I want to try driving 4 q5's in series at 1200ma or even 1400ma, don't worry major heat sinking....
What's my best option for battery voltage and driver or drivers?
I know KD do a 2.8 driver, i could wire 2 of them with 2 parllel led of each.
Also already know dx do the 1400ma board but that would mean using 4 of them and they have been back ordered for months.
Are there other options?
There certainly are options, lots of them
If possible you want to keep them all in series, not a parallel design so that each emitter will be driven at the same current level.
Buck circuits are more efficient than boost circuits when well designed.
4 q5's at 1400mA would probably need somewhere between 14.4~15.6 volts to achieve what you want. One option for that would be the Shark Buck from the sandwich shoppe. I believe you could order the 2A version and adjust the trimpot down to get your 1.4A. If not, it might require changing the sense resistors, but between 2 of them you should be able to get most any combination you want. There is going to be a certain amount of drop out voltage with the shark buck, I am afraid I don't know exactly how much. So, I am going to guess your batter voltage should be a minimum of 1 volt higher than needed for your leds, probably more would be better. Max input is 24V recomended for that particular driver. I don't know how much space you have to work with or what battery chemistry your prefer, but one possibility is 5 lithium cells.
There may be other buck circuits to meet your needs, dunno.
Next efficient would probably be a quality CC boost circuit again from either the sandwich shoppe, or task led. IE the shark, blue shark, maxflex, etc. Check there websites for specs. For a boost circuit, your battery voltage will be lower than led voltage, so you can get away with a smaller pack. But, the closer the bat voltage is, the less work the driver will have to do. So, better efficiency and more reliable. Taskled for one has a formula to figure safe input current. As I recall it is something like 3A max, and much over 2A you need to heatsink the driver.
Then it would be possible to parallel the leds and run each one from its own seperate driver, perhaps allowing cheaper drivers to be used, but you would need 4, which would add to the cost, and perhaps a loss of efficiency and reliability.
Other than that, there are linear regulators, IE amc7135. They have a max voltage input that is below what you will need. But, there is a thread here by download called poormans multi emitter or something like that. It addresses using the linear regulator at higher voltages. A good read.
Next would probably be direct drive from the battery pack with a current limiting resistor. Series would be better, but parallel could be done with a seperate resistor for each emitter. Least efficient probably and output will dim. But, with lithiums it would be less apparent than with other chemistries.
If you haven't already, check the download's thread, the driver sticky, taskled.com and the sandwich shoppe.
I am sure others can point out options I have missed, but this should get you pointed in the right direction at least.
