Characterisation of charge voltage of lead-acid batteries: application to the charge control strategy in photovoltaic systems

Abstract

In stand-alone photovoltaic (PV) systems, charge controllers prevent excessive battery overcharge by interrupting or limiting the current flow from the PV array to the battery when the battery becomes fully charged. Charge regulation is most often accomplished by limiting the battery voltage to a predetermined value or cut-off voltage, higher than the gassing voltage. These regulation voltages are dependent on the temperature and battery charge current. An adequate selection of overcharge cut-off voltage for each battery type and operating conditions would maintain the highest battery state of charge without causing significant overcharge thus improving battery performance and reliability. To perform this work, a sample of nine different lead-acid batteries, typically used in stand-alone PV systems including vented and sealed batteries with 2 V cells and monoblock configurations have been selected. This paper presents simple mathematical expressions fitting two charge characteristic voltages: the gassing voltage (V g ) and the end-of charge voltage (V fc ) as function of charge current and temperature for the tested batteries. With these expressions, we have calculated V g and V fc at different current rates. An analysis of the different values obtained is presented here focusing in the implication in control strategies of batteries in standalone PV systems.

Rechargeable nickel–iron batteries for large‐scale energy storage

“…Lead acid batteries are the earliest and well recognised as the leading technology for renewable applications, hence, their low energy density (about 30 Wh/kg), the toxicity of raw materials, and low cycle life [15, 16]. In contrast, invented and commercialised in the early 20th century, nickel–iron (NiFe) cells could provide 1.5–2 times the specific energy of lead/acid batteries, with their increased ruggedness and longer cycle life at deep discharge state (2000 cycles at 80% Depth of Discharge) [8, 11, 13, 16, 17].…”

Sistema autónomo para carga de baterías mediante una instalación fotovoltaica con aplicación directa al vehículo eléctrico y usos

“…El voltaje de carga final de la batería, depende de la corriente de carga y de la temperatura según el tipo de batería, y debe tenerse en cuenta en el funcionamiento del regulador de carga, Vela et al (2015). incluye un condensador de capacidad C, una resistencia R una inductancia L que hacen posible determinar la corriente en la batería y la tensión mediante integración numérica.…”

“…El voltaje de carga final de la batería, depende de la corriente de carga y de la temperatura según el tipo de batería, y debe tenerse en cuenta en el funcionamiento del regulador de carga, Vela et al (2015).…”