heatsink help

sixstring2112

sixstring2112

Well-Known Member
thats a pretty good hunk of aluminum,i would guess its safe for 65 to75w passive and at least 100w with a decent 12v fan on it. @robincnn would prob be the best one to ask for better details
 
Moflow

Moflow

Well-Known Member
Hopfully a maths expert will chip in.

I've something similar I bought on fleabay. 250x200x40mm thick base around 10/12mm.
I run a single cob at 50 watts passively on it....
I'd imagine if you put a 100mm fan on it you could do 50 watts on it.
Hope that helps.
 
Moflow

Moflow

Well-Known Member
sixstring2112 said:
thats a pretty good hunk of aluminum,i would guess its safe for 65 to75w passive and at least 100w with a decent 12v fan on it. @robincnn would prob be the best one to ask for better details
Click to expand...
Lol
I just measured my chunk of alloy against the heatsink usa specs and thought ok, this will do 50 watts passively!
No maths needed! Lol lol
 
sixstring2112

sixstring2112

Well-Known Member
well the ngl sstx heatsink is only 125mmm x 125mm x 60mm and it handles 100w passive.now understand that hs is a splayed pin so much better heat disapation,but still i would think because the op's aluminum chunk is quite a bit larger it should handle slightly more than 50w passive. @Moflow have you ever taken temp readings on your cob setup @50w ?
 
Moflow

Moflow

Well-Known Member
No, I've a thermometer lying about somewhere, I must check it.
Heatsink is lukewarm to touch and you could put your hand on it all day long.
8-).
 
JavaCo

JavaCo

Well-Known Member
Really no way to calculate the Heat sink. Should have a thermal resistance number per a watt. Without that there is no way to calculate how many watts it can handle.
 
JavaCo

JavaCo

Well-Known Member
Moflow said:
I just done it by eyeball ..... lol lol
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If you want to do it half assed maybe.
Saying a heat sink can handle 100 watts of LED is a really bad way of doing it. Because it does not take in to account the efficiency of the LED.
For example if you say a heat sink can handle a 100watt LED. Then you have a LED thats 70% efficient and one that 30% efficient. Ones putting off 30% heat or 30watts and ones putting off 70% heat or 70 watts. Thats a big difference in heat. So efficiency is a big factor that needs to be taken into account. Once you factor in the efficiency then you can see how many heat watts to the total amount of watts the heatsink really has to deal with.
 
sixstring2112

sixstring2112

Well-Known Member
JavaCo said:
If you want to do it half assed maybe.
Saying a heat sink can handle 100 watts of LED is a really bad way of doing it. Because it does not take in to account the efficiency of the LED.
For example if you say a heat sink can handle a 100watt LED. Then you have a LED thats 70% efficient and one that 30% efficient. Ones putting off 30% heat or 30watts and ones putting off 70% heat or 70 watts. Thats a big difference in heat. So efficiency is a big factor that needs to be taken into account. Once you factor in the efficiency then you can see how many heat watts to the total amount of watts the heatsink really has to deal with.
Click to expand...
For what the majority of us use 50% eff is safe.mars is 30% but you dont see alot of use buying shitty diodes for our diy builds.cree,vero,shitizen,lumipuss are all very close
 
Moflow

Moflow

Well-Known Member
JavaCo said:
If you want to do it half assed maybe.
Saying a heat sink can handle 100 watts of LED is a really bad way of doing it. Because it does not take in to account the efficiency of the LED.
For example if you say a heat sink can handle a 100watt LED. Then you have a LED thats 70% efficient and one that 30% efficient. Ones putting off 30% heat or 30watts and ones putting off 70% heat or 70 watts. Thats a big difference in heat. So efficiency is a big factor that needs to be taken into account. Once you factor in the efficiency then you can see how many heat watts to the total amount of watts the heatsink really has to deal with.
Click to expand...
I can't find the spec on that heatsink I got, was a while ago but I knew it would handle 50 watts of cob at around 56% efficiency
 
R

rainy165

Well-Known Member
wow thanks for all the replies

looks like it might run a bit more than I thought

am hoping to run the new vero c @1.4 on these

just have to haggle with the boss on price now
 
JavaCo

JavaCo

Well-Known Member
rainy165 said:
wow thanks for all the replies

looks like it might run a bit more than I thought

am hoping to run the new vero c @1.4 on these

just have to haggle with the boss on price now
Click to expand...
If you are talking about a Vero 29 C @ 1.4 then it would be running @ 95 watts. Would run at about 68 volts @ 1.4. . A 700mA driver would give you 45watts to the LED. This is just a guess but that Heat sink you posted i doubt can handle much more then 25 watts of heat while keeping a cob at a respectable temperature.
 
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