Scheduling of Battery Charge, Discharge, and Rest

Abstract

Abstract-Electric vehicles operate inefficiently with a naive battery management system that charges or discharges battery cells in a pack based solely on application load demands. The battery pack's operation-time and lifetime can be extended significantly by effectively scheduling (the cyber part) battery charge, discharge, and rest activities, based on the battery characteristics (the physical part). We propose a set of policies for scheduling battery-cell activities, called the weighted-k roundrobin (kRR) scheduling framework. This framework dynamically adapts battery-cell activities to load demands and the condition of individual cells, thereby extending the battery pack's operationtime and making them robust to anomalous voltage-imbalances. The framework comprises two key components. First, an adaptive filter estimates the upcoming load demand. Then, based on the estimated load demand, the kRR scheduler determines the number of parallel-connected cells to be discharged simultaneously. The scheduler also effectively partitions the cells in the pack, allowing the cells to be simultaneously charged and discharged in coordination with the battery reconfiguration system we developed earlier [17]. Besides the kRR scheduling framework, we characterize the discharge and recovery efficiency of a Lithiumion battery cell. The kRR scheduling framework is shown to outperform three alternative scheduling mechanisms with respect to the operation-time by 7-56%, and improve the tolerance of voltage-imbalance by up to 50%.

Design and Management of Satellite Power Systems

“…Rechargeable battery cells are known to possess many unique, non-linear characteristics [9][10][11]. One of them is called discharge efficiency-the higher discharge rate, the less efficiency.…”

“…On the other hand, battery cells supply power during the eclipse phase or the sun phase in case of a peak power demand. Their discharge behaviors are known to be non-linear [9][10][11], e.g., discharge efficiency-higher discharge rate, less deliverable power, and recovery efficiency-resting a battery cell will recover its voltage that was temporarily dropped. Battery cells' performance also varies with their efficiency and operating temperature.…”

DESA: Dependable, Efficient, Scalable Architecture for Management of Large-Scale Batteries

“…The rest period depends on a discharge rate; the lower the discharge rate, the longer the rest period. It is determined based on a battery-activity scheduling mechanism in [11].…”

“…First, for the battery's operation-time, the global BMS feeds the aggregated voltage and current into a reference model [11]. This reference model includes functions of time-dependent charge and discharge rates.…”

Study on the Voltage Characteristic of Lithium Ion Battery during Rest Period after Charge

“…According to the HEV theory, the batteries are in the alternating state of discharge, charge and rest when HEV experiences the process of acceleration, deceleration, and parking [2]. According to the theory of electrochemistry, the battery's voltage becomes unstable under the influence of electrode polarization, and it varies with time when the battery rests after charge, which will lead to big error of SoC estimation and have difficulty in implementing the dynamic control strategy of HEV.…”