LiFePO4 batteries are the safest high-ratio energy batteries in the lithium-ion battery family. The discharge voltage of LiFePO4 battery is very stable, generally 3.2V, the voltage changes rapidly in the later stage of discharge (mainly refers to the remaining 10% capacity), and the cut-off voltage is generally 2.5V. Ambient temperature, especially low temperature, will affect the discharge capacity of LiFePO4 battery: the discharge capacity of -20 ℃ is 45% of the normal temperature capacity, -10 ℃ is 65% of the normal temperature, -5 ℃ is 80% of the normal temperature, 0 ℃ is 90% of the room temperature, 0 ℃ to 20 ℃ of the discharge capacity change is very small. The low temperature performance of LiFePO4 battery is better than that of lead-acid battery.Installation considerations.Although the lithium phosphate battery at the factory positive and negative plates have been charged and discharged, but if the installation date of LiFePO4 battery from the factory date is far away, after a long period of self-discharge capacity will inevitably be lost. In addition, LiFePO4 battery at the factory charge is generally 60%, the initial installation should be recharge the battery pack. Due to the difference in self-discharge of the unit battery, the voltage imbalance at each end of the battery may occur. The open circuit voltage must be measured before the LiFePO4 battery pack is installed, the open circuit voltage difference should not be greater than 50mV, and the battery test should be done and recorded. With false load, the battery pack can be pressed 0.1C10 and 0.2C5 capacity test, this test does not need to be connected to the battery management system, only the battery pack series, but the discharge process must strictly detect the battery unit voltage, the total voltage of the battery per hour, discharge current, battery unit voltage measurement and recording. Battery in the discharge after every 10min detection discharge battery unit voltage low battery, if there is a battery end voltage to 2.5V immediately stop discharge, calculate the actual battery discharge capacity and battery rated capacity is consistent, if basically consistent to prove that the battery discharge test qualified, and then charge the battery. If discharge to termination voltage, the difference between the capacity discharged 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, the manufacturer should be promptly contacted to deal with.Influencer factors.1. Effect of temperature on LiFePO4 batteries.The effect of temperature on LiFePO4 batteries is much smaller than that of lead-acid batteries, especially in the case of discharge. For temperature characteristics testing of two batteries of the same size, LiFePO4 batteries have a 20% higher capacity than sealed valve-controlled lead-acid batteries. Due to the electrochemical properties of the lithium phosphate material, the low-temperature charging performance of the battery is slightly worse, the charging temperature is higher than 0 ℃, otherwise the irreversible capacity of the battery will increase with the decrease of temperature. LiFePO4 batteries can still be recycled and discharged in an environment of about 55 ℃.2. Effect of intermittent floating charging on LiFePO4 batteries.Since the electrolyte of the lithium phosphate battery is an organic liquid, and lithium metal is very active, the battery must be sealed. The battery produces almost no gas under normal charge and discharge conditions, and even if the battery is intermittently charged for a long time, there will be no higher pressure inside the battery. In addition, the backup power supply of the communication base station is in the floating charge state for a long time, and the voltage of the battery is about 3.65V for the long time. This voltage is stable for both the battery plate and the electrolyte, so LiFePO4 batteries are ideal for communication base stations.BMSCharge and discharge, extrusion, needles and other abuse conditions are still safe, but will have a great impact on the cycle life of the battery. The production process of LiFePO4 battery is more complex, the consistency difference of single battery will be longer than the sealing valve-controlled lead-acid battery, which leads to the rapid rise of the voltage of individual unit batteries in the later charging period of the battery pack, coupled with the communication base station long-term unattended state, not easy to find in time, resulting in a short life of lithium phosphate battery pack or damage phenomenon. In order to avoid the above phenomenon, BMS is required to ensure the safety and reliability of the battery. BMS is a core component of battery protection and management, not only to ensure the safety and reliability of the battery, but also to give full play to the performance of the battery and extend its life. As a backup power for communication, BMS acts as a bridge between switching power supplies and batteries. BMS's safety management mode is critical to battery safety and includes data acquisition units, computing and control units, balancing units, control execution units and communication units.LiFePO4 batteries should be used in support of switching power supplies.In view of the characteristics of the above-mentioned LiFePO4 battery, in the selection or setting of power supply equipment, only the floating charging pressure or the average charging voltage is adjusted to the charging voltage required for the LiFePO4 battery. It should be noted here that, as opposed to sealed valve-controlled lead-acid batteries, the charging process of LiFePO4 batteries is not a float-charged charging mode, as long as the charging voltage required to charge the lithium phosphate battery can be met. Iron phosphate lithium battery even if the long-term average charging state, due to its own protection function, battery performance will not change, LiFePO4 battery in this regard is very obvious advantages. In addition, the real-time monitoring of switching power supply, regulatory limit flow, automatic conversion of floating charge, battery temperature compensation, intelligent management and secondary power down and other functions of the setting can directly refer to the lead-acid battery settings, only need to increase the charging voltage to the LiFePO4 battery required charging voltage. For example, a mobile base station