27 Led Light Mod





Introduction: 27 Led Light Mod

And yes, It's yet another Harbor Freight 27 Led light mod ! I get these free from HF, and thought I might make one a little more useful. These lights are quite bright, even with the cheap batteries provided. I would recommend, even if you don't mod them, that you take a look inside. These batteries can ruin your light, depending on how long they've been sitting on the shelf. I was thinking one day after a power outage, that these little lights could be powered by a 12 volt DC adapter. I already had an adapter, that will provide multiple voltages from a 12 volt source. I'll put in a link to the one I have.

Remember, safety is YOUR responsibility. This is a DC only device. Do not use with AC current ! This Information is for educational purposes only.

Tools and Materials :

1. 27 Led Light - Harbor Freight.

2. Soldering iron and solder.

3. Light gauge wire

4. Power Jack

5. Step drill bit (optional)

6. Hobby Knife

7. Small heat shrink tubing (optional)

8. DC Adapter

9. 12v Socket extension cord

10. Here's a coupon for a free light. This way if you destroy it, at least it didn't cost you anything ;) Expires 1/3/18

So on to step one.

Step 1: Take It Apart !

These things are fairly easy to take apart. First take out the 3 screws on the back. There's a convenient magnet on the back, to keep the screws handy. Next remove the batteries, and then the four screws that hold on the front panel. Finally remove the 2 screws that hold the Led circuit board. Be careful when you move the Led board from its slot, that you don't break the wires.

Step 2: Modify Center Section

I disconnected the wires from the center battery section, to make it easier to work on. I then used a step drill or Unibit to drill through the peg on the battery section. You could probably use a standard drill if you're careful. I didn't want to crack to plastic, hence the step drill. After the peg is gone, I enlarged the hole with a hobby knife. You need to make room for the power jack, which is installed next.Just below the new cutout there is a thin wall. You will need to cut a half moon shape there for the wires from the jack.

Step 3: Drill Hole for Jack

I used masking tape to mark for the jack hole. There is a mold line in the plastic of the battery case. I centered the mark on that and used the center of the cutout I made earlier to mark the center horizontally. I used my hobby knife to make a small indent for the drill bit. Then with the step drill I drilled a hole slightly smaller than my jack. I did this so I could make flats in the hole to match the jacks barrel. Your jack may not have these flats. I used my hobby knife to make the flat sections. I just took a little off at a time, checking with the jack for fit. You don't won't to make the hole too big. I installed the jack and tightened the lock nut with needle nose pliers. This was just a test fit, I soldered on the wires and added heat shrink before installing the jack permanently. That is the next step.

Step 4: Install the Jack

I started the wiring by tinning the ends of the wires with solder. I soldered the wires to the jack and added some heat shrink tubing. I put the jack in the hole made earlier, and threaded the lock nut over the wires. I cut the wires to length and soldered them to the positive and negative connections. You probably want to run the wires around the screw posts as shown. That way you won't crush them when you put it back together. You can find polarity of the points, by looking in the battery box. I don't know if polarity actually matters here, but I connected the wires the way they were originally.

Step 5: Button It Up !

Now you can put it all back together. Be careful when tightening the screws, the plastic posts are easy to strip. Don't ask me how I know, ;) I tested the light first with the supplied batteries. Just to make sure it still worked. I removed the AAA batteries. I set the adapter on the 4.5 volt setting and hooked it up to a 6 volt battery I had sitting around. Voila , what do you know, it works !

I'm sure with this adapter, it will work on any battery from a 6 volt to a 12 volt. I tried it on a 6 volt wall wart type adapter and it worked, but it flickered badly. Probably not a regulated adapter. You'll probably want to remove the AAA batteries before running on an external battery. I don't know if it will hurt the AAA,s, but no need to chance it.

This thing will probably run for weeks on a fully charged 12 volt battery. Haven't tested that yet, but I will, and will post an update later. Hope this is useful to someone. Let me know how you use this, Enjoy,


P.S. I know somebody will say, Man, that's a lot of stuff hooked up, for what was a portable light ! Well, this is true. But to be able to run it on many different types of batteries may come in handy. Unless you have stock in a AAA battery company, that is. ;)



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    Updated links and added recent coupon for free light, enjoy !

    WARNING: If you reverse the polarity to an LED you will cook it for sure.There is even the chance it will physically pop. Also putting any amount of current on to a non-rechargeable battery WILL cause extreme heat and the thing might explode.

    Don't get me wrong, I'm it saying reverse polarity won't hurt leds, I'm just saying in my experience luckily it hasn't been an issue for me. I'm also not working with high voltage on my leds.

    Did this the other day by accidentally reversing the power from a pair of AA batteries. Piece nailed me in the cheek!

    Led 1.jpgLed 2.jpg

    Talk about popping, wire an electrolytic capacitor backwards...boy it blows like a big ol firecracker. Amazingly loud. Never had it hurt an LED though. It just doesn't light.

    Did this the other day by accidentally reversing the power from a pair of AA batteries. Piece nailed me in the cheek!

    Led 1.jpgLed 2.jpg

    I've worked with many, many leds, mainly with Arduino and adding them to my rc vehicles and never once had an led burned up or popped from reverse polarity. They just don't work with reverse polarity. Set it properly and they work fine even after reversing it.

    If you dump too much voltage and current into an led it has the potential to pop.

    I was actually wondering about this instructsbke becsuse I'd imagine that something designed to run on 4.5v isn't going to handle 12v very well at all for very long. I'm not surprised it works on 6v but surely the lifespan of the light will be decreased.

    Well, I do not say anywhere in this instructable that I run this light directly on 12 volts. Many people are reading that into the instructable, but this is not what I said. Please read the instructable carefully again. All five steps ! Thanks,


    Commented on and answered, several times, thanks,


    Great! thanks for posting....Anyone know a way to find technical spec's for these types of lamps. I've just rigged one up to the Arduino and altered fade tempo and intensity. Just wondered if I could determine what the LED's are and the resistors needed for other projects. Thanks.