Introduction: 100W LED in PVC Flashlight

This is a modified version of the 100W LED flashlights on Instructables. I have looked at several of them.

While they look really great, none seem to have portability, and they all use massive, heavy, expensive batteries.

I developed this project over a few days while trying to make it more portable, using common rechargeable batteries.

Credit to: https://www.instructables.com/id/100w-LED-Flashlig...

This light does drain batteries rather quickly, and is really more proof-of-concept than actually useful as a utility light, but I really enjoyed designing this and putting it together. I hope you do as well, or at least get some good ideas out of this.

Disclaimer:

This device will use a high output voltage. BE CAREFUL! Basic safety steps (such as rubber gloves, etc) can be very useful.

This light is EXTREMELY BRIGHT, do not shine directly into someone's eyes. Trust me, it will hurt.

Also, it should be mentioned that rechargeable batteries carry a voltage of about 1.2V, while alkaline batteries are 1.5V. Do not mix these batteries or the resulting output will not match. This project can be done with alkaline batteries as well, and less batteries will be needed. But it would cost more $ long-term and you would be less green. Shame on you for even considering it.

UPDATE: I thought that I was not outsourcing the heat properly and some LEDs burned out, but what actually happened was that all LEDs work just fine. After reading the batteries with the multimeter, I see that this light works perfectly, but it does drain the batteries rather quickly. In the future, I will hopefully be putting out an instructable with an ungraded light output and more efficient heatsink.

Step 1: Supplies

Tools List:

Small Flathead Screwdriver

Drill + bits

Rotary tool (like a Dremel) or Hacksaw

Wire stripper/Crimping Tool

Digital Multimeter

Dry Silicone Spray (optional, but worth it)

Soldering Iron

Solder

Heat shrink or Electrical tape

Supplies:

100w LED

44mm lens+ reflector kit

Colored Wire (red and black)

Step-Up Transformer

12V Power Switch, preferably lighted

Thermal paste

JB Weld Epoxy adhesive

12V 40mm fan+ heatsink

2” PVC pipe

2” Cleanout plug

2” Cleanout Adapter (2)

1 ¼” PVC Pipe

Two 1 ¼” PVC End Caps

4 Nuts

2 Bolts

2 Ring Wire Connectors

4 AA-to-D size battery serial converter to 4.5V

12 AA rechargeable batteries

The total cost for me was about $20, but I had a lot of this laying around except for the step up transformer and reflector kit. If you are buying all from scratch, it would probably cost closer to $35.

Step 2: Making the Battery Pack

The input voltage for the LED is 34V, but we will do it using the step-up transformer. In order to do that, we need a special battery configuration.

Side note: PVC tends to cut with rough edges. Smooth everything down between steps so nothing tears (ie wires or your skin).

1) Take both 1.25" end caps and drill a hole as close to center as possible that will fit the bolt.

2) On ONLY ONE OF THEM, drill a second hole on top, about half an inch or so away from the first hole. This will be the positive end.

3) Crimp the ring style terminals onto the wires. Easiest to remember of you are using red for + and black for -, but you can just use whatever you have available if need be.

4) Attach the positive ring terminal to the outside of the hole on its end cap using the nut and bolt.

5) Attach the negative ring terminal to the inside of the hole on its end cap using the nut and bolt.

6) Measure and cut your 1.25" PVC pipe to fit the 4 battery converters inside it, fitting snug with the end caps on. On mine, it was 7.5", but it may be slightly different depending on your exact converters.

7) Load the battery converters with your rechargeable AA's, and assemble your new battery casing, with the negative wire inside the tube, poking out of the second hole in the positive end cap. The picture does a better job of describing this.

8) Measure output voltage, it should be in the realm of 14.4V. These batteries were freshly charged so it ran a little higher.

Step 3: Configuring the Main Tube

1) Cut the 2" PVC pipe to about 19". Smooth the edges.

2) Scratch up the flat side of the 40mm heat sink/fan, and scratch up the backside of the LED module.

3) Carefully mix together the JB Weld Epoxy, and mix in a little of the thermal paste. About a teaspoon of epoxy with literally 1-2 drops of thermal paste should do it.

