Introduction: Solderdoodle Pro 2.0: USB Rechargeable Soldering Iron

About: After being laid off in 2009, I got rid of my car to save money. The difficult transition from a car to a bicycle led me to start Solarcycle and design USB chargers that keep smart phones alive.

Please click below to visit our Kickstarter project page for Solderdoodle Pro 3D Print Finishing Tool attachments and pre-order a production model!

Solderdoodle Pro does what other portable soldering irons have failed to do, and that’s the ability to last at full power for over a half hour above 800ºF, over 2 hours above 500ºF, and charge the soldering iron from a USB port. You can literally go anywhere and still have a way to charge your Solderdoodle if there is a laptop, USB battery, wall adapter, or even a USB solar charger nearby!

Solderdoodle Pro uses a high-efficiency, high-power charge controller, uses the same battery that's used in the Tesla electric car, and uses replaceable tips.

Positive Reviews and Feedback:

"I brought the solderdoodle prototype to a class I teach at Portland Community College. Everyone always brings the worst radio shack soldering irons to the beginner soldering class. The solderdoodle pro performed as well as my $45 50W Sparkfun Soldering Station. It was a real benefit to the class. Here's the class I teach : - hydronics

"Thank you for letting me try out your creation, the Solderdoodle. I enjoyed using it on various projects and tasks in my home and in the lab. The design is pretty solid and much easier to use over a corded giant. The folks I showed here at OSU in the EECS department really liked the hand held portability of it. The mechanical engineers thought it was neat as well." - Eric

Solderdoodle Pro Specs:
* Time to Fully Charge @ 5V 2A: 2 hours | @ 5V 1A: 3 hours | @5V 500mA: 4.5 hours

* Capacity: 3350mAh/3.6V * Type: Panasonic NCR18650B Lithium-Ion

* Size: Diameter: 1.6 inches * Length: 8.1 inches

* Body Material: Nylon * Weight: 96g (3.4 oz)

* Input Cable - 3' Nylon Braided Male USB Type A to Micro Connector

* Input - Current: 450 to 1300mA | Voltage: 5 to 6 Volts

* Output - Current: 1400mA | Voltage: 2.5 to 4.2 Volts

* Battery Life Under Typical Use: Over 5 years * Replaceable battery

* Provides over an hour and a half of soldering

* Solder up to 24 gage thick wire (Flux recommended for lead-free applications, thicker wire, or large ground planes)

* Heats up to over 700ºF (371ºC) in just 30 seconds

* For use with leaded solder and lead-free solder

*WARNING: Be careful when handling any Lithium-Ion battery because shorting the battery can cause burns. Always wear safety goggles. Please use recommended battery and circuit components because of the higher 2000mA max battery charge current involved. 3D printed parts may warp under high temperatures.

FCC Compliance: NOT Required because the circuit frequencies are below 1.7MHz

Step 1: Materials, Tools, and Files Required

Here is a list of the materials, tools, and files required.


QTY Description

1 Weller BP645 Soldering Iron

1 Lithium-Ion Charge Controller Circuit (Schematic, Gerber Files, etc. can be downloaded from the previous page. The main IC component is the Maxim MAX8903G charge controller)

1 NCR18650B 3350mAh Unprotected Panasonic Lithium Ion Battery (If lower cost is necessary, try the Panasonic NCR18650A battery with a slightly less capacity of 3070mAh. Make sure it's unprotected and check the battery part number carefully. Protected batteries have added length with a built-in circuit, which may affect performance. Reference Other brands of batteries are NOT recommended because the charge controller current to the battery can be as high as 2000mA and the Panasonic NCR18650 chemistry can handle it. If you need to use other brands, make sure that they meet the same specifications, chemistry, and can handle up to 2 Amps of charge current. Using batteries that don't meet these specifications can lead to dangerous battery damage.)

1 LED light pipe 492-1334-ND

2 Hirose 2-pin connector DF3-2S-2C

4 Hirose Socket 24-28 AWG Crimp Pin DF3-2428SCC

1 3' USB Male Type A to Male Micro Cable

1 1/2" Wide Kapton Tape Roll

2 1" Kapton Tape Disc

1 1" Diameter Piece of Heat Shrink Tubing 2.7" Long

1 Roll of solder wire

1 3D Printed case (Files available on previous page)

3 2-28 x 1/2" Thread Forming Screws

Various Lengths 26 AWG Standard Red and Black Stranded 4 Amp Max Wire Listed Below:

1 6.10" Black Wire .06 strip one end .20 strip the other end

1 8.00" Red Wire .06 strip one end .20 strip the other end

1 4.60" Black Wire .06 strip one end .20 strip the other end

1 1.75" Red Wire .06 strip one end .20 strip the other end


QTY Description

1 2-28 Torx driver

1 Power Core Battery Fixture

1 Wire Strippers 24-26 gage range

1 Wire Crimper 20-24 gage range

1 Tape Measure

1 Third Hand Soldering Clamp

1 Soldering Iron

1 Heat Gun

1 Scissors

1 Hobby Knife

Step 2: Battery Assembly

Insert the NCR18650B battery in to the Battery Fixture with the positive side facing up. The fixture will align the Red and Black wires as you solder. Do not touch the soldering iron to the fixture because it can melt. You might be able to solder the battery without the fixture, but it is much harder and you would still need something to keep the battery from falling over. The fixture can be used for other battery projects too.

