DIY Dynamo Hub USB Charger

If you are going to travel by bike and sleep in the tent, then you will need a device to charge your electronics during your bicycle tour. For these purposes, there are solar panels and dynamo hubs. With solar panels for traveling, everything is simple – they always contain a ready-made USB port for charging your electronics.

But the main drawback of solar chargers for bicycle touring is that for their effective work you need a bright sun. In cloudy weather, they can work up to 10-15 times worse. And if you are going to travel around Europe, then the cloudy weather will often follow you. But if the weather is fine and you have about two hours to hold the solar panel towards the sun, then, in this case, the good solar chargers show much better results. Some of them have the power output of around 1A, so you will be able to charge an average smartphone in about 2 hours.

Dynamo hubs provide stable charging regardless of the weather. However, to charge your power bank or another device from a dynamo hub, you will need a special USB charger. There are many ready-made dynamo hub USB chargers on the market, but they all have a very high cost for such a simple device.



How to make a dynamo hub USB charger?

Since the cost of ready-made solutions is too high, I decided to make a self-made dynamo hub USB charger and decided to share this information with you. The cost of such dynamo hub USB charger is very low, and it can be done by anyone. You do not have to be a super electrician to do this.

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DIY: Dynamo Hub USB Charger: Tools and parts that you will need

Wires and box for the charger

First, look for unnecessary components in your house: old USB wall chargers, power wires for a printer or other small household electronics that you no longer use. From the old power adapter or USB wall charger, you can make the perfect box for your new dynamo hub USB charger, and old wires (not very thick) can also come in handy.

For example, I found an old adapter at home from the printer and it had very good wires. I cut it off and it came in handy for a dynamo hub – these wires go from the dynamo hub connector to my new charger. In addition, I found other wires from old electronics that I used for my USB charger.

Also, I found an old USB wall charger, which I do not need. From it, I made a perfect and compact box for the new charger.

If you do not have unnecessary old chargers, look for plastic boxes from some candies or something else. Otherwise, you can buy special ABS boxes and wires.

Tools that you will need

You will need a soldering iron, most likely you already have it. But if not, then you can buy Vastar Soldering Iron Kit. Also, I recommend you to buy the Helping Hand for more comfort while working, but it is not necessary, I soldered without it.

It is also very desirable to have a dremel. With this device, you can not only easily make a box for the dynamo hub USB charger, but also cut off the brake cables, install the SKS mudguards (which requires stays cutting). Also, with it, you can drill, polish (I even polished the headlight of the car once with this device), sand and many more.

If you do not have a dremel and you are not going to buy it, then probably a compact hacksaw and file will be ok.

Also, it’s good to have a glue gun.

Electrical components for dynamo hub USB charger

Now let’s move on to the main part, other components mentioned above, and tools you can probably find at home, but below are the electrical components that you will have to buy anyway. But the good news is that their cost is very low. I spent only 5 dollars to buy them.

Electrical Components:

-USB Step down DC-DC 6~40V to 5V 3A Charge Converter LM2596 Module

  1. Link 1 (eBay)
  2. Link 2 (Aliexpress)

If the links are not working, then search on eBay for “Step Down LM2596 Module” and look at the photo below to get to know which one to look for.

DIY Dynamo Hub USB Charger: LM2596 Module

-Bridge Rectifier 100V 4A KBL01

-Capacitor 220uF 50V

Heat shrink tubes

TVS Diode 1.5KE36CA 36V (Like this one)| Polarity: Bidirectional (Desirable) (This is an optional component, but it’s good to have it for LM2596 module protection.)

-Male-Female Connector (If you have old PSU from the computer and computer fan with a female connector on it, then you can use it. Also, it’s a good source of wires). Otherwise, just buy something from the list below

1) Example 1 

2) Example 2

3) Example 3



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DIY: Dynamo Hub USB Charger: Part 1

Now, when you have the right components and tools, let’s start creating our DIY dynamo hub USB charger. If you find an old, suitable for size USB wall charger, then take a dremel or a hacksaw and cut it along the seam. When you open it, remove a charging module and throw it away, but keep the socket pin and its wires.

The size of my old USB Wall Charger which has the perfect size for the LM2596 module:

DIY: Dynamo Hub USB Charger: Case for the charger

Height: 44mm Length: 63mm Width: 26mm

Old USB wall charger and new module LM2596.

