Lithium Ion Flashlights

I think I’m almost done learning about flashlights. This weekend I researched lithium ion batteries and how they relate to flashlights. This is because the tiny flashlight I bought can be powered by a lithium ion battery, though it is not recommended (this is different from disposable lithium batteries like Energizer sells that you only use once but have more power than alkalines). But if you put one in there it will make the flashlight much brighter (and potentially burn it out if you leave it running for very long on the highest brightness setting). One problem with Li-ion batteries is they tend to explode or catch fire. Just about all of the cases where laptops, iPods, or other devices catch fire are because of Li-ion batteries. Many Li-ion batteries come with circuit protection that is supposed to kick in if the voltage of the battery gets too high or if it gets too low (both are bad).

There are a lot of different sizes of Li-ion batteries denoted with a number that tells you the diameter, length, and shape. For instance the battery that replaces a AAA battery is called a 10440 which breaks down to 10 mm diameter, 44 mm long, and 0 for a round shape. These batteries are too small to include protection circuits. Most of the batteries supply 3.6 (or 3.7) volts nominally but you charge them 4.2 volts and they need to be recharged when they get down to 2.8 volts or something like that. Because they are supplying more than twice the voltage of a regular 1.5 volt alkaline or 1.2 volt NiMH battery, it makes sense they will be brighter. But you have to make sure you get a flashlight that is made for that higher voltage.


It seems like most of these batteries are just a little larger than their non-lithium counterparts and some don’t have buttons on the positive end. I guess if the manufacturer wants to prevent you from using them, they can build the flashlight so that you can’t use the bigger battery. My Fenix flashlight can use lithiums when it is set up for a single AA, but not for the longer version with 2 AA’s (that would be 7.2 volts). Apparently the 1xAA version shines as bright as the 2xAA version on a 14500, but you lose all of the modes except the brightest one for some reason, so I don’t know that I want to do that.

There is a website that sells gadgets direct from China called DealExtreme. They have kind of a shady reputation and stuff takes weeks to arrive. The quality of the items can be very spotty to poor and they have been known to sell Eneloops which turn out to be fake. But they also sell a lot of cheap flashlights. One of the ones people seem to like (when they work) is the AKOray K-106 which uses 1 AA battery. It comes in two different varieties. One is a 5-mode light(misspelled on the website as an NKOray) with different brightness levels and flashing modes. You get to Mode 1 by turning the flashlight on, turn it off and on again (either clicking or halfway pressing the button) and you are in Mode 2, etc. It is also nice because it remembers the last mode you were in, so if you were in bright it will come on again in bright. Some don’t like that because they have no idea what mode it will come on in, but it seems like a good idea to me. It is only $13.99 shipped. The other variant, for $19.13, is advertised the same way. The description is also wrong since it says it is a 6-mode with memory when in fact it is a 3-mode light that is programmable (in Nov 2009 people started receiving actual 6-mode lights sometimes that are not programmable; KaiDomain seems to carry programmable ones). Programmable means you can set the three modes to anything you want, whether it is any brightness level (it does this by varying the brightness, called “ramping,” and then you click when you get to the brightness you want) or one of the flashing modes. So you could have a low, high, and flashing mode if you wanted. It also seems to remember the mode you were in last. Both variations of these lights are 50% brighter with 14500 batteries, about the same brightness as my 2xAA Fenix with NiMH’s. This solves one problem with my Fenix setup, which is that I like the 1xAA size, but I want the 2xAA brightness and I would like to do away with the flashy modes if possible. The problem is the K-106 isn’t the same quality as a Fenix and the brightness and color of different LED’s varies from light to light, sometimes substantially. So it would be crapshoot on whether I’d really get a light that could be as bright as the 2xAA Fenix. And the color of the light could be very blue, which I don’t like (here’s a post with pictures of beams from a bunch of flashlights and the K-106 looks the most blue).

Another possible flashlight that would cost more money would be the Quark AA Tactical or the neutral white version of that light (more orange than cool white). Both of these are brighter on 14500 cell and retain their modes (also programmable with two modes: one with the head tightened all the way, and one with it slightly loosened). Because you pick the mode by turning the head instead of clicking the power button, you always know which mode you will enter and you can turn the flashlight on and off momentarily without switching modes. Either of those lights are $57, so they are a lot more pricey, but a good value for that level of quality and functionality.

The decision then is whether to get a light that can excel with Li-ion batteries and then of course you have to buy some 14500 batteries ($5.64/pair) (higher quality, much more expensive AW cells available direct from China, LightHound, or Four Sevens, the company that makes and sells Quark lights) and, since they won’t charge in a regular charger, get a charger as well. Deal Extreme has a couple of chargers. The $12.30 UltraFire WF-139 can be pretty good, but it won’t do the small 10440’s. I could get a charger that is known to slightly overcharge batteries, called a TR-001 ($8.81), but charges all of the main sizes. There is also one that people seem to like that charges 14500’s and 10440’s only.

