4 x XP-E with a fatman driver?- Mtbr.com
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  1. #1
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    4 x XP-E with a fatman driver?

    Hi Team,

    I've recently found some more time to spend on the bike but needed some better light to ride with so I wanted to make a 4 x XP-E light using a fatman driver run at 700-800mA using a 7.2V 3000mA radio control battery, probably with a mix of narrow and medium optics. (setup as a 2x2 Achesalot type thing)

    Is this possible? is it a good way to do it? will heat be an issue?

    and I'm sure I'm wrong but will that give me 800-900 lumen and a bit more than 4 hours on full beam. and if anyone feels like pointing me in the right direction - I dont understand the boost driver principles.. please explain

    thanks heaps

    Mike

  2. #2
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    Quote Originally Posted by Mickey Blue
    Hi Team,

    I've recently found some more time to spend on the bike but needed some better light to ride with so I wanted to make a 4 x XP-E light using a fatman driver run at 700-800mA using a 7.2V 3000mA radio control battery, probably with a mix of narrow and medium optics. (setup as a 2x2 Achesalot type thing)

    Is this possible? is it a good way to do it? will heat be an issue?

    and I'm sure I'm wrong but will that give me 800-900 lumen and a bit more than 4 hours on full beam. and if anyone feels like pointing me in the right direction - I dont understand the boost driver principles.. please explain

    thanks heaps

    Mike
    Yes a fatman and 4 XPEs will work just fine though I have never used a fatman as I prefer the Maxflex.

    heat issues will be addressed in your housing design and if I may make a suggestion design in extra heatsinking properties so you can upgrade to the more powerfull Xpgs and run them @1000ma if you wanted to later.

    quite simply as I am not electronically savvy
    the boost driver takes the lower battery voltage and lifts it to suit the higher voltage required for your 4 leds , its magic

  3. #3
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    I use exactly that Fatman with 4 XRE's or XPE's with 7.2V Lion Pack.
    In fact rode last night well over 2 hours at 900mA with 5200mA pack.
    Fatman Rules!

  4. #4
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    so what are the difference between the maxflex and fatman - maxflex is $20 dearer, can handle more, can be heat sinked, has a UI / menu system, what else?

    and if I wanted to use the fatman to get a high / low setting at say 800ma and 350ma (or less) how would I go about that?

    and thanks for the replies guys

    mike

  5. #5
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    Hi Mickey Blue

    The Maxflex is totally programmable from output current, temp and battery voltage alarms it has to be the ultimate in drivers. It takes a bit of time to learn how to program it but once done you never need to touch it again. The new Maxflex 4 is bullet proof from reverse polarity protection to open circuit truly amazing,

    The Fatman has a potentiometer on it to adjust the current output but one can easily add a switch across this to provide two level dimming which is what I normally do. So when you are stopped whilst repairing a tube or some such a quick flick of the switch lowers the brightness so as to save battery life or not blinding people.

    Both of the drivers should be heat sinked and this is easily done on the Maxflex as it has a solder pad to attach say a piece of copper, the Fatman needs Arctic Alumina epoxy to attach it to a heatsink.

    I see you have a 7.2 volt 3000mA battery and want to run for 3 hours unfortunately the current drawn by either of the drivers to drive your 4 XPE's would mean you will get less than an hour with your battery. This is because being boost drivers they convert your 7.2V into 16 volts to drive your LED's and even though it is fairly efficient at doing this say 85% you have a loss right there. Secondly some of the components generate heat which again is lost energy so unless you can get another battery and paralell it together to provide 6000mA you should get 2 hours continuous use.

    Hope this helps.

  6. #6

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    Quote Originally Posted by Mickey Blue
    Hi Team,

    I've recently found some more time to spend on the bike but needed some better light to ride with so I wanted to make a 4 x XP-E light using a fatman driver run at 700-800mA using a 7.2V 3000mA radio control battery, probably with a mix of narrow and medium optics. (setup as a 2x2 Achesalot type thing)

    Is this possible? is it a good way to do it? will heat be an issue?

    and I'm sure I'm wrong but will that give me 800-900 lumen and a bit more than 4 hours on full beam. and if anyone feels like pointing me in the right direction - I dont understand the boost driver principles.. please explain

    thanks heaps

    Mike
    Hi, Run time calculation follows - I'll assume 700 mA led current,all leds in series.

    At 700 mA, the forward voltage of each led is 3.5V - see led specs - so the total led voltage is 3.5x4 = 14V.

    Recall that power in Watts is given by Voltage x Current, so power required to run the leds is 14 x 0.7 = 9.8 Watts.

    As the converter efficiency will be around 85%, the input power to the converter, which is the power drawn from the battery, will be 9.8/0.85 = 11.5 Watts.

    The current drawn from the battery will be 11.5/7.2 = 1.6 Amps. Check, 7.2 x 1.6 = 11.5W

    Assuming the battery delivers it's rated capacity of 3.0 amp-hrs, the run time will be 3.0/1.6 = 1.9 hours.

    Not so difficult.

  7. #7
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    thanks all, my creative juices are simmering away nicely --
    maybe one more question: if I am to use 1 inch square alu tube with a maxflex and run the whole thing really hot (4 leds at 1000mA) should I use arctic alumina to hold it all together, so it resembles a solid piece of alu like the sexy new troutlight?

  8. #8
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    Quote Originally Posted by Mickey Blue
    thanks all, my creative juices are simmering away nicely --
    maybe one more question: if I am to use 1 inch square alu tube with a maxflex and run the whole thing really hot (4 leds at 1000mA) should I use arctic alumina to hold it all together, so it resembles a solid piece of alu like the sexy new troutlight?
    Thanks Mickey there is an even sexier one out soon for the XPGs 4 or 6

    would not run at 1000ma - use the rated 700 ma unless your casing is very well heat capable the XPE does get hot fast and 4 needs a good housing design

    I dont think AA epoxy is strong enough for structural stuff probably better to use paste and bolts if possible
    can you put up some pics of your design ( so we can steal it ) and folks can say if they think it will handle the heat.

  9. #9
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    troutie-mtb -- can you put up some pics of your design ( so we can steal it ) and folks can say if they think it will handle the heat.
    so forgive my cardboard mockup and digital alterings, but basically a 25mm aluminium square tube with a section of tube on the front for the 4 leds. the back section (25 x 25 x 25mm) needs to house the maxflex, mom switch and power input. the switch can go on the top or back depending where it fits. each side is then covered with a sheet of aluminium with some grooves for extra surface area. im thinking to put it on a bar mount of some description.

    hows this eh?? its way smaller than i expected!! fingers crossed its workable
    Attached Images Attached Images

  10. #10
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    thoughts anyone?

  11. #11
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    Hi Mickey, Great origami/computer skills to show your clean design!

    I would say that a bit more surface area will be required as I think that here or on CPF I read that you need about 1sq inch per watt minimum, or just ride flat out all the time to keep the air flowing!!!

    Stay cool, Mr Bump

  12. #12
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    Looks Familiar

    Quote Originally Posted by Mickey Blue
    thoughts anyone?
    I think odtexas makes/made something very similar.
    Slow-core. -.. .-. .. -. -.- .... --- -- . -... .-. . .--

  13. #13
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    A few of us here have used the 1 inch square tube. Achesalot comes to mind...........
    Here is a thread by .40AET.
    More information on my lights can be found by doing a search for threads started by me or you can dig through the DIY Light Database at the top of the page.

  14. #14
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    ahhh I guess my searching methods need updating, that thread answers heaps!!

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