Research On The Usage Characteristics And Management Of Lithium Iron Phosphate Batteries For Communication Applications

With the miniaturization, decentralization and long-term high-temperature using environment of communication devices, communication back-up batties are required to be of small size, high specific energy and high temperature resistance. Therefore, lithium-ion batteries are good candidiates for lead-acid batteies. However, it is necessary to further study the safety and battery management system of lithium-ion battery due to its poor safety. Focusing on lithium iron phosphate batteries with relatively good safety, this dissertation carried out a seires of safety tests including acupuncture, overcharge, short circuit, thermal shock and extrusion tests using the lithium iron phosphate batteries produced in my compa ny. At the same time, the cycling performance, consistency, and high-low temperature performance were researched. And a balanced current-limited management system of battery packs was designed.The safety tests indicate that the lithium iron phosphate batteries can pass all the harsh tests without firing and explosion, such as needling, overcharge, short circuit, thermal shock and extrusion. The discharge measurement in a wide temperature range shows that the lithium iron phosphate batteries can discharge in the temperature range from-40 ℃ to 60 ℃, and the cycling life under 100% DOD(depth of discharge) at 25 ℃ is more than 2100 cycles, which can be used for communication back-up power. However, the consistency deterioration, resistance scattering and self-discharge rate diversity occurred when the batteries were storedat 45℃ after 14 days. Consequently, the balanced management is necessary.A sub-charge equilibrium model was designed for the scene features of communication back-up lithium-ion battery pack. The designed management system has the function of charging current limiting and sub-charge balancing. The results of 1000-cycle test exhibit that the remaining capacity of the battery pack using the sub-charge balancing model is 10.7% higher thanthat using the traditional shunt resistor in a balanced manner. This result indicates that the designed sub-charge balanced management system can improve the battery life for float charging. The function of charging current limiting can be used to limit the cha rging current to the set value under the circumstance that the charging current damages the battery pack, and thus ensures that the battery pack can be adopted for communication scenarios with different supply power, and supports the battery pack for parallel expansion.