USB Battery Bank Conversion for Stunt Sabers

Almost immediately after purchasing my Ultrasabers grab bag lightsabers, I hit the forums to see how I could customize my new acquisitions. Sure, the hilts hadn’t actually arrived yet and I had no clue which models I would ultimately receive, but I’ve never been one to leave things be and I wasn’t about to change.

While cruising Ultrasabers’ official forums, saberforum.com, I came across a guide from user CJ-Nihilus detailing an intriguing battery modification for Ultrasabers’ stunt (no-sound) sabers. As you might remember from my reviews, the standard battery configuration for Ultrasabers’ stunt blades is a pack of four AAA cells wired in series to give the necessary voltage to the LED. AAA batteries are naturally small, which limits even the highest density cells to around 1,000 mAh. Moreover, wiring them in series helps on the voltage front, but doesn’t help at all from a capacity perspective. CJ-Nihilus found a solution: USB battery banks.

The issues with AAA batteries aren’t limited to capacity, either. Wired in a series, four AAA alkaline cells put out 1.5V each and 6.0V total with a full charge. Unfortunately, this voltage does not last for long and after around 15 minutes of use (at 1A), the batteries can only muster 1.2V (4.8V total). By the time a high-density alkaline is ready to croak (around an hour later), it is lucky to be pushing 1.0V (4.0V total) to the LED. Throughout this process, the saber gets dimmer and dimmer before eventually turning off.

Some people’s solution to this is to swap the alkaline cells for NiMH rechargeable batteries. AAA-sized NiMH cells put out a relatively consistent 1.2V each, so a 4-cell pack should deliver 4.8V and will do so for the life of the charge. There are still problems with this solution, though. At 4.8V, the saber will be dimmer than it would be with 6.0V from four fully charged alkaline cells. Furthermore, NiMH batteries are still very limited in capacity.

USB battery banks solve both of the above issues. While USB specifications prevent them from providing 6.0V, they can do 5.0V, which is a slight improvement over the 4.8V average from NiMH rechargeable cells. However, most importantly, Li-ion-powered banks come in capacities that alkaline and NiMH cells can only dream of. For this project, I chose a 5,000 mAh pack from Aukey. In order to get 5.0V and 5,000 mAh from NiMH batteries, you would need 20 cells wired in a combination of series and parallel circuits. Good luck fitting that in your hilt!

The Project

As with any project, you’ll want to first make sure you have everything you need. At minimum, this includes:

1. Stunt saber that is configured to run at between 4.8 and 6.0 volts
2. USB battery bank that fits inside the saber’s hilt
3. Soldering iron
4. Solder
5. Wire stripper
6. Spare USB cable
7. Heat shrink tubing (I used 3/16”)

Once you’ve got everything, we need to prep the USB cable. Snip the female connector (or whatever is opposite the male end) and strip away the insulation/shielding. Once you’ve revealed the four inner wires, go ahead and slice the white and green data lanes; we only care about the red and black power lines.

With the red and black wires exposed, we now need to strip the insulation from each. Be careful! The wires are likely very thin and it won’t be difficult to cut through them while stripping. Once stripped, take the individual filaments and twist them together. This will make them easier to manage.

With the USB cable ready to go, it is time for us to turn our attention to the saber. Leaving as much wire as possible, carefully remove the battery holder. Next, strip away the heat shrink and insulation from the saber’s wires. With all of that removed, again twist the filaments together for management’s sake.

Now that both wires are stripped, we are almost ready to solder them together. First however, we will want to apply a small amount of solder to each wire before we fuse them together. This is called tinning the wires and it helps to expedite the joining process later on.

With the wires properly tinned, measure and cut enough heat shrink to cover the joint and any remaining bare filaments. Make sure you slide the shrink onto the wire before you solder the leads together! You won’t be able to add it after the joint is formed.

Now that the wires are prepped, it is time to mechanically join the filaments. Essentially, you just want to wrap the two bare wires around each other to form a close, tight spiral that won’t easily come apart if gently pulled. Black goes to black, red goes to red.

With the wires woven together, we are ready to solder the joint. Remember that we already applied a small amount of solder to the filaments before we twisted them together. Holding the soldering iron to the wires at this point will re-melt that solder and will help to join the two segments together. However, we also need to add a small amount of solder to the outside of the joint to ensure a proper bond. Do this for both sides, red and black.

Now that the wires are properly soldered, wait for them to cool before sliding the heat shrink over the joint. If you get impatient, the heat will cause the shrink to, well, shrink before you get it in place. With heat shrink covering all bare wire, use a controlled heat source (such as a heat gun) to shrink it around the joint.

With the wires have been joined and properly shielded, you’re ready to rock. Plug in your USB bank and enjoy your saber’s improved runtime and more consistent brightness.

Final note: Some hilts may be too short to fit the Aukey USB bank shown in this article. Though it fits my Initiate, I would prefer for it to be a little shorter. When installed in my hilt, it does press the USB cable into my saber’s switch, which could negatively impact my conversion’s longevity. Unfortunately, I have yet to find a shorter bank that will fit inside this hilt.