uses 48 to 300Ah LiFePO4 battery two sets, in order to replace the battery in order to ensure the safety of power supply, two sets of LiFePO4 battery offline testing. After testing the total voltage of each set of batteries, adjust the switching power supply DC supply voltage corresponding to each other, respectively, two sets of LiFePO4 battery access system to supplement the power. At this point, the switching power charging voltage is set to 56.4V and the charging current is limited to 30A per set. The initial charging current of the two battery packs is 29A and 31A, respectively, as the battery pack voltage increases, the charging current will decrease accordingly, when the battery pack voltage and switching power supply charging voltage is very close, the charging current of the battery pack is gradually reduced to 0, at this time the battery pack BMS played a protective role, the charging system through the BMS and battery disconnect, battery charging is complete. When fully charged, the two sets of batteries are stationary 8h for discharge testing. In order to test the high current discharge capacity of the two battery packs, 0.2C5 current discharge is used, i.e. 120A. The total discharge time is 5h, the current shown in the smart load cabinet display is basically 120A, the battery pack released capacity of 600Ah. LiFePO4 battery released 100% of the rated capacity, so the battery pack released the capacity to fully meet the rated capacity requirements, the entire discharge process intelligent false load is very stable.Test of LiFePO4 battery.(1) The test of the discharge of sex.According to the operating characteristics of LiFePO4 battery, the measurement of battery end voltage should not only be in the intermittent floating state, but also in the discharge state of detection. The voltage at the end of the battery is an important parameter to reflect the working condition of the battery. Due to the presence of the added voltage, the voltage of the battery end voltage is measured in the intermittent floating charge state, and its voltage can easily create the illusion. Therefore, the battery should be regularly carried out on a regular basis with a checked discharge test, released 30% to 40% of the actual capacity of the battery, and the battery monitoring system for real-time testing and printing archive of the battery pack, while checking the battery connection strip contact, the battery connection strip is loose to fasten, to ensure the safe and stable operation of the battery.(2) Quantity discharge test.In the current communication power supply system, switching power supply and LiFePO4 battery for the side-by-side intermittent floating charge power supply, so the battery pack can not be separated from the power supply system, can not be separated to the battery capacity test. Due to the low environmental temperature requirements of lithium phosphate battery, long battery life and so on, the battery pack can be tested every 3 years, the battery after 6 years of annual capacity test, requiring more than 80% of the released capacity is qualified. In general, such tests are carried out under conditions with actual load (or actual load plus false load). In order to ensure the safe and reliable supply of dc power in this case, the diesel generator set should be inspected to ensure that the diesel generator set is properly powered, and the discharge multiple of the battery pack is determined to meet the discharge rate of 3 hours, 5 hours or 10 hours for the load of the DC power supply system. The 3-hour rate discharge current is 0.25C3, the 5-hour rate discharge current is 0.168C5, and the 10-hour rate discharge current is 0.10C10, preferably at an ambient temperature of about 20 ℃ at a capacity test of 10 hours. Because the lithium phosphate battery has BMS protection, the floating charging voltage of the switching power supply is set to 45V when the battery capacity test is carried out, and then the AC input of the switching power supply is disconnected, and the discharge current of the battery is detected with the DC clamp type meter to ensure the safety of the base station power supply.Maintenance of LiFePO4 batteries.(1) Environmental requirements.According to the environmental requirements of the battery, room temperature should not exceed 55 ℃, it is recommended that the ambient temperature should be kept at 0 to 55 ℃;(2) Precautions.LiFePO4 batteries of different sizes and models are prohibited from using in the same DC power supply system, and batteries of different degrees, old and new, should not be mixed in the same DC power supply system. If there is a dynamic and environmental centralized monitoring system, the total voltage, current, unit voltage and temperature of the battery pack should be monitored in real time through the dynamic environment centralized monitoring system and BMS. At the same time, through the battery monitoring device to understand the battery charge and discharge curve and performance, regular measurement, timely detection of faults and treatment.(3) Check the item.The pole column and connecting strip of LiFePO4 battery should be checked frequently for looseness, damage, deformation or corrosion, looseness at the connection, damage, leakage and deformation of the battery housing, abnormal temperature rise at the battery and connection, according to the manufacturer. Provide technical parameters and on-site environmental conditions, check whether the battery pack and unit voltage meet the requirements, detect whether the charging current when the battery pack is intermittently charged is within the required range, and detect whether the battery pack charging limit setting, low voltage alarm, high voltage alarm setting is correct. If there is a secondary power-down device in the DC power supply system, the secondary down-voltage setting should be checked correctly.(4) Voltage requirements.The intermittent charging voltage of LiFePO4 battery is generally set to 3.60 to 3.76V for single battery and 56.4V for battery pack. Measure the battery pack voltage and the end voltage of the unit battery on a monthly level.
