Economical multi LED Chip Projects for Growing

[Jaybodankly]

I found a video of a guy who was pre-heated large pieces of aluminum on a outdoor grill then soldered them. Epoxy is fine for this work. Especially for tiny pin hole leaks. I used a basic drillpress, tablesaw and chopsaw for most of the aluminum milling.

It is hard to say how the shit will will fly with D.T. & Crew. Except that it will. Keeping a low profile is always wise and I appreciate the reminder. It is easy to say we won and let the freak flag fly. Even now in MA they are talking about changing parts of the law. The law right now is six plants per person. Twelve plants per/house max. Some of my genetics is clone only. Nothing spectacular just some phenos I grew from seed. I have kept them up and enjoy em. Now, I got to learn to graft and put them all on one mother tree to be legal or dump some. Not ready to give them up yet. The shit I got to do to not be a pirate anymore.
I like your CO2 supplementation ideas. Much simpler than CO2 rigs. Do you measure a known volume of liquid for 12 hours or just let it burn out? I have an old kerosene storm lantern. That might work they are pretty safe.
You are totally correct on maximizing yield by vegging large plants. It is the future for most legal home growers. It will make me go back to my roots and start SCROGing again. Return of the bondage master lol. I dont allow them to break thru the screen until they are done stretching and start to flower. Some guys use SCROGs as a trellis. Which is fine but call it a trellis. I love the beauty of a full even canopy a SCROG create. Even canopy structure allows you to move the lights closer with less chance of burning your tallest buds. I have grown some good plants before. Decent light, rich organic soil, steady temps. Then I got some new seed. fugg. Blows my other plant genetics away. Realized I needed to drop some $ and step up my genetics game. I am about to harvest some real nice GSC Thin Mint, second week of Jan. Next run Kimbo Kush, Gorilla Bubble, and Bruce Banner. I think it is about 80% creating optimum environment and 20% excellent genetics.
I agree, water cooled COB's have a real benefit for those running sealed rooms. Heat build up is one of the main reasons growers have to exhaust a sealed room. Less air changes the better is my understanding. This is where I am headed on a new room. My flower room will become my veg room.
Is this a crazy idea? I was stoned at LowDepot wandering around and came across some hydronic baseboard heating radiators. The design is made of a copper pipe in the middle with square radiator fins tightly packed around the length of it. They come pre-made in many different lengths and seem easily adaptable to water cooling.
I believe they can be used in reverse to cool a room instead of heating it without air exchange. Someone more educated than me could do the math on it. What I was brainstorming on was to flatten out a fin on the bottom and thermal epoxy COBs to it every foot. Spray them flat black, attach hoses, pump, water and roll. A few fans blowing down on it will make it much more efficient. Much easier/quicker/efficient than building aluminum heatblocks. Copper is twice as efficient as aluminum in moving heat. I can probably score some at the scrap yard for cheap or a contractor friend doing a remodel. I could see a room with three or four runs of these on a manifold with a pump. It would be cooling the COBs and absorbing room heat at the same time!
Going all the way this and you add a small water heater to the loop. It could store the heat and return it to the room thru the radiators during dark period. Condensation could be an issue. You can tell me if this a bullshit idea or not.
Another idea is a salvaged truck radiator/fan combo running on a watercooled loop. Dump the heat into a 50gal drum buried in the ground. Thermosiphon is another option if you have storage space and height for overhead watertank. Then you can get rid of the pump.

 

[DIY-HP-LED]

I found a video of a guy who was pre-heated large pieces of aluminum on a outdoor grill then soldered them. Epoxy is fine for this work. Especially for tiny pin hole leaks. I used a basic drillpress, tablesaw and chopsaw for most of the aluminum milling.

