BioLogic Joule HG Dynamo Hub

The Holy Grail

HG stands for “Holy Grail” and that’s what this hub is to us. All of us here at Tern love dynamo hubs for their free electricity, but we hate the drag they add when we’re riding during the day and don’t need lighting. We’ve been dreaming for years about a dynamo hub that can be turned “on” when we need power, and “off”, with zero drag, when we don’t need it. Now we have it. The Joule HG has a switch on the side of the hub that can be rotated “on” and “off”. In the “on” position, the Joule HG is one of the most efficient hubs on the market. In the “off” position, the magnets are pulled away from the core of the hub so that there’s zero extra drag. Dreams do come true.