Thanks, Haertig. That's something so basic to me now that it totally slipped my mind. Yes, these different batteries may all have basically the same form factor, but they have different characteristics, most importantly for most users, voltage.

Fortunately, as lithium ion batteries have become more common--at least among flashlight hobbyists and certain power users--more and more LED lights designed for one or two CR123 cells are capable of also using either primaries or rechargabeables. It's critical to double-check that before use.

It really sucks to unwrap that cool DX light that you've waited two months to be shipped from China, and then you fry it because you put lithium ions in the light when it couldn't handle the extra voltage. Then all you have a cool looking paperweight.

Due to the differing voltages of rechargeables, some devices won't use them. IIRC Surefire warns not to use them in their lights.

do you mean 16850 battery? the 16340 battery is very hard to find. I think it must be misspelled word.

for that light, you can use rechargeable CR123A. The light isn't strong enough for the large battery. I have several high power flashlights.

In my Surefires I usually use 16340 LiFePO's. E1B Backup and Surefire Minimus headlamp work fine on them. Surefire recently started selling 16340 LiFePO's + charger on their website.

For the 6P Nitrolon w/Malkoff dropin I use a 17670. I prefer single cell lights.


16340 Li-co's are 3.7V

16340 LiFePO's are 3.0V so are interchangeable with CR123 primary batteries.

That's not saying the lights "that won't use them" are somehow ethically/morally/engineering-wise superior. "Don't" is probably a better word to use than "won't". Truth be told, those lights suffer from an inferior electrical design. They may be good lights, but they are older designs and failed to keep up with recent trends. Much like what happened to Maglite.

This is one reason why I bought both a 4Sevens and an Olight over a Fenix. Fenix makes good lights, but they suffer in the design department in that they cannot use the higher voltage cells. That is not a plus for them. That is a minus. 4Sevens and Olight (at least the specific models I bought) don't suffer from that deficiency.

So definitely check out the light you are considering purchasing for what voltages it will accept (and build quality, and other things too). Simply buying a well-known brand name is not good enough anymore.

ireckon, since it's not clear if you're referring specifically to IMR-type 16340 cells, or just generically to rechargeable CR123 sized cells, I'll keep my answer fairly generic.

I tend to use rechargeable RCR123 cells in my EDC lights (which I use regularly, too), but I also make sure to top them off periodically. Takes very little time to do a top off charge. For versatility, my EDC lights are LED lights that have multiple modes so I can tailor the amount of light to the task. More efficient use of precious battery life that way, especially for a light that I'm not necessarily carrying spare batteries for at all times. However, most multi-mode LED lights are going to slowly drain your batteries to keep the electronics in them active. For example, any multi-mode light that remembers what level you used last is definitely drawing power to remember that setting. Most lights are not bad about this drain, so this is not a universal problem, but sometimes you'll come across a light that will leave you with a dead battery in a couple of months or even in weeks.

For lights that I have stashed primarily for emergency use, like the lights in my cars, I tend to use non-rechargeable batteries and pick lights that either do not draw any power when not on, or which you can adjust to not draw power (or just remove the batteries and store them outside the light). For those lights, I change out the non-rechargeable batteries annually.

So, for lights that you use often or at least handle often, it makes a lot of sense in most most cases to use rechargeables, I think. Much eaiser to make sure that you'll have a full or pretty full charge when you need it. At least if you're always starting fairly full, you have some idea of how much runtime you may have left. With non-rechargeables in a light that you use periodically or regularly, you may not have any idea at all unless you carry a spare cell.

Also consider your preference in "regulation". An unregulated light will just keep getting dimmer and dimmer until it finally goes out. You have plenty of advance warning that you need to replace the batteries. [ But many people seem to ignore that warning. For some unknown reason they prefer to shake and beat on the light in a futile ritual to get it to turn back on. Strange folks they are - shaking a dead battery doesn't make it spring back to life. You see this all the time in the movies. ]

Anyway, ...

With a highly regulated light, the brightness stays the same, or very close to it, throughout the battery life. The lights I carry daily are all highly regulated. To the (almost ridiculous) point of staying at full power and then just suddenly turning off when they're dead. Luckily, I can switch all my lights to a much lower power setting and turn them back on for a few more minutes to a few more hours after "lights out!", so I'm not totally in the dark. But it is a little disconcerting for the first few seconds after your blazingly bright flashlight just turns off instantaneously. Until you remember to turn it back on using a lower power level and go grab some other freshly charged batteries.

Although an important distinction, I think we might confuse some readers by mixing apples and oranges. Now we're talking about differences in flashlights, rather than differences in battery types.

That said, back to batteries, you can also be left in the dark with an unregulated light if you're using Li-Co rechargeable RCR123's if you run the cell down enough to trip the low voltage protection circuit built into most RCR123 cells. At that point, switching modes won't help. The only way to reset the protection circuit in the battery is to recharge the cell.

This wouldn't happen with an IMR-type rechargeable cell because it doesn't have a protection circuit. Nor would it happen with a non-rechargeable CR123 cell. (Not being able to turn the light back on, that is. The light itself might still switch off because it has its own low voltage cutoff circuit, but in that case, switching to a lower mode would probably let you continue at a lower illumination level, like Haertig was describing above).

Hahaha! I was trying to keep it and short, avoiding writing a book, but you had to go there... Okay, yeah- it's an "ought" more than a flat prohibition. The issue is that there are a multitude of rechargeables with myriad voltages. Some voltages are within the range of specs that can safely drive the emitter of a Surefire lamp. Others are not. Over voltage can ruin the light. Since Surefire has no control over what kind of Chinese rechargeable batter you decide to slap in there, they simply advise you not to use rechargeables at all. Probably a sensible precaution for their marketing/legal department. If you do decide to use rechargeable batteries you want to make sure the voltage is correct.

I agree that Surefire doesn't keep up to date with the latest and greatest, but I think it's a bit off base to compare them with Maglite. The latter is truly stuck in the wrong century. While there are brighter LED lights than Surefire (and I own many of them) if I had to bet my life on one of them working I'd grab the Surefire every time. IMOHO that's probably why they don't play emitter-of-the-week with all the Chinese companies and don't try to walk the razor's edge with their microprocessors. They don't market to flashlight geeks- they market to professionals in the military and law enforcement fields. Surefire focuses on making pretty bright lights that are bomb-proof. For all that I don't think they compare to badly when it comes to light output, either. Most of my Chinese lights carry somewhat optimistic ratings; Surefire lights are generally the opposite. And my X300 Ultra weapon light is among the brightest hand held light I've seen.

Not trying to open a can of worms here, just making some observations.

Yikes! Would you guys please stick to English? I'm reminded of trying to follow a heated discussion in a language I don't understand!