It is hard to say how the shit will will fly with D.T. & Crew. Except that it will. Keeping a low profile is always wise and I appreciate the reminder. It is easy to say we won and let the freak flag fly. Even now in MA they are talking about changing parts of the law. The law right now is six plants per person. Twelve plants per/house max. Some of my genetics is clone only. Nothing spectacular just some phenos I grew from seed. I have kept them up and enjoy em. Now, I got to learn to graft and put them all on one mother tree to be legal or dump some. Not ready to give them up yet. The shit I got to do to not be a pirate anymore.
I like your CO2 supplementation ideas. Much simpler than CO2 rigs. Do you measure a known volume of liquid for 12 hours or just let it burn out? I have an old kerosene storm lantern. That might work they are pretty safe.
You are totally correct on maximizing yield by vegging large plants. It is the future for most legal home growers. It will make me go back to my roots and start SCROGing again. Return of the bondage master lol. I dont allow them to break thru the screen until they are done stretching and start to flower. Some guys use SCROGs as a trellis. Which is fine but call it a trellis. I love the beauty of a full even canopy a SCROG create. Even canopy structure allows you to move the lights closer with less chance of burning your tallest buds. I have grown some good plants before. Decent light, rich organic soil, steady temps. Then I got some new seed. fugg. Blows my other plant genetics away. Realized I needed to drop some $ and step up my genetics game. I am about to harvest some real nice GSC Thin Mint, second week of Jan. Next run Kimbo Kush, Gorilla Bubble, and Bruce Banner. I think it is about 80% creating optimum environment and 20% excellent genetics.
I agree, water cooled COB's have a real benefit for those running sealed rooms. Heat build up is one of the main reasons growers have to exhaust a sealed room. Less air changes the better is my understanding. This is where I am headed on a new room. My flower room will become my veg room.
Is this a crazy idea? I was stoned at LowDepot wandering around and came across some hydronic baseboard heating radiators. The design is made of a copper pipe in the middle with square radiator fins tightly packed around the length of it. They come pre-made in many different lengths and seem easily adaptable to water cooling.
I believe they can be used in reverse to cool a room instead of heating it without air exchange. Someone more educated than me could do the math on it. What I was brainstorming on was to flatten out a fin on the bottom and thermal epoxy COBs to it every foot. Spray them flat black, attach hoses, pump, water and roll. A few fans blowing down on it will make it much more efficient. Much easier/quicker/efficient than building aluminum heatblocks. Copper is twice as efficient as aluminum in moving heat. I can probably score some at the scrap yard for cheap or a contractor friend doing a remodel. I could see a room with three or four runs of these on a manifold with a pump. It would be cooling the COBs and absorbing room heat at the same time!
Going all the way this and you add a small water heater to the loop. It could store the heat and return it to the room thru the radiators during dark period. Condensation could be an issue. You can tell me if this a bullshit idea or not.
Another idea is a salvaged truck radiator/fan combo running on a watercooled loop. Dump the heat into a 50gal drum buried in the ground. Thermosiphon is another option if you have storage space and height for overhead watertank. Then you can get rid of the pump.

I originally was gonna weld or solder the end caps on, but realized that the system had no pressure and figured a modern adhesive should work. I thought about pre-heating the aluminum before brazing, but figured gluing the caps in would work well enough and with epoxy, it does. I also wanted to do the job in a way that others could do the same thing with minimum cost, tools and equipment.

I use a small kerosene lamp that holds around 6 oz of methanol and I burn 2 or 3 oz a day in my 10'x8'x7'H flower room. I'm planning on buying a cheap CO2 monitor from ebay to adjust the burn rate until I get the levels right.I vent my room periodically using a timer on the carbon filter blower to control humidity, so there's a dehumidifier in my future too.

I have a friend who is going to use some baseboard radiators he has laying around as a cooler for his build and they should cool his setup well enough, though they are hard to actively cool. It would be cheaper and better to buy a car/truck radiator/ heater core for a cooler, these are designed to transfer large volumes of heat, have a massive surface area and because they are compact, they can be cooled with a fan or blower. The efficiency of the cooler goes down as the difference in temperature decreases, say your coolant temp is 25C degrees and you're dumping the heat in a 20C room, so there's only a 5 degree difference between the coolant and ambient air, there are a ton of formulas and calculators online that cover this. Needless to say, at our latitudes you could super chill your coolant for about 8 months of the year, by running a separate loop from the reservoir to the outside and running antifreeze in the loop. But that presents a host of other issues including insulating the reservoir, hoses and cooling blocks, condensation and a loss of heat at a time of the year when we can use it!

The problem with using a baseboard radiator fin bent over to mount a COB on, is heat flow. Look at how thin the aluminum fin is and it's going to have a 90 degree bend for the heat to go round. The contact area on the copper pipe is not very great and heat transfer from the thin aluminum to the copper pipe is small. It seems to defeat the purpose of removing the heat from the grow by re radiating it back in.