The full name of the LiFePO4 is the lithium iron phosphate battery. Since its performance is particularly suitable for power applications, the word "power" is added to the name, i.e. lithium iron phosphate battery. Some people call it a "lithium iron power battery", and iron phosphate lithium charging skills you all understand? Here's a look at the charging techniques for lithium iron phosphate batteries.1, Before solving the problem, first of all, we need to understand the structure and working principle of lithium iron phosphate battery LiFePO4 as the positive pole of the battery, by aluminum foil and battery positive connection, the middle is the polymer diaphragm, it separates the positive and negative poles, but lithium ions can pass and electrons can not pass, the right side is composed of carbon (graphite) battery negative pole, by copper foil and the negative pole of the battery connection. Between the upper and lower ends of the battery is the electrolyte of the battery, which is enclosed in a metal enclosure. When charging a lithium-iron phosphate battery, the lithium ions in the positive pole migrate through the polymer diaphragm to the negative pole, and during discharge, the lithium ions in the negative pole migrate through the diaphragm to the positive. Lithium-ion batteries are named after lithium-ions that migrate back and forth during charge and discharge.2. When the battery is charged, the lithium ion migrates from the surface of the lithium iron phosphate crystal to the crystal surface, under the effect of electric field force, into the electrolyte, through the diaphragm, and then through the electrolyte to the surface of the graphite crystal, and then embedded in the graphite lattic. At the same time, electrons flow through the conductive body to the positive aluminum foil assembly electrode, through the polar ear, battery pole column, external circuit, negative pole column, negative ear flow to the negative pole of the copper foil collection fluid, and then through the conductive body flow to the graphite negative pole, so that the negative pole charge up to balance. After lithium ion is de-embedded from lithium iron phosphate, lithium iron phosphate is converted into iron phosphate.3, When the battery discharge, lithium ions from the graphite crystal out of the inlay, into the electrolyte, through the diaphragm, and then by electrolyte migration to the surface of the lithium iron phosphate crystal, and then re-surface embedded in the lattib of lithium phosphate. At the same time, the battery through the conductive body to the negative pole of the copper foil collection electrode, through the polar ear, battery negative column, external circuit, positive pole column, positive ear flow to the battery positive aluminum foil collection fluid, and then through the conductive body flow to the lithium iron phosphate positive pole, so that the positive charge up to balance.Note: Again remind lithium iron phosphate battery in use should pay attention to waterproof and dustproof, so the storage place can not have water, which will affect the performance and service life of the battery.The correct charging method for lithium iron phosphate battery pack.Charging of lithium iron phosphate battery packs is recommended using the CCCV charging method, i.e. constant flow and constant pressure. Constant flow recommends 0.3C. Constant voltage is recommended 3.65. i.e. 0.3C current charge during constant current, when the battery voltage reaches 3.65V, charge at 3.65V constant voltage, stop charging when the charging current is below 0.1C (or 0.05C), i.e. the battery is fully charged. When you charge with a counterweight power supply, also look at the charging current, it is recommended not to charge with too high voltage, adjust the voltage, to ensure that the charging current is below 0.5C, so good for the battery.General lithium phosphate battery charging upper voltage 3.7 to 4V, discharge lower voltage 2 to 2.5V, comprehensive consideration of discharge capacity, discharge medium voltage, charging time, constant flow capacity percentage, safety of these 5 aspects, the use of constant current constant voltage charging scheme For lithium iron phosphate battery pack, the charging limit voltage is set at 3.55 to 3.70V, the recommended value is 3.60 to 3.65V, and the discharge lower voltage is 2.2V to 2.5V.The charger of the lithium phosphate battery pack is different from the ordinary lithium battery. The maximum termination charge voltage for lithium batteries is 4.2 volts, while the lithium phosphate battery pack is 3.65 volts. Iron phosphate lithium battery pack charging, is balanced charging plate line, generally from both ends directly series overall charging, charger voltage is greater than battery pack voltage. The line detects the voltage of each unit core, which is equivalent to a regulator in a side-by-side, and the single charge voltage does not exceed the regulatory value, while the other unit batteries continue to charge through the regulator bypass charging.Because at this point the power of each unit is close to full, just balancing each monolith, so the charging current is small, supplementing the balance of each core full. Charger can only be to protect the entire battery pack end voltage, balanced charging plate is to ensure that each unit overcharged and each unit is full, can not be because there is a charge cell full and cause the entire lithium battery pack to stop charging.The charging method of lithium iron phosphate battery pack.(1) Constant voltage charging method: During charging, the output voltage of the charging power supply remains constant. With the change of the charge state of the lithium iron phosphate battery pack, the charging current is automatically adjusted, and if the specified constant voltage value is appropriate, it can not only guarantee the full charging of the power battery, but also minimize the degassing and water loss. This charging method only considers the change of the single state of battery voltage and does not effectively reflect the overall charging condition of the battery. Its starting charging current is too large, often causing damage to the power battery. Due to this disadvantage, constant voltage charging is rarely used.