So the cheap route is the K-106 programmable, 2 cheap 14500’s, 2 cheap 10440’s (to play around with in my iTP A3), and the TR-001 charger. $37.82 total (everything on DealExtreme includes shipping). That’s a lot of overhead for a cheap flashlight. I could dip a toe in the water by getting the 10440 (maybe the 14500’s to try in the Fenix) and charger to try out or just get the K-106 to play around with using AA NiMH’s.

The expensive option would be to get the Quark AA neutral white flashlight ($57, ships free from 4sevens), with two AW 14500’s ($9 each) and two of his 10440’s ($4 each) plus $4.50 shipping. Then get the 10440/14500 charger for $12.58. $100.08 total. That’s kind of crazy.

There are other Li-ion cells too. To replace a CR123 cell (also called a CR123A), use a 16340, though people also call that a RCR123 (they make 3 volt and 3.6 volt versions). To replace two CR123 cells, use a 18650 (fatter than CR123’s plus I’m not sure how the voltage on that works out since an 18650 would be 3.7V and two 3V CR123’s would be 6). The 18650 is also what is used in most laptop battery packs. All of these can be ordered with or without protection circuits.

Anyway, I don’t think I’ll buy any of these, but I wanted to write down what I have learned about all of this. Since my Fenix light does most of what I want, I could just wait until something significantly better comes out in a year or two. The Fenix can be used like the Quark by having bright on tight and low on loose and not using the other modes, which is basically how I use it now. If I want super brightness I can just use 2 AA’s and be as bright as the K-106 or Quark are with a single li-ion battery.

3 thoughts on “Lithium Ion Flashlights

  1. Well, I couldn’t stand it anymore. But I am just trying out li-ion batteries by buying 2 10440’s, 2 14500’s, and a really cheap charger. The total was less than $20. I can test a 10440 in my iTP light and a 14500 in my Fenix L1D.

    I didn’t get the AKOray K-106. Though I’m intrigued by the programming, the brightness seems to really vary, with some people getting 200 lumens and some people getting more like 130 lumens from a 14500 battery. The lower end of that is about the same as my L1D on NiMH’s. If I knew I could get 200 lumens, I would probably buy it. But I figured I would see what these new batteries will do first before I commit to another light.

  2. My DealExtreme order still hasn’t shipped yet. But I ran across an interesting idea for a free Li-ion battery charger. You can take the battery out of your cell phone and then connect some leads from the positive and negative terminals of a regular Li-ion battery to the ones in the phone. Then connect the phone to a charger. Cell phones use 3.7 volt Li-ion batteries so it should work. It will just take longer if the battery you are connecting has more capacity in mah than the cell phone battery has. Looking at the back of my LG phone, there are two negative terminals on the left side and two positive on the right. If I measure the voltage across the second negative and second positive terminals (terminals 2 and 4) while the phone is plugged in without a battery, I get exactly 4.20 volts which would make a good charger. I’m not sure what the other terminals do, but if I measure the voltage on terminals 1 and 4 I get 1.59 volts. If I do 2 and 3 I get 2.61. If I do 1 and 3, nothing (or something really small). If you add 1.59 and 2.61, that’s 4.20.

  3. The DX order shipped October 26 and I got it today. The universal charger is scary: It has no English on it or its packaging at all except for a few numbers. But it seems to work with either 110V or 220V, is very compact, and charges all different sizes of batteries with a spring-loaded lever that expands from 30 mm to 66 mm. It also will charge either NiMH batteries to 1.4 V or Li-ion batteries to 4.2 V. And yet it does not have any switches or controls.

    All 4 batteries arrived and tested at 3.6-3.8 V which is good. They are a little larger than AAA and AA batteries so they don’t fit in my cases and it was a tight fit getting the 14500 in my Fenix L1D, but I got it in there. It helps to loosen the head a little which usually would put you in the less bright modes, but on li-ion batteries the less bright modes are lost and replaced by bright. It is definitely brighter on a fully charged 14500, but I don’t like losing the lower modes. One thing with flashlights that aren’t made for li-ion batteries is that they are usually “direct driven” on a li-ion so the brightness is proportional to the voltage of the battery. And that varies a lot from 4.2 volts fresh to 2.8 volts when it is time to recharge (actually people recommend recharging li-ions when they get down to 3.6 volts to increase battery life).

    The tiny flashlight is definitely brighter on a fully charged 10440, but with only 15 seconds of use, the flashlight gets warm. That’s kind of scary. It is ridiculously bright for something so small though, brighter than the L1D with an AA battery, but it doesn’t throw as far.

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