#0042: Creating a charging cable for a pair of Hatteker RFC-691 electric hair clippers

Otto

#0042: Creating a charging cable for a pair of Hatteker RFC-691 electric hair clippers

Preamble

This article will contain a guide to creating a basic DIY replacement charging cable. This cable is for a battery powered portable pair of electric hair clippers. Brand “Hatteker”, model “RFC-691”. A simple Chinese brand cheap pair of clippers whose proprietary charger has been misplaced. In addition to the tutorial itself, I will also opine on the value of ad-hoc crafts such as this.

Technical specifications (from device label information)

Description: Battery powered portable shaver
Brand: Hatteker
Model: RFC-691
Input: 5V DC @ 1000mA
Battery: 1x Li-ion 18650 – 1200mAh
Charge time: 1.5 hours

Hatteker RFC-691 official cable examination

The cable being replaced here is a simple DC-to-DC charging cable. It has a male USB-A plug on one end, and an IEC 60320 C7 style female plug on the other. Albeit miniaturised, polarity-keyed, and proprietary. It only has 2 lines, positive and negative. Additionally it has no active electronics. Simply passing the power directly from any standard USB-A power source to the clippers. The cable’s device is rated for 5 watts. Specifically: 5 volts direct current, at a 1 ampere max current. (It is assumed that the official cable would be built to that specification.) Very straight forward, very simple.

Why make a charge cable in general?

Why make a charge cable over buying a replacement? There are several reasons. These may include: saving time, saving money, being unable to source a replacement, or simply wanting to for fun.

With regards to saving time: it may be quicker to simply make a replacement, here and now from junk. Then it is to buy another one and wait for delivery. This is whilst also having to deal with all the potential issues that could arise within that process. One may not have the luxury of waiting the time required in order to get one’s device operable again. It may need to be working ASAP.

Now with regards to saving money. There are two factors to consider here. One is: whether or not it is in the budget. If there is no money for it, then there is no money for it. Period. It doesn’t matter how small the sum. However in my case, I simply do not want to spend the £5 odd pounds that I am seeing for what essentially is a low quality random after-market cable. One that is likely to break in a few months simply from use. Not when I can either make a better one that will last, or a free one (monetarily speaking) of comparable quality that I can then replace/fix whenever it does break.

The third reason I listed is being unable to source the exact accessory for my specific make and model. This is an issue that I have encountered after a cursory search on eBay (at the time of repair in 2025). The cable that I have found supports both model RFC-690 and RFC-692. So in all likelihood it will support my RFC-691. However it doesn’t explicitly state that it supports model RFC-691. So there is a chance that I could end up wasting time and money on an incompatible cable, even if I return it. Since I will have to pay return postage.

The fourth reason stated is for fun (aaaand profit). It’s enjoyable to make things. It is even more enjoyable to make useful things. Since one will be periodically reminded of their own abilities and competency whenever they use an item that they actually made themselves. It’s human nature. It provides a Rimworld style small mood buff: “+3 mood: used self-made tool”. (Or maybe I am just talking for myself.)

2026: Do! Not Buy.

One final reason to make this cable is that this is inline with this year’s (2026) assigned theme for my personal growth and improvement. This year’s theme is: “Do! Not Buy.” This means I am trying to focus on DO-ing more things to get to my goals, rather than BUY-ing things, that give the dopamine/illusion of progression. I am trying to build up my general skill-set experience, and simultaneously save money across the board. So make make make.

Tools and materials used

Tools:

  • snips
  • helping hands (Neilsen brand 240mm soldering aid pliers)
  • utility knife / precision knife
  • multimeter (Neoteck NTK098)
  • lighter
  • power-bank (Intempo EG0289MIX)
  • marker pen
  • nylon pry tool
  • soldering iron (Yihua 937D)
  • soldering iron wool cleaner

Materials:

  • [2x] crocodile clip jumper cables (black and red)
  • USB-A (power) cable
  • leaded solder
  • rosin solder flux
  • assorted heat shrink

PPE:

