If you go the AA route, I would recomend picking up some Eneloop Pro batteries and a charger. They will maintain 80% of their charge after a year of storage. An alkaline battery does store a little more power, but the Eneloop gives a better discharge profile and does not cause corrosion if it leaks. After having over $400 in gear destroyed by leaky alkaline batteries I have stopped using them in anything other than toys.
I'm going to be a nerd for a moment as having an AA backup headlamp would be nice due to ease of getting batteries. Such as, if there was a massive earthquake that nocked things into the dirt I'm sure AA's would be brought in by aid agencies, but if you cannot charge the 18650 I'm willing to bet one would be out of luck.
Lithium AA's will give you the most energy storage, are lightest, and don't cause corrosion. The down side is price.
On high output, you will get longer run times out of the ostensibly lower capacity Eneloops. In the low power modes you can take full advantage of the alkalines capacity.
Power wise, the mAh ratings of a good AA lithium and an 18650 are about the same. However, this does not give equal run times. As an example:
-AA Eneloop Pro (2550 mAh) is listed as giving 13 days of run time at 1.0 Lm
-18650 (max capacity of 3500 mAh, which I will assume Zebralight tested with) gives 2 months of output at 1.06 Lm.
-AA Eneloop Pro give a max output of 285 Lm for 0.9 hours.
-18650 gives a max output of 1616 Lm for 2.5 hours. and 305 Lm for 5.3 hours.
Clearly both work, I remember thinking that a 60 Lm Surefire was bright before LEDs.
I'm going to be a nerd for a moment as having an AA backup headlamp would be nice due to ease of getting batteries. Such as, if there was a massive earthquake that nocked things into the dirt I'm sure AA's would be brought in by aid agencies, but if you cannot charge the 18650 I'm willing to bet one would be out of luck.
Lithium AA's will give you the most energy storage, are lightest, and don't cause corrosion. The down side is price.
On high output, you will get longer run times out of the ostensibly lower capacity Eneloops. In the low power modes you can take full advantage of the alkalines capacity.
Power wise, the mAh ratings of a good AA lithium and an 18650 are about the same. However, this does not give equal run times. As an example:
-AA Eneloop Pro (2550 mAh) is listed as giving 13 days of run time at 1.0 Lm
-18650 (max capacity of 3500 mAh, which I will assume Zebralight tested with) gives 2 months of output at 1.06 Lm.
-AA Eneloop Pro give a max output of 285 Lm for 0.9 hours.
-18650 gives a max output of 1616 Lm for 2.5 hours. and 305 Lm for 5.3 hours.
Clearly both work, I remember thinking that a 60 Lm Surefire was bright before LEDs.