell, and go from there.

Dave

 

[hoongern]

i have a few lifepo4's i was thinking about using in my 9p with a EO-9 drop in....

is that safe for rechargables to be drained that fast?

(20 min runtime on primaries)

The EO-9 is designed for 3xCR123 and draws 2A. At that current, CR123s run at about 2.25V - so the bulb would be getting ~ 6.75V (See CR123 discharge tests here).

Running it on (I'm not sure which lifepo4s you have) 3xAW LiFePO4s (discharge graph here) would give in excess of 3V each, which means that you'll be overdriving the bulb at around 9V (Current will be > 2A). i don't know much about the EO-9, but you may risk flashing the bulb and you'll get reduced bulb lifetime.

At least for AW's LiFePO4 16340s, they don't work too well > 2A in terms of capacity. But most larger LiFePO4 cells are very capable of delivering high currents.

Another option would be to use 2x18500 cells (LiCo/ICR or LiMn/IMR) which should work fine - in fact they'd still be overdriving the bulb. EDIT: seeing that you're using the 9p, it can't accept 18mm cells. You'll have to bore it or use 17500s)

 

[nasa779]

theyre these
http://www.cfrlights.com/servlet/the-457/rechargeable%2C-2000%2C-times%2C-3.2v%2C/Detail
and i see they say discharge rate <550ma

so id be better off using primaries?

and if the answer is yes... i bought tenergy cr123's from cfr lights a few weeks ago and i just noticed i got 20 "propel" lithiums instead...... anyone try these?

btw what does "1C" mean?

 

[45/70]

I hadn't even thought about watching the voltage, as hoongern pointed out, as I'm not familiar with your setup. Anyway, yeah, a 2A load would be too much for those cells. It might work, but it would more than likely greatly reduce the cycle life of those cells.

I would look into some LiMn cells for that setup. Yes, you could use primaries, but personally, I'd stay away from non US/Japan CR123A cells. None of the others have a very good reputation.

"C" is the equivalent of the capacity of a battery cell in mAh. It is used as a rate of charge or discharge though, so it is mA, not mAh. For example a 2000mAh cell discharged at 2000mA (2A) is a 1C discharge rate. The same cell discharged at 1000mA, would be a 0.5C rate and so on. Works for charging rates also.

When charging, sometimes "C" is in reference to the charge rate, rather than the cell's capacity. This is usually associated with charging Li-Ion cells with a hobby charger, or similar setup though.

Dave

 

[hoongern]

theyre these
http://www.cfrlights.com/servlet/the-457/rechargeable,-2000,-times,-3.2v,/Detail
and i see they say discharge rate <550ma

so id be better off using primaries?

and if the answer is yes... i bought tenergy cr123's from cfr lights a few weeks ago and i just noticed i got 20 "propel" lithiums instead...... anyone try these?

btw what does "1C" mean?

I assume you have the 9p. You can use primaries, or as I mentioned - you may want to try the 2x17500 setup. I suggest quality cells such as AW's, which can be found in the marketplace / other places. You want the protected ICR17500s (They are Lithium Cobalt cells), spec'ed at 1100mAh. Most Li-Co cells are safe up to 2C discharge, which means the 17500s can be discharged up to 2.2A safely.

If you looked at the link I sent earlier on the discharge rates for incans, here are the runtimes for the EO-9 (I think they are approximate - not sure if they were actually measured):

3xCR123A 35min
2x17500 30min
2xIMR16340 15min

Just in case you don't know, IMR refers to Lithium Manganese / LiMn cells, which are capable of very high discharge rates.

 

[nasa779]

so its essentially the ratio of capacity to charging/discharging?

 

[45/70]

"C" is usually referred to as "C rate". So yes, it is a rate of charge or discharge in relation to the capacity of a battery or cell (but in some cases, actually refers to the charge rate itself, as I mentioned previously). Again, it is not a quantity, as in mAh, but a rate as in mA. Hope that helps.

When I suggested LiMn, I was thinking 17500 cells were available (as in 2x17500. 3x16340 LiMn's would the bulb, as they are 3.6-4.2 Volt cells), but I see that AW anyway, only offers 18650 and 18500 LiMn cells.

I haven't ventured into LiMn cells myself......yet. I have no need for their high current ability. When I get back into hotwires, I'll more than likely be checking them out though.

Dave

 

[mdocod]

Using LiFePO4 cells as replacements for CR123 primary cells in direct drive lights will almost always result in premature bulb or LED failures. Please avoid it.

As mentioned, for driving the EO-9 in a 9P, the preferred method is to use 2x quality protected 17500 size lithium cobalt cells from AW. The 17500 size cell is 1.5X the length of a CR123, so 2 of them will fill the space of 3 CR123s and deliver very similar operating voltage in use. You'll need to get a proper 3.7V cell charger to use these cells. Ideally, a properly made one like the Pila IBC, but other options that are safe and reliable are being found so stay tuned to CPF.

Please avoid Tenergy brand CR123s. In fact, all Chinese manufactured CR123s. Chinese made CR123 cells have proven time and time again to be the most likely battery to explode in a flashlight. They are not worth the cost savings either since they often do not perform at the same capacity as well made cells. Paying $1.50 for a USA made cell (RayoVac, SureFire, StreamLight, Panasonic, Duracell, etc) is often going to buy just as much runtime per dollar as paying $0.90 for a Tenergy.

Eric

 

[nasa779]

Using LiFePO4 cells as replacements for CR123 primary cells in direct drive lights will almost always result in premature bulb or LED failures. Please avoid it.

As mentioned, for driving the EO-9 in a 9P, the preferred method is to use 2x quality protected 17500 size lithium cobalt cells from AW. The 17500 size cell is 1.5X the length of a CR123, so 2 of them will fill the space of 3 CR123s and deliver very similar operating voltage in use. You'll need to get a proper 3.7V cell charger to use these cells. Ideally, a properly made one like the Pila IBC, but other options that are safe and reliable are being found so stay tuned to CPF.

Please avoid Tenergy brand CR123s. In fact, all Chinese manufactured CR123s. Chinese made CR123 cells have proven time and time again to be the most likely battery to explode in a flashlight. They are not worth the cost savings either since they often do not perform at the same capacity as well made cells. Paying $1.50 for a USA made cell (RayoVac, SureFire, StreamLight, Panasonic, Duracell, etc) is often going to buy just as much runtime per dollar as paying $0.90 for a Tenergy.

Eric

i guess im SOL because i have 20 of them