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Thread: Never tell a flashaholic "it's too dim"

  1. #1
    Flashaholic
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    Default Never tell a flashaholic "it's too dim"

    My Olight H2R arrived in the mail today, only 4 business days after placing the order on-line - yay, Post Office! Yay, Canadian stock! I was specifically told by the better half not to wear it to the family dinner tonight. OK, but I have many pockets in the cargo pants and so it came with me anyway.

    My niece was impressed at my new gadget, though she thought over a hundred dollars (Canadian) was a lot to pay for it. I said "But look how bright it is!" and put it on...moonlight mode. She said "That's not very bright." Oh, you may regret that. With a double click, I went to full 2200 lumens (toward the table top, not in her face). She was impressed, and said "Why doe anyone need a flashlight that bright?" Noone needs a flashlight that bright, they are just fun to have.

    Regrettably, the power stayed on in the restaurant the whole evening, even though I was prepared to light the place for hours if necessary.


    The family is gradually learning that if I had them a black anodized aluminum tube, that they should not look into the lens and click the button.

    Quite enjoying the H2R, was using it on the workbench already this afternoon to look deep into the battery compartment of a walkie-talkie. My much loved HP11 will stay on workbench duty.

    Oh good, it's getting dark....time to compare it to the car headlamps.

    Bill
    Last edited by Kitchen Panda; 08-11-2019 at 01:35 PM. Reason: Wrong brand name, sorry!

  2. #2
    *Flashaholic* PhotonWrangler's Avatar
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    Default Re: Never tell a flashaholic "it's too dim"

    Quote Originally Posted by Kitchen Panda View Post
    Regrettably, the power stayed on in the restaurant the whole evening...
    Yep, that's the definition of a flashaholic!

  3. #3

    Default Re: Never tell a flashaholic "it's too dim"

    Did you mean an Olight H2R?
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  4. #4
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    Default Re: Never tell a flashaholic "it's too dim"

    Quote Originally Posted by parametrek View Post
    Did you mean an Olight H2R?
    Indeed I did ! Fixed my original posting.

    Today I dropped my Olight H2R into a glass of water and let it run on "turbo". It kept going for 37 minutes with no step down, near as I could tell with my light meter. It then shut off. I'd measured the tailcap drain as about 4.5 amps on "turbo" so this indicated that the test run took about 2800 mA-hr out of the battery, which is rated at 3000. The headlamp still ran on low and medium mode, so there was some capacity left (blinked to warn of low battery).

    The 240 grams glass of water warmed up from 19.3 C to 38 C in 37 1/2 minutes - so it picked up at least 8 watts of heat. 4.5 amps x 4.2 volts is 18.9 watts, so 8 watts of losses leaves over 10 watts for the beam, checks out! (White light is about 200 lumens per watt...and some of the light got trapped in the water, too.)

    My calorimetry setup is strictly kitchen table but I was entertained with the results. Looking forward to a test run outdoors, when our natural climate will go a long way toward keeping the LED cool.

    The Budget Department was very amused, saying "You put your brand new $100 flashlight into a glass of water?". I said that if it couldn't survive a half-hour dunk in the water, it wasn't worth $100!

    Bill

    I

  5. #5
    Flashaholic* Slumber Pass's Avatar
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    Default Re: Never tell a flashaholic "it's too dim"

    So the water didn't boil?!?! I was hoping I could brew some coffee with mine in a pinch.

  6. #6
    Flashaholic* LeanBurn's Avatar
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    Default Re: Never tell a flashaholic "it's too dim"

    For me when showing a light I usually turn it on low, then they say "well that is not very bright" then I put it on moonlight/firefly mode and really show them what dim is...and am always dang proud of it.


    ...then finally almost in passing....I show them the high mode for just a brief second, and then put the light away.


    Moonlight/firefly mode is where its at!
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  7. #7

    Default Re: Never tell a flashaholic "it's too dim"

    Thermal losses should be a little higher than that. White LEDs are only like 30% efficient so the majority of the energy should go into heating the water.

    Was the glass covered? At 38C there is probably substantial evaporative cooling.
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  8. #8
    Administrator Kestrel's Avatar
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    Default Re: Never tell a flashaholic "it's too dim"

    Now I really want to brew a small cup of tea using my BOSS, lol. I know it won't be piping hot; IIRC the thermal cutoff on the PCB for initiating step-down is 65C, so that provides a /theoretical/ upper limit (which of course cannot be obtained either). But it will at least be an interesting experiment ...

  9. #9
    Flashaholic
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    Default Re: Never tell a flashaholic "it's too dim"

    Quote Originally Posted by parametrek View Post
    Thermal losses should be a little higher than that. White LEDs are only like 30% efficient so the majority of the energy should go into heating the water.

    Was the glass covered? At 38C there is probably substantial evaporative cooling.

    My setup wasn't even as good as a kitchen table setup could be. I didn't attempt to control evaporation and probably should have at least used a foam cup with a lid to keep the heat in. Measuring the temperature of the water and mass of water was really a lark, my main purpose was to see how the run time would be with adequate cooling.

    I thought the efficiency of an LED is a bit higher than 30% - Cree claims 149 lumens/watt out of the XHP-50, and there's only about 200-300 lumens in a watt of white light (depending on how you define "white"), so the LED has to be well over 50% - a little less with a driver circuit.

    And no, I don't think you can boil water this way...the H2R cuts back at round 55 C, and water won't boil that low even in Denver.

    Bill
    Last edited by Kitchen Panda; 08-14-2019 at 01:00 PM.

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