I think you'll find that rectangular aluminum tubing and car radiators/heater cores are the simplest and most cost effective solution to water cooling COBs. I find that turning the blower on periodically with a timer through the night works well enough to control night humidity and warm up the grow from air drawn in from the rest of the house. Later I plan on better arrangements for environmental control, but this will do for now and it produces results. Like you, I want to use better, more efficient COBs that produce more light and less heat. I figure when I switch over to the Citizen COBs things should improve considerable in terms of light and heat. The grow is an evolving thing, when I figure out what the law will allow up this way (in the spring), then I'll get a better idea of where I want to go with the grow.

Here's a thought and perhaps a way of leveraging your genetics. Do they allow you to sell clones in MA? An in state business selling clones might be lucrative, set up your own bedding plant business in the spring!

 

[Jaybodankly]

I appreciate that you do it in a way that others can replicate your work. I have a small shop and been hackin at things since I was a kid. Always, bustin apart my toys to see how they worked.
I am going to stop by the junkyard and see if I can find a baseboard radiator. You are right about the thin fins. I am going to clear a spot and braze on some thick round copper pads. Water has a tremendous capacity to move heat. I barely moved the temps with 5-100w chips on a 4' bar. I like the idea of a water-cooled lighting and room cooling all-in-one. It may not be enough all by itself but I think it can make a dent in the heat load. Truck radiator/fan combos are the time tested best options. Cars were initially air cooled then went and stayed water cooled.
There is an average of 25-35 degree difference between my basement and flower room. Could it be set up with 2- radiator/fan combos and a pump. One in the flower room blowing cold and one outside dumping heat in a loop?
Here in MA last night in a emergency session they curtailed rec shops from opening till 2018.
12 plant limit is the rule. Other than the fiction that I am selling a plastic pot which holds the plant. Or the baggie is being sold not the weed it's self. I like the clone business idea. I worked in greenhouse and grew for the local farmers market for many years. Juggling a few thousands starts in successions was an easy days work for me. There are no rules yet for that kind of business except having +$15G's to do the paperwork for 2018.

 

[mahiluana]

I appreciate that you do it in a way that others can replicate your work.

I recommend to close the ends of the tube by flanges because not everybody is able to solder.
For my chinise cob chips I cut squareholes 2x2cm into my aluminium tube to connect the chip-platine directly with the water. Now i can touch my chips even if I run them at 100%-
without burning my fingers. The system is patent pending and I`m looking for producers in USA
who are interested in dealing a licens.


The most important - is to use the hot water for energysavings - and there are plenty of posibilities. To cool the water down with fans and radiators with aditional electricity is just counterproductive.

 

[Jaybodankly]

Ha

I recommend to close the ends of the tube by flanges because not everybody is able to solder.
For my chinise cob chips I cut squareholes 2x2cm into my aluminium tube to connect the chip-platine directly with the water. Now i can touch my chips even if I run them at 100%-
without burning my fingers. The system is patent pending and I`m looking for producers in USA
who are interested in dealing a licens.


View attachment 3866658 View attachment 3866659 The most important - is to use the hot water for energysavings - and there are plenty of posibilities. To cool the water down with fans and radiators with aditional electricity is just counterproductive.

Have you thought about a thermosiphon and get rid of the pump? Use the heating water to create a natural fluid loop.

 

[DIY-HP-LED]

I recommend to close the ends of the tube by flanges because not everybody is able to solder.
For my chinise cob chips I cut squareholes 2x2cm into my aluminium tube to connect the chip-platine directly with the water. Now i can touch my chips even if I run them at 100%-
without burning my fingers. The system is patent pending and I`m looking for producers in USA
who are interested in dealing a licens.


View attachment 3866658 View attachment 3866659 The most important - is to use the hot water for energysavings - and there are plenty of posibilities. To cool the water down with fans and radiators with aditional electricity is just counterproductive.

Nice design, always good to have other options for sealing the tube ends, a bit more expensive and trouble than epoxy, but it will work fine. Directly cooling the COBs should work great, if you can overcome some technical challenges. How are you attaching the COBs to the tube? Sealing around them to make them water tight? The backs of the cheap Chinese 100 watt COBs have holes in them and some might not be water proof!

As for patents, it is generally not worth the expense and assuming there is no prior art, difficult to obtain and is very difficult to enforce. If it's a popular item, they'd be knocking them off in China in no time flat and selling them cheaper than you could make em. Years ago when GM made the LUV car in China, they found a duplicate factory making better counterfeit cars than the original for a cheaper price, they cut a deal and made the counterfeiter a sub contractor!