(2) Constant current charging method: The charging current is kept constant by adjusting the output voltage throughout the charging process. Keep the charging current unchanged, its charging rate is relatively low. Constant current charging control method is simple, but because the acceptable current capacity of lithium battery pack is gradually decreased with the process of charging, to the later stage of charging, the power battery power capacity is reduced, the charging current utilization rate is greatly reduced. The advantage of this method is that the operation is simple, convenient, easy to implement, charging power is easy to calculate.(3) Constant current constant voltage charging method: This charging method is a simple combination of the above two. The first stage adopts the constant current charging method, which avoids the charging current at the beginning of constant voltage charging. The second stage adopts the constant voltage charging method, which avoids the phenomenon of overcharging when the constant current is charged. Lithium iron phosphate battery pack, like any other sealed rechargeable battery, should be controlled for charging and should not be overcharged, otherwise it is easy to damage the battery. Lithium iron phosphate batteries generally use the charging method of the first constant current and then the pressure limit.(4) Chopper charging method: The chopper method is used to charge. Under this method, the current of the constant current source does not change, and the switch tube is controlled so that it is turned on for a period of time and then shut down for a period of time, cycle back and forth, the advantage of this method is that when charging the battery through an external circuit, the ion generation inside the battery needs a certain response time, if it is continuously charged, it may reduce the potential of its capacity. And after charging for a period of time, add a shutdown time, you can let the battery polar ions have a diffusion process, so that the battery has a "digestion" time, which will make the battery utilization greatly increased, improve the charging effect.
With the problem of energy shortage and environmental pollution becoming more and more prominent, electric vehicles have attracted wide attention for their advantages of energy saving and environmental protection. Power batteries need to be decommissioned when the power battery capacity used in electric vehicles drops to a level that does not meet the range requirements of electric vehicles. With the increasing prosperity of the electric vehicle market, the "way out" problem of decommissioned power batteries is becoming more and more prominent. The power battery capacity of electric vehicles has been reduced to 80% and has been decommissioned due to insufficient battery life, but it can still be used for power storage at base stations after step-by-step utilization. Vehicle power battery pack to communications with 48V backup power supply as the basic module, electric vehicle power battery through a number of 48V modules in series, the formation of vehicle power battery module for electric vehicle use, after the end of power battery service can be directly used in the field of communications.The basic characteristics of the Renewable LiFePO4 battery.1, The multiplied characteristics of battery capacity.With the increase of discharge current, the discharge capacity of the battery will be reduced, when the discharge ratio is less than 0.33C10, the discharge capacity of the LiFePO4 battery is affected by the discharge multiply rate is very small, the discharge capacity is not very different, it can be basically determined that the battery capacity can be 100% released. 2, The temperature characteristics of the battery capacity.When the ambient temperature is above 0 ℃, the attenuation speed of the battery capacity is slower, while when the ambient temperature is below 0 ℃, the attenuation speed of the battery capacity is faster, and the internal resistance of the battery increases sharply with the decrease of the temperature.3,Renewable LiFePO4 battery and lead-acid comparison advantages.1, High temperature resistance: lead-acid battery stable operating temperature range of 25 to 28 ℃, rising temperature will damage the battery, reduce battery life.2, High energy density: LiFePO4 battery product weight ratio energy can exceed 130Wh/kg (0.2C, 25 oC), volume ratio energy of 210Wh/L.3, High current charge and discharge performance: LiFePO4 battery can be high current 2C fast charge discharge, starting current up to 5C or more, lead-acid battery now has no such performance. Therefore, LiFePO4 battery charging time is short.4, Green environmental protection: LiFePO4 battery does not contain any heavy metals and rare metals (nickel hydride batteries need rare metals), non-toxic.The comparison between lead-acid batteries and Renewable LiFePO4 batteries is in Table 1.Battery performance indexLead-AcidRenewable LiFePO4 batteryCycle life (times)2001200~2000Mass specific energy (Wh/kg)30~4560~110Volume specific energy (Wh/L)70125~250Mass specific power (W/kg)200~3004000Volume specific power (W/L)10000Self-discharge rateHighLowrange of working temperature (℃)25~28-20~+55Operating voltage range (V)1.75~2.352.5~3.65Nominal cell voltage (V)23.2Memory effectYesNo5, Rung use of power lithium battery life is long, the number of cycles, Renewable utilization can still theoretically remain 6 years of actual life and 400 to 2000 times of actual cycle times, compared with the lead-acid battery 3 to 6 years of service life, 200 times of the actual number of cycles has been greatly improved.6, High temperature resistance, lithium battery to meet the limit operating conditions below 45 ℃, the current communication base station commonly used lead-acid battery temperature limit is only 35 ℃.7, Discharge characteristics are good, high capacity utilization rate when high current discharge.8, Charge and discharge conversion efficiency is high, the energy conversion efficiency of the rung battery is 10% to 15% higher than the lead-acid battery.9, Small footprint, light weight, low transportation costs, rung battery weight and volume of the same capacity lead-acid battery 1/2 or 2/3.Technical solutions for the application of LiFePO4 batteries (Table 2)Technical solutionsspecific contentsSupply sideProcessing sideProcessing costCell-level reorganization planDisassembling the cascade battery into the cell level, sorting, reorganizing, and processing into a battery productBattery companiesBattery companiesHighModule-level reorganization planDisassembling cascaded batteries into module levels, sorting, reorganizing, and