[Billrush]

The junction box B will be in the down tube just above the bottom bracket. I don't want it to rattle in there while going over bumps. So should I wrap it and if so what with and how to attach. Thanks for your input.

 

[bdaghisallo1]

I didn't wrap mine and haven't heard it rattling. If you put enough zipties on the four wires that are connected to it, that should be sufficient to hold it wherever it ends up in there.

 

[Bevo]

I looped the extra cable around the junction and covered with one open loop of electrical tape then zip tied it into place.
Leaving the tape open will allow it to dry as opposed to wrapped tight and holding water.