Lithium iron phosphate batteries are the safest high-energy battery in the lithium-ion battery family. The discharge voltage of lithium iron phosphate battery is very stable, generally 3.2 V. The voltage after the discharge (mainly the remaining 10% capacity) changes rapidly, and the cut-off voltage is generally 2.5 V. Ambient temperature, especially low temperature, will affect the discharge capacity of lithium iron phosphate battery: discharge capacity at -20 °C is 45% of normal temperature capacity, -10 °C is 65% of normal temperature, -5 °C is 80% of normal temperature, 0 °C It is 90% of normal temperature, and the discharge capacity change from 0 °C to 20 °C is very small. The low temperature performance of lithium iron phosphate battery is better than that of lead acid battery.
Although the lithium iron phosphate battery is charged and discharged at the time of shipment from the factory, if the installation date of the lithium iron phosphate battery is far from the factory date, there will be a loss after long-term self-discharge capacity. In addition, the lithium iron phosphate battery is generally 60% charged at the factory, and the battery pack should be recharged at the initial installation. Due to the difference in self-discharge of the individual cells, there may be a phenomenon in which the voltage at each battery terminal is unbalanced. The open circuit voltage must be measured before the lithium iron phosphate battery pack is installed. The open circuit voltage difference cannot be greater than 50 mV. The battery test should be done and recorded. With the dummy load, the battery pack can be tested for capacity by 0.1C10 and 0.2C5. This test does not need to be connected to the Battery Management System (BMS). It is only necessary to connect the battery packs in series, but the battery must be strictly tested during the discharge process. The cell voltage, the total voltage of the battery, the discharge current, and the cell voltage are measured and recorded every hour. The battery detects the battery with low discharge cell voltage every 10 min in the late stage of discharge. If one of the battery terminals stops discharging at 2.5 V, it is calculated whether the actual battery discharge capacity is consistent with the rated capacity of the battery. If the battery is basically the same, the battery is proved to be the same. The discharge test is passed and the battery is charged. If the voltage is discharged to the termination voltage, the difference between the capacity released by the battery pack and the rated capacity is greater than 15%, indicating that there may be a problem with the factory capacity of the battery pack. Contact the manufacturer for disposal.
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