Corded tools are great, you don't need the batteries to power them. But, everything seems to be heading the wireless/ cordless route, even the new iPhone 7, 8 &10 has no audio jack.

I build stuff, and I use my hot glue gun most of the time. Having a cord frustrates me a lot; those awkward maneuvers, those tangling wires are no good.

In this Instructables, I want to share with you my idea of building a cordless glue gun from a cheap, corded hot glue gun.

You will need:

Materials:
1. Corded hot glue gun $3 from Michaels
2. Rechargeable batteries $7 from IKEA
3. Battery holder w/ switch $0.75 each from ebay
4. Step up converter $0.78 from ebay

Tools:
1. Screwdriver
2. Scissors
3. Soldering iron and solder
4. Wires
5. Multimeter

The total cost of materials would probably be around $12 or lower.

Step 1: Background

Here's how it works.

The 4 AA batteries will be connected to a step up converter, and the converter increases the voltage. The one I use is a generic brand MT3608 step up converter, capable of outputting 27V max. Theoretically, the higher the voltage, the faster the hot glue gun heats up. I do recommend some research of your own to get the higher output voltage converter instead (55V max), but the MT3608 works fine.

I have seen dozens of DIY cordless glue gun out there but I have found most of them used nichrome wire as the heating element. Nichrome wires are great for low voltage and has faster heating properties. But, they are hard to find and dangerous to work with. The thinnest ones will break if they are exposed to high voltage. Also not to mention they require a physical switch, otherwise you may overheat everything.

The PTC ceramic heating element in most corded glue gun has a "self-thermostat" material property. A physical switch is highly recommended for this project though, such as the battery cover that I used.

Step 2: Determining the Power Source

The MT3608 step up converter steps up low voltages (2V minimum) to a higher voltage of your choice within given range. I use 4X AA rechargeable NiMH batteries that summed up to be 4.8V. Thus, I will step up the voltage from 4.8V to 27V.

Here's the thing: using 2 or 3 batteries work too but the converter may draw more current from the batteries and it may be bad for the batteries. A divided load is safer. Law of conservation of energy states that the amount of energy you put in is conserved.

Step 3: Connecting the Converter Circuit

Connect the battery holder to the MT3608 Vin+ and Vin- by their polarity. Unscrew and disassemble the glue gun. Snip away the wires on the glue gun and connect them to the Vout+ and Vout-, polarity is not important here. Solder the connections if you will.

Insert the batteries. By turning the potentiometer on the MT3608 I use a multimeter to determine it has reached its maximum output voltage at 27V. You now will have a higher voltage on the heating element.

Step 4: Finish

I 3D printed an adapter for the glue gun to be stuck on the battery holder. I super-glued the bottom handle to the 3D printed part, and I used double sided tape to stick the 3D printed part to the battery holder. You may use the good old duct tape to tape the handle to the battery holder.

The heating may take some time but it is much safer and convenient to use, it took about 10 minutes for mine to heat up in a well ventilated 26'C/ 79'F room. Heating time may vary according to power source and operation environment. You may also use low temp glue sticks for shorter waiting time. Do not forget to turn off the power after use!