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Best setup for blue shark, dual MC-E, 11.1v li-ion battery


Newly Enlightened
Aug 4, 2008
I have 11.1v cells, rated max charge of 12.6v down to 9v cutoff. I want to run a dual MC-E setup. The LEDs that I ordered are supposed to be wired in series. I original plan was to run the two LEDs in parallel, letting them get around 500mah across each. I don't see any issues with this for this if I run the driver at the full 1000mah. I might run into problems in lower current situations when the Vf of the LEDs drop, then I might get some overlap and end up with DD. Maybe I can live with this, still waiting for parts so I have some time.

Would I be better off running the two LEDs in series, giving me a Vf of 27.2v at 700mah? I probably will have the max current cutoff to around 500mah, so I might be closer to 26.4v. These are all based on the spec sheet "typical values" so I don't know what it will really be. Cree says the Vf can be as high as 3.9v for 350mah, so if that's true, I'd be at 31.2v Vf for 350mah. What worries be about this setup is when the battery is lower, I'm got a Vin around 9v and Vout might be near 27.2v. With about 80% efficiency, I think my current is (27.2v*700mah)/(.80*9) = 2644mah. I guess that's fine.

Which setup is better for my driver in terms of efficiency, which I assume is also tied to thermal issues. Thanks.

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