How to Make a 40W LED Flashlight – Electronics Projects Circuits

As I mentioned in my “Handmade 50W LED Flashlight” post, I built myself a high-powered flashlight. I can say it’s the best I could do with the materials I had on hand. 🙂 Except for the 12V 10W Power LED and 3S BMS, the other materials were salvaged or taken from scrap.

I used an old P4 ATX power supply case for the casing. The 18650 li-ion batteries were salvaged from a rechargeable drill battery; their condition is acceptable. I used a P4 heatsink to cool the LEDs; the fan is directly connected to the batteries and starts working when I turn the switch on. Since it doesn’t draw much current, I didn’t add any limiting or temperature control circuits.

As I mentioned in my “Balanced Charging Circuit for Li-ion/Li-polymer Batteries” post, I used a 3S 20A BMS module to prevent premature failure of batteries connected in series. A lower current BMS could be used, but I used this one since I had an extra one on hand.

I rushed a bit while mounting the 10W power LEDs to the heatsink and had some trouble with the screws, but it was resolved. When mounting these LEDs to the heatsink, you should mount them from all four corners to ensure full contact. Of course, applying thermal paste is also necessary.

I couldn’t find a ready-made LED reflector, so I cut an FR2 PCB board and made one. Soldering the copper layer made it reflect better. The LED flashlight runs for about an hour and a half with used 18650 li-ion batteries, which is more than enough…

Maximum power for 10W LEDs. The current is 1A. When connecting 4 LEDs in parallel, I needed to limit the current to 4A. I used a classic resistive current limiter: two 1-ohm 5W resistors connected in parallel. It draws approximately 3.8A. Since the batteries don’t constantly provide 12V, the voltage drops, so the current draw decreases slightly over time, which will extend the lifespan of the LEDs… Ideally, I would connect a separate resistor to each LED, but I didn’t want to bother with that, and it won’t be running continuously anyway…

I could use DC-DC modules for LED dimming, but these modules draw an extra 1 Ampere to operate, which isn’t necessary for this system. Because I wanted wide-angle lighting, I didn’t bother with a lens system; currently, it illuminates a very large area like an LED projector.