 

[DIY-HP-LED]

Ha

Have you thought about a thermosiphon and get rid of the pump? Use the heating water to create a natural fluid loop.

Thermo-sypioning probably won't move enough water for effective cooling, also the COBs will get far too hot. What's the point of water cooling COBs if your coolant temps are in the 80 degree C range! I don't know that much about thermo-sypioning and haven't done the calculations, but just roughing it out in my head tells me the hose sizes and temp differences would have to be enormous. This would work, if the COBs were mounted on the bottom of the reservoir

 

[Jaybodankly]

A quick look on wikipedia "A thermosiphon can handle heat output at a much wider temperature range than any heat sink and fan, and can maintain the processor 10–20 °C cooler. Thermosiphons must be mounted such that vapor rises up and liquid flows down to the boiler, with no bends in the tubing for liquid to pool. Also, the thermosiphon’s fan that cools the gas needs cool air to operate. The system has to be completely airtight; if not, the process of thermosiphon will not take effect and cause the water to only evaporate over a small period of time."

 

[DIY-HP-LED]

A quick look on wikipedia "A thermosiphon can handle heat output at a much wider temperature range than any heat sink and fan, and can maintain the processor 10–20 °C cooler. Thermosiphons must be mounted such that vapor rises up and liquid flows down to the boiler, with no bends in the tubing for liquid to pool. Also, the thermosiphon’s fan that cools the gas needs cool air to operate. The system has to be completely airtight; if not, the process of thermosiphon will not take effect and cause the water to only evaporate over a small period of time."

Jay
I believe you're referring to "heat pipes" that use the phase change of a working fluid to absorb and then get rid of heat. Usually the working fluid in these systems is ammonia or alcohol that can change states from fluid to gas at low temps, it takes a lot more energy to change from a liquid to a gas or back again to a liquid (phase change).

If your working fluid is water, forget phase changes for cooling unless you want to run your entire system under a partial vacuum. It's simpler to use the water as a heat transport medium and move the water (and heat) outside the grow to a low cost, simple, time tested, high capacity cooler like an automotive radiator or heater core. These devices are designed to dump tens of kilowatts of heat when there's a 100 C temp difference and will work well enough to keep a couple of kilowatts of grow lights a couple of degrees C warmer than the ambient temp of the cooler location.

You could spray water over the cooler and get a few degrees cooler through evaporative cooling, but it's not worth the effort and mess.

 

[Jaybodankly]

I have seen thermosiphon in passive solar designs. No phase change. It works on hot water rising and cool water settling creating a loop.

https://www.google.com/search?q=thermosiphon+water+heater&safe=off&source=lnms&tbm=isch&sa=X&ved=0ahUKEwjY78GBxabRAhUH3IMKHRNjC4AQ_AUICSgC&biw=1440&bih=772

 

[mahiluana]

about a thermosiphon

Sorry guys - the only thermosyphon I remember - was a bamboo-bong filled with whisky.
me captain coolmac entered in a hugh thermosyphon after drinking that whisky
and leaving next morning a siphon without thermo but full of ugly stinking. But for vertical grow it`s a great sleeping idea -

My 2,4W pumpy is able to move up to 200L per hour.
You can play with temp. and amount of water by regulating the pump power.
Just calculate your needs eg. here:

https://rechneronline.de/chemie-rechner/heat-capacity.php

My pump is able to cool 2400W lamp power if you want.
I just couldn`t find one with less power.
By the way some led lamps with fans need up to 10% of the wattage in fan power
- my pumpy down to only 0,1% with a suspicious better result in temp.

The very basic cooling methode is, just to have enough water in a closed circuit. (10L / 100W)
You ! decide if your growroom stays cooler whether you install your watertank outside or not.
In wintertime, inside it can help you a lot to mantain a more constant temp. during the night.

With a second circuit you can make money ! Just save your energy costs for hot water.
Don`t know if you guys and girls always take cold showers ??? - The USA citizens have the highest average power consumption of the world. In Europe only 25% of that and third(4th) world less than 4%.
Look for a strategic place between growroom and bathroom or kitchen and install a watertank.
Hang an aluminium-radiator into the watertank and cool your lampwater down with the incoming cold water that you might need during the day. In future constructions, architects
can find much smarter solutions to integrate this part of energy.

~ 50-60% of the electrical energy can be used, recovered and stored in form of hot water.

