• 28Feb

    VRLA battery Substation Operation and Maintenance(c)

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    2.3 improve the maintenance job to do a good job maintaining the quality of

    2.3.1 the use of a new battery and maintenance

    New VRLA batteries in and put into service, first of all to carry out supplementary charge (that is, both the charge). At 25 ℃ when the voltage value of 2 35V / monomer ± 0 02V. Charging time about 16 ~ 20h. If the standard temperature should not amend its charging voltage. Adequate electric battery only when the circumstances in order to check the capacity of the pilot, while the battery charge and discharge standards should be carried out (Ministry standard), because the battery electrode active material from the surface to the interior of the chemical reaction when the full required a certain amount of time, so Recommendation 2 times charge-discharge time interval should be larger than 10d (depth of discharge cases). The longer the charging time is relatively deep depth of discharge some.

    2.3.2 rechargeable batteries online maintenance

    Battery and put into service, shall, in accordance with the manufacturers of rechargeable battery requirements of battery charging parameter settings. Particularly at a charge of microprocessor-based equipment, intelligent manner and extent are different on the valve-regulated battery charging should be able to request the following.

    a) VRLA battery float voltage at 25 ℃ 2 25V ± 0 02 / monomer, the best check in 2 25V ~ 2 26V / monomer, that is slightly higher than the center value.

    b) battery systems are often more than the monomer by the use of batteries in series, so the system depends on the current floating充充电one of a lower float current monomer. Under normal circumstances, even if the tandem system of individual monomers higher voltage, but because of floating charge current is limited, its value will not exceed the specified value. Therefore, the provisions of the float current value (normally 2mA/Ah), improve the proper float voltage value is still not sufficient for individual capacity and also in a backward voltage battery monomer are beneficial.

    c) Float Voltage unmanned stations can not be