I avoid the e-"harbor" and bought supercaps from Digikey. Attached is a picture of how I set them up. The plug and wires come from a discarded battery. Given my labor, I would say that BCR's price is not unreasonable. But turning out a couple of dozen of these kept me out of trouble (Mrs RJR's hair) for a few hours. Note that the 8.4 volt BCR uses additional components to assure even charging of cap "cells," which is not needed for the 3-volt boards.