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Thread: Boost or Buck?

  1. #1
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    Boost or Buck?

    I just finished a light similar to what Joe Breeze built utilizing a Marwa housing and three XPG's with a bFlex driver my battery output is 14 volts. The unit works great and now I would like to try a 4 XPG setup still utilizing the same 14 volt battery.

    My question is, if I max out at 14 volts on my battery will that be close enough for a bFlex or should I consider a booster? It seems that I am on the high end for a boost driver. By my calculations, between the 4 XPG's and the bFlex I need 14 volts. How much "wiggle room" do I have with the voltage? What happens if I am off by say 1/2 volt high or low?

  2. #2
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    depends on your battery if it is a Li Ion then it will be 16.8 v of the charger and will stay in regulation for half or more of the burntime then it will go out of regulation and dim
    you will still have a useable light and get long enough for a good ride . lots use that setup .

    boost is a no go as it never will be in regulation as the battery volts will nearly always be over the VF of the 4 leds

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    I'm using this setup om a motorbike, so the voltage will be constant at 14V.

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    Go 5 XP-G and boost

  5. #5
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    Quote Originally Posted by emu26
    Go 5 XP-G and boost
    Going from 3 to 4 leds you wont see a big change. Why not get another triple and bflex. Run them both.
    DIY LED Bike Lights:
    A few Dynamo builds and some Small battery lights

  6. #6
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    Quote Originally Posted by Dave T.
    I just finished a light similar to what Joe Breeze built utilizing a Marwa housing and three XPG's with a bFlex driver my battery output is 14 volts. The unit works great and now I would like to try a 4 XPG setup still utilizing the same 14 volt battery.
    Are you using a 35mm triple optic in the Marwi housing? If you go with 4 LEDs, are you going to just switch to a 35mm quad optic in the same Marwi house?

    If so, then my opinion is it's not worth the trouble. I did some testing and measured light output with a light meter and there isn't enough increase of actual light on the ground to make it worthwhile. That's because the quad optic isn't as efficient, and light output from the quad LED board goes downs some because of increased heat. In the end, you end up using 25% more electrical power for a fairly small increase in actual light.

    As someone has already suggested, if you want more light you'd be much better off just adding another triple light. That also fixes the voltage issue as well.

  7. #7
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    I am using the 35 mm optics from Cutter. I bought their bFlex triple kit. Thanks for the input on the light output... I think I will stick with the triple setup.

    Has anyone used one of the Marwi new style housings that are the bullet shaped? I wonder if I could cram a PCB, optics and bFlex into one?

  8. #8
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    Quote Originally Posted by Dave T.
    I am using the 35 mm optics from Cutter. I bought their bFlex triple kit. Thanks for the input on the light output... I think I will stick with the triple setup.

    Has anyone used one of the Marwi new style housings that are the bullet shaped? I wonder if I could cram a PCB, optics and bFlex into one?
    Now that you mention it, yes. Have a thread here on those: Another first semi-build

    The second one with the aspheric high beam lenses with it here: Road Beam Experiment

    There is another, here too.
    Home Made Bike Light Database Post 24


    The low beam was to use Lisa2 10 mm which were 6.5 mm on top of the 2mm thick 10 mm MCPCB XP-G R5's. The LISA2 was a no go so Plan B: the three Carclo 10417's which are 7 mm. Use square 10 mm if you go the 10417 route, I wouldn't, the 35 mm triple narrow would be better. I got there by default not intent.

    The high beam has a smaller lighter more deeply mounted heat sink (helmet mounted) and I was able to fit 15 mm of lens barrel and lens between the lexan cover and the heat sink 'firewall'.

    You likely need more room. No problem. There is another 1-1.5 mm if you don't mind the bezel not being close to the bottom of the threads. But if you use a simple aluminum plug heatsink instead of a pipe cap, more is available. The inside of the body front to back is 1" (25.4 mm) of cylinder followed by 3/4" (22 mm) of cone. So if you used a 5 mm thick aluminum firewall/slug/plug (thickness as recommended by Troutie for good thermal path), it would leave 20 mm to the front for MCPCB and lens, if it was made the ID of the cylindrical part and jammed against the conical part. The Bflex fits nicely on the backside there. Just make sure to use the small guage wire recommended for the Bflex hookup to aid in closing it up in there.

    I used a light pipe from a PC for the status LED, with the pipes tip coming out at the apex of the slide-in plastic back and I used a plastic a prop glued on the front end. A piece of plexiglass rod with a small diameter tip, would do, it you don't have a scrapped PC with one. The momentary switch from the Bflex glued on top of it, and a little trimming of the inside actuating knob of the button cover, and all was well. If I was doing it again, I'd solder the leads to the switch before mounting it. I tried PC slide on clips and they worked but were too fiddly

    I used copper heatsinks that you can see in this thread :http://www.candlepowerforums.com/vb/...70postcount=27

    Hope that helps, EL34 has some he'd like to see being used.

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