Passive heatsik

I can get 200x100x18mm black anodized heatsink really cheap. I wonder how much watts can they take passive with no fans in growbox. Eyeballing of course...
20, 50, 60...?

Safe zone probably 80-100w, 150-70-10 is rated good for 60-70w...all rough estimate
You have link for them?

keep in mind youll be losing a fair amount of efficiency with out fans

Note that this is not pin fin heatsink, but flat one. I have plan to run two COBs on two of them, just don't know which one they can take it (veg light, so I don't need much W).
If it's too small dispasion, then I will buy bigger heatsink and mount fan on it like already have one.
But as said, price is really good...

KonopCh said:

Note that this is not pin fin heatsink, but flat one. I have plan to run two COBs on two of them, just don't know which one they can take it (veg light, so I don't need much W).
If it's too small dispasion, then I will buy bigger heatsink and mount fan on it like already have one.
But as said, price is really good...

Click to expand...

How many mm is the base, 5-6mm?

KonopCh said:

Note that this is not pin fin heatsink, but flat one. I have plan to run two COBs on two of them, just don't know which one they can take it (veg light, so I don't need much W).
If it's too small dispasion, then I will buy bigger heatsink and mount fan on it like already have one.
But as said, price is really good...

Click to expand...

You need to calculate the surface, mounting plate x2 (front and backside), plus number of fins x fin area. You need 110cm² "cooling area" per heat watt. I need a few more data, how thick is the baseplate and how many fins have these heatsink?

If it have 14 fins, 15mm high, and the baseplate is 3mm it would look like this:
Baseplate is 20x10cm=200cm2 *2=400cm²
Fins are 1,5cm * 10cm=15cm2 one side, 30cm² both sides and there are 14 of them, so 30x 14=420cm².
So around 825cm² with the rest of the small surfaces. If we divide this with 110cm² the heatsink is good for 7,5 heat watts. So max. 20w of efficient LED's on such a small heatsink! We have to take into account that there is always a bit of airflow in a tent so maybe you could also get away with 25w.
36v COB's at 700mA(24,5w) with these heatsinks would probably run at Tc. of 65-85°C without additional airflow.

Oh, really nice from you. It's 16 fins, base plate is 3mm. So yours calculations are close enough. I see that I cannot drive 50W COB on it.
So I will go with little larger heatsink and mount Arctic alpine fan on it with 2 or 3 COBs.

KonopCh said:

Oh, really nice from you. It's 16 fins, base plate is 3mm. So yours calculations are close enough. I see that I cannot drive 50W COB on it.
So I will go with little larger heatsink and mount Arctic alpine fan on it with 2 or 3 COBs.

Click to expand...

As long as you're going active, here's an option; https://www.cdiweb.com/ProductDetail/ICELED450--mechatronix/573530/

Intel stock CPU cooler for i5/i7 desktops are rated with 95w, choose the one with copper core. They are cheap to get on e3by, maybe 5-6$, the fan is dimmable, should easily handle 50w also with fan at 5v.

I have Arctic alpine 11 plus. But I don't like them because they vibrate/shake too much. I decided to buy bar heatsink instead. I also can mount more COBs on them and only one fan to cool them is enough.

KonopCh said:

I have Arctic alpine 11 plus. But I don't like them because they vibrate/shake too much. I decided to buy bar heatsink instead. I also can mount more COBs on them and only one fan to cool them is enough.

Click to expand...

Yeah, I like those bar heatsinks.

I've made my own simply by using a 4mm alu plate and a few additional alu c-channels with the same lenghs and screwed them to one side of the plate. This is far cheaper and they work as good as the paid one(1-2°C warmer maybe, not more). No thermal tape or grease, only self tapping screw each 8" and what is best, you can make them exactly according to your wishes and do not have to compromise.