In the electric vehicles market the need for advanced storage systems that allow fast and very fast charging and discharging has highlighted, in order to offer competitive products. The necessity of fast discharging in normal exercise of electric vehicle requires new specific storage systems. In fact increasing the amperage, losses increases, with production of heat that can lead to thermal instability with catastrophic consequences. Further the fast charging can induce stress that reduces battery. This paper deal with the thermal characterization of lithium-ions batteries with lithium-iron phosphate (LFP) cathode technology, prismatic and pouch type; and lithium-ions batteries with nickel-cobalt-manganese (NMC) cathode technology, pouch type. It is presented a comparison between different geometries (for the same chemistry) and between different chemistry (for the same geometry), covering the different types of batteries currently used in most automotive and stationary applications. For this purpose the charge and discharge currents used to test the batteries are based on specifications defined by the manufacturer. The tests were performed on a facility where such batteries are subject to charge/discharge cycles with current intensity gradually increasing, reaching maximum values declared by their manufacturers: during the cycles, electrical parameters are recorded together the acquisition of thermal behaviour using both thermocouples and infrared camera. From the analysis of the data obtained it is possible: to define the thermal behaviour of each type of batteries, to carry out a comparison of the different types, to identify critical points related to the geometry or chemistry and to assess the need for cooling during operation. The presence of hot spots seems to be independent on the geometry used; on the contrary the wear of the cell over time determines the onset of hot spots on the surface of the battery (as detected by tests performed on cells NMC). With regard to the different chemical, using new cells, it is possible to deduce that: • LFP cells do not reach temperatures exceeding safety range even if subject to discharge over the maximum specified by the manufacturer • NMC cells reach temperatures that exceed the safety range at maximum discharge rate specified by the manufacturer.
Experimental study of thermal behavior of batteries for electric car / F., D’Annibale; A., Mariani; Menale, Carla; Bubbico, Roberto; F., Vellucci. - ELETTRONICO. - (2014). (Intervento presentato al convegno 32nd UIT (Italian Union of Thermo-fluid-dynamics) Heat Transfer Conference tenutosi a Pisa nel 23-25 June 2014).
Experimental study of thermal behavior of batteries for electric car
MENALE, CARLA;BUBBICO, Roberto;
2014
Abstract
In the electric vehicles market the need for advanced storage systems that allow fast and very fast charging and discharging has highlighted, in order to offer competitive products. The necessity of fast discharging in normal exercise of electric vehicle requires new specific storage systems. In fact increasing the amperage, losses increases, with production of heat that can lead to thermal instability with catastrophic consequences. Further the fast charging can induce stress that reduces battery. This paper deal with the thermal characterization of lithium-ions batteries with lithium-iron phosphate (LFP) cathode technology, prismatic and pouch type; and lithium-ions batteries with nickel-cobalt-manganese (NMC) cathode technology, pouch type. It is presented a comparison between different geometries (for the same chemistry) and between different chemistry (for the same geometry), covering the different types of batteries currently used in most automotive and stationary applications. For this purpose the charge and discharge currents used to test the batteries are based on specifications defined by the manufacturer. The tests were performed on a facility where such batteries are subject to charge/discharge cycles with current intensity gradually increasing, reaching maximum values declared by their manufacturers: during the cycles, electrical parameters are recorded together the acquisition of thermal behaviour using both thermocouples and infrared camera. From the analysis of the data obtained it is possible: to define the thermal behaviour of each type of batteries, to carry out a comparison of the different types, to identify critical points related to the geometry or chemistry and to assess the need for cooling during operation. The presence of hot spots seems to be independent on the geometry used; on the contrary the wear of the cell over time determines the onset of hot spots on the surface of the battery (as detected by tests performed on cells NMC). With regard to the different chemical, using new cells, it is possible to deduce that: • LFP cells do not reach temperatures exceeding safety range even if subject to discharge over the maximum specified by the manufacturer • NMC cells reach temperatures that exceed the safety range at maximum discharge rate specified by the manufacturer.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
