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Does anyone know which battery i must use. I have bought a bflex driver and 2 (series) cree XR E R2's. I want to use a li-ion battery pack of 7.4V or a 11.1V pack. My problem is as follows: Because there is @ 1000mA a voltage of 2 * 3.7V over the leds = 7.4V I think i have not enough voltage left for the driver. Therefore i think the full power mode (1000mA) wil not last for a long time.

On the other hand, when i take a 11.1V pack, the bflex wil not power down my lamp in time (the li-ion protection of the bflex is at a higher level of the li-ion cell pack) Is the efficiency at this voltage the same then when using a 7.4V pack?

I don't know what to do.

thanks
 

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Not familiar with the Bflex driver.

I run a dual - in series R2 setup with a 1000 ma Buckpuck. My battery is 11.1 Li-Ion. I get nearly 3 hrs of run time on that setup in the high setting. Very rugged little driver and idiot proof.
 

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Bandolero
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R T F M on bFlex

Josken said:
On the other hand, when i take a 11.1V pack, the bflex wil not power down my lamp in time (the li-ion protection of the bflex is at a higher level of the li-ion cell pack) Is the efficiency at this voltage the same then when using a 7.4V pack?
The bFlex's cut off voltage is configurable to any value between 0v-25v. The default is 12v.

See section 8.6 of the manual on how to set it.
 

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aka RossC
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Josken said:
Because there is @ 1000mA a voltage of 2 * 3.7V over the leds = 7.4V I think i have not enough voltage left for the driver.
My R2's from cutter have a Vf of 3.2V at 1000mA. It seems to be the consensus that the newer R2's have a lower Vf than Q5's etc.

On the other hand, when i take a 11.1V pack, the bflex wil not power down my lamp in time (the li-ion protection of the bflex is at a higher level of the li-ion cell pack)
I don't quite follow what you are asking here? The Bflex will ship with a low voltage shut off set to 13 V however it is user configurable so you can set the low voltage shut off to whatever you would like.

Your Li-ion packs should also have low voltage protection and that is what I use to prevent over discharge on my packs.

Is the efficiency at this voltage the same then when using a 7.4V pack?
The efficiency will still be pretty good. With a 7.4V pack, you won't have enough overhead for the driver so that option isn't really viable.

The other thing to consider when you are buying batteries is what future projects you think you might undertake.. If you like buck drivers then you will find that an 11.1v pack with a triple LED light gets you back to the same problem of insufficient overhead voltage for the driver (and then you start wishing you had bought an 14.4 v pack - until you start thinking about quad LED designs :D )
 

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Was just looking at that photo yetibetty and originally thought 'what did you do to get your hope light to look like that!?' but then realised its not quite like a hope light.

I then looked and saw your thread showing the hope clone and I must say its very nice work. How did you make it?
 

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aka RossC
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yetibetty said:
Thanks kangaroomadman, I will be doing another soon and will do pics to show how it's done.
I think that is the fist light of yours that I have come across Betty. It looks really professional :thumbsup: I wouldn't have known it was a DIY at first glance! (salty heads off move his lights to the fugly thread :( )
 
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