Place the .20" stripped end of the long Red wire in the trench labeled +RED and solder the Red wire to the battery. Try to solder to the battery quickly because too much heat to the battery may damage it. If there is any solder sticking out, smooth it out with the soldering iron. After soldering, tilt the fixture and push the battery out from underneath with your finger. Turn the battery upside down and insert the battery in to the fixture with the Red Wire in the +RED trough and the negative end of the battery facing up. Crimp the end of the Red wire with the Hirose Pin and insert the pin in to port 1 of the Hirose 2-Pin connector. You want to attach the connector at this point because it is dangerous to leave a dangling bare end of a battery wire exposed and can potentially cause a short or burns if it touches the negative end of the battery. Place the .20" stripped end of the long Black wire in the trench labeled -BLK and solder the Black wire to the battery. The negative end of this battery usually requires more heat to solder because there's more surface area in contact with the mass of the battery, but try to solder quick. If there is any solder sticking out, smooth it out with the soldering iron. After soldering, crimp the end of the Black wire with the Hirose Pin and insert the pin in to port 2 of the Hirose 2-Pin connector. Tilt the fixture and push the battery out from underneath with your finger. Bend the black wire straight down over the edge of the negative end of the battery and guide the red wire to loop around along the side of the battery. The effect should be that the Red wire coming down from the positive end of the battery is 120º apart from where the Black and Red wires meet. This wire geometry allows for the positive and negative wires to come out from the same side and gives the snug fit. Wrap a piece of 1" wide Kapton tape once around the middle of the battery to hold the wires down. Place a 1" Kapton tape disc at each end of the battery and fold the edges over the side of the battery. Then slide the 1" Heat Shrink Tube over the battery with the tube flush with the positive end of the battery. All the tube slack should be sticking out the negative end. Now use a heat gun to shrink the tube to complete the battery assembly.

Step 3: Heating Element Assembly

Unscrew the Weller soldering iron and remove all the parts. Remove the coiled wire from the heating element and replace it with the 4.5" black cable by soldering the .2" stripped end to it. Then solder the 1.75" red wire to the metal spring where the AA battery would touch. Crimp the connector to the other ends of the wire and connect the Hirose 4-Pin connector to the wires as indicated below:

Red Wire pin to port 1

Black Wire pin to port 2

Step 4: Solderdoodle Pro Assembly

After printing the new soldering iron case, clean it with a hobby knife, then place the heating element, LED window, switch, and metal springs in the locations shown in the image.

Connect the battery cable to the "Battery" connector on the circuit board and lay them in the rear of the case shown in the image. Make sure the Micro USB connector is sticking out of the hole in the back. Place the LED light pipe in the groove above the circuit along the rear wall.

Before closing the case, plug the USB cable to the circuit and push the power button to ensure everything is working correctly. Both the green and red LEDs should turn on.

Tuck the wires in away from any protrusions so that they don't get crushed when the two halves of the case are screwed together.

Place the 3 screws in to the 3 holes in the case and screw them in with the Torx driver.

Test again Safety and Troubleshootingto make sure the power turns on when the switch is activated and charges correctly when plugged in to a USB port.

CONGRATULATIONS! Your done building the Solderdoodle!

Step 5: Safety and Troubleshooting

This test shows that the quality of the Solderdoodle is very high.

Solderdoodle only turns on by sliding the safety switch and pressing the spring loaded button down, so I taped it down and let it run with a temperature sensor touching the tip. I took photos of the test and plotted it in a chart, which are shown above. You can see that the temperature is above 700ºF for a full 1.5 hours. The battery is completely drained after 2.5 hours. Under normal use, the power button isn't held down this long, so it should last much longer during normal use.


Do Not leave Solderdoodle in direct sunlight. Keep it covered or in the shade. Heat from the sun can cause the charge circuit and battery to get very hot, stop charging, degrade the battery, and shorten its lifespan.

Acceptable Temperatures: Solderdoodle is designed to be operated in temperatures between 0º and 45º C (32º and 149º F).

Storage: Store the Solderdoodle in room temperature. Solderdoodle should be recharged about once a year to prevent over discharge.

For best results, fully charge Solderdoodle before using.


Solderdoodle LED doesn't light up when charging from my laptop:

1) This can occur if Solderdoodle is completely drained and goes in to a trickle charge mode. Keep Solderdoodle plugged in for about 15 minutes and the LED charge light should turn back on.

2) Some older laptops have a low current limitation in their USB ports and will disable the USB port if the current exceeds the limit. Try plugging Solderdoodle in to another USB port.

Make it Glow!

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MAKE ENERGY: A US-Mexico Innovation Challenge

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