Bicycle power supply

One of the advantages of keeping a USB battery pack on my bike is that it can power more than just my headlight. Instead of pulling three devices off the bike and charging individually, I can route USB cables to each device and charge the brick. This simplifies charging and gives my flashers a lot of extra life.

The pack I bought has an ultrasonic weld around the edge, making most of it watertight (or at least close to it - I had intended to caulk the weld just in case). Potentially with some selective waterproofing of the ports and button, maybe as simple as packing with lithium grease, I could have it exposed to the elements without issue. Or potentially I could pull over something stretchy and sealing like a glove and route the USB cables through the fingers. I sketched some options along these lines, but I took the simpler route of putting it in a watertight container and sealing the port.





Before locking everything in place I made sure the cables on hand would do. One to the front flasher, one to the back flasher, and the power cable for the headlight.



To secure the container to the bike rack, I modeled and printed two brackets that slide into the top of the rack.



These have a nut trap that allow me to bolt the container to the rack. The container is polyurethane and cracked easily when the drill broke through, but otherwise it's working fine.





In home position and charging. The voltage converter now lives inside the watertight container. I had no issues with the hot melt encapsulation, even during the ~8 hours of rain on my last ride.



All charged and packed away.



I haven't tested this yet but I do not expect any serious issues. There is a chance that the cracks in the drill holes will propagate, but that should be fixable if it occurs. One issue with the system is that the  front flasher cannot be plugged in and flash at the same time so I need to unplug it when I want to use it. This is fine for now, but I will likely replace it. Ideally the lights would charge while being used, but this may not be the case - ultimately I may need to replace them with battery-less lights.