How would you build this project?

[ratkins]

As a Burning Man project, I want to build an ah-beng/bogan/chav/redneck/ricer-style underlight for my bicycle. Because, well, it'd be funny. Do I need a better reason?

I have acquired a couple of these really ******* bright blue LED bars from DealExtreme. My question is how best to drive them. They're 600mA/12.5V/8W each and I'll want to run them from 4-6 hours on a charge and I'm fine with the battery being stupidly expensive.

What I do want is constant brightness over the life of a charge. I got some of these constant current drivers also from DX, but then realised I'd need a > 25V battery to run both 12.5V LED bars off one driver in series. I don't think I want to do that.

So which buck/boost regulator and battery combination would you use, given these requirements?

[Update: searching for replies to this post I realised I made almost the exact same one about a year ago. Sorry for the repeat, but maybe the state of the art has changed since then ]

Cheers, Robert.

 

[somename]

Looks like you already found a driver that will handle 1 light bar. So why not use one driver for each light bar so you don't need more voltage to drive them in series. I would think buying 2 drivers (~$2.50 each) would not be out of the question when you are already considering that very expensive $140 battery.
Plus when you get them in place, then you would have the option to dim/brighten the light bars individually if needed.

 

[ratkins]

I didn't want to run two different drivers because I thougt it wouldn't be so efficient, but the impression I get is two small buck drivers are at least as good as one big boost driver (even if I could find a boost driver which would do 12Vin—>25Vout.)

I need to beg borrow or steal a variable constant current bench supply so I can just see how bright these are individually and I might end up making two separate enclosures.

Cheers, Robert.

 

[emu26]

I agree with somename, two drivers with their own controllers.
Lots more options for you that way. Also gives you the option to just run one light with a smaller capacity battery if you wanted to for weight reasons