Looking around, for the ultra-bright one, it probably makes more sense to use one like this. I could get just one heat sink and it would be a LOT less soldering. I would just operate it at a lower power, and maybe have the ability to operate it at full power for a brief moment.
https://www.amazon.com/Chanzon-6000K-6500K-Intensity-Components-Lighting/dp/B01DBZIE4E/ref=sr_1_8?s=industrial&ie=UTF8&qid=1535652271&sr=1-8&keywords=circular+heat+sink&th=1#customerReviews

A large heat sink will still be required if you only intend use it at 4 watts. 4 watts is still 4 watts.

Also, did you notice that it needs at least 34 volts to operate?

 

That 100 watt one looks good for your high power color flashlight. Note that if you scroll down on the ad they recommend a fan driven heat sink for it which I defiantly recommend--not necessarily that one, but one like it.

 

"The so-called specifications are nonsensical. For one thing, it is *not* really a heat sink. It is a heat spreader intended to be mounted to a heat sink. There is absolutely no way this small surface can dissipate several watts. Again, physics gets in the way."
So it's a waste of money?

 

A large heat sink will still be required if you only intend use it at 4 watts. 4 watts is still 4 watts.

Also, did you notice that it needs at least 34 volts to operate?

I know. I'll use a microcontroller-controlled constant current boost converter to get that from a 4-6s lithium battery. Also, I would like to have adjustable focus so it can be really focused on one spot or dispersed. I have a flashlight that does that well, and it is very useful. What kind of lens would I need to do that? And would the three colors blend well enough that I could get decent white light without a diffuser?

So if I needed it to be very, very bright for a few minutes, and operated it at close to 100W, would a heatsink with fan like this suffice? I don't want to waste power on a fan if I don't have to, so I may try to use a thermocouple to see if it's necessary at different power consumptions.

 

I know. I'll use a microcontroller-controlled constant current boost converter to get that from a 4-6s lithium battery. Also, I would like to have adjustable focus so it can be really focused on one spot or dispersed. I have a flashlight that does that well, and it is very useful. What kind of lens would I need to do that? And would the three colors blend well enough that I could get decent white light without a diffuser?

So if I needed it to be very, very bright for a few minutes, and operated it at close to 100W, would a heatsink with fan like this suffice? I don't want to waste power on a fan if I don't have to, so I may try to use a thermocouple to see if it's necessary at different power consumptions.

100 watts. That's not a flashlight, that's a torch.

You don't want the LED to get more than about 80 degC if you can avoid it. That temperature is very hot to the touch. Also, at higher temperatures the LED's start getting less efficient.

I am guessing that you will need some kind of diffuser. You might want to consider non-focusing or non-imaging optics. Imagine a reflective cone with the LED's at the wide end of the cone with the light coming out the small end.

That heat sink and fan combo looks like it would work. Note that if the LED is running at 100 watts, the few watts the fan is using is a non-issue.

 

I think you are drastically underestimating the number of cells you will need. Suppose you are going to operate it, usually, at 1/3 the max power. 33 watts. Ten cells in series would give you the required voltage and, if you buy good ones, they will last about an hour delivering 1 amp. Really good ones might last two hours. That doesn't count the fan (which you ARE going to need).

Is a two hour flashlight worth while?

Do you really need a range of colors; that will mean you have to make four PWM supplies instead of one.

 

I think you are drastically underestimating the number of cells you will need. Suppose you are going to operate it, usually, at 1/3 the max power. 33 watts. Ten cells in series would give you the required voltage and, if you buy good ones, they will last about an hour delivering 1 amp. Really good ones might last two hours. That doesn't count the fan (which you ARE going to need).

Is a two hour flashlight worth while?

Do you really need a range of colors; that will mean you have to make four PWM supplies instead of one.

I know the typical lithium cell voltages. Due to how much 10-15 cell batteries can cost, a constant current boost converter makes more sense. I know the battery life may not be the best, but I want a pretty bright flashlight with a life of a few hours that can be insanely bright if needed.

 

100 watts. That's not a flashlight, that's a torch.

Because it catches on fire? If that's the case, do you know what the lumens per watt is of a flaming LED?

 

I recently found these 8 pin RGBW LEDs. It looks like a good deal. I may get them soon to use in a DIY flashlight. It's surprising that you can get them without a common gnd. So how necessary is a heat sink when they are being operated at full power, and would a random steel washer or bolt suffice? I really don't want to spend too much. Also, what is the cheapest way to drive them reliably? Is there any way to make a current source that can supply 300mA for less than the cost of an LM317 or other linear regulator? Would a BJT work, or is the gain too unreliable?

The reason they don't have a common ground is because of the amount of power involved. 8 pins = 4 LEDs. + (anode) & - (cathode/ground) for each. I haven't used these, but a common ground might also defeat how they are controlled. I get the feeling these are continuous current with a variable voltage type of control. I'd love to see an actual manufacturer datasheet for these.

