I've been considering getting an mc-e light or drop-in. I have some grey ultrafire protected 17670 cells rated at 1800mAh on the label. Would this be safe to use at 2800mA draw, or would I have to get some 18650 cells instead?
mc-e on 17670?
- Thread starter NigelBond
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LumenHound
Flashlight Enthusiast
2800 mA would be slightly beyond the maximum safe continuous draw rating of those cells if they did indeed spec out at a capacity of 1800 mAh.
For the sake of safety you might want to think of those cells as having a capacity of 1700 mAh. 2500mA would be a more realistic safe maximum continuous draw.
For the sake of safety you might want to think of those cells as having a capacity of 1700 mAh. 2500mA would be a more realistic safe maximum continuous draw.
mdocod
Flashaholic
Most modern LiCo cells are rated for a maximum discharge rate of between 1.5 and 2C.
The 1800mAH claim is inflated, so to be safe, we have to calculate based on a more conservative expected capacity at high discharge rates.
Lets say, they deliver 1350mAH into a heavy duty load, and they are rated for 2C discharge rates. Then 2700mA is the maximum recommended safe discharge rate. That's pretty close to what you have in mind.
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Honestly, for a 17670, pushing a P7 or MCE to the limit is definitely pushing the limits of this size cell, however, in this circumstance, I would concern myself less with the math of it all, and more with the quality of it all. I would not personally trust an over-rated ultrafire cell to operate day in and day out at a 2C rate with a good safety margin. Experience on this forum dictates, that the UF brand of cells is pretty "shady" to say the least.
The 1800mAH claim is inflated, so to be safe, we have to calculate based on a more conservative expected capacity at high discharge rates.
Lets say, they deliver 1350mAH into a heavy duty load, and they are rated for 2C discharge rates. Then 2700mA is the maximum recommended safe discharge rate. That's pretty close to what you have in mind.
---------
Honestly, for a 17670, pushing a P7 or MCE to the limit is definitely pushing the limits of this size cell, however, in this circumstance, I would concern myself less with the math of it all, and more with the quality of it all. I would not personally trust an over-rated ultrafire cell to operate day in and day out at a 2C rate with a good safety margin. Experience on this forum dictates, that the UF brand of cells is pretty "shady" to say the least.
I would get some AW IMR 18650 cells from lighthound if i were you.
These cells laugh at P7's and MC-E's
Seriously though these cells were designed for HIGH current consumption,their rated at 1600mA but they will still last longer than a reg.18650 because they won't sag under a heavy load.
These cells laugh at P7's and MC-E's
Seriously though these cells were designed for HIGH current consumption,their rated at 1600mA but they will still last longer than a reg.18650 because they won't sag under a heavy load.
Kestrel
Flashaholic
+1.I would get some AW IMR 18650 cells from lighthound if i were you.
These cells laugh at P7's and MC-E's
Seriously though these cells were designed for HIGH current consumption,their rated at 1600mA but they will still last longer than a reg.18650 because they won't sag under a heavy load.
Saying it another way, the posted capacities are generally for relatively low drain rates.
IMR has a lower capacity at a low drain rate than standard chemistry LiIons, but the capacity of standard chemistry LiIons falls off considerably at high drain rates. Therefore, IMR has higher capacity at high drain rates. Plus they are safer, especially at high drain rates. And probably more reliable in the long term, without a protection circuit. And they have that groovy red color.:thumbsup:
My two lumens,
Im not so sure that the 1800 is inflated. I've never seen any capacity tests on 17670 cells but there have been capacity tests on 18650 cells and they usually come pretty close to the stated capcaity. Typically cheap brands such as trustfire and ultrafire have more capacity than aw cells in the 18650 category, perhaps because they oversize them. A 17670 is not that much smaller than 18650 and the capacity claim is 600-700 less. Sounds like a reasonable capacity loss from the reduction in size.
Anyway, I wanted to get a mc-e drop in for my solarforce L2 but it's the older L2 and wont fit 18650 cells, thats why I have the 17670 batteries. I guess my plan is no good now so I'll have to look at getting a whole light instead.
Anyway, I wanted to get a mc-e drop in for my solarforce L2 but it's the older L2 and wont fit 18650 cells, thats why I have the 17670 batteries. I guess my plan is no good now so I'll have to look at getting a whole light instead.
