Comprehensive Design and Optimization of an Onboard Resonant Self-Heater for EV Battery

As the primary power sources of electric vehicles (EVs), lithium-ion batteries suffer from substantial capacity and power degradation at cold climates. An onboard battery preheater is essential for EVs to avoid degraded battery performance. This article proposed a resonant battery self-heater for internally preheating the batteries without external power supplies, thereby providing great flexibility for EVs in different parking areas. To achieve the optimized performance, a detailed analytical model of the self-heater is derived, illustrating the effects of the switching frequency and resonant tank parameters. Considering the size, heating speed, and efficiency, the detailed design methodology of the proposed self-heater is presented by utilizing a nonlinear optimization method, in which the battery impedance variation is included. The downscaled experiments on 18650 cells validate that the optimally designed self-heater can warm up the batteries from -20 °C to 0 °C rapidly with the minimum energy consumption compared with previous heating schemes.