Power Bank Inside a USB Cable




About: Make you happy

In this instructable I show you how to make power bank hidden inside USB cable. Main point of this project, make cable witch can jarg small devices such as: smartwatches, wireless headphones or prank your friends also save data transferring capabilities.

Parts for this project you can find lying in your house, for example: reuse broken USB cable, battery from old Bluetooth headset or tiny RC helicopter, salvage charging board from chip single cell power bank (today you can find them almost everywhere). Lets go Started.

Step 1: Prepare All Necessary Tools

  • Soldering Iron;
  • Soldering Wire;
  • Desoldering Wire;
  • Hot Glue;
  • Prying tool;
  • Set of Files;
  • Multimeter;
  • Scissors (Wire Cutters);
  • Stationery Knife;
  • Electrical Tape;
  • Heat Shrink Tubes;
  • Tweezers.

Step 2: Prepare All Necessary Parts

  • USB Step UP power cable or USB Project box;
  • USB micro B, Type C, Lightning cable (based on your needs);
  • Power bank bord “T3845-I” ver. 1.0 or analogs;
  • Tiny two position slider switch;
  • Tiny Li-Po battery USB Type A male connector

Step 3: Remove Cable From the Case

You can skip this step if you already have suitable USB project box.

This is peaty easy, just find right spot, on the front of the connector and pry a little beat, than simple do rest following seam belong two parts. For this you’ll need guitar pick shape prying tool.

Step 4: Remove USB Connectors From the Power Bank Board

This is very complicated step.

First remove USB type A female connector.

  • Remove as much solder as you can can from main contact points, for this you’ll need desoldering wire;
  • Pick Stationery Knife or a piece of soda can and place it between board and connector, like on the photo below.

Second, remove micro USB type B female connector. This is most difficult because connector glued to the board with very strong adhesive.

  • First remove all solder from main connectors using desoldering wire;
  • Second heat up whole connector and try gently pull it up;
  • If you can’t remove connector in one piece easily, simply cut it in small pieces using side cutters.

If you remove soldering pads, don’t be scary because board shares ground and you also can find positive (main) signal from one of the capacitor lag. See photo.

Step 5: Board Preparation

Notice! Some important traces located close to edges of the board, pay attention to not cut them completely.

For this step you’ll need a set of files.
All necessary cuts you can see on photos.

Step 6: Cut Case to Fit Power Bank Board

Because space inside the case very small and we save traces instead of shaving them and replacing with jump wires, we need some extra space to fit our board also cut off for slider switch.

For this step you’ll need: Stationery Knife and Files pair of protective gloves also necessary.
Dimensions and positions for cuts you can see on photos.

Step 7: Soldering

Now when we prepare our board and case time to solder all main components together.

  • First of all remove USB type A female connector from the cable and strip outer jacket, ruffly 50mm in length.

Black wire is ground, red positive, green and white data wires.

  • Put cable gland. You can reuse one from SteUp Power cable;
  • Put heat shrink tubes on data wires;
  • Soldering positive wire from USB cable to central of slider switch, also don't forget put heat shrink tube before soldering;
  • Soldering another switch leg to the power bank positive out pad (see on the photo);
  • Twist two wires together and solder one to the USB type male connector another to the slider switch.

This allows you switch between battery and USB power.

  • Soldering second end from twisted wire assembly to the board positive contact pad;
  • Now we can solder ground, because it shared all over the board you can strip ground wire a little bit in the middle and solder to the ground pad on the board and to the USB type A male connector;
  • And last one solder battery to the board. You can find soldering points appropriately marked on the board itself.

Step 8: Assembling

Because USB connector very fragile it is good idea to simply hot glue it to the case with a switch. The rest of the assembling process is easy, just place our assembly inside, align and close, that ia all.

Step 9: Testing

Now let's go and test what we made.

As you can see we can get 5V out, data transfer also work just fine.

