OK, so here's my attempt at the most definitive answer possible for a regulated LED module which runs at or near spec from 3.7v up to 7.4v:
Reading the most recent posts for the actual tested capacities of the
AW protected RCR123's, I'm going to go with
550 mAh @ 1 amp drain rate (data posted above by RTTR and HKJ, and which is probably comparable to 600 mAh @ 0.5 amp drain rate which was also posted above).
For the
AW protected 17670's, I'm going to go with 0.99 x 1600 =
1584 mAh @ 2 amp drain rate, since the similarly-sized 17500's tested at 99% of their claimed 1100 mAh for that drain rate, from SilverFox's data cited in my earlier post
(#9) in this thread.
For the
AW protected 18650's (2600 mAh), I'm going to go with
2440 mAh @ 2 amp drain rate, from my interpolation of data cited in my earlier post
(#14) in this thread.
So, again using a hypothetical wattage drain of 7.4 watts as in my Post # 9 (This was chosen for ease of amperage drain calculations - remember, we often only have capacity data for
specific drain rates such as 1 or 2 amps, for example).
So for this example, we are drawing
one amp from 2xRCR123 vs. drawing
two amps in 1x17670 & 1x18650 to maintain the same wattage throughout our comparions:
- AW RCR123's: (0.550Ah) x (3.7v) x (2 cells) = 4.07 watt-hours of total energy capacity
- AW 17670's: (1.584Ah) x (3.7v) x (1 cell) = 5.86 watt-hours, a gain of ~45% for a configuration of the same length.
- AW 18650's: (2.440Ah) x (3.7v) x (1 cell) = 9.03 watt-hours, a gain of ~120% for a configuration of the same length.
I have tried my best using data and information posted on CPF to come to a definitive comparison of the three common AW LiIon configurations for a regulated LED module which can operate
at or at least near spec from 3.7v up to 7.4v. The only oversight (besides possible internal improvements to subsequent generations of LiIon cells) that I can see at the moment are slight differences in voltage drops under load - this will give the 18650 a slightly greater performance edge, as the calculated watt-hours will be slightly higher than the above (perhaps ~3.
8v vs ~3.7v from the smaller LiIon cells of considerably less capacity :shrug
.
Edit: As an aside, let's see how many watt-hours we might get from 2x SureFire CR123
lithium primaries for the same wattage draw, as the OP for this thread was hoping to make that comparison:
7.4 watts / (~2.5 volts
under load x 2 cells) = 1.48 amps, let's call that 1.5 amps.
Using this data from Silverfox and interpolating the total delivered watt-hours between the 1 amp and 2 amp drain rates:
3.123 watt-hours @ 1 amp, 2.073 watt-hours @ 2 amps, interpolated to 2.60 watt-hours @ 1.5 amps.
2.60 w-h x 2xCR123 =
5.2 watt - hours for 2xCR123.
Therefore, the only way to match the capacity of 2xCR123 lithium primaries in the same length host is to use 1x17670. In addition, the capacity of 1x18650 beats 2x CR123 lithium primaries by ~
75% in a host of the same length, a very impressive achievement for rechargeable cells. :thumbsup:
I understand that this is for a relatively high drain condition (7.4 watts), as the Malkoff M60 generally operates at ~4.5 watts, but remember, we generally get LiIon mAh data posted for 1A & 2A drain rates in CPF, and I chose this 7.4 watts as a result of that, to facilitate comparisons between 1x LiIon and 2x LiIon. Things should be reasonably comparable for lower wattage conditions, as the above situations should still be proportional. I suppose I could re-run all this for a 7.4W / 2 = 3.6 watts condition (probably pretty close to the wattage of the OP's Malkoff M61), as we can come up with RCR123 capacities @
0.5 amps & 18650 capacities @
1.0 amp, but it should pretty much demonstrate the same thing.
And as 'Forrest Gump' said:
"And that's all I have to say about that."
. The M61 is suppose to run for 2 hours on two cr123's. You guys have any thought on this??? Thanks.