4) Attach the heat sink to the LED module using the mixture of paste, and let sit for 24 hours to fully cure.

5) Drill a hole in the 2" PVC tube to fit the power switch. (I prefer a lighted switch, because it cuts troubleshooting time in half. If the light does not turn on when you press the switch, you know the problem lies before the switch. If it turns on but the device does not, you know the problem lies after the switch.)

6) .Screw one cleanout plug to a cleanout adapter and spray the inside lightly with the silicone lubricant spray. This will be the battery end of the tube, and the silicone will help make that end easier to put on and remove so you can recharge the batteries using your standard AA recharger.

7) On the other cleanout adapter, drill 4 tiny holes (otherwise it will crack) to match up with the holes on the reflector kit.

8) Set up the step up transformer by attaching the 14.4V battery to the input. Then attach the multimeter to the output, and rotate the screw using the small flathead screwdriver until the output reads 34V.

9) Assemble the electronics using the diagram above. Keep in mind that there is polarity on the LED module, so you need to keep track of which side is positive and which is negative.

10) Now slide the electronics into the tube, with the battery pack on the end with the cleanout plug, and screw the reflector kit into place. When the batteries run low, you can just take them out of that end to charge them, and the rest of the electronics should never move.

11) Now shine a light, you crazy diamonds! Please feel free to comment with any questions.

Comments

author
redrooster (author)2016-01-10

Could you use a metal pipe instead of plastic so that it could double as a heatsink?

author
DakLak (author)redrooster2016-02-08

An alumin(i)um tube would be best as that metal has superior heat conducting propertoes.

author
jaksherry (author)redrooster2016-01-10

I don't see why not. but take into consideration that it would likely be heavier and mote expensive. also, be very careful about sealing the electrical connections or the tube could short it out. Good luck!

author
Charles Gibbs (author)jaksherry2016-01-11

And also< I would like to see how long your going to hold on to that tube with 100W dissipating form it..... :-O

author
redrooster (author)Charles Gibbs2016-01-16

I would use a computer heatsink for the LEDs and a thick walled aluminum pipe for the battery,fan,etc... the fan would draw the heat away from the heatsink along the inside of the pipe and extract it out the back,so the pipe is dissipating the heat as well.Beats plastic for this application.

author
Charles Gibbs (author)redrooster2016-01-17

Hi redrooster, yes as did I, scroll down further and read what I did with my 100w chip and a CPU heat sink, as I say it has been running for two years now no probs, its not portable as such but I use it on camping trips and in roofs etc..

Have a blessed day.

author
hanelyp (author)Charles Gibbs2016-01-16

If the tube doubling as heatsink is too hot to hold, it's not really getting rid of heat fast enough for the LEDs.

author
hanelyp (author)Charles Gibbs2016-01-16

If the tube doubling as heatsink is too hot to hold, it's not really getting rid of heat fast enough for the LEDs.

author
Tanishq Jaiswal (author)2016-01-16

From where you got the step up transformer ?

author
PhilKE3FL (author)2016-01-11

Another tip & a question, First the tip: When using heat sink compound you want to use as little as possible. If you can see it clump up you're using way too much! Use your finger and wipe it all off till you can see a sheen but no clumping, do this to ONE side only. The object of heat sink compound it to fill in the gaps NOT to place a buffer between the two surfaces. You want the two surfaces to touch in as many places as possible with NO heat sink compound between them. The perfect join, using no heat sink compound, could be obtained IF we could machine the two surfaces to join together perfectly. (This can be done, but is still cost prohibitive for our purposes.)

Question: Is this "100 W" LED an LED that puts out the equivalent of an old style incandescent 100W bulb, or is it really using 100 W of power?

author
jaksherry (author)PhilKE3FL2016-01-11

First, thanks for the tip.

To answer your question, I believe that the LED module has 10 rows, each row has 10 1watt LEDs.

author
PhilKE3FL (author)jaksherry2016-01-12

To get 100W from 14.4 Volts (12 * 1.2) you need close to 7Amps, for 2.5 AHr batteries they last about 1 minute at most probably less. This is from a calculation & I reduced it with a bit of guess work. So, how long to they last?

