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  1. #1
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    Halogen MR11 to LED

    I did a search a found a couple of threads dealing with replacing a halogen bulb with a LED type, but still have some questions.

    First off my knowledge lighting is not great, as my questions will likely show. I have an older BLT Beta-Ray NH40 light. It has a 10w halogen MR11 bulb that appears to be 4.8v. The battery is quite small and can fit in a jersey pocket, onto th frame or in a camelback. I have two batteries. See link on BLT light http://www.mtbr.com/spotlight/lightshootout/blt.shtml

    The system works okay for what it is but perhaps could be better with new LED technology. The problem is that most LED MR11 bulbs that I can find seem to either be 12 or 24v. I have seen both single LED or multiple LED light setups for the MR11 bulb.

    What would the LED light output be in comparison to a 10w halogen

    Are there MR11 LED bulb available that will work with the system as is 4.8v

    What happens if I put a 12v MR11 LED bulb in?

    Lots of questions I know, just trying to experiment a little with this light. I also have Princeton Tec SB 3 that I picked up last year, that works well but ... somewhere down the road it would be interesting to change out the LED to the more current versions.

    Be nice to the light newbie.

    Cheers

    Jeff

  2. #2
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    I have an old NiteRider dual setup that uses MR11 bulbs that I am starting to consider retrofitting to use LEDs. Where are you finding these MR11 LED replacements?

    Oh, and I'm no expert, but you can use a 12v LED bulb with your battery, it'll just be roughly a quarter of it's normal brightness. You'd be better off just buying a new 12v battery.
    NKAWTG

  3. #3
    I spelled Knievel wrong
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    You can drive a MR11 sized group of 3 Cree LEDs (available from Cutter) using your 4.8v battery. LEDs require a constant current driver to maintain consistant brightness. There are two basic kinds of constant current drivers: buck drivers and boost drivers. Buck drivers step voltage down to the level necessary to provide a constant current (if you had a 14.8v batttery you would use a buck driver), while boost drivers provide a voltage "boost" so that you can run smaller batterys like your 4.8v. I have been running a fatman boost driver from Taskled with my MR11 Cree conversion using a 6v 4ah battery with no problems. The Maxflex is another, more advanced boost driver that they make with a programmable user interface. Search "fatman" or
    "maxflex" and you will learn more.

  4. #4
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    Quote Originally Posted by StevelKnivel
    You can drive a MR11 sized group of 3 Cree LEDs (available from Cutter) using your 4.8v battery. LEDs require a constant current driver to maintain consistant brightness. There are two basic kinds of constant current drivers: buck drivers and boost drivers. Buck drivers step voltage down to the level necessary to provide a constant current (if you had a 14.8v batttery you would use a buck driver), while boost drivers provide a voltage "boost" so that you can run smaller batterys like your 4.8v. I have been running a fatman boost driver from Taskled with my MR11 Cree conversion using a 6v 4ah battery with no problems. The Maxflex is another, more advanced boost driver that they make with a programmable user interface. Search "fatman" or
    "maxflex" and you will learn more.
    Maybe this is a stupid question, but I don't know too much about electrics... so are the buck and boost drivers interchangeable? The reason for me asking this is because I'm going to buy a DIY light which uses some kind of a regulating driver, expecting at least 12V as input (3 leds connected in series), but I have two 4ah 6V NiMh battery packs already, and it would be so nice if I could use them. I could connect the batteries in series, but in that case I'd need to carry both in my back pocket, which is not very nice... So is it possible to simply replace the driver circuit, or is there anything else that must be done?

  5. #5
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    radirpok,
    Can you give us some info on the LED kit that you're looking at? That'll help some. It depends on the voltage needed for the light kit you're looking at. Is it a single or multi-LED kit?

  6. #6
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    Quote Originally Posted by dnlwthrn
    radirpok,
    Can you give us some info on the LED kit that you're looking at? That'll help some. It depends on the voltage needed for the light kit you're looking at. Is it a single or multi-LED kit?
    Sure, try to read my post again :-] (3xCree, min. voltage ~10V, max voltage ~18-24V, it is designed to run from 14.4V packs)
    In the meantime I got an answer from the builder of the light, and he said it should be absolutely fine. I know this is not a very effective solution (~85%?), but it should work nevertheless.

  7. #7
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    sorry, I was looking for more info on the driver. I guess you don't know which one it is. Based on the 3 Cree LEDs, you're looking at a Vf of 11.1 V (if you're driving them at full power, 1000mA). So unless you have a boost driver, you need to supply at least the 11.1. If you swap it out for the boost driver (I'm getting a kit with the Fatman), you are supposed to supply it with LESS than the 11.1V. What I'm not sure on is if there's any negative effects of running a buck driver at a lower voltage than the Vf of the system. I'm guessing it just means less output.

    But yes, if you're electrically inclined, you can swap out the drivers. They're just soldered in between the battery and the LEDs.

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