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Thread: Can I direct drive a Luxeon from 3 NiMh?

  1. #1

    Default Can I direct drive a Luxeon from 3 NiMh?

    Would it be bad to direct drive a luxeon star from 3 AA NiMh batteries for a short time?

  2. #2
    Flashaholic* FalconFX's Avatar
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    Default Re: Can I direct drive a Luxeon from 3 NiMh?

    I DD my LGI with NiMHs, but that's me... with current on the LGI so high, the heatsinking is your best bet to answer wether or not the LS can take the heat... I'd say, it's probably okay to DD an LS with NiMHs, if they're AA/AAAs... But Cs and Ds are a different story, as their resistance is so low that your current can shoot through the roof...

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    Default Re: Can I direct drive a Luxeon from 3 NiMh?

    I have a LGI made by Mr. Bulk. It is direct drive to what appears to be (never confirmed) a Q2H Luxeon. With 3 NiMH AA cells, it pulls over 1,500mA [img]/ubbthreads/images/graemlins/icon15.gif[/img]

    It survived this for many hours before I thought to measure. Now I know why the LGI is such a hand warmer. I added about .3 ohms of resistance to the LGI to drop the current to 1,100mA. Still way overdriven - but not as insanely [img]/ubbthreads/images/graemlins/grin.gif[/img]

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    Flashaholic* Pellidon's Avatar
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    Default Re: Can I direct drive a Luxeon from 3 NiMh?

    How about direct drive one in a 6 AA double barrel? Not with NIMH but with regular. I'd think NIMH's would cook one immediately in parallel like that. [img]/ubbthreads/images/graemlins/mecry.gif[/img]

    I just whipped one up with a Q3K attached to a 1/4 thick aluminum plate in one. Gets warm quickly and draws .8-.85 amp with three batteries and .7+ on one side with the other running. I don't have it figured out how to measure both at the same time for combined amps. My edikated guess would be that it is drawing maybe 1.5 amp with both sets of batteries.

    Anyone had experience with this setup?




  5. #5

    Default Re: Can I direct drive a Luxeon from 3 NiMh?

    Ray-O-Vac makes a rechargable Alkaline now that comes in over 1.5V, so you could drive a Luxeon with two of them. I have had very good experience with on of our InReTech AA adapters running on a pair of Ray-O-Vac rechargable alkaline batteries. We have not run this through our digital recording lightmeter, so I don't have graphs to show you. My informal tests roughly indicated comparable performance to standard alkalines, which is much better endurance than most NiMh batteries I have seen.

    The thing I like about the Ray-O-Vac's is that they are much cheaper than name brand NiMh batteries. Any rechargable that is less than 2X the price of disposable batteries with roughly comparable performance is a bargain.

    Our company is not in a business relationship with Ray-O-Vac, although if they called, we'd love to talk. Since our flashlight products are direct drive, we are wild about 1.5V rechargable batteries. Yes, as a matter of fact; that does make us nerds.

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    Flashaholic* Slick's Avatar
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    Default Re: Can I direct drive a Luxeon from 3 NiMh?

    I routinely build my mods to run direct-drive from 3 (1.2v NiMH's). You need to do 2 things.. Dissipate heat!, and NEVER insert batteries direct from the charger…

    I’ll tell you what, I‘ve never suffered a heat-induced Luxeon failure, BUT I finally DID kill a Luxeon with “FAT” batteries. The batteries were C cells (3 of’em) and sitting in the charger on trickle at 1.41v I decided to load them in the flash light but make a mental note not to power it – I had planned to leave the light downstairs for use a couple hours later after the batteries had “cooled”. Well, dumb ass that I am, I quickly forget my mental “note” and test it…. [img]/ubbthreads/images/graemlins/eek.gif[/img]

    Whoops. [img]/ubbthreads/images/graemlins/frown.gif[/img]

    It sure was bight for that half second or so.. [img]/ubbthreads/images/graemlins/mad.gif[/img] What pains me most is that I killed the absolute all-time lux-champion emitter I had ever tested! (6800+ lux for a 1W white SE) Sorry I’ve rambled….

    Lesson is NEVER use HOT recharged NiMh’s!!! Otherwise, you’ll be just fine.

  7. #7

    Default Re: Can I direct drive a Luxeon from 3 NiMh?

    [ QUOTE ]
    Pellidon said:
    How about direct drive one in a 6 AA double barrel? Not with NIMH but with regular. I'd think NIMH's would cook one immediately in parallel like that.


    [/ QUOTE ]

    Pellidon, if i were you, I would be using 5 watt instead of 1 watt. However, you need to modify the connection on the DB so that it takes the 6 AA not in paralel anymore, but in series. I did the mod using my DB 8AA and instead of direct driving my 5watt by 8AA batteries, I use a 2.2 ohm resistance in place of the eight battery. Again, don't forget heatsinking.
    For a light as big as DB, it is just a waste (in my opinion) to mod it to 1 watt. go 5 watt.

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    Flashaholic* FalconFX's Avatar
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    Default Re: Can I direct drive a Luxeon from 3 NiMh?

