The influence of SOC of lithium iron phosphate battery life

Source: 2020 - 04 - 04 13:04 hits: time for SOC lithium iron phosphate battery life abstract: the influence of lithium iron phosphate batteries was studied under different charged state of cycle performance. The experimental results show that the lithium iron phosphate battery SOC variation law of the cycle of life in line with expectations. If the SOC cycle life is set to 1, 100%, 90% of SOC is 1. 42 reached % SOC to 2. 98, 60 % SOC is 6. 62, 50 % SOC is 12. 28, 30 % SOC is 19. 44. IOO % ~ 30% relative life change rate of SOC can be divided into four stages. Soc for 0 ~ 60%, and changes the slope of 1. 56. Phase 3:6 0 ~ 50%, SOC change slope 5. 66; Soc 4:50 ~ 30% right, change slope is 3. 58. Lithium ion battery has many advantages, such as high working voltage, Nickel cadmium battery and nickel metal hydride battery 3 times) , large specific energy ( 165 Wh/kg, nickel metal hydride battery 3 times) , small volume, light weight, long cycle life, low self-discharge, no memory effect, and no pollution. In lithium ion batteries, lithium iron phosphate batteries more promising, although this kind of battery is bigger than cobalt acid lithium battery energy, but its high safety, single cell cycles can reach 2000 times, discharge stability. Therefore, lithium iron phosphate battery is now very popular a kind of lithium ion batteries. No matter what kind of battery is used in different fields, its operating conditions is not the same, the charging and discharging rate, the use of SOC, discharge the defense department, whether to have a floating charge, and so on, there may be differences, such as some shallow, shallow discharge, some need depth charges and deep discharges. Battery life in any field is a very important indicator. And battery life characteristics of the laboratory, generally in accordance with the 100% of full charge and discharge cycle in the SOC, through its discharge capacity attenuation cycle token to a certain value, and only 100% of the SOC of life, and other such as 90%, 80% and 60% under the SOC of life, however, can he know them, only reference to the lead-acid battery SOC and cycle life curve analogy experiment. But after all the lithium iron phosphate battery and lead acid battery is two completely different cell types, only the reference cannot be copied. For this reason, this paper studies the lithium iron phosphate batteries in 90%, 80%, 60%, 50%, 30%, five charged state of the cycle of life, and in the condition of 100% charged the cycle of life. Table 11. 1 select qualified 3 factory. 2 v/lOAh specifications of lithium iron phosphate battery 18 as the research sample. 1. According to table 1 2 18 cells can be divided into 6 groups, respectively in 100%, 90%, 80%, 60%, 50% and 30% under the condition of the cycle life of inspection charge charged condition. 1. 3 test equipment: ct - 3008 w5v20a - Tf high-precision battery performance testing system. 1. 4 complete charge and discharge plan: for the constant current charging current third C ( 3. 333). , rechargeable battery voltage limit, constant voltage charging, when the charging current decreases to zero. 01 c ( 0. 1) , 10 minutes after charging, electricity, entered the stage of constant exile and exile 1 C constant current ( 10) Discharge end voltage of 2. 0 V, 10 minutes after discharge. This is a complete charge and discharge cycles. 1. 5 test plan: 1. 5. 1 constant voltage mode: first determine the cells of the charged state of the corresponding charging voltage value, and then charged by the voltage to the voltage value as to charge and discharge cycle, examine changes in discharge capacity. 1. 5. Constant volume 2 modes: adopt the constant voltage mode, cycle under constant volume model. Corresponding to the specified charged state capacity = rated capacity & times; The corresponding charged state %; Under the mode of constant current charging to corresponding charged state capacity after discharge, the prescribed after complete charge and discharge cycles (4 times See table 2) , it is a constant volume flow. When the constant current charging reaches 3. 65 v, still did not reach the specified SOC ability, fixed capacitance loop is thought to be over, then complete charging - Discharge cycle is continued until the discharge of the battery capacity is less than 80% of the rated capacity, and the cell life is judged to be terminated.