State-Based Control of Primary–Standby Battery Switching in Standalone Photovoltaic Systems

Reza Satria Rinaldi; Afriyastuti Herawati; Ika Novia Anggraini; Melian Tri Yulianto

doi:10.56741/IISTR.esl.002471

Authors

Reza Satria Rinaldi
reza_s_r@unib.ac.id
University of Bengkulu https://orcid.org/0009-0007-4602-9262
Afriyastuti Herawati University of Bengkulu
Ika Novia Anggraini University of Bengkulu
Melian Tri Yulianto University of Bengkulu

Keywords:

automatic switching, electromechanical relays (EMRs), Low-Voltage Disconnect (LVD), standalone PV(SAPV)

Abstract

Off-grid photovoltaic (PV) systems are a viable solution for electrifying remote areas. However, the intermittent nature of solar energy necessitates the use of properly managed batteries to ensure a continuous power supply and preserve battery lifespan. While various battery control systems have been developed, most rely on relatively complex digital controls, making them less suitable for small-scale household applications. This study aims to develop an automatic switching system for charging and discharging between primary and standby batteries in a 12 V DC standalone PV (SAPV) system, utilizing state-based control logic. The proposed system employs two Valve-Regulated Lead-Acid (VRLA) batteries, two Low-Voltage Disconnects (LVDs), and three electromechanical relays (EMRs) to control charging and discharging operations based on battery voltage, which represents the State of Charge (SoC) and Depth of Discharge (DoD). The control system features four operating states and eight state transitions, prioritizing full charge-discharge cycles for the primary battery while utilizing the standby battery to maintain power supply continuity during the primary battery's charge. Test results demonstrate that the system successfully automates operational switching in accordance with the designed control strategy, thereby preserving the primary battery's full cycling and ensuring continuous power supply. The system is simple, cost-effective, and easy to implement using LVDs and EMRs. Observed transition voltages do not always align exactly with the set threshold values because of the dynamic characteristics of VRLA batteries.

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Author Biographies

Reza Satria Rinaldi, University of Bengkulu

Reza Satria Rinaldi received an S.T. in Electrical Engineering from Andalas University, Padang, Indonesia, an M.Eng. degree in Electrical Engineering from Universitas Gadjah Mada (UGM), Yogyakarta, Indonesia, and the Professional Engineer (Ir.) qualification from Andalas University, Indonesia. He is a Professional Engineer (IPM) certified by the Institution of Engineers Indonesia (PII). He is currently a Lecturer in the Study Programme of Electrical Engineering, Faculty of Engineering, University of Bengkulu, Indonesia. His research interests include Integrated Renewable Energy, electronics, and instrumentation and control. He is the author and co-author of several publications in the fields of electrical engineering.

Afriyastuti Herawati, University of Bengkulu

Afriyastuti Herawati received the S.T. degree in Electrical Engineering from Andalas University, Indonesia, in 2004, and the M.T. degree in Electrical Engineering from Institut Teknologi Bandung (ITB), Indonesia, in 2012. She is currently a Lecturer in the Study Programme of Electrical Engineering, Faculty of Engineering, University of Bengkulu, Indonesia, where she also serves as the Head of the Undergraduate Electrical Engineering Program. Her research interests include power electronics, renewable energy systems, photovoltaic systems, and electric power systems.

Ika Novia Anggraini, University of Bengkulu

Ika Novia Anggraini is a Lecturer in the Study Programme of Electrical Engineering, Faculty of Engineering, University of Bengkulu, Indonesia. She received the S.T. degree in Electrical Engineering from Universitas Sriwijaya, Indonesia, and the M.Eng. degree in Electrical Engineering from Universitas Gadjah Mada, Indonesia. She is a Professional Engineer and holds the Insinyur Profesional Madya (IPM) certification. Her research interests include renewable energy systems, electrical power systems, power system protection, and grounding systems. She has actively contributed to research and community service projects in the field of electrical engineering.

Melian Tri Yulianto, University of Bengkulu

Melian Tri Yulianto received the S.T. degree in Electrical Engineering from the Study Programme of Electrical Engineering, Faculty of Engineering, University of Bengkulu, Indonesia, in 2025. He completed his bachelor's thesis defense on July 9, 2025. His research interests include standalone photovoltaic (SAPV) systems and automatic battery switching systems.

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