| At present,most of the coal mining equipment still use lead-acid batteries as a power supply,the use of lead-acid batteries have the following deficiencies:low capacity density, bulk mass,heavy,not easy to carry;internal equipment corrosion and personal injury caused by sulfuric acid spilled;lead-antimony and other heavy metal in the battery polluting the environment;short use cycle life,rigmarole of maintenance.Despite of these shortcomings, they are used until now,because of its low prices and high security.A new battery--lithium-ion battery is developed in 1990s.With its high load voltage,great energy density,no memory effect,little self-discharge,long cycle life and a series of advantages,lithium-ion battery is widely applied.However,general safety performance of lithium-ion battery applications can not meet the requirements of the mine,so it has not been applied in the coal mine equipment until LiFePO4 battery is developed in recent years.Because of high stability of the cathode materials and superior performance characteristics,LiFePO4 battery can be applied to the field of mining.The nominal voltage of the LiFePO4 battery is 3.2V,different from the voltage of general lithium battery.The nominal voltage of general lithium battery is 3.7V or 3.6V.If charging the LiFePO4 battery with an ordinary charger,the LiFePO4 battery will be overcharged or damaged.The existing charger chip specially developed for LiFePO4 battery did not use intrinsically safe design,and can not be safe working in the mine environment.In order to solve this problem,the paper designed intrinsically safe mine LiFePO4 battery charging device with reference standard GB 3836.4-2000,which realize the safely charging in the mine to avoid embarrassment of the interruption of power supply of the LiFePO4 battery powered equipment.In addition,this paper specially designed intrinsically safe power supply for the LiFePO4 battery-powered instrument to ensure its security work.The supply of intrinsically safe power input is underground power supply network and its voltage is 110V AC.The output voltage is 6V DC which is the LiFePO4 battery charger need.The maximum output current is 3A.The output terminal of the intrinsically safe power supply set multiple voltage limit and current limit circuit to reach the intrinsically safety requirements.According to the result of experimental tests,the charging curve of the charger in line with characteristics of LiFePO4 battery charging.The charging ripple is small,precision of the termination charging voltage is high.It reaches charging requirements of LiFePO4 battery.Its safety performance is in accordance with the national standards GB 3836.4 - 2000 and it can work safely in the mine.With small offset of output voltage,short voltage setup time and good function of over-current and over-voltage protection.The multi-charger is controlled by the MCU,taking on greater flexibility.It can regulate the current in constant current period and voltage in constant voltage period to the value needed;Charging ripple is low to±10mV;precision of the end charging voltage is high,±0.8%.The charger placed in the mine,convenient to the emergency charging of underground equipment which is supplied by LiFePO4 battery.It has important practical value.
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