For 2.5 Ahr batteries I believe that the rating is determined using about 125 mA (for lead-acid batteries the Ahr rating is determined using a 20 hr discharge rate so 2.5/20 = 0.125A) 7 Amps is 56 times faster and the faster a battery is discharged, above the 20 hour rate, the more the life of the battery decreases. So if it were perfectly linear we would divide 2.5/56 * 60min ~2.7 min, and 56 times faster than the the normal 20 hour rate would decrease the life even more so I estimated it at 1 min.

author
Charles Gibbs (author)2016-01-11

Hi All!

What I on occasion have done (with great success I might add) is to take a bit of ultra fine rubbing compound on a super soft cloth with water and lapped the heat sink and LED chip and then put just a dab of heat sink compound on the LED chip and pressed them together with a cloth on both sides so nothing gets fouled up and once that is done I took Q-Bond which is a form of super or crazy glue depending on what you want to call it and traced the edges of the LED chip. This bonds both surfaces permanently and because you have basically lapped the two faces and used minimal heat sink compound heat transfer is aces! You have to make sure to use as little heat sink compound as possible though, once this stuff contaminates a surface it a bugger to get clean and then the glue does not stick, be very careful when matting these two items as there is a big and very real chance of damage happening to the LED chip. But, sitting in 40 degree C heat I must say I have had no problems with heat build up or transfer and my chip has been working for close on two years now. As far as maintenance goes, I just make sure that my heat sink remains clean and that my fan is in good working order, the heat sink I chose was from a computers CPU probably overkill I know, but, out here those things are way pricey so better safe than sorry.

Charles Namibia.

author
david.roseman (author)2016-01-11

Scratching the heatsink is exactly what you do NOT want to do. You want a polished surface to avoid any discontinuities in the gap between the LED and the "heat sink".....also, JBweld?! If you want to have little to no thermal condutivity between the LED and the heatsink, you can use JBweld, else, use all thermal grease, or thermal epoxy. You need to get that heat out of that COB!

And so on about the lack of heatsink, but everyone already mentioned that.

author
jaksherry (author)david.roseman2016-01-11

Thanks, noted. Will keep in mind for future builds :-)

author
darksb3r (author)david.roseman2016-01-11

Absolutely correct - lapping the heatsinks and the mating surface is the solution. The flatter the mating surfaces, the better the thermal conductivity. The thermal grease/epoxy is just there to help fill the inherent gaps formed from the polishing process.

Take a look at this chart of the thermal conductivity of different materials (JBWeld is 0.59 W/mK!)

http://reprap.org/wiki/Thermal_Conductivity

It is at least a little better than air, hehe.

author
Lee Wilkerson (author)2016-01-11

Great idea, but what in the world are you going to do with a 100W flashlight (spotlight?) any way? I'm thinking a 10W flashlight would be plenty and the 10W/900 Lumen LEDs SKU060051 which I bought require 12 VDC to operate. I purchased them from banggood.com for $0.59 each. You could even place 10 - 10W LEDs in parallel if you wanted more light or use a selector switch to select 1 or multiples. This eliminates the DC/DC converter which means less power consumption and it also eliminates the shock hazard.

Use 140 grit or higher sandpaper or sand cloth to roughen up the surface of the metals. This will render far more surface contact resulting in much better heat dissipation.

author
jaksherry (author)Lee Wilkerson2016-01-11

Thanks for the interest! I have NO need whatsoever for a 100w flashlight. I just like to tinker :-)

author
Lee Wilkerson (author)2016-01-11

Great idea, but what in the world are you going to do with a 100W flashlight (spotlight?) any way? I'm thinking a 10W flashlight would be plenty and the 10W/900 Lumen LEDs SKU060051 which I bought require 12 VDC to operate. I purchased them from banggood.com for $0.59 each. You could even place 10 - 10W LEDs in parallel if you wanted more light or use a selector switch to select 1 or multiples. This eliminates the DC/DC converter which means less power consumption and it also eliminates the shock hazard.