In case of my COOLMAC-300 - a total consumption of 290 watts lamp power

enables to rewinn 160 Watt stored as waste heat in the cooling water.

Other chips and drivers may differ a bit.

OK. if your bathroom is far away - it`s a pitty - but cooler growroom, chips and drivers can somewhere be a good idea itself. Or put a second bathtube in your growroom to celebrate the gardeners longhardday.

There are still a lot of other issues not yet tested. Corrosion eg. is still my main concern
- also the long term test with siliconseal under a chip has to show " long life".
Another reason why to let the tube "open" and have a look and inspection from time to time.

So things may need time - and I still keep on rolling.
Next week more about chip-temp. and others...
Hope to find some cool watercoolers here - greetings

 

[Jaybodankly]

No offense, I think it is going to be difficult over time to maintain water tightness with your design. Aluminum likes to expand and contract as it heats and cools. You will need to use the very best silicone possible. Not all are made the same. Adding more holes to something that is supposed to be water tight is hard to justify in my opinion. Water-cooling works so well. It seems unnecessary to do more than surface flattening the COB chips and thermal bonding. Upgrading to a new chip design will be difficult at best for you.
I like your ideas on reclaiming heat. I take the the hot air that goes thru my charcoal filter is oxygenated and humidified by plats thru a floor register. Looks like all the others in the house except it aint.

 

[mahiluana]

Chinese 100 watt COBs have holes in them and some might not be water proof!

The square hole is just 2 x 2cm directly under LES. You have to mark the borderline of the chip-platine on the tube to get exact results in position.


Dimension:

see: http://www.lumen-laden.de/products/a50-w-led-grow-light-chip-380nm-840nm/

For other chips you can drill different holes
(round LES is much easier) Silikon should be heatresistant anyway and is the same for fixing the drivers on the tube.I used a product called OTTO SEAL S54

As for patents

I know it`s not worth at all - but here in Germany you can do it online for only EURO 30,-
and days of paperwork.
I just wanted to smell a little bit into this jungle full of corrupt lawers and other rats.

The advantage against the chinise can only be cheap quality.
By reducing these led lamps on very cheap ingredients ( bit of aluminium, drivers and chip cost me buying also in bigger scales ~ EURO 150,- // 300W lamp all incl. )

For a led flood light with pasive heat management, same cobs and power with similar drivers
I pay EURO 210,- in China -
also buying 10 pcs to get this price.
It`s not easy but possible always when creativity and know how is a little step forward the mass
production. That`s why I offer different kits in grand variation. From Meanwell to noname and Cree Chips to chinise cobs,10-30-50W chips all handcraft and trying to stabilize a price
~ 1$ / 1W of lamp power. Some friends recommend me to ask for the doble - and may be they are right.

 

[mahiluana]

I like your ideas on reclaiming heat. I take the the hot air that goes thru my charcoal filter is oxygenated and humidified by plats thru a floor register. Looks like all the others in the house except it aint.

first award in architecture - great - these thing(s) i want to know more about

 

[mahiluana]

I was dreaming and scheming of ways to "promote" water cooling and get a few folks trying some cheap experimental setups to post here. I know you nerds are lurking out there, time to come out of your shell!

 

[frica]

The square hole is just 2 x 2cm directly under LES. You have to mark the borderline of the chip-platine on the tube to get exact results in position.


Dimension:

see: http://www.lumen-laden.de/products/a50-w-led-grow-light-chip-380nm-840nm/

For other chips you can drill different holes
(round LES is much easier) Silikon should be heatresistant anyway and is the same for fixing the drivers on the tube.I used a product called OTTO SEAL S54



I know it`s not worth at all - but here in Germany you can do it online for only EURO 30,-
and days of paperwork.
I just wanted to smell a little bit into this jungle full of corrupt lawers and other rats.

The advantage against the chinise can only be cheap quality.
By reducing these led lamps on very cheap ingredients ( bit of aluminium, drivers and chip cost me buying also in bigger scales ~ EURO 150,- // 300W lamp all incl. )

For a led flood light with pasive heat management, same cobs and power with similar drivers
I pay EURO 210,- in China -
also buying 10 pcs to get this price.
It`s not easy but possible always when creativity and know how is a little step forward the mass
production. That`s why I offer different kits in grand variation. From Meanwell to noname and Cree Chips to chinise cobs,10-30-50W chips all handcraft and trying to stabilize a price
~ 1$ / 1W of lamp power. Some friends recommend me to ask for the doble - and may be they are right.

