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.