Use 140 grit or higher sandpaper or sand cloth to roughen up the surface of the metals. This will render far more surface contact resulting in much better heat dissipation.

author
Lee Wilkerson (author)2016-01-11

Great idea, but what in the world are you going to do with a 100W flashlight (spotlight?) any way? I'm thinking a 10W flashlight would be plenty and the 10W/900 Lumen LEDs SKU060051 which I bought require 12 DC to operate. I purchased them from banggood.com for $0.59 each. You could even place 10 - 10W LEDs in parallel if you wanted more light or use a selector switch to select 1 or multiples. This eliminates the DC/DC converter which means less power consumption and it also eliminates the shock hazard.

Use 140 grit or higher sandpaper or sand cloth to roughen up the surface of the metals. This will render far more surface contact resulting in much better heat dissipation.

author
starphire (author)2016-01-10

I don't see any instructions or even a photo on using the 44mm lens and reflector kit in the parts list. It seems rather an important thing to leave out since without a lens the sideways output will also be blinding to anyone standing to the side of it.

There is a sort of rationale with allowing LED flashlights to be driven past their safe thermal limits for continuous operation, being that they are usually used for short amounts of time. For example, the first LEDs rated for 5 Watts were actually 3 Watt LEDs with a rated lifetime of only 1,000 hours instead of 30,000 because at 5 W they would cook themselves to an early death. But for a flashlight, 1000 hours was enough.

I literally laughed out loud when I saw the heatsink for this 100W array. Yonatan24 comment about heat dissipation isn't too far off - even with a fan, that heatsink is woefully inadequate to maintain the LEDs within their rated temperature at full power - something that you can't easily measure directly. There seem to be more makers and experimenters every day using misguided rationales and seriously undersized or poorly coupled heatsinks to cool their LEDs. If they haven't failed outright by the time they write it up and put it on the internet, it serves to misinform others about proper thermal management of their project when they borrow ideas. I would say 70-85% of all recent Instructables I've seen using >1W LEDs suffer from insufficient heatsinking to make it reliable in the long term - that is, to get the kind of life the manufacturer rates their LEDs for. And that proportion is growing, probably due to others publishing undercooled designs of their own. Again, it may not matter for a flashlight but people should at least be aware of the tradeoff they are making and never fooled into thinking something like this would suffice for a room light fixture.

author
jaksherry (author)starphire2016-01-10

1) There is a pic of the reflector kit

2) You are correct that the heatsink is not a perfect fit for the job, but for proof of concept for a PVC, it's fine- as was mentioned in the instructable. So far, for short term use, the LED's have had no power loss or thermal damage

3) Who said anything about turning this into a room light fixture?

author
starphire (author)jaksherry2016-01-10

I won't get into an argument about how adequate or inadequate the heatsink is for your application. As I noted before, if it only lasts for a hundred hours on average instead of 20,000 it's probably sufficient for a homemade flashlight using a cheap LED.
I tried to be clear why I expressed concern about another reader possibly extrapolating this LED/heatsink pairing into something like a room light. It's not obvious to all that the stresses and long-term requirements are very different. You might realize that it wouldn't be good for something that's left on for hours at a time but others may not and your instructable doesn't point that out at all.
The trend I've seen in the last few years in homemade LED lights is drifting towards less heat dissipation capacity for a certain power level, without doing the kind of testing that would be considered essential by a company with a reputation and warranties to watch out for. Instead, the testing is empirical: "I've used it for a while now, and it hasn't failed yet". Just because you can't see the damage until the day it stops working doesn't mean it isn't taking place at an accelerated rate. For semiconductors, the Arrhenius equation rules the relationship between junction temperature and time-to-failure, just as it always has.

author
blorfadillo (author)2016-01-04

Nice. Based on a quick look around and noting that these 100W/9000lumen LEDs consume about 3000mAh, I'd guess it has maybe 20-30 minutes run time using 2500mAh rechargables. A couple mods that came to mind were to use 4 Li-Ion batteries @ 3.7V each to achieve approx the same working voltage/capacity or possibly 9 to give you a ~34-36V output either in a 9 in series or 3x3 in series config. That would eliminate the DC stepup part. The plus with the 3x3 config is that you could use a charger made for a 12 volt pack. Seems like with a little redesign, you might be able to charge in place although at a fairly low rate to avoid overheating the batteries since there's no air circulation to speak of. Maybe a few holes around the area where the fan is mounted, and a few holes elsewhere for exhaust. Another thought might be to get a 2" diameter heatsink an few inches high, "star" shaped [looking at the ends] that glued to the LED but fit inside the cleanout adapter, and then a 2" coupling into which the body would fit on one side, the heatsink on the other.