DIY Dynamo Hub USB Charger: Body and Module

Now you need to cut the body of USB wall charger along the seam and make a hole for the USB port. Ideal tool for these tasks – dremel. If you bought an ABS box then start cutting a hole for the USB port.

DIY Dynamo Hub USB Charger: Body

The green thing on the wire is a heat shrink tube.

As you can see, I saved the pins that are plugged into the socket, but I cut off 1 wire from it. This component and 1 wire on it, will be needed later.

DIY Dynamo Hub USB Charger: Body 2

In the place where the yellow arrows, I had to cut a little material, so there was a place for future wires since fitting was tight. The LM2596 module should not dangle in the box, however, if the casing is larger than the module, then the module can be fixed with a glue gun.

DIY Dynamo Hub USB Charger: Image 1

Next, solder the TVS Diode to the wire from the socket pin. If you bought Bidirectional TVS Diode, then it does not matter which side to solder it. TVS diode is needed in order to protect the 2596 module from overvoltage. The module itself is designed to work up to 40 volts, but the TVS diode should start to work at about 36 volts and should protect the LM2596 module from the overvoltage. You can read more about TVS diodes on the Internet.

DIY Dynamo Hub USB Charger: TVS Diode

Green “tape” on the wires are the heat shrinks tubes.

If you have picked up another plastic box, without a socket pin, then you need to solder one end of the TVS diode to one of the 4 pins (ground) on the module (yellow arrows on the photo). These pins lead to the body of the USB connector, so they will not transmit the voltage to where you do not need it.

DIY Dynamo Hub USB Charger: TVS Diode 2

Now it looks like this. Do not pay attention to the Arduino pin on the other end of my TVS diode, later I cut it off. First, all this design was on the breadboard for testing, so that’s way there is a pin.

DIY Dynamo Hub USB Charger: TVS Diode 3


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DIY: Dynamo Hub USB Charger: Part 2

Now it’s time to prepare Bridge Rectifier. Sorry, forgot to take some photos. Take the male-female connectors, and the long cable (which will go to the dynamo hub) and the Bridge Rectifier.

  1. Solder the female connector wires to the wires that will lead up to the dynamo hub. Polarity is not important since in this section the current will be still AC.
  2. Solder the male connector wires to the Bridge Rectifier, to the pins over which AC is written – the polarity is unimportant here.

DIY Dynamo Hub USB Charger: Bridge Rectifier

Now take extra wires and solder one wire to “+” and one wire to the “-” on the bridge rectifier. Also, make a hole in a plastic box for connector cable. In the end, it should look like this.

DIY Dynamo Hub USB Charger: Bridge Rectifier 2

 

It’s time for the final step. Take the capacitor and solder it to the Bridge Rectifier (just like in the photo below). Positive to positive, negative to negative. Then take the wire from TVS diode, positive wire from the Bridge Rectifier and take 1 extra wire, twist them together and solder them.

On the negative wire, you do not need 2 wires to solder together (like on my photo), I just had this design on the breadboard and I was too lazy to cut off the old wire and solder a new, longer wire. So I just soldered 2 wires together.

DIY Dynamo Hub USB Charger: Bridge Rectifier 3

DIY Dynamo Hub USB Charger: Bridge Rectifier 4

I forgot to take a photo, but you have to wrap the tape around the exposed parts of the wires that you just soldered.


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DIY: Dynamo Hub USB Charger: Part 3

Now insert 2 wires from the Bridge Rectifier, into the connectors on the LM2596 module. Positive to positive, negative to a negative. On the LM2596 module, there are inscriptions that will help you to “find” polarity. You don’t have to solder anything, the wires are tightened by the screws that are on top of the connector.

DIY Dynamo Hub USB Charger: LM2596 Module

Now put it all in a plastic box. If the box is small, as in my case then it will be a little difficult to fit all this inside of the box, so do it carefully and slowly. If you are using a larger box, then before assembling, secure the LM2596 module in the box with the glue gun. When you insert a USB cable into the socket, the module should not stagger and move.

This is how it looks after assembly.

DIY Dynamo Hub USB Charger: Results

Later, I applied a little glue with a glue gun to fix the wire in place. This increases the reliability. Also, on the side of the USB connector, I applied glue to give it more reliability and rigidity. Since this place can be physically loaded when the USB cable is inserted.