  • nitrile gloves
  • safety glasses

Build procedure summary

  1. insure that all relevant tools and materials are identified and within reach.
  2. acquire donor parts: USB-A to USB-C power cable and 2 crocodile jumper cables (AKA test leads).
  3. using snips cut off the USB plug that is not being used.
  4. using a utility knife slice down the outer insulation of the USB-A cable to expose the inner wires.
  5. using pry-tool: splay open and pull back the outer insulation, then pull out inner wires.
  6. using snips nip the insulation on the inner wires ~1cm in from the end then pull it off.
  7. twist each wire’s exposed copper strands into a tight braid.
  8. using snips cut off one side of each of the red and black crocodile test leads.
  9. using snips nip off around 1cm of the insulation of each test lead, and pull the insulation off.
  10. twist each wire’s exposed copper strands into a tight braid.
  11. plug the USB-A cable into a power-bank, and test voltage polarity of the wires using a multimeter.
  12. slide heat-shrink onto each individual wire, and onto the crocodile pair and USB-A outer cable.
  13. pair the crocodile clip wires (+/-) with their respective USB-A counterparts.
  14. wind the paired wires together into a mechanical bond (western union splice).
  15. using a soldering iron, leaded solder and solder flux – solder the western union splice.
  16. using a pair of snips: Neaten the splice profile. Remove any excess solder blobs or wire.
  17. cover the soldered splice with heat shrink then use lighter to tighten the shrink over the splice.
  18. repeat with the larger cable heat shrink to add protection and support to lead.
  19. inspect the created adaptor cable for any visual flaws.
  20. using multimeter test the outputs on the shaver, then mark them positive and negative on the device.
  21. using a power-bank, test the created cable by connecting it to the shaver.
  22. assuming success: discard waste materials from the job, and stow all tools and materials used.

Build procedure write-up

  1. Get, prepare, and test the parts.

Get a donor (known good) USB-A to USB-(irrelevant) cable. I used a random cheap power cable that came with a miscellaneous USB powered device. If you routinely buy USB powered devices, then you should have plenty of cables of this calibre on hand. As they seem to come boxed in as standard.

Cut off the irrelevant plug. Likely either a Micro-USB or USB-C plug. Then carefully slice down the outer insulation sheathing, and splay open the wires within. Unsheathe the insulation on the two wires within. If you used a data cable then they’d be more wires within. A typical USB-A to micro-USB cable contains four wires. Two power and two data wires. Typically colour coded as red (positive power), black (negative power), green and white (data +/-). Key word: typically. I recommend using a power-only cable: as they are both cheaper (to replace), and simpler to work on.

Regardless of what you have, the next step is to prep the wires and test the cable out. Splay out all the individual wires, then carefully snip the sheathing at about 1 cm down their length. Pinch this point with your finger nails and pull the insulation off. Repeat for all wires. Next use a multimeter test each wire to find the power positive and power negative. To verify the negative wire, test its continuity with the male USB-A plug’s outer metal. They are usually connected. Since this line is also typically used as a ground.

Alternatively test point the negative pin, once you have already identified the positive pin. Since it is its paired opposite. To test for positive power: plug the USB-A into a power bank, then using DC voltage mode on the multimeter test each cable until you came across something approximating +5 volts. Then do a continuity test from that wire to one of the two large edge pins within the USB-A male plug. This is the positive pin. With power positive and return identified, cut down and seal any other wires as they are not necessary.

Next prepare the crocodile clip jumper wires (or test leads as they are otherwise known). I like to use both a red and black cable to differentiate polarity. However you could alternatively just cut one test lead into 2 halves, and use both sides of it for the adaptor cable that we are making. Just have a way to mark the polarity of the otherwise identical clips. I chose to just use two differently coloured cables to save on confusion. I also have more of these cables then I need in the foreseeable future. So I had little reason to save on materials in that way. Using a pair of sharp snips, carefully nibble at each wire’s insulation at around the 1 cm from the tip of each wire. Then carefully pull the insulation off using finger nails.

  1. Setup inline heat-shrink!

This stage is the one easiest to overlook. I even forgot about it while writing this up – skipping straight to the splice segment. I have been in situations where I soldered a splice I was proud of – only to find out that I forgot to slide in some heat-shrink prior. And now facing a situation where I will have to either cut it open and start again; or just use tape to insulate the cable. Both are bad choices. There is a third choice but it involves a specialised tool: liquid insulation. You could paint the joint with liquid insulation providing that you have it to hand.