 

You wrote, "Due to how much 10-15 cell batteries can cost, a constant current boost converter makes more sense. I know the battery life may not be the best, but I want a pretty bright flashlight with a life of a few hours that can be insanely bright if needed."

But boosting the voltage from half the number of cells just doubles the current they have to supply. 33 watts, assuming you are running at 1/3 power is still 33 watts. 10 amps from a 3.3 volt supply; 5 amps from a 6.6 volt supply; 2.5 amps from a 13.2 volt supply. A 33 watt battery operated power supply is going to be heavy and even more so if you want 2 hours.

I suspect you will be a lot happier building a 10 watt light first, to familiarize yourself with the problems.

 

I suspect you will be a lot happier building a 10 watt light first, to familiarize yourself with the problems.

Agree 100%

I'm often surprised how many people on this forum refuse to start small and learn from experience at a manageable scale.

 

You wrote, "Due to how much 10-15 cell batteries can cost, a constant current boost converter makes more sense. I know the battery life may not be the best, but I want a pretty bright flashlight with a life of a few hours that can be insanely bright if needed."

But boosting the voltage from half the number of cells just doubles the current they have to supply. 33 watts, assuming you are running at 1/3 power is still 33 watts. 10 amps from a 3.3 volt supply; 5 amps from a 6.6 volt supply; 2.5 amps from a 13.2 volt supply. A 33 watt battery operated power supply is going to be heavy and even more so if you want 2 hours.

I suspect you will be a lot happier building a 10 watt light first, to familiarize yourself with the problems.

I know, but I can't find and 10s chargers or 10s batteries that are only 1-2Ah.

 

Buy one hell stop guessing you'll find that it don't use as much power as you think.
The 34 volt is getting normal for led lighting I just did to car washer they have light bar's with leds something like these. Bars have 6 sets there bright. the supply is set to feed current it's set for 350mA I been dying for one to be bad so I could open it up and look at it I really cant see how these work so good but the supply pumps out the 350 mA the voltage can raise up to 56 volts to keep the leds getting there 350

 

Agree 100%

I'm often surprised how many people on this forum refuse to start small and learn from experience at a manageable scale.

I think I'll start out with the 4W ones and then get the 100W one later. But I don't think it makes sense to build a smaller version that's exactly the same and scale it up.

 

Buy one hell stop guessing you'll find that it don't use as much power as you think.
The 34 volt is getting normal for led lighting I just did to car washer they have light bar's with leds something like these. Bars have 6 sets there bright. the supply is set to feed current it's set for 350mA I been dying for one to be bad so I could open it up and look at it I really cant see how these work so good but the supply pumps out the 350 mA the voltage can raise up to 56 volts to keep the leds getting there 350

I know 100W is insanely bright, but that's what I'm going for. And I would not need it continuously, just for maybe a few minutes. It would be operated at 5-10W normally.

 

Buy one hell stop guessing you'll find that it don't use as much power as you think.
The 34 volt is getting normal for led lighting I just did to car washer they have light bar's with leds something like these. Bars have 6 sets there bright. the supply is set to feed current it's set for 350mA I been dying for one to be bad so I could open it up and look at it I really cant see how these work so good but the supply pumps out the 350 mA the voltage can raise up to 56 volts to keep the leds getting there 350

Well, if they are properly heat sinked and operated at the rated current, I don't see how those LEDs would die. So unfortunately you may have to wait a long time to do so. This is another topic completely, but I fell like higher voltages should be used in general. Why just 12V for cars? If people open it up and electrocute themselves on 48 or 60V, it's probably not going to be fatal and it's a foreseeable outcome. You could drastically cut wiring costs, improve efficiency, and improve available power.

 

You wrote "I think I'll start out with the 4W ones." I think that is wise. Please, when you get it bread boarded send us a photo and then another when you get it enclosed. If you decide to go bigger, tell us that too.

We all know it takes a while from China, so we won't expect results instantly.

 

Most of the heatsinks I've found that might fit the 4W ones just list the dimensions, not any thermal properties. So would using heatsinks without listed thermal specs really be so bad?

 

Man there is always a chance one don't work LOL but the watt's you read on the box or ebay doesn't mean much. Even on the power supply's
lets take the work light it has what you see listed as 1 watt leds now this thing has a 10 x 10 of these that's 100 watt's 8 of these light's it up to work on the equipment it's better then being outside in the sun but they use 1.8 amps each. That's 18mA a led come on no way right.
But I'm sure these lights leds are 1 watt just like these something is a little off some where cause I ran all the led lighting of on cord so we could see to hook up the motors and controls and the TCS which is a fancy car wash name for PLC.
We been using a generator 75 kW while building this.
But the point is there are 26 x 100 watt led lights that's for seeing things LOL that should be 52 amps all the general lighting inside only draws
19 amps and all these and the supply clearly tells you there 2 amps each so does the box and yes I know what I'm reading and doing I been at this a long time now.
But The car washes is fun We got 4 more to do and 2 done kind of a break from what I been doing but wring is in my blood 38 years

 

This 150 watt flood it's bright you can't look at it with your eyes it 1/2 amp.