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A Study of Capacity Fade and Life-Cycle Estimation of LiFePo4 Battery Based On Two Years Field Data

TA Abera, G.Bekele, T.Walter, P.Adelman

In this paper a capacity fade and cycle-life estimation of lithium iron phosphate (LiFePO4) battery based on a two year measured field data is reported. The testing was done to complement the tests made by research institutes in a laboratory by cycling charge/discharge profiles that represent solar home systems scenario. The battery testing laboratory at further training institute (FTI) laboratory ofAdama science & Technology University, Ethiopia is used for testing.Five Pico systems consistingof LiFePO4 (LFP), 18650 type batteries with a nominal capacity of 4200mAh were distributed in a neighboring village. Capacity fade and Cycle-life estimation analysis was done on the data collected over the course of two yearswhere measurements were taken every month. Using the data collected, the capacity fade and the cycle-life of these batteries have been calculated, accordingly the result showed average capacity fade of 8% of the initial measured capacity and average cycle-life of about 6.5Years. These results exceed well above even that of what the manufacturers give as specification, which is in most cases is estimated to be 2000 cycles (5.5 years).The resulting conclusion is that the LiFePO4 battery could be the best alternative to solve one of the prominent pitfalls of solar home systems (SHS),specifically reliability and running cost. Therefore it is recommended to deploy this battery more oftenin new designs. In addition to that the result obtained from this work can be used as an input for further studies in the area of SHS.