I NEED HELP!!! 14.8 V LiPo, but what LED's- Mtbr.com
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  1. #1

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    I NEED HELP!!! 14.8 V LiPo, but what LED's

    ok I was planning on running 4 X cree XR-E R2 at 1000ma from a bflex buck driver but i have been told that this wont be possible as the foward voltage is to close to the input voltage,



    So i neeeeed help,

    If you were to make a dive light (narrow beam less then 10 deg) from a 14.8V Lipo battery what LED configuration would you use?



    Maximum external diamater of the optics 50mm preferable less (somethis like 40mm would be nice



    Run time would have to be atleast 2 hours but preferable more



    I open to suggestions, please help me



    thanks in advance,

    Bradley

  2. #2
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    fully charged your battery pack will be in excess of 16v, ...
    the forward voltage of 4 X cree XR-E R2 will be in the region of 12.8 > 14v
    i have been using this combo for a year, no problems!
    .....
    you would be hard pushed to beat a narrow MR11 35mm quad optic
    or they do the same in a triple

    .........................http://www.cutter.com.au/proddetail.php?prod=cut781
    ...Scun.thorpe, UK

  3. #3

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    I thought the foward voltage of one R2 is 3.7 V which would bean that 4 X R2 would be 14.8v????

    I know LiPo's are generally higher voltage when fully charged but what about when the voltage drop's how does your light fair then?

    I would love to see some pic's and possible beam shots of your 4 X r2 if you wouldn't mind,
    and are you using the cutter quad optic? if so how tight is it really?

    Cheers,
    Bradley

  4. #4
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    Quote Originally Posted by frozenwarp
    I thought the foward voltage of one R2 is 3.7 V which would bean that 4 X R2 would be 14.8v????

    I know LiPo's are generally higher voltage when fully charged but what about when the voltage drop's how does your light fair then?

    I would love to see some pic's and possible beam shots of your 4 X r2 if you wouldn't mind,
    and are you using the cutter quad optic? if so how tight is it really?

    Cheers,
    Bradley
    R2s are now 3.2-3.3V at 1A (much lower than when first released).

    Personally when night diving I like only a small amount of light, but I usually dive in the tropics with 30m viz

  5. #5

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    I completely agree about less light, and will prob use my back-up lights for most of my ocean dives but this can light is going to primarily for when im cave diving, maybe the ocasional deep wreck.
    I Def need a fairly good hotspot mainly for comunication purposes

    cheers for the help guys, looks like i may be able to do my 4 X R2's with bflex like i origanaly planned.

    thanks,
    Brad

  6. #6
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    i`ts the cutter medium quad optic
    in the background is a double triple narrow i never finished
    beam/ spread is really outstanding!
    she aint pretty but very functional
    and it aint no dive light lol
    troutie has some beam shots of the cutter quad somewhere .....





    ...Scun.thorpe, UK

  7. #7
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    Quote Originally Posted by znomit
    R2s are now 3.2-3.3V at 1A (much lower than when first released).
    I wish mine were that low, I got a quad R2 WH board from Cutter and the total vf is 14.8v at 1A (drops to 14.4v when hot) and I only received them in March, I waited 'til well into the new year before ordering in the hope of getting the lower vf.

    From what I had read I was expecting them to be lower so I had a 14.8v Li-Ion ready.

    I now use an 18.5v Li-Ion with a bFlex.

    Point being.....you won't know untill you get them.

    Edit found my beem shots. Medium optic, crap camera
    Attached Images Attached Images
    Last edited by yetibetty; 04-18-2009 at 07:37 PM.

  8. #8
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    From what I had read I was expecting them to be lower so I had a 14.8v Li-Ion ready.

    .............. this is not the charged voltage of 4s pack
    i don`t know where it originated ie 3.6v per cell, but
    1 cell is 4.2v charged my 4s pack is usually 16.5v after 10 minutes off the charger
    so 5 cell will be 5 x
    my 6s cell is just under 25v
    Last edited by HEY HEY ITS HENDO; 04-18-2009 at 07:28 PM.
    ...Scun.thorpe, UK

  9. #9
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    Quote Originally Posted by HEY HEY ITS HENDO
    From what I had read I was expecting them to be lower so I had a 14.8v Li-Ion ready.

    .............. this is not the charged voltage of 4s pack
    That's correct...they run from 16.8v down to 12v but with my higher LED vf I would only get full power from 16.8v to around 15.2v (allowing a bit for the bFlex) then just dimming for the rest/most of the ride.

    The 18.5v battery runs from 21v down to 15v so full power for whole of the battery discharge.

  10. #10
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    yes a valid point yb
    i have 8 cells 4s2p so voltage drop/sag is very very slow
    i agree, as you say 5s cell is better voltage (but shorter rut time than 4s2p/8cell)
    the other problem is general availability of 5 or 6 cell chargers...
    frustrating sometimes innit!
    ...Scun.thorpe, UK

  11. #11
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    frustrating sometimes innit!
    __________________
    Yep it can be.
    So I now use a balance charger and make my own Li-Ion packs with balance plugs on for charging, no PCB just use the bFlex for overdischarge protection.

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