processing into battery productsBattery and automotive companiesFoundry companiesMediumPACK application schemeMeasure and divide the entire retired battery pack and apply it to the base stationAutomotive companiesFoundry companiesLow1, The decommissioned power battery for centralized disassembly, core centralized screening, reassembly into a standard module, is conducive to the centralized screening and maintenance of decommissioned core to ensure quality.2, On the basis of decommissioned power battery direct transformation, is conducive to the battery set Renewable utilization of simple modularity, capacity advantage, easy production methods, low labor costs, but the land requirements are higher.3, Step battery process: screening battery core, test voltage, core distribution group, internal cable, BMS, chassis or rack.The basic structure of the Renewable LiFePO4 battery.LiFePO4 battery consists of positive and negative plate (positive active substance is LiFePO4, negative active substance is graphite), diaphragm, electrolyte, polar ear and aluminum plastic membrane shell. Positive and negative plate is the area of electrochemical reaction, diaphragm, electrolyte to provide Li transmission channel, through the process of chemical processing after the battery plate surface will form a dense SEI membrane (also known as solid electrolyte interface membrane), the polar ear plays a role in guiding the current. The positive active substance is LiFePO4, which is an olivine structure.LiFePO4 is mixed with conductive agents and binders in a certain proportion, coated on aluminum foil to form a positive pole, negative active substances are usually graphite-like materials, attached to copper foil by adhesive. The positive and negative poles are separated by a polyethylene diaphragm (or polypropylene and polyethylene composite diaphragm) to prevent short circuits in the battery. The diaphragm is a porous film in which Li passes through its pores during charge and discharge, while electron e-cannot pass through. The electrolyte of the battery is an organic solvent of lithium hexafluorophosphate.Renewable LiFePO4 battery works.When the battery is charged, Li migrates from the LiFePO4 material to the crystal surface, from the positive plate material, under the effect of electric field force, into the electrolyte, through the diaphragm, and then by electrolyte to the surface of the negative graphite crystal, and then embedded in the negative polar layer graphite material. At the same time, the electron flow through the positive aluminum foil, through the polar ear, battery pole column, load, negative pole column, negative ear flow to the negative pole of the copper foil electrode, and then through the conductive body flow to the graphite negative pole, so that the charge up to balance.When the battery discharges, Li is de-embedded from a layered graphite crystal, enters the electrolyte, passes through the diaphragm, and then migrates through the electrolyte to the surface of the LiFePO4 crystal, which is then re-embedded in the material of LiFePO4. At the same time, electrons flow through the conductive body to the negative copper foil electrode, through the polar ear, battery negative pole column, load, positive pole column, positive ear flow to the battery positive aluminum foil electrode, and then through the conductive body flow to the LiFePO4 positive pole, so that the charge up to balance.Management system for Renewable LiFePO4 batteries.Battery management system is mainly used to manage the battery charging process and discharge process, improve battery life, and provide users with relevant information of the circuit system.Battery management system, composed of monitoring, protection circuit, electrical, communication interface, thermal management device, is the core component of battery protection and management, not only to ensure the safe and reliable use of batteries, but also to give full play to the performance of the battery and extend the service life, as a backup energy for communication, management system between the switch power supply and battery plays an important role in the bridge. The requirements of the battery management system must meet the requirements of the communication power supply system, so the safety management mode of the battery management system is very important to the safety of the battery. Battery management system mainly includes data acquisition unit, calculation and control unit, equalization unit, control execution unit and communication unit.The practical application of LiFePO4 battery pack in the tower base station.For the characteristics of the lithium battery pack, in the base station DC switch power application settings, only the floating charging voltage and the average charging voltage adjusted to the lithium battery pack required charging voltage can be, (at the same time must be in the communication equipment DC supply voltage range) because the lithium battery pack even if long-term in the charging state, due to its own BMS protection function, battery performance will not change.For example: a base station backup battery pack, using 48V-300Ah Renewable LiFePO4 battery pack, each set of batteries consists of 16 3.2V/100Ah single battery series, of which 300Ah battery is composed of 3 groups of 100Ah battery pack in tandescing, each battery pack has a BMS control system.After installing the battery pack to recharge the battery pack, the battery pack was tested and discharged online at 0.33C10.After testing with a smart battery pack discharger, it is included online in the DC power supply system. At this point, the switching power charging voltage is set to 56.8V and the charging current is limited to 30A per set.Renewable LiFePO4 battery configuration requirements.1, Rung battery module in accordance with the standard capacity can be divided into 15, 25, 30, 50, 100, 130, 150, 200Ah and other capacity series. The standard capacity shall be the post-group capacity of the decommissioned lithium battery.2, Rung battery specification series in accordance with the installation method can be divided into embedded, floor-to-ceiling frame and floor-to-ceiling box three, the capacity of 50Ah and below the rung battery, mainly embedded.3, Capacity requirements: rung battery in different operating temperature conditions should meet the