Need some advise please...serious newb here.

OK so I have been reading every thread that I can think of before I attempt my first bike light. I am going to be building this light
http://myfwyc.org/Timberlake/CreeLEDLight
I will be using 3 Cree XP-G R5's...that's about all I am sure of. I was looking at the Maxflex5a but I am not 100% if this is what I should be using. I like the features that it offers...dimming, strobe and so on but as far as the technical jargon I am not sure if it's the optimal driver to use. Then there is batteries this is where I get even more lost. How the heck do I figure out how much power I need to get the max output from my Cree's

ANY help would be greatly appreciated!

Thank you

Kroz

Being a boost driver the battery voltage input to the maxflex must be less than the output voltage to the leds. So lets say you run your XPG's in series, then the typical forward voltage at 1000mA would be 3 x 3.3v= 9.9volts, that means that a 2 cell 7.4 volt li-ion or lipo pack would be the most efficient if you choose these packs. From memory a 2 cell lipo and li-ion fully charge puts out around 8.4 volts, 4.2v per cell.

One thing to remember however is that the boost drivers generate heat to lift the voltage up to match the led's requirement. As you use lower battery voltages the boost driver will generate more heat and therefore be less efficient but will also require better heat sinking to dissipate the heat. Running you battery voltage as close the the combined forward voltage of the led's is the most efficient.

Your other option is to go for a buck driver like the BFlex or Buckpuck. In your case you would use a 4 cell 14.8 volt battery pack. I know that my triple XPG run off a 14.8v 2200mA battery pack gets around 3 hours minimum of run time at 700mA. The run time would be less if you ran them at 1000mA but i could not tell you buy how much. I run my leds at 700mA as although 1000mA is brighter I can barely tell and would rather have less heat and longer run times running at 700mA.

Just remember to use protected lipo or li-ion cells as they can explode if overcharged of discharged. Rare but does happen.

Hope this helps a bit

brad72 said:

Being a boost driver the battery voltage input to the maxflex must be less than the output voltage to the leds. So lets say you run your XPG's in series, then the typical forward voltage at 1000mA would be 3 x 3.3v= 9.9volts, that means that a 2 cell 7.4 volt li-ion or lipo pack would be the most efficient if you choose these packs. From memory a 2 cell lipo and li-ion fully charge puts out around 8.4 volts, 4.2v per cell.

One thing to remember however is that the boost drivers generate heat to lift the voltage up to match the led's requirement. As you use lower battery voltages the boost driver will generate more heat and therefore be less efficient but will also require better heat sinking to dissipate the heat. Running you battery voltage as close the the combined forward voltage of the led's is the most efficient.

Your other option is to go for a buck driver like the BFlex or Buckpuck. In your case you would use a 4 cell 14.8 volt battery pack. I know that my triple XPG run off a 14.8v 2200mA battery pack gets around 3 hours of run time at 700mA. The run time would be less if you ran them at 1000mA but i could not tell you buy how much. I run my leds at 700mA as although 1000mA is brighter I can barely tell and would rather have less heat and longer run times running at 700mA.

Just remember to use protected lipo or li-ion cells as they can explode if overcharged of discharged. Rare but does happen.

Hope this helps a bit

Click to expand...

This helps me out allot. Thank you very much :thumbsup: