The document describes how to design a hybrid power management circuit for batteries and electric double-layer capacitors (EDLCs) using LTspice. It presents models for lithium-ion batteries and EDLCs. The circuit uses batteries to power loads below 0.6A and EDLCs to power higher loads over 0.6A. Simulation results show the battery state of charge decreases less when using a hybrid battery-EDLC system compared to using batteries alone.