A Novel Algorithm for Concurrent Charge & Discharge of a Non-Monolithic Battery Energy Storage System

With PV (Photovoltaic) panels and BESS (Battery Energy Storage Systems) becoming more affordable, consumers are beginning to install these backups systems. Even with decreasing lithium cost, they are still relatively expensive to an average consumer. This is apparent when the system is purchased alongside the PV panels and hardware. Since ad-hoc batteries are too expensive, the systems purchased by consumers are often a combination of several ESUs (Energy Storage Units) connected in parallel. This paper proposes an algorithm that takes advantage of this non-monolithic BESS by allowing for concurrent charge and discharge of the BESS while some ESUs charge and others are discharged. The proposed algorithm also considers the rate capacity effect and charge recovery effect in order to optimize the discharging and charging periods of the BESS. The results show the algorithm is able to effectively charge certain cells while others are discharged, preventing deep DoD (Depth of Discharge) and theoretically increasing the lifespan of the BESS, reducing the overall cost of the system making them affordable and longer lasting to the average consumer. The algorithm is also non-computationally intensive and can be implemented on a low cost controller.