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  • For the Price, It's Good

    posted by Rusdy on 06/04/2011
    0 0

    Involvement:General (knows how to use it) - Ownership:1 day to 1 week

    Pros:

    - Very bright, as I expected (further comments on lumens output on 'Other Thoughts')

    - Build quality is OK, O-Ring seals throughout

    - 2 batteries means longer life. This is useful for me. I originally intend to use this for cycling in dark winter mornings. This intention is still true IF I manage to upgrade the heatsink considerably ("IF" -> because proven to be elusive effort by me so far). More on this by lots of other people in forum below.

    Cons:

    - 'High mode' only works for 5 minutes on room temperature, then the flashlight dims. My guess, the internal driver heat protection kicks in due to insufficient heatsink (lots of this under forum discussion). 10W is a lot of heat!

    - Sharp edges and 'metal dust' here and there, but this is no prob for me

    OtherThoughts:

    On lumens output:

    I don't have lumens meter, so I measure the LED voltage and check CREE datasheet for the corresponding current, and lumens output.

    I used Digital Multimeter and no oscilloscope, so yes, you can doubt the results. There may be voltage ripples and other thingamajig that skew the actual figure.

    The measurement shows 3.17V accross LED on 'High Mode'. This steadily drops due to heat build up (pretty fast too!). On CREE datasheet, this corresponds to around 2A -> 250% relative luminous flux -> 250% x 280 lumens (T6) -> 700 lumens.

    I'm a bit dissappointed, but that still good! Beside, if this thing goes to 3A, I'm not sure what happen to the driver and LED in unmodified heat sink!

    In term of efficiency (High Mode):

    I measured current consumption of 1.84A @ 6.9V. This means 12.7W consumed by driver + LED. As per above, LED alone is 3.17V (which corresponds to 2A says datasheet), or 6.3W output.

    I hope there was a flaw on my measurement method. 50% is definitely too low for any type of buck driver, this driver should have more efficiency than that, shouldn't it?

    On heat management:

    Poor, very poor at the moment. But, easily fixed by (my personal opinion):

    - Manufacturer, PLEASE supply alumunium disc (5mm thick, doughnut shape) -> act as a heat bridge between the flashlight insert to the outer shell. The outer shell itself is a good heatsink, why not use?

    - Alumunium foil (suggested by user JHM64). I'm still toiling at this at the moment, no success for me so far :'(. I think it's just me being lazy to roll alumunium foil properly -> flashlight insert super-hot, foil just warm.

    Bottomline:

    - Good BRIGHT flashlight for it's price

    - Poor heat management (only can use High mode for 5 minutes)

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