Step 10: Conclusion

Here I must to say, because battery has low capacity it hard to use with moder smartphones which requires a ton of energy This power bank can definitely give some juice to the smartphone but only very small amount in the same time this can be useful for small devices, such as: Bluetooth headphones, wireless mouses, smartwatches, fitness trackers you can even power Arduino with it.

Nevertheless this project proves that today's battery capacity or better to say size to capacity efficiency is not enough to power smartphone.



    • Colors of the Rainbow Contest

      Colors of the Rainbow Contest
    • Backyard Contest

      Backyard Contest
    • Frozen Treats Challenge

      Frozen Treats Challenge

    29 Discussions


    Question 1 year ago

    I’m afraid I don’t understand how tiny lipo like that could even charge something like Bluetooth earbuds. The battery looks like it’s 100-150mah 1s, and aren’t earbuds usually a higher capacity?

    1 answer
    Barely PaintedMidnightQuads

    Answer 1 year ago

    There a lot of different Bluetooth headsets on the market, for example " Jaybird FREEDOM 2" has battery, with capacity less than 70 mAh.


    1 year ago

    The space inside a USB cable could be used to hold a Flash drive set up to boot up a LInux operating system. It would make a good 'hidden' boot drive. If you are traveling internationally, and carry a laptop, the computer could be set up with Windows and have only innocuous files in it (and not set up with any of your online logins). This would satisfy any Customs officials, who might want to run your computer and check your social media and other online presence. Then, when you want to do anything personal, you plug in your 'USB cable' to boot up to a LInux system with all of your appropriate credentials and incriminating documents.


    1 year ago

    I love the way all the parts fit inside your enclosure..cool "tiny" power banks..:)


    1 year ago

    This could be funny gag! Someone asks for a charge so you stick one end of your cable in your mouth and the other end in their phone and imagine the look on their face when their phone lights up and starts charging! lol Or tell them you'll charge their phone using static electricity and start vigorously rubbing the other end of the cable against your hair or sweater.


    1 year ago

    That's pretty cool and super useful. I need to work on my soldering before working on something this small!


    Question 1 year ago on Step 10

    I have actually seen something like this before. It looks like a cable that has been rolled into a ball. Apparently that one can be used to charge phones. I'm unsure about data transfer though.
    Could you make something like that?

    1 answer
    Barely PaintedLaserbean00001

    Answer 1 year ago

    You probably mean “Bold Knot” as far as I know, this is only startup, which not released finial product.

    As far as I can say, small battery can't provide enough power for smartphone, not yet, maybe in the future.

    Battery capacity in this project less than 70 mAh, phone battery capacity at least 2500 mAh, which almost 36 times smaller.

    LiPo battery discharge rate very high and this charging board can provide at least 500mAh out current, which mean, this battery can provide power for charging a phone only for a couple of seconds.

    This is basics of thermodynamics.

    My answer on question “can I made power bank so tiny which will charge the phone properly” is no, not quite yet, maybe in the future, we discover new chemicals combination which will be more efficient.


    1 year ago

    A suggestion:

    You should be able to use diode(s) to eliminate the need for the slide switch... Making whole operations transparent.

    1 reply

    1 year ago on Step 6

    In step 5, I'm going to say that using a knife like that where you are cutting toward you is never a good idea. :(
    Don't ask me how I know that fact. ;)

    BUT this is a nerdy cool project, so it's got my vote for being clever! :)

    1 reply
    Barely Paintedmharmon12

    Reply 1 year ago

    Thanks for support. USB case very small, this is not easy precisely cutting and filming in the same time. I found that this is the best position for filming, completely agree that's this looks unsafe, but actual work, has been done very carefully, behind the camera. It is much better to use rotary tool.


    1 year ago

    Any chance you have links to that small of a battery or a link to the t3845 board ...as i am doing a search but i cannot come up with either ....i've come up with plenty of batteries of multiple sizes but none are that small! And as for the board i am not finding anything on it ....could very well just be my luck as i am just new to all the electronics searching lol

    1 reply