capacity requirements shown in Table 3:Ambient temperatureDischarge currentBattery capacity requirements-10℃1.0I3The measured capacity should not be less than 70% of the nominal capacity0℃1.0I3The measured capacity should not be less than 80% of the nominal capacity25℃1.0I3The measured capacity should be between 100% -110% of the nominal capacity40℃1.0I3The measured capacity should not be less than 98% of the nominal capacity55℃1.0I3The measured capacity should not be less than 97% of the nominal capacity4, Rung battery cell requirements: Renewable battery used by the single core capacity to reach 70% of the initial standard capacity of the cell.5, Output voltage range: rung battery should use 16 series mode, battery pack rated voltage of 51.2V, operating voltage range of 41.6V to 60.0V.6, Environmental requirements: rung battery packs should be non-corrosive, explosive and damage to insulation gas and conductive dust environment. Operating temperature range: -5 to 45 ℃. Note: Heating and insulation measures should be taken below -5 ℃. Relative humidity range: ≤95% (45 ℃±2 ℃), atmospheric pressure range: 70kPa to 106kPa.7, Service life: under the ambient temperature of 25 ℃±2 ℃, the battery pack 80% DOD0.33C3 cycle life should not be less than the number of times listed in Table 4 operating conditions.The life of the lithium iron± phosphate battery pack should not be less than 6 years under the condition of electricity preparation under the condition that the ambient temperature is 25 ℃ and 2 ℃.The function requirements of the Renewable LiFePO4 battery.Sleep function.The rung battery should have a sleep function, in the transport, storage or offline state, the battery pack BMS should be in a completely disconnected state, when the battery pack from the online state (i.e., the battery pack output positive and negative, communication interface and the outside world connected state) to the offline state (i.e. the battery pack output positive and negative, communication interface and the outside state disconnected state), BMS should have the screening function, according to the power and battery pack conditions automatically into hibernation. When the battery pack is brought online from the offline state (i.e., the positive and negative of the battery pack output, the communication interface is disconnected from the outside world) to the online state (i.e., the positive and negative of the battery pack output, the state of the communication interface connected to the outside world), the BMS shall be able to judge and activate automatically, and adjust the working state according to the power and battery pack conditions.Electric heating function.When the rung battery is used for scenes of -5 ℃ and below, the DC heating device should be configured (the temperature should be controlled according to the actual situation), and the battery pack should have a special thermal design to ensure that the heating is uniform so that the equipment works properly.Charging limited flow management function.The rung battery should have an autonomous limited-flow charging function to ensure that the battery pack can charge properly when the voltage input is in the operating range. The charging limit should be set between 0.1C3(A) and 0.2C3 (A), with a default value of 0.2C3 (A).The total charge voltage is too high to protect.Renewable battery should have the function of charging the total voltage too high protection function, when charging to the total voltage alarm point alarm, to the protection point protection, acting on the cut-off, when the total voltage falls to the recovery point to resume charging.The total discharge voltage is too low to protect.The rung battery should have a low discharge total voltage protection function. When discharge to the total voltage low warning point should be cut off the discharge circuit and alert, after a period of time the battery pack should enter sleep mode.The discharge unit voltage is too low to protect.Renewable battery should have the function of low single battery voltage when discharged, alarm when discharged to single-body voltage warning point, protection at protection point, acting on cutting off, after a period of time the battery should enter sleep mode.Discharge overflow management.Renewable batteries should have output overflow protection based on the user's needs, and the circuit should be cut off and alerted during protection.Battery high temperature protection.Renewable battery itself should have the battery high temperature protection function, when the battery temperature reaches the alarm point alarm point, to the protection point protection, act on cutting off, the temperature falls back to a certain value after automatic recovery.Battery low temperature protection.The rung battery itself should have the low temperature protection function of the battery, alert when the battery temperature reaches the alarm point, protect it when it reaches the protection point, act on the cut-off, and automatically recover when the temperature returns to a certain value.Battery pack charge status (SOC) calculation.The rung battery should have dynamic charge calculation function, and the error between the calculated value and the actual battery charge should not be greater than 5%.Output short-circuit protection.In the event of a direct short circuit at the positive and negative ends of the rung battery output, the circuit should be automatically cut off and alerted in an instant, and the BMS and cell should not be damaged (including non-fire, deformation, leakage, smoke, fire or explosion).Renewable battery monitoring technology requirements.Remote measurement.The functions of battery pack/battery voltage, charge state (SOC), battery pack charging/discharge current, cycle times (discharge exceeding 80% of the standard capacity is 1 cycle), ambient temperature/battery pack temperature, battery pack resistance (optional) telemetry monitoring, as well as historical data query, fault log query, etc. can be carried out.Remote confidence.The charging/discharge status of the rung battery can be collected, the battery pack overcharge/overflow alarm, the battery pack discharge underpressurization/overflow alarm, the monocharge overpressurization alarm (optional), the single discharge under voltage alarm (optional), the battery pack polarity reverse alarm Remote