The other idea would be to rig up a variable output via resistors/switch, either a hi/lo or hi/med/lo using hi for searchlight mode, med and lo to conserve battery. Alternately, you could use a 2" to 3 or 4" adapter and mount 3 different LEDs, say maybe a 3 or 5W for "lo" (or something in the 1-300lumen range) giving maybe 10-20hrs run time, a 30W for "med" (around 1000lumen) with maybe 1hr run time, then the 100W for blinding/searchlight mode.

Also, I think your parts list should call out 2 cleanout adapters, and only one plug rather than the other way around.

Where did you get the lens assembly? It would be nice to see a picture also.

Thanks.

author
jaksherry (author)blorfadillo2016-01-10

Thank for the heads up! I fixed the items error. As for the different batteries, the thought came to mine during the build, but I specifically wanted to use batteries that I (and other people) already had lying around

author
jaksherry (author)blorfadillo2016-01-10

I think you might find this interesting:

https://www.youtube.com/watch?v=70JqKX_tt_g

author
daniel.stillmunks (author)2016-01-10

oh duh I forgot my contact info> captaindandan@msn.com (Hesperia, CA 92345-3466, USA)

author
daniel.stillmunks (author)2016-01-10

My son & I want to build a custom TOY ray-gun RIFLE. This flashlight is a start but

I was wondering how to have a light in the body of the RIFLE BLINKING and another light in the end of the RIFLE also blinking.? Would you be able to help us with a project like this .?

author
Constructed (author)2015-12-30

Thanks for crediting me! I love your flashlight design!

author
jaksherry (author)Constructed2015-12-30

Thank you! Couldn't have done it without you. It was an enjoyable learning experience.

author
Yonatan24 (author)2015-12-26

Ummm, The heat-sink you used can dissipate only a watt or two, You need a heat-sink like this one. Your LED will burn out!

author
CurtR (author)2015-12-25

Your step-up transformer is not a transformer but rather a DC step up voltage regulator. A transformer works with AC and you are using DC in the circuit. Here is a link to one such item:

http://www.dx.com/p/dc-4-5-32v-to-5-42v-step-up-voltage-regulator-converter-blue-214310#.Vn1_xFJ2FKs

A smooth surface on the LED and heat sink and a little more thermal paste would probably give a better heat transfer. The trick is to maintain good physical contact between the two. By drilling a couple of small holes in the heat sink and using very short self tapping screws you could attach the LED unit.

author
jaksherry (author)CurtR2015-12-25

CurtR- appreciate the feedback. I was actually considering both of your ideas during the build. However, I was hesitant about drilling into the LED module for risk of damage. That's why I ended up using metal epoxy with the thermal paste, to bind the two pieces together without drilling. Someone more proficient than myself may be able to do that.

author
CurtR (author)jaksherry2015-12-25

I noticed some holes in the LED unit and thought they might work if the alignment was correct.

author
thestip (author)2015-12-24

Cool instructable, however you really don't want to scratch up the LED base or the heatsink. They both should be as smooth and clean as possible when applying any thermal paste or adhesive to avoid any tiny air pockets. =)

author
jaksherry (author)thestip2015-12-24

Thank you for your input. However, I find that without the scratching, there is not sufficient surface are for the JB Weld to cling to.

author
MikeR3 (author)2015-12-24

How do you keep it cool?

I made one, and filled it with mineral oil as a coolant, sealing it with silicone RTV. I keep in in the car and it plugs right into the 12V outlet.

author
jaksherry (author)MikeR32015-12-24

I keep it cool with the heat sink/fan combo. I also mixed thermal paste into the epoxy. it's not perfect, but it has not overheated yet.

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