This invention pertains to reliable, lightweight and efficient hybrid electric powertrain and components thereof to power hybrid electric aircraft from one or more sources of electrical energy. In particular, a novel architecture is proposed for power panels that receive, condition and distribute high levels of electrical power to and from the propulsion electric motors and the one or several sources of electrical energy. Systems and methods for architecting the power panels using efficient, reusable and modular power electronics building blocks (PEBBs) is described, along with additional systems and methods for the optimal control of the power panels and components thereof. In addition, novel systems and methods are described for the efficient and lightweight thermal management for hybrid electric powertrain components, ranging from distribution manifolds for the powertrain or power panels, to micro fluid channels for cooling electronics with extreme heat flux. Additional disclosures are made pertaining to fail-safe architectures for plug-in series hybrid-to-electric powertrain, to the efficient in-ground charging of the stored electric energy sources, to the efficient control of permanent magnet generators, and to novel inverter technologies for the hybrid electric powertrain.