Hey Guys,
I just picked up a few flashlights, the Nitecore Ex10 and Eagletac M2, so I am debating if I should should go with regular CR123 batteries or rechargeables. I am not a heavy flashlight users, so these lights will be left in the car or home for emergency use. Is is worthwhile for me to spend on qualiy rechargeables and charger? I have heard of the dangers with rechargeables, so I am not sure if I really want to deal with it.
Any suggestions would be great!
Tuan
Lithium primaries have an amazing shelf life, not at all like the regular C and D cells that we grew up with.
For car emergency lights, it's definitely cheaper to go with primaries. While it's nice to have a bright mode, most of your tasks will likely need only 10-40 lumens - so I would guess that 2 sets of batteries, original plus spare, will last the lifetime of your car. And there's a good chance the spare will never be used!
For general purpose household flashlights, kept in the kitchen drawer for utility purposes, such flashlights may see action less than once a week. And they may see only a few minutes of runtime with each use. Again, 10-40 lumens are adequate for most household tasks - so one set of batteries may last you a year.
(For my family's use, if I stuck an M2 in our kitchen drawer, I'd estimate that one set of primaries would last between 2 and 3 years - depending on how many fishing and camping trips we took. Strictly used around the house, I think I'd be competing with this thread. :green
I'd suggest that you would need to go through at least three to five sets of batteries a year for rechargeables to make economic sense. Even at that, the care and maintenance issues might not be worth the few dollars saved.
If you decide to go the rechargeable route, please educate yourself about the risks. Here are just a couple to start with:
Li-Ion cells
Charging cells
I'd recommend going with a quality charger (such as the Pila IBC) and quality cells (such as AW). However, regardless of which cell or charger that you use, I'd suggest you do a CPF search of the product. The risks are manageable to the extent that you keep yourself well-informed and follow prudent practices.
And I'd like to remind you to be careful when using lithium primaries, too. (1) Don't insert them backwards. (2) Don't use damaged cells (dented or otherwise visibly distressed). (3) Don't use mismatched cells.* (4) Don't put primaries in a charger. (5) Store the primaries in a cool, dry place.** (6) Dispose of lithium cells properly.***
* _ This applies to multi-cell flashlights. Don't mixup old cells (different remaining charges) and toss them into your M2. Keep sets together or, preferably, use each set until completely spent.
** - Lithium primaries have been reported to tolerate the summer heat quite well in car glove compartments, even in places like Arizona. At the other extreme, there's no reason for you to store lithium primaries in the refrigerator. If you do store them in an exceptionally cold place (like an unheated garage in winter), it's a good idea to bring the cells up to room temperature before using them - more to avoid condensation, than chemistry issues. After all, one of the lithium primaries' advantage over rechargeables is cold weather performance.
*** - Recycle your lithium cells. Check your local retailers, some of them, like Radio Shack, accept used cells.
P.S. I forgot one: (7) Don't short out your cells.
Not that you would do so intentionally, but you should be aware of the potential fire/explosion hazard when cells are accidentally shorted. 