I actually made a mistake at this stage and that was that I did not employ enough heat-shrink. I used four pieces of heat-shrink. One to directly insulate each exposed copper line (yellow), one to bind the opened insulation of the USB cable (blue), and one to cover and bind the 2 crocodile lines and the yellow splice heat-shrink (red). This setup works fine. However it would have benefited from having one more large piece to cover the whole assembly.

With regards to choosing specific sizes of heat-shrink. I recommend purchasing a kit of assorted sizes, and use whichever fits the specific diameters of your wires at the time. This is because wires (in the wild) come in a myriad of non-standard sizes. (I.e. independently variable wire conductor, and wire insulation diameters.) Keep in mind that most cheap heat-shrink, shrinks to around half its default size. So size it to be snug, but leave room to allow for bumps. Sometimes you may even have to use short segments of shrink to cover just the conductor if the insulation on that wire is too thick to both snugly cover a wire’s thin conductor and bridge its fat insulation segments. This is especially true for cheap wires which skim on copper conductors, but employ a thicker insulation to give the impression of being a larger gauge wire than they are.

After doing this, then use a larger sized, longer piece of heat-shrink to cover the whole patch. This is to provide a strong protective layer for the joint. With my piece I failed to do this, thus leaving a hole into the layers of insulation which could be a path of ingress for dirt, dust, and other contaminates. I’ll just seal it with a little tape. (Not pictured.)

  1. Splice the wires together.

Next individually (and gently) twist all four wires exposed copper strands in a tight braid that resembles a solid core wire. Now pair up the wires. The positive end of the USB-A, with the end of the red crocodile clip wire. And negative with black crocodile.

Now twist the paired strands together using my splice of choice: the Western Union splice. This is done by making an “X” by crossing the 2 lengths of wire over each other. This should be done at a middle point for both wires. I will call the exposed copper of each wire between the intersection of the “X” and the rest of the wire the standing end, and the copper past the “X” the working end. Just like knot tying.

Carefully fold and twist one end of each wire’s working end over the other wire’s standing end. Repeat until the two wires are tightly twisted into each other. One tip, make sure that you are twisting the wires together in the same direction (counter/clockwise) as you twisted the individual wires themselves. This is so that they tighten, rather than loosen their structure when they are making the WU splice. Once the splice is complete: trim any excess that stands out. As this could cause an obstruction when applying heat-shrink. The sharp ends could also pierce holes in the heat-shrink once applied.

  1. Solder the splice.

Now that there is a strong mechanical (or physical) bond (or knot) connecting the two pairs of wires together. It is time to solder the connection. Making it permanent. When soldering I typically start by warming up and cleaning the iron. This is done by applying leaded solder and repeatedly dipping the iron into a metal mesh cleaner. Do this until all dark oxidation is removed, and the iron wicks solder readily. You could also apply rosin flux in this process to aid it. I personally just dip the hot iron into the flux dish as I go.

I mention this because in my opinion when it comes to soldering: preparation is of paramount importance to the successful execution of the task. Especially when using bog standard or subpar tools. As you can not rely on a tool of this quality to work readily despite poor conditions.

The actual soldering is easy enough. Apply flux to the wire joint. Then apply a little solder to the iron, enough that it adheres to iron without forming an unwieldy blob. Now line up a section of leaded solder wire to the joint. Then run the iron across the (fluxed) joint, while feeding the solder wire into the iron; and letting it melt and run into the wires of the WU splice.

Be careful to manage the heat that is put into the splice. Too little heat and the solder won’t take to the splice, too much heat and the insulation at either end of the splice will burn, melt, and curl back. Exposing more wire than desired. Perhaps more than the prepared heat-shrink could even cover. I have even had heat shrink that was placed too close to the joint shrink on me in situ. Before being positioned. So be cognisant of how much heat is actually put into the wires.

Now. Once the soldering is completed go over it with a pair of snips to remove any bumps, excessive solder blobs, or wire ends that the solder adhered to and exaggerated its profile.

  1. Apply the prepared heat-shrink.

Heat shrink should already be present on the wire at this stage. Slide it over the exposed segments then apply heat to activate it. Start with the smallest diameter segments to cover the exposed conductors, then move on to applying the larger bands that tidy and seal off the wires. Be careful not to accidentally apply any heat to heat-shrink that is not in place yet. As it will tighten and lock into place where ever it currently is. I used a simple disposable lighter for this. Alternatively you could use a heat gun or hot air rework station if you have one to hand. I KISS-ed this simple job. There was no need for anything more.

