Jupiter Discovery X5 E-bike - Adding Onboard Power to Tail Light

Something a little odd with this bike is that the rear tail light runs off a 3 volt button cell and does not get its power from the main bike battery like the headlight does. I wanted to rectify this situation so I bought what's called a DC-DC Buck Converter, or Step-down Converter. It will take 40 volt bike battery voltage and step it down to pretty much anything you'd like. In this case it will step down to 3 volts (or 12 volts as you will notice further down the blog). Here's a photo of the converter. The small rectangular blue thing is an adjustable potentiometer which is used to adjust the output voltage.

One step in the process is to find the power line for the front headlight. In this case it is a green and a black wire. I will tap into these wires to power the voltage converter.

This next photo below shows the tail light LEDs and board with a pair of wires soldered to the battery terminals. I was setting things up in the basement so I was using a 30 volt power supply as the input so I could adjust the output to the necessary 3 volts. Well...... something went wrong and I put too much voltage to the tail light board and fried the LED lights and chip. Hmm, now what do I do?

I then remembered that I had some left-over 12-volt LED light tape from another project that I could possibly use for this purpose. I cut off a section that had six LEDs on it. They were spaced too far apart so I folded the tape over onto itself between the lights to get the LEDs closer together and make the whole mess short enough to fit into the red tail light lens. I also adjusted the voltage converter to put out the necessary 12 volts.

Folding the light strip did seem to work and so I hot glued the LEDs into the lens.

This next photo shows the folded light strip a little better.

It looks promising.

Here's the dead board. I couldn't see anything out of the ordinary but something is obviously dead.

I don't know if I've shown this snake pit of a mess before. This pile of wires and controller fit into a small cavity in the bike frame but now I also have to fit in the small step-down converter and extra wiring also. I did manage to get it all stuffed back in after fighting things for ten minutes.

The light and bike are all back together and the light is actually quite a bit brighter than the original light on the right (the wife's bike), which I used to think was pretty bright. The nice thing is, when I turn on the headlight, the rear tail light also comes on. With the old battery powered light, I'd have to turn it on separately and it is easy to forget. It's also easy to forget to turn the tail light off again after a ride.