DIY Dynamo Hub USB Charger: Results 2

DIY Dynamo Hub USB Charger: Results 3


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DIY: Dynamo Hub USB Charger: Testing

Before buying a dynamo hub I was trying to find real tests about how effective dynamo hubs are. I wanted to see the real numbers about power output. But I could not find real numbers and users usually wrote “dynamo hub works well” or “during the bike trip I was able to charge my phone.”

I never found the results. So I decided to write the results of my test for you if you are interested.

Dynamo Hub: Shutter Precision PD-8

Wheels size: 700x37c

Testing Conditions: Testing was conducted in poor conditions, in a busy city. Very often I had to travel slowly because of cars and people. But despite this, the USB tester showed the following results:

DIY: Dynamo Hub USB Charger: Power bank charging

In 1 hour and 12 minutes, dynamo hub was able to charge my power bank for 247 mAh. Not the worst results, especially when you consider that the traffic in the city is very dense, the speed was often too slow (around 10 km/h). It is also worth considering the fact that my bike has 700c wheels. Which also affect the power output (not in a good way). The smaller the wheels, the better the power output at the same speed.

By the way, after I assembled DIY dynamo hub USB charger, I recorded a video. In the video below, you can see the power output when I spin the wheel with my hands. Sorry for shacking. Something was wrong with the camera.

I hope this article will help you to build your own dynamo hub USB charger. By the way, despite the fact that this module has 2 USB ports, you can use only 1. The dynamo hub does not have enough power output to provide power for two devices at once. So, you can use any port, but don’t connect 2 devices at the same time, otherwise charging will be really slow or will not work at all.

Also, it is better to charge the power bank from the dynamo hub USB charger, and then charge the phone from a power bank. This will be more efficient than connecting your phone directly to the dynamo hub USB charger.


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Dynamo Hub Efficiency: Test Results | Updated

Dynamo Hub: Shutter Precision PD-8

Wheels size: 700x37c

Finally, I was able to do a real test of the dynamo hub USB charger. My tour lasted for 2 days and every day I cycled 110 km. At the end of the day I looked at the data of the USB Voltage Tester and I could see how fast my SP PD-8 dynamo hub and USB charger was able to charge my 2600 Mah power bank. On the day one, my average speed was 14.8 km/h and dynamo hub charged my power bank for 1846 Mah in 5h 40 min. However, on the first day, I was on the road for 7 hours. But since my power bank was not completely discharged, it seems that’s why it stopped charging after 5 hours and 40 minutes.

In any case, this is a good result. Every 6 hours, you can charge the iPhone battery from 0 to 100%.

Dynamo Hub Efficiency: Test Results

When I cycled back, my speed was a little slower (around 11-12 km/h) because of the headwind. However, despite the slower speed, in 5 hours and 50 minutes, I was able to charge my power bank for 1770 Mah. After that, my power bank was fully charged perhaps, since in total I was cycling for 7 hours and 18 minutes and the power bank stopped charging after 5h 50min.




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5 Comments
  1. Reply
    xavier maher March 1, 2019 at 4:28 pm

    Hi
    can you please explain the use of the plug pins and why the tvs diode is joined to one of them,it seems it would be easier to run the tvs direct from the pos input to the usb shroud.Thanks for the design it is a neat solution.

    • Reply
      NomadTraveller March 2, 2019 at 6:02 pm

      Hey! Yes, usually people connect tvs diode to a USB shroud, but I was just afraid that if I do something wrong during soldering then I will ruin this USB charger module just before my departure. So, I decided to solder tvs diode to a pin instead of USB shroud and for me, it was easier. After around 3000 kilometers it still works 🙂

  2. Reply
    xavier maher March 8, 2019 at 11:18 am

    thanks for the answer,but what is the pin connected to.
    yours xavier.

  3. Reply
    Gregersenartpoint.Com April 16, 2020 at 4:42 pm

    I would like to do it without that stripboard but the circuit connections seem a kind confuse to figure out to me thanks anyway, this is just what im looking for, a stable powering out of a fluctuating dynamo source ??

    • Reply
      NomadTraveller April 16, 2020 at 5:17 pm

      You will need all components that are listed by me. Especially “stripboard” – I’ve guess you mean LM2596 module. Without that module you will have to made it by yourself which is hard and not cheaper. Soldering everything is easy – wires from Dynamo hub to bridge rectifier to AC pins, then wires from bridge rectifier + – to lm2596 + – connectors. That’s simple design. But you can also add capacitor which is easy and you can see on the picture where to solder it. Also, you can solder overvaltage protection which is also not that hard. With this you can charge your gadgets or power USB lights.

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