Two stage heating strategy for electric vehicles based on electric-thermal collaborative optimization in low temperature environments

In low-temperature environments, reduced discharge capacity in lithium-ion batteries and increased heating energy consumption from thermal management system (TMS) severely shorten electric vehicle (EV) range. This study proposes a two-stage heating strategy combining battery preheating and TMS power optimization to enhance both battery discharge capability and EV operational efficiency in cold climates. Integrated system models including lumped-parameter TMS model, electro-thermal-aging coupled battery model, and vehicle dynamics and energy consumption model are established. In the preheating stage, the sequential quadratic programming algorithm is exploited to optimize the target temperature of battery self-heating, ensuring elevated battery initial temperature for improved discharge performance. In the driving phase, a multi-objective optimization problem is formulated that jointly considers cabin thermal comfort, battery capacity degradation, and heating energy consumption. The optimized problem is resolved for optimal heating power allocation via Pontryagin's minimum principle. Coordinated optimization of preheating target and TMS power reduces total energy consumption while maintaining the driving and thermal comfort requirements. Simulations across five WLTC cycles demonstrate 9.92 % reduction in energy consumption and 13.06 % decrease in battery capacity degradation compared to non-optimized baseline strategy. Multi-scenario simulations further reveal the strategy effectiveness in preserving battery longevity and extending EV range under cold conditions.