That Chinese led isn't cheap.
30 euro for a "50 watt led" is expensive.

A Citizen chip that can do 250W is cheaper actualy. (CLU048 181

I have a very easy time finding LEDs way cheaper than a generic epistar/epiled chink crap.

http://www.reichelt.de/LED-Modules/SDW-85F1C-G10/3/index.html?ACTION=3&LA=2&ARTICLE=158940&GROUPID=3031&artnr=SDW+85F1C+G10&SEARCH=%2A
http://www.reichelt.de/LED-Modules/GW7MM-C40/3/index.html?ACTION=3&LA=517&ARTICLE=158927&GROUPID=3031

In fact, they're the same price as a CXB3070 on Mouser.

 

[mahiluana]

finding LEDs way cheaper

Ok. - the problem is not about chip prices - but to bring chip-temperature down,

you can use nearly all kind of high power smd chips and seal them on this coolbar

and connect them directly to the cooling water. This coolmac is easy to copy and everybody can try it - I can touch a 50W cob chip running at 100% 34V @1,5A with my fingers - that`s magic
- and not many growers can do that without burned fingers.

I tried to mesure with digital thermo-meter - but without sucess.

The LES of a running chip makes it impossible to mesure a very small area close by.

But my fingers told me that temperature of chip-platine is around ~ 45°C. (~ 113°F)

 

[nfhiggs]

Here is how I'm protecting the lamp, so far. I'm using a 60 C thermal cut off switch that I happen to have. For the big rig I'll use a 40 C thermal cut off and a 65 c thermal fuse in series with the lamp power supply as a final fail safe. Primary thermal cut off will be via a digital thermostat set at 35 C

View attachment 3773160
The center chip is tie wrapped on and it's cold to the touch after hours of operation as is the tie wrap. Note the 60 c thermal cut off switch under the tie wrap with cheap thermal tape.

Instead of all the thermal fuses and cutoffs, you should be using a series current limiting resistor to prevent thermal runaway. For mine I use a 1 ohm, 2W resistor on th input power wire of each COB.

 

[DIY-HP-LED]

Instead of all the thermal fuses and cutoffs, you should be using a series current limiting resistor to prevent thermal runaway. For mine I use a 1 ohm, 2W resistor on th input power wire of each COB.

What kind of COBs do you run and at what amperage? How many watts is the resistor dissipating in heat? A 100 watt COB running at 32V x 2A = 64 watts of total power dissipation across the LED and should produce around 3 or 4 watts of HEAT in the resistor. Use current limiting drivers and under drive COBs in high power LED applications, not resistors, which are appropriate for low power applications where energy wastage and heat are not issues.

Thermal cutoffs and fuses are almost as cheap as resistors. The purpose of the thermal protection system is to protect the lamp in the event of a cooling system failure, say a pump dies or the system becomes clogged or, springs a leak. With a liquid cooled system passive cooling won't get you very far and if you start boiling water with COBs, that can't be good.

 

[nfhiggs]

What kind of COBs do you run and at what amperage? How many watts is the resistor dissipating in heat? A 100 watt COB running at 32V x 2A = 64 watts of total power dissipation across the LED and should produce around 3 or 4 watts of HEAT in the resistor. Use current limiting drivers and under drive COBs in high power LED applications, not resistors, which are appropriate for low power applications where energy wastage and heat are not issues.

Thermal cutoffs and fuses are almost as cheap as resistors. The purpose of the thermal protection system is to protect the lamp in the event of a cooling system failure, say a pump dies or the system becomes clogged or, springs a leak. With a liquid cooled system passive cooling won't get you very far and if you start boiling water with COBs, that can't be good.

1 ohm resister will dissipate 1 W per amp of current, and will drop one volt per amp - total voltage really doesn't matter. I'm running six 100W cobs in parallel, at 32.8 volts, 9 amps total, 1.5 amps per COB. Each COB has its own 1 ohm, 2W series current limiting resistor to prevent thermal runaway. I'm not terribly concerned about 6W of wasted heat - not out of 300W total.

Yeah, constant current is the preferred method, but its roughly 4-6 times the cost per watt. A 400W Meanwell CC driver is $170. My 420W 36V supply cost $35.

For your setup, yeah they (thermal cutoffs) make sense. I tend to look at things through the lens of my own setup sometimes. Carry On!