50Watt Led portable

catch the rabit in the dark garden

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I am led fetishist.
If i see a led torch i have to buy.

But this isn't enough for me, so i designed a 3000 Lumen portable led flood light power by lithium battery.
technical details:
100% density one hour

Because there was no really existing led driver, i developed a boost circuit with the LT3756 from linear. The driver handle 50watt led with 30V and 1.6A without heat sink.

And the usecase:
my children us the led flood light to catch there rabit in the evening.

The flood light have several main components:

1) Led

2) Led cooling

3) Led driver

4) lithium battery

5) aluminium  housing

The description

1) Led

If i started 6 years ago with the project a 50W led was not know in our region and costs up to 100usd. Today i saw a led on ebay 100watt for 10usd ?

The challenge with this cob Led module is  cooling. A 50Watt emit about 50% heat from the 50Watt power. And 25Watt heat in an electronic ciruit are very heavy.

2) Led cooling

I found a simple way for the flood light. I set some frame condition:
max led temperatur <90°C, the aluminium case schould below 45°C.

For the Led cooling thee was a simple trick, put enough aluminium on the led.

A aluminium block with about 100x100x20mm is enough for one 40min with 3000lumen.

In the meantime there would be a better solution: synjet from nuventix.

but this another project.

3) Led driver

This was my first boost circuit. I deside to you use the LT3756 from Linear.
The circuit is build from the application note as booster to work in a range 12-20V input. 

Below 12V the current increase to much and the mosfet goes to hot.
It takes me 2 weeks to identified the right mosfet for the swiching circuit. 

With minimal changes the circuit would be a buck-boost converter from 12V - 40V.

Brightness for the led could be changed with a poti.
The ic had also the possibility to use pwm for dimming but also another project.

You can download the eagle file from my private blog:

to be continued...

  • 1 × 12V/4.2AH Lithium Battery
  • 1 × Boost Circuit 50Watt
  • 1 × 50Watt High Power Led
  • 1 × U-profil Aluminium for case
  • 1 × Aluminium Block for Led

  • Updated detail section

    Michael03/08/2014 at 06:41 0 comments

    Started with the project description in the detail section.
    Explain the led cob and risk
    Explain the led cooling
    Upload the schematic for the led driver

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akhilesh chauhan wrote 07/28/2014 at 04:50 point
Give me Rs.100

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Norman wrote 07/20/2014 at 19:15 point
I created an LED hand-holding flashlight with 100W LED.

i know the blue lithium battery pack.
it is big bullshit. inside of the batterypack are 9 mobilephone batteries. take your hand of this.
dont usw it, cause there not made for such an discharge energie, the LED need to use.
Use LiPo, its the only way. But be careful and read information in using LiPo and its charging

I used:

100W LED Cold-white
Fan (starts, when LED temperature is over 45°C)
150W Power converter
LiPo battery (
battery controll

when someone whats to know more about is and much details, message me:

iam from germany

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Michael wrote 07/20/2014 at 19:55 point

The Lithium Battery is the smallest issue, because my buisnes is to build lithium batteries.
see at

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syntroniks wrote 03/15/2014 at 00:56 point
Very cool. If you don't already have a TM26 flashlight, get it! I love mine. Now all I need is to build your flashlight but with more LEDs!!

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Michael wrote 03/15/2014 at 05:20 point
you are right this is a must have flashlight :-)

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Andrew wrote 03/08/2014 at 09:05 point
Here is the link to the stepper I got:

And the battery:

The batteries are usually a little less amp hours than they state but they are still good. They make up to 14amp hour in the same style, but that was too big to fit my torch.

And yes I would LOVE a 3d printer, but I'm waiting just a bit longer until they get a bit better/cheaper. Maybe another year or so.

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Michael wrote 03/08/2014 at 09:32 point
thx for the link is your friend in the meantime

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Andrew wrote 03/08/2014 at 07:04 point
I love that torch, very cool. I'm basically making the same thing but I'm trying to use all ready made parts. So far I have:
1x100W LED (all parts from ebay) +Lens kit
1x12v-35v stepper
1x12v 7000mah lithium battery
1x2.5cm 12v fan for cooling
1xNorthbridge heatsink from old IBM PC
"Eveready Dolphin" brand torch. Normally used 6v lantern battery and incandescent bulb.

I plan to hack the components into the dolphin torch. I have no idea how well it will work. I worked out roughly will get around 1.5 hr of light on single charge, maybe less. I will post it on my page once I make it, problem is components from China take 1.5 months to arrive to Australia.

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Michael wrote 03/08/2014 at 08:47 point
do you have alink for the 12V-35V stepper circuit and the lithium battery?
For cooling led you can also check:

3d printer would your friend to insert the components into an existing torch.

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Mike Szczys wrote 03/08/2014 at 00:41 point
Pretty neat. Can you add a picture of the populated board? What about a schematic?

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Michael wrote 03/08/2014 at 05:45 point
hi mike. i waited for a request :-)
I will add today the led driver design and the schematic for the alu-case.

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