Investigation of Magnetic Couplers in Bicycle Kickstands for Wireless Charging of Electric Bicycles

This paper investigates closely coupled lumped magnetic coupler configurations, which could potentially be installed within or around a kickstand of an electric bicycle to provide wireless charging capability to the on-board battery pack. Options considered for the bicycle kickstands were the side stand and the bracket stand. Both a cylindrical solenoidal vertical pickup (PU) and a horizontal solenoidal bar PU are investigated for the side and bracket stand, respectively. Two primary pads are proposed for each of those PUs. Each configuration designed in simulation was able to provide at least 40 VA at the expected worst case pad misalignment of 20 mm in the x- and y-axis, and were compared in terms of their power transfer capability, variation in inductance due to misalignment, magnetic leakage, and material usage. It is shown that a solenoidal bar PU with a double-D primary provides an excellent coupling and low magnetic field emissions. A solenoidal bar PU and primary appears to be the cheapest option, using the least amount of ferrite and copper. A double-D primary pad with a solenoidal bar PU was built. Practical measurements showed a good agreement with simulation. The PU was series tuned and connected to a regulator, providing an output of 200 W with an efficiency of ~90% even with misalignment.