Did anyone else notice the OP said this is for a car?
Gulp.

 

Did anyone else notice the OP said this is for a car?
Gulp.

for night riding 4x4 camping type of thing or at dunes. never never ever near a road that would be dangerous

 

Getting closer. Now change Q2 from LM350T to something like N ch FET, IRF540, 28A, 100V, TO220 pkg. Rfd is not critical as it will be operating in linear range. There are hold down clamps for some high W LED's, maybe for Cree?
I like .22Ω for R4, R5.
Also, I would measure Vf of each LED to match strings Vf as close as possible.

Like this? what for is it higher heat cap or something it was my understanding that by using the transistor and R3 to create a switching power Supply.

woudlnt this be more for using it solely with a resistor to create a regulator?

 

I'm leaning the same way. The extra components are not so expensive, and they would help spread out heat dissipation to more surface area. The OP could eliminate the balancing resistors I suggested earlier, as long as the MOSFETs can take all the heat.

Well i can do this it seems like everyone is recommending this to be the case and if i do this i would only use a .22Ohm 3W i believe resistor as well as no R4 or R5 which is fine as well... im thinking if i go this rout i may as well shoot for 4 LED's per string to require a current something around 13.2 requiring a minimum of around 13.8 i think.

the leds will run just a little dim around 11.5 so i think that will work to help keep that MOSFET from overheating so much and burn the energy as light...

what do you guys think

 

thanks for all the help you guys are giving me on this i really do appreciate this

 

thanks for all the help you guys are giving me on this i really do appreciate this

Also check pirate 4x4 where there are a couple of guys who bbuilt there own led bars ..

 

good morning everyone time to bring this back to life. i have found a boost converter complelty adjustable i am going to use and just place all my LEDS in parallel but do you think a resistor would be required between each LED?

here is something im thinking to buy http://www.ebay.com/itm/100W-DC-DC-Boost-Adjustable-Power-Converter-LED-Driver-Constant-Current-Voltage-/271455842760?pt=LH_DefaultDomain_0&hash=item3f340771c8

 

Each parallel string only cares about the current running thru it, whereas this controller only cares about the total current thru all strings. Without balancing resistors, there's a possibility that one string will hog more current, get hotter, and go into runaway. Then the next string will blow as the current per string goes up and up.

So yes, I don't see how you could do without the resistors.

BTW, the minimum output voltage of that device is 12V, so you will still need series strings.

 

Do you mean all in series? If supply is current adjustable, then no resistor is needed.

 

yes lol i meant all in series. i have purchased it to begin testing to check on reliablity and amount of hea it puts out i will have to see it might need an extra heatsink but i will remote mount it away from LED's to help keep from Heat

 

yes lol i meant all in series.

Well that changes everything! Ignore my previous post. No resistors are needed.