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  1. #1
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    Calculating lumens

    Hi gang,

    Could someone help me out with calculating lumen output. I know there's a formula for it but I can't remember where I've seen it

    I'm trying to work out the output from 3 MCEs, M bin, WH tint, on 20mm individual addressable stars wired 2S2P run in series by a maxFlex3 @ 1000ma
    14.8V 5400ma battery.

    Cheers, Steve

  2. #2
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    http://www.cree.com/products/pdf/XLampMC-E.pdf

    M bin, minimum flux @ 350ma = 430lumens
    @500ma approx 1.35 x 430 = 580
    less 15%ish optic losses, so around 500 each
    ...Scun.thorpe, UK

  3. #3
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    Quote Originally Posted by HEY HEY ITS HENDO
    http://www.cree.com/products/pdf/XLampMC-E.pdf

    M bin, minimum flux @ 350ma = 430lumens
    @500ma approx 1.35 x 430 = 580
    less 15%ish optic losses, so around 500 each
    To add on to Hendo's fine calculations...

    For those wanting to do some maths:

    WARNING - EXTENSIVE USE OF "NOMINAL" VALUES FOLLOWS - Do your own bloody calculations if you want to factor in 'exact' forward voltages, variable voltages dependent on current rates, 'actual' battery voltage after charging, electrical efficiency losses, etc.

    Deesta's Maxflex @ 1000 mA will have it's current flow 'split' into 2 parallel pathways due to the 2S2P wiring configuration for each star, therefore each path will 'see' 500 mA as stated by Hendo above (wired in parallel divides current).

    Presuming a 'nominal' forward voltage of 3.5 V for each die, there will be a 'total' forward voltage of 7.0 V due to the 2S2P wiring configuration for each star (wired in series multiplies voltage).

    However, each star is then wired series with each other (3 stars total)... so the sum total forward voltage for all three stars wired together will be 3 x 7 V = 21 V.

    Then the battery... nominal voltage of the pack is 14.8V with 5400 mAh (milliamp hours). So 14.8 V x 5400 mAh = 80 Wh (watt hours).

    Then light 'power' consumption... 21 V x 1 A = 21 W

    Then run time... battery 'capacity' / power consumed = 80 Wh / 21 W = 3.8 hours runtime at full power.

    Factor in 9% Maxflex losses, but counter with higher than stated (fully charged) battery voltage, extrapolated with decreasing battery capacity due to aging, counter balanced with intermittent use of dimming... and actual runtimes will be between 3.5 to 6 or so hours.

    YMMV

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    pct.cree.com

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