PowerTube Vr. 1 for Bicycle Headlight





Introduction: PowerTube Vr. 1 for Bicycle Headlight

Recently purchased one of those bicycle lights using the XML T6 LED x3.

Came with a 18650 8.4v 6400mAh Battery Pack and a Pouch with Velcro.

The headlight has a voltage status function via a multi color LED but to be honest i am not satisfy with what function so i decided to add a voltage meter.
Furthermore, i decided to forget the pouch as a battery case and make a new one instead.

So, the new battery case it has to be cheap, durable, waterproof, nice, with some extra space and easy to work with.

The answer came from the plumbing tubes!

I have included a lot of pictures, so the whole assembly process is fairly easy to follow.


For those who wish to follow me on this project here is the instructable and the materials needed.



x1 female plumbing tube 10.5cm in length x 50mm in diameter with O-rings seal at both ends.
From Praktiker at about 1.80 euro.

x2 male end plumbing tubes 50mm in diameter.
From Praktiker at about 1.80 euro in total.

x1 LED DC3.0-30V Blue Voltage Meter Display Digital Voltmeter Self-Powered.
From ebay at 2 euro. See here.

x1 Micro JST 1.25 2-Pin Male&Female Connector plug with Wires Cables.
From ebay at 0.24 euro. (4.72 euro 20 set) See here

x1 Silicone Tailcap for Flashlights 14mm.
From Deal Extreme at 0.15 euro. See here x1 Clicky Switch for Flashlights 12mm.
From Deal Extreme at 0.30 euro. See here

x1 clear acrylic sheet at 5mm or 3mm width with a 14mm hole at 8 euro from local store.

x1 Velcro strap at 1.5 euro

1x shrinkwrap tube = 10cm in length x 16 - 20cm diameter for the battery.
2x shrinkwrap tube = 3cm in length x 14mm diameter for the JST micro connector.
2x shrinkwrap tube = 15cm in length x 6mm diameter for the JST micro connector's cable.
All the shrinkwrap tubes will cost about a euro.

Total cost: about 17 euro.




Step 3: Sanding and Painting Preperation

Sand all tubes using a Nr.400 sand paper.
Then use a modeling knife to cut as shown in picture the holes for the volt meter and for the Silicone Tailcap.

Step 4: Painting the Tubes

Apply at list 3 layers for the color paint following the spray can manufacturer's recommendations.
Apply at list 3 layers for the clear varnish following the spray can manufacturer's recommendations.

Step 5: Glue the Faceplate

Step 6: Disassemble the Battery

Step 7: Prepare & Connect the JST MICRO Connector

Step 8: Connect the Manufacturer's Wire and Shape the Shrinking Tube

Updated pictures:

Step 9: Prepare the Circuit and Assemble the Parts

Step 10: Assemble the Tubes

Connect the female JST connector from the battery to the male JST connector from the circuit.
Assemble the tubes by pressing the male tubes to the female tube.

Step 11: It's Time the Place the PowerTube to the Bicycle

Use a Velcro strap to hold the PowerTube to the bicycle and connect the light.
You are done!

Hope you like it!

UPDATED at 19/5/2013 ( pictures and materials )



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    17 Discussions

    Output: Voltage = 8.4 DC, Current = 1000mA.
    fast charging for (18650 x 4) approximately 3-6h depending on battery pack discharge status.
    nominal battery pack voltage = 7.4V
    nominal battery pack current = 6400mA
    It is always best to use protected cells. A little circuit is added at the top of the battery to protect it from overcharging / discharging cycles.
    Also, do not discharge/use a cell below 2.7 - 3V.

    1 reply

    Thnks for specs ;) (you should better use "reply" button so peopleget noitified when you reply their comment )

    thanks for replying and one more question- can you tell me what is the output voltage at the AC charger ? you know, voltage, current etc. and again- Thanks a lot!

    actually it is from a bicycle headlight kit. Those sets consists from the headlight itself,the battery pack which is a set of 4x(18650) type cells. Each cell have 3.7V x 4 = 8.4V and the AC charger.
    Laptop battery packs also use those 18560 type cells.

    is that battery pack made out of laptop cells?

    we are talking about the battery pack's diameter here which is almost 13.5 cm.
    The shrinkwrap tube should be wider in order to shrink and fit on the battery.
    See the updated pictures.

    With the shrinkwrap that you put around the battery you said 20cm diameter, should that be 20mm diameter?

    This is a very neat and likeable project. My only disappointment is that I've never seen a pipe fitting like that in a local plumbing store.

    Thank You for your advice on vinyl dye spray paint.
    The JST micro connectors supply power to the voltmeter,so there is no need for high current connectors.

    Are you sure the micro connectors are rated for enough current?

    Also, try using "vinyl dye" spray paint, available at automotive stores. It bonds with the plastic so it is permanent, won't flake or scratch off nearly as easily as other paint options, even more durable than paint claiming to be for plastics and no clear coat is needed, you may not even need more than one coat in total, and the tube would not need sanded, only washed first.

    The downside is you have limited color options since most people wouldn't want orange upholstery, but it does come in some desirable colors like black, silver, etc.

    1 reply

    It would seem that the micro connectors are just for the digital voltmeter, as is the clicky switch. I would assume that you merely switch it on the see the voltage reading and then back off again.
    The main lead for the supply to the headlamp is piggybacked off the battery pack and exits the tube on its own, with the on off for the headlight being controlled by its own clicky switch mounted at the back.

    Συγχαρητήρια για την κατασκευή σου! Πολύ έξυπνη κ πιο βολική από την ένδειξη με LED.