The influence of current in off-grid PV systems on lead–acid battery lifetime and hybridization with LFP battery as solution

Abstract

This paper describes test results of two sets of VRLA GEL batteries that included various phenomena which might accelerate their degradation process in off-grid PV systems like: incomplete charges (bad recharges), low start current and remaining in partially discharge state. The test shown in the paper included two cycling experiments lasting 45 days and 98 days during which the batteries where constantly charged and discharged in different cycles. The results show strong acceleration of degradation process for incomplete charges (bad recharges) which are specifically difficult to avoid in off-grid systems. In order to avoid the premature destruction of lead–acid battery in off-grid PV systems the hybrid battery system consisting of lithium-iron-phosphate and lead–acid batteries connected with DC/DC converter is proposed.

Keywords

• Hybrid battery
• Battery ageing
• Off-grid
• PV system
• Lead–acid battery
• Lithium-ion battery