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AA vs 14500 question!

  • Xumixu Thursday, December 31, 2009 3:18 AM Reply
    Hi, i bought it a pair of 14500 . . .

    but reading later the topics posted here, a question came up . . .

    wich are the difference beetwen AA v/s 14500 batteries

    >Life span of the led?
    >Continous runtime?

    I really want to know, cause i really prefer life span over brightness

  • JohnJackGit Thursday, December 31, 2009 4:40 AM Reply
    Lifespan of led is ridiculously high with both AAs and 14500.
    Runtime is longer with AAs.
    Brightness is better with 14500.
    Generally, good AAs (alkalines or NiMh) have same amount of stored energy as 14500 LiIons, but 14500 have higher voltage and are better for drawing more current.
  • ICanuwundra Thursday, December 31, 2009 5:19 AM Reply
    AA size NiMH are heavier than 14500 LiIon. 14500 degrade (lose capacity) more quickly then NiMH. 14500 have higher fireworks potential than NiMH AA.

  • James_C Friday, January 29, 2010 7:13 PM Reply
    In a multimode light that takes both AA and 14500 Li-Ion, you can often get near the same light on medium brightness setting with Li-Ion as you can on high with NiMH/Alkaline AA cell, but the Li-Ion will then give longer runtime.

    All these lights are terribly inefficient running on one NiMH, for example if you put a 2nd NiMH in series they either stay same brightness or get brighter, but with far less than half the current consumption. But NiMH are common, inexpensive, more forgiving of abuse, and having a stockpile charged and ready to use comes in handy for powering other compatible equipment.

    Lifespan of the LED varies per light (driver) design and the forward voltage your particular specimen of LED has. Some of these lights end up direct driving the LED at too high a current in AA sized lights when Li-Ion cells are used. The lights simply don't have enough heatsinking ability for LED drive current much beyond 1A, if that much, and permanent degradation to the LED can result.

    LED lifespan is very long if used as directed, but driving a 3W LED to 5W strapped to a poor heatsink, you have to start deciding if it's worth the cost vs size of the light to do it.

    To get more lifespan over brightness, go for a 2 x AA light, or of course a larger Li-Ion format than 14500, OR use 2 x 14500 and add/replace existing driver with your own buck driver board suited for 8.4V peak input voltage, or just carry the 2nd cell fully charged as a spare you swap in as needed. That can work out well if you carry the spare (NiMH) in a light barely bigger than the spare itself so you have both a backup battery AND a backup light should you need one. For example, http://www.dealextreme.com/details.dx/sku.24125, as a nice way to carry a spare AA cell, though runtime is only so-so at 90 minutes give or take.
  • cave42 Thursday, April 01, 2010 5:10 PM Reply
    The one I got March 27 worked fine on AA at first, but a 14500 fried the driver. Now there is no light with either battery. It still draws current. I think the driver just short circuits the battery. I think others have reported the same thing.
  • cave42 Thursday, April 01, 2010 5:10 PM Reply
    The one I got March 27 worked fine on AA at first, but a 14500 fried the driver. Now there is no light with either battery. It still draws current. I think the driver just short circuits the battery. I think others have reported the same thing.
  • James_C Thursday, April 01, 2010 6:04 PM Reply
    Despite what DX claims, and whether one person has success at it, it's always a gamble to put a Li-Ion cell in a light spec'd as capable of running off a ~1.2-1.5V battery too.

    Individual variations in the current sense resistor, LED forward voltage, and even what voltage your Li-Ion charger terminates at can effect whether a light survives it a little while, survives longer but dies prematurely still, or survives long term.

    The best bet is to always first measure the current from the battery and if that current exceeds about 1A, immediately terminate the test as that is too high for a AA sized flashlight using an economical driver intended only for the amount of heat/current that size flashlight can handle.

    Personally, I wouldn't even want to exceed 800mA from Li-Ion in this sized flashlight as the diameter is limiting of the driver transistor size/heatsinking-copper/capacity as well as LED heatsinking.

    The other option is sometimes a charger that only charges up to 4.0V or so, it's a capacity loss for sure but it's also going to give you many more recharge cycles from a standard Li-Ion cell than going up to 4.15V or especially beyond 4.2V.
  • James_C Thursday, April 01, 2010 6:04 PM Reply
    [double-post removed]
    Posts(1699) | Reviews

    post edited by James_C on 12/26/2011 at 11:56 PM
  • Xumixu Saturday, August 27, 2011 4:12 PM Reply
    Sorry for not answering but seems like didn't send me notifications to my mail.

    Well, I finally jumped into the pool with 14500, and it fried the driver, it works, but only with 14500 (not AA) as you stated, the flashlight is considerably brighter and is still alive.

    As foot note, the driver is welded to the heatsink and that way it makes contact with the flash light and the battery positive pole. That welding get easily broken, and welding it again is a pain in the ass 'cause tin doesn't like to stick to the bronze heatsink (I'm not very good with soldering iron so maybe for a more experimented user will be easier to fix).

    Posts(433) | Reviews

    post edited by Xumixu on 10/16/2011 at 9:45 PM
  • alsarcar Monday, December 26, 2011 11:28 PM Reply
    Driver dies quickly. I've gone through three of these lights. ONLY use AA.
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