New build, as the title describes I am building an actively cooled quad sbt90.2 with completely scratch made battery carrier housing 12 cells in 4s3p confuguration. Around 150Wh in total.
Custom 105mm, 6mm thick copper heatsink with 250x 3mm copper rods is being made.
Host is a Mateminco MT35. Unfortunately noone was interested in selling me one used so I had to buy a new one.
Also noone was willing to give any form of advice or answer the questions I had at the topic I started when I was planing this beast so I had to pm certain members which were very kind and willing to help even though they are really busy. Thank you! There are many nice people around here.
Here are some photos of the carrier and the head that has already been cut at a local machining shop with a lathe as I dont have so many tools at home.
The battery carrier is composed of four 3mm thick plexiglass discs. 0.3mm copper sheet cut to the apropriate shapes is used as the pcb traces. I didnt want to use “normal” springs because of current limiting and I dont like solutions like small wires bridges etc. The connecting rods are from 3 sucrificial normal 2s battery carriers (Astrolux+Mateminco) which have been reduced in length to 69mm. Were 74mm before if I am correct. The side of the carrier that will contact the driver is not ready yet as I am waiting for the driver to arrive and then decide which is the best way to do it. The center rod is the + and one of the side ones the -.
I am also waiting 3 different reflectors to see what is working best with the sbt90.2s and then order 4 of this kind.
A question I have is about the fan speed control. I have a really serious 40mm fan(around 8.5W) from an rc car esc unit. Is it possible to wire the fan parallel to the leds and increase the speed according to the mode I am in? So the fan will turn faster at higher brightness levels.
The fan is 2s so I will use a tiny step down board to prevent burning it. Another idea is to use a simple pwm module with a potentiometer for really accurate control of the speed. Have found one but takes extra space so I would like to avoid it if possible. Any ideas here?
3 reflectors arrived: 60mm, 67mm (L6) and 65mm. 2 more on their way. I didnt like the 60mm one as it has a different angle at the first 12-15mm above the emitter. The 65mm one is too high so I just used it as a comparison. The best until now is the L6 reflector. I have read that the L6 reflector needs some tuning to focus properly. As you can see I sanded it down and the base is paper thin now. Unfortunately I got worse lux readings with sanding than with the original height, I took material slowly off and meassured it every time. I started at 12700 lux at 3,4meters (4.75A around 2000lm) and droped to 11000 after sanding. I dont know what I am doing wrong. Should I go even lower? The beam looks ok. The reflector is siting exactly on the green part of the led unit. Is it the right place?
Quick preview of the fan placement. Will be facing to the other direction when ready…
Diagram for the heatsink hand drawn to 3x scale for more accuracy/easier. Then printed 3 times smaller. Each small dot/line will be a 3mm copper pin.
Thanks for reading and for any help. I will update the post when I make progress.
That is going to be something! Impressive start.
About the fan parallel to the leds: since with leds the voltage is not lineair with the output (voltage difference from very low to turbo is fairly low) and cooling power of a fan may be much closer to lineair with the voltage, it is not optimal, but at least better than having the fan at constant speed.
I really like your plan on this one. Where did you get the driver ? And what size reflectors are you looking at ?
Cool project! I’ll be following this one. In my fan cooled lights I run the fan at a constant speed and call it good. I set the fan speed with appropriate resistors and use a fan rated at close to the led voltage (5v or 12v).
What driver are you going to use for the 4 leds?
Reflectors that will be tested are 60-73mm. Including a 67mm L6 reflector.
BLG GT94 driver will be used for this one.
I like your plan and I like you nickname:-)
Awesome, interested in the end result!
Following with interest Kourtinoksylo. All the best for the build.
Update, see first post. 3 refelctors tested, 2 more on the way.
The project is progressing pretty good. I tested 5 reflectors and decided to go with the 73mm from kaidomain.(ordered 4 of them). I managed to focus it really good on my sbt90.2. (3 more one their way from Hank). Delays in delivery are unfortunately unavoidable so I am concentrated on the heatsink for now.
I have drilled the 280holes (2.9mm) in the 6mm copper disc and will later add the 3mm thick copper pins. These will vary in length from 46mm to 16mm depending on the space avaliable in the head.
Question I was thinking and researching a little about how to increase the surface area of my pins. I came up with the idea to cut threads to each of the copper pins that will run their whole length. I found some rough calculations that a screw has around 50-65% and maybe up to 100% more surface area than the same diameter cylinder/rod. This sounds pretty amazing to me.
What do you think about that? Will the threads possibly improve cooling? The airflow will be parallel to the pins and perpenducular to the threads. My main concern is to not make things worse, because the airflow will be perpendicular and wont hit directly the valleys of the threads. Any other ideas to increase the surface area?
The heatsink is finally ready, here are some photos of it
It weighs 907gr/1.99lbs and has and an actively cooled surface area of aproximately 720cm2/111square inches. This is only the copper, didnt include the head of the flashlight.
(If I remeber corectly) it has 278, 3mm copper pins that reach through the 6mm thick copper to the leds. It took ages to drill all the holes and press fit/hammer all the pins but I had enough time during the holidays and enjoyed it. The other side doesnt look so nice for now as some pins are longer and some shorter, it needs some more work…
I managed to calculate the surface area of a BLF GT94 from pictures and found out that it has around 1450cm2 of fins and probably some more surface area if you take into account the rest of the head. This is twice as much as my heatsink but it is not actively cooled. The heatpath is also shorter with my heatsink. Honestly I have no idea what is better and from which point is a passively cooled heatsink equal to an actively coolled one. Material wise copper is better than aluminium, but I dont know if I managed to build somehing superior to the the GT94. probably yes. (But also extremely inpractical due to the weight).
The battery tube and the contact point to the driver are also ready. I visited the local machining shop again and had the tubes done there. Then JB welder them together. The contact points are just 1mm thick copper sheet and I made them with a dremel, didnt use a lathe for these.
And a small preview. The upper part of the head is missing of course. I am waiting for the reflectors to come.
This is looking great so far. Im looking forward to seeing how well the copper heat sink dissipates the huge amount of heat that will be conducted to it. If anything, it should dramatically increase run times at the higher power levels. Thanks for sharing.
That is a lot of work ’ Kourtinoksylo ’. And you have our attention.
I do believe this light may become epic
The heatsink is completly ready
Also screwed onto the head, already some copper patina from the constant handling…
This is the cooling concept and almost final assembly of the head:
I milled out the existing fins using a drill press, a 2mm end mill and a jig to hold the head stable to create the air intake. Then the final work with a small file. Also drilled through the tripod mount at the back side to allow slightly more air flow.
Next step is to cut the 4x 73mm reflectors and epoxy them together. After that I need to make some centering rings for the leds and finally screw them on the heatsink. The speed controller for the fan will be probably at the upper compartment where the reflectors are and not near the driver, because I dont want any extra components near my air intakes obstructing airflow to the pins. The potentiometer for the fan speed controler will be placed at a random location that I will need to figure out and consider comfortable to use. I wanted to use the tripod mount (drill through) as place to put the potentiometer but it seems the least comfortable place, plus I need this hole for extra air flow.
That’s pretty incredible. The heat sink looks like an under water creature.
Wow!! amazing build… Thanks for sharing.
I love your ambition! Can't wait to see how this light turns out as you progress! Keep it up for sure!
Ohhh wow…bookmarked this share!