    Cs and Ds are a completely different kind of beasts alltogether compared to AA/AAAs. I don't think you'll have to worry about NiMH AAs flashbulbin' an LED off the charger; their current delivery's not that wildly out of control. But I've seen 9Ah Ds (my green China cells) fresh off the charger deliver almost 3Amps of current to an LS (Charlie's 3D-Mag was the unintentional guinea pig), and the LS literally turned a shade of blue...
    [img]/ubbthreads/images/graemlins/ooo.gif[/img]

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    Default Re: Can I direct drive a Luxeon from 3 NiMh?

    What if I used 3 2/3 AA NiMH batteries in my Inretech 2AA? Would that damage the LS?

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    Flashaholic* FalconFX's Avatar
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    Default Re: Can I direct drive a Luxeon from 3 NiMh?

    It shouldn't... The IRT should be able to handle it well. I believe somebody stuck 3N cells into an LS and it handled it quite well...

    I'm in the process of ordering a few 2/3AA NiMHs to run my BB modules...

  11. #11

    Default Re: Can I direct drive a Luxeon from 3 NiMh?

    If you are using the light for brief periods over an extended duration, you will probably get away with it. If you leave the light running for an extended period, you will probably eventually cause a breakdown. I could give numbers, but that would imply a greater warrantee than we feel reasonable. Additionally, we simply haven't tested that particular failure case.

    I expect that if you leave the light on for more than one minute an hour at high power and low NiMh resistance, you will eventually destroy your adapter. I could be wrong, I haven't tested it. Please keep in mind that I fully expect well treated InReTech adapters to be fully functional in the 22nd Century, so my ideas of eventually may exceed yours.

    Try to think of this in terms of thermal buildup. We have used some methods to increase the endurance of the AA adapter, but it is designed to operate with two standard 1.5V Alkaline batteries and we have never had a failure while operating within parameters.

    Once again, I strongly reccomend Ray-O-Vac rechargable alkaline batteries.

  12. #12
    Enlightened
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    Default Re: Can I direct drive a Luxeon from 3 NiMh?

    I made the same mistake as Slick. My light worked great with NiMh till I used batteries fresh off the charger. Instantly the light went dim. With batteries a day off the charger the current was just over 2 amps. quickly dropping to 1600 ma.
    Ted

  13. #13
    Flashaholic* FalconFX's Avatar
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    Default Re: Can I direct drive a Luxeon from 3 NiMh?

    Well, when in doubt, play it safe on batts fresh off of their cookers...

  14. #14
    Flashaholic* Ray_of_Light's Avatar
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    Default Re: Can I direct drive a Luxeon from 3 NiMh?

    LED are current driven device, and batteries are voltage source. To convert a voltage source in a current source, in is enough to put a resistor in series... as high value as possible. This theory doesn't take the "efficiency" factor into consideration... so many of us are not using limiting resistors at all. This MAY be ok, if somehow you can ensure that the Luxeon doesn't exceed tha maximum rated temperature, by using an heatsink. Just to make an example, if a Luxeon is powered with 5 W, and considering an efficiency of 60%, the other 40% of the 5 W (2 W) is dispersed as heat, by increasing the temperature of the chip.
    Now, the grade of temperature dispersion of an heatsink is measured in Celsius/W, or how many Celsius degree the surface temperature increases per watt of thermal energy dissipated. By simple arithmetics, if you do not want to exceed 60 Celsius at the junction between the Luxeon and the heatsink, and supposing the ambient temperature to be 30 Celsius, a 15 °C/W heatsink may suffice, even if a 10 °C/W is more advisable.

    To test an heatsing, stick a wire wound resistor driven to dissipate 2 Watts (i.e. 10 ohm resistor with 2 volts across it) with some thermal compound, and after one minute measure the temperature at the junction by using a thermometer.

    The absolute best way to drive the Luxeon is to use a switching power converter, like the chips built from Linear Technology, where is possible to include a diode as temperature sensor. Even a two-transistor switching power converter with current sensing (I call it "dirty" design) is OK; while proper current limiting, done with series resistor, can be rock-stable if correctly calculated. The disadvantage of passive drive is that the resulting circuit is too sensitive to the source voltage, so it may be necessary to resort to lithim disulphide battery or rechargeable alkaline. In any case, the heatsink is the most important component after the Luxeon itself.

    Hope to have been clear enough.

    Anthony

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    Flashaholic* Pellidon's Avatar
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    Default Re: Can I direct drive a Luxeon from 3 NiMh?

    [ QUOTE ]
    shipinretech said:
    Please keep in mind that I fully expect well treated InReTech adapters to be fully functional in the 22nd Century, so my ideas of eventually may exceed yours.


    [/ QUOTE ]

    That would work out to an average use of 165 mintutes per day every day for 100 years. Get busy [img]/ubbthreads/images/graemlins/grin.gif[/img] and don't lose it.

    I have two so I have to work twice as hard [img]/ubbthreads/images/graemlins/twak.gif[/img]

  16. #16
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    Default Re: Can I direct drive a Luxeon from 3 NiMh?

    I think that I will just get the rechargeable alkalines and stay away from the NiMH for my Inretech. I can get the rechargeable alkalines for less $$! [img]/ubbthreads/images/graemlins/grin.gif[/img]

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