  1. Testing the hair clipper.

Before we go on. We need to gauge the status of the hair clipper. Specifically I needed to know the polarity of its two pins. To do this, just apply a multimeter across its pins. Set in an appropriate DC mode. Note the read out, then swap the probes with each other and test the pins again. Note this result.

If the result is positive. It means that the positive probe is on the positive pin; and if the result is negative, then it means that the negative probe is on the positive pin. Once the positive and negative pins have been identified: mark them on the device. This is to prevent accidentally reverse charging the clipper. Which risks damaging it, and/or the charging circuitry. (Powerbank, PSU, USB wall outlet, etcetera.)

  1. Cable test.

Test the finished cable. This involves a visual inspection. Does it look good? Fit for purpose? Is there anything notably broken on it? If it looks good; then perform a handling test. Pick it up, handle it roughly like you are actually using it without taking mindful tender care of it. Does it hold up to rough handling well? Or does it crack and fall apart? Better it breaks now, than in the moment when you need it.

Providing it passes (reasonable) rough handling. It is now time for an electrical test. I chose to use a powerbank as a power source. This is because it creates an isolated system. And limits any damage caused by short-circuits etcetera to just the created cable, clippers, and powerbank. Use a multimeter to verify polarity and electrical continuity.

  1. Final test.

With everything else worked out. Now is the time to plug it all in and see if the cable actually charges the hair clippers. Providing that the product passes this final testing. Then it is done. If it charges as expected from the power bank, then enough confidence in the cable is present for it to be plugged into a wall charger, to charge the clippers properly. Observe the first charge cycle for signs of heat build up, shorts, or any malfunctions. Otherwise: job done.

Acronyms used

AKA – Also Known As
ASAP – As Soon As Possible
CM – Centimetre
DC – Direct Current
DIY – Do It Yourself
IIRC – If I Remember Correctly
KISS – Keep It Simple Stupid
PSU – Power Supply Unit
USB-A/C – Universal Serial Bus (A type / C type)
WU – Western Union

Closing thoughts

A brief note on time. This little project was actually completed in June of 2025. This article is one of many that have been sitting in stasis for an extended time. It feels like I only did this a couple of months ago, however to my surprise, and according to the picture file names: they were taken in 2025-06. Only recently (2026-09) did I wrap up this article and make it publishable. This “wrap up”, included additional content that makes it relevant to 2026. Such as the incorporation of this year’s theme. Forgive me this deception.

With that out of the way, there is not much to say about this article or project that I haven’t already covered above. So let’s go for a more personal note. This cable was made out of junk I had on hand, and with a time limit. A family member lost the charger for the hair clippers and needed to trim their hair by Monday, it was the weekend IIRC. The point is that there was a time limit preventing the sourcing of a ready replacement. This is the perfect scenario where an electronics hobbyist should come in clutch with a DIY cable or what-have-you. (Akshully. This cable was made shortly after this time limit, I remember just charging the clippers using a bench PSU for an hour or two. But that is a less compelling story… Apocryphal story telling == More deception!)

The point is that these types of situations will emerge, they will come suddenly with little/no notice, and usually at an inconvenient time. So it pays to become accustomed to doing this type of work at the drop of a hat, and using whatever you happen to have on hand at the time. Such is the way of things. Keep in mind that a bodged solution is still a solution. Even if it only lasts as long as it takes to source a better quality replacement. As as long as it solves the problem in the moment it arises. Buying time in process. Then it is a success.

That being said the cable I created here is of decent quality, and will last as long as it is not abused, or misused. The only issue with it is that it doesn’t have the idiot-proofing; protecting the device from user error – that the original cable had. Due to the plug’s polarity keying preventing it from being inserted backwards. That’s my final point here, be cognisant of your creations’ weaknesses. And inform the user(s) of them, while also disclaiming any damages that may be caused by using the ad-hoc component that you provided. This is key to maintaining good customer relationships. From experience it often pays to overstate the risk. This is because it causes them to take active responsibility for employing it.

In the cable’s defence, as of 2026-09 I have noticed that it is still employed by my family member. More than a year after its creation. This is a genuine credit to its quality since they evidentially haven’t felt a need to replace it in the interim. How’s that for (real-world) feedback. 😀

Thank you for reading.