confidence indicators such as ambient/battery pack/PCBA board high temperature alarm (optional), ambient cryogenic alarm, battery pack capacity too low alarm, battery pack temperature/voltage/current sensor failure alarm, monosome failure alarm (optional), battery pack failure alarm (optional).The amount of remote control.Remote control operations such as alarm sound on/off, intelligent intermittent charging, limited-flow charging, charging on/off, discharge start/stop, etc. can be carried out.Remotely adjusted.The functional status and parameter setting range of the various detection items of the BMS of the rung battery should include the contents shown in Table 5.Renewable LiFePO4 battery installation and maintenance requirements.1, Battery pack surface should be clean, no obvious deformation, no mechanical damage, interface contacts no rust, battery pack surface should have the necessary product identification, and clear identification, battery pack positive, negative extremes and polarity should be clearly marked, wiring mode should be front-line mode, easy to connect, battery pack power interface, communication (or alarm) interface should be clearly identified.2, Rung lithium battery pack 19-inch standard mechanical electrical unit container housing, mounting frame or box should be metal material, and structurally easy to handle.3, the installation of rung battery in order to facilitate testing and post-maintenance, the LiFePO4 battery panel needs to be outward-facing, the Renewable battery is reliably fixed to the battery rack or integrated cabinet.4, Rung battery cloth Renewable battery cable, the battery cable is connected to the power cabinet insurance copper row terminal or battery management empty open, do a good job of cable label identification.5, put the battery monitoring line, the lithium iron battery pack connected to the FSU-RS485 communication terminal.6, LiFePO4 battery rung battery access system, all kinds of cable connection is completed, with a million meter on the battery's output voltage, testing will detect the data to do a good job of recording, adjust the switch power output voltage to the current voltage value of the Renewable battery.7, Adjust the switch power parameters, all kinds of cable connection is completed, with a million meter to detect the output voltage of the battery, the detection of the data to do a good job of recording.8,Renewable LiFePO4 battery operating environment requirements: according to the environmental requirements of the battery, room temperature should not exceed 55 ℃, to avoid direct sunlight on the battery, windows should be shaded, to ensure that the battery pack between the reserved sufficient maintenance space.9,Renewable LiFePO4 battery use precautions through the dynamic ring centralized monitoring system and BMS real-time monitoring of the total voltage of the battery pack, current, unit voltage SOC, SOH, temperature monitoring. At the same time, through the battery monitoring device to understand the battery charge and discharge curve and performance, regular measurement, found that the fault timely treatment.10,Renewable LiFePO4 battery often check the items: should often check the Renewable LiFePO4 battery module pole wire (bar) is loose, whether there is damage, deformation or corrosion and other phenomena. BMS data cable contact, and the battery pack output insurance temperature check and signal insurance alarm test. According to the technical parameters and field environmental conditions provided by the manufacturer, through the BMS system to check whether the total battery pack voltage and unit voltage meet the requirements, to detect the battery pack intermittent charging current is within the required range. Check that the switching power supply, the charging voltage of the battery pack, and the limit values are set correctly. Detect whether the battery pack's low-voltage alarm, high-voltage alarm, high-temperature alarm, etc. are set correctly.The technical and economic demonstration of the LiFePO4 battery pack of the Renewable.At present, compared with the application of lead-acid batteries, electric vehicle decommissioned batteries have high energy density, high power density, (small size, light weight), good temperature characteristics, long cycle life, low self-discharge rate, these excellent characteristics make it more suitable for the tower base station backup power supply, the current step battery, its cycle life of more than 800 times, strong manufacturers, its battery cycle life is longer. The cycle life of decommissioned batteries will generally be better than 1000 times, and the quality is expected to reach 2000 times.At present, according to the current market situation, the cycle life is low (as long as more than 400 times can be achieved at present) batteries for one, two, three, four types of municipal electrical conditions and high temperature conditions, high cycle life batteries for new energy (more than 800 times) and peak filling (more than 1200 times) conditions.Decommissioned batteries are remanded and applied to the battery pack of base station backup power supply, and their cost composition includes the remanding process of core procurement, transportation, testing, screening, recombination, etc. According to the indicators of the 13th Five-Year Plan, it is expected that the number of decommissioned batteries will increase significantly in the future, and the recovery and re-manufacturing system will have a scale effect, and the cost is expected to be further reduced.In the treatment of end-of-life power batteries, because the base station is mainly used in commercial vehicles decommissioned LiFePO4 batteries, the main material value is not high, so the scrap LiFePO4 battery residual value is very low. But there are already some end-of-life battery treatment manufacturers to start this business, and is expected to recycle end-of-life batteries for free.In short, Renewable battery applications should follow the principles of small modules, low voltage, high redundancy, small current, non-mobile use, so communication base stations are more suitable for Renewable battery applications than other scenarios. Compared with lead-acid batteries, Renewable batteries have certain advantages in cycle life, energy density and high temperature performance, and the performance indicators are better than lead-acid batteries. Renewable battery in technology to fully meet the current network of various operating conditions to prepare electricity needs, different cycle life Renewable battery is suitable for different applications, the economy also has certain advantages. Renewable battery application is a major innovation in the development of national strategic emerging industries, such as energy conservation and environmental protection, new energy, and so on, which is of great practical significance for promoting the development of low-carbon economy, green economy and circular economy.
LiFePO4 batteries and lead-acid batteries are used in base stations, mainly taking into account that different discharge rates have less impact on the discharge capacity of such batteries and are resistant to a wide ambient temperature. The following is an analysis of the battery capacity selection for the power consumption and back-up time of the base station.Base stations can be divided into two types:(1) Acer station and indoor distribution source station.GSM Acer station power can be calculated according to 3.5A / carrier frequency, divided into townships (4/4/4) 46A, urban (12/12/12) 130A, mega-dense urban areas (15/15/15) 160A.The power of TD Acer station is divided into single-band station (including 1 BBU and 3 RRU) 1200W25A, dual-band station (1 BBU and 6 RRU) 2100W44A, of which 1 BU300W and 1 RRU300W.The power of indoor distributed source stations is divided into single-band stations (including 1 BBU and 5 RRUs) 1000W21A, dual-band stations (1 BBU and 10 RRu) 1400W29A, three-band stations (1 BBU and 15 RRu)2100W44A, 1 BU600W, 1 RBUUSOW.Acer station and indoor distribution of the source station battery backup time: urban 3h, township 5h, mountain 7h.(2) Indoor distribution of RRU indoor distribution of RRU, may include 1 or more RRU, a single RRU power consumption of 80W1.67A, battery backup time of 4 hours.According to the calculation, the configuration of the lead-acid battery is as follows:Wireless device configurationInstallation LocationCurrent(A)Time(h)Capacity(Ah)Voltage(V)Lead acid information12 carrier frequencies(46A)Town505423.9148500Ah*1 / 200Ah*212 carrier frequencies(46A)Mountain507554.8448300Ah*236 carrier frequencies(130A)Urban area1343796.9548500Ah*236 carrier frequencies(130A)Town13451133.7148600Ah*245 carrier frequencies(160A)Urban area1643975.1548500Ah*2TD macro base station or sourceUrban area483286.1148150Ah*2TD macro base station or sourceTown485407.0148200Ah*2RRU*1Urban area1.66514.084850Ah*1RRU*3Urban area5542.254850Ah*1Limited by the product type of lithium phosphate battery, the current mature for 50Ah, 100Ah, 150Ah, 200Ah. Taking 48V/50A communication load operation 5h as an example, the selection and investment comparison is carried out.The constant current discharge data for LiFePO4 batteries are shown in the table below:LiFePO4 BatteryConstant current discharge Discharge time(h) and termination voltage(2.6V)300AhTime(h)114.301.951.050.33Current(A)3075165300900Capacity(Ah)330323321316296Discharge rate0.10C0.25C0.55C1C3C200AhTime(h)12.654.922.214.171.124Current(A)2050110200600The use of LiFePO4 batteries at base stations has the following advantages:1, The capacity is small: LiFePO4 battery discharge capacity by different discharge rate is not as obvious as lead-acid battery, so optional smaller capacity of the battery to meet the same communication load of electricity demand.2, High temperature performance is good: the existing base station air conditioning is set to 28 ℃, if raised to 35 ℃, the lead-acid battery needs to be separately configured with a heat insulation box, otherwise, the temperature for every 10 ℃, battery life reduced by half. The LiFePO4 battery can withstand high temperature of 55 ℃, life is not affected, the base station temperature setting value can be directly increased, to achieve energy conservation and emission reduction.3, Small size, light weight: 3.2V/200Ah LiFePO4 battery size (long x width x high) 360 x 55 x 250, weight 8.1kg; Long x W x H) 360 x 55 x 306, weight 9.6kg, 2V/300Ah lead-acid battery size (long x W x H) 124 x 181 x 365, weight 19kg.1 set of 48V/200Ah LiFePO4 battery pack and 1 group of 48V/300Ah lead-acid battery pack in the same installation mode, the former covers an area of 59% of the latter, the former weight is 28% of the latter. If consideration is given to the same load-bearing conditions in the engine room, LiFePO4 batteries can be installed in double-layer double columns, while lead-acid batteries need to be installed in single-layer double-columns, the former covers an area of 29% of the latter. The same set of 48V/300Ah LiFePO4 battery pack and lead-acid battery pack, in the same installation, the former covers an area of 59% of the latter, the former weight is 34% of the latter.4, Long cycle life: LiFePO4 battery has more times the cycle life, especially suitable for use in the four types of power base stations with repeated power outages.5, The investment is flat: 1 set of 48V /300Ah lead-acid battery price of about RMB8640 (set price: RMB1.2 / 2V. Ah), a set of 48V/200Ah LiFePO4 battery price of about RMB25,600 (market price: RMB8 / 3.2V. Ah), 1 set of battery insulation box price of about RMB10 million, 1 set of LiFePO4 battery (no insulation box) price is 1.37 times the price of 1 group of lead-acid battery (including insulation box). When the price of LiFePO4 battery fell to RMB6 / 3.2V. Ah, a set of LiFePO4 batteries (no insulation box) price is RMB192,000, the two costs are basically equal. In addition, the room area reduction, weight reduction can reduce the cost of building the engine room, LiFePO4 battery cycle life can be better can extend the battery replacement cycle, high temperature performance can save air conditioning electricity and so on.6, High ambient temperature: lead-acid battery for outdoor stations, need to be installed in the insulation cabinet, in areas with particularly harsh climatic conditions, but also need to be buried under the permafrost layer, to installation and maintenance are extremely inconvenient. LiFePO4 battery is suitable for high ambient temperature, charging ambient temperature of 0 to 55 ℃, discharge ambient temperature of -20 ℃ to 60 ℃, suitable for inarguable room, no air conditioning, ambient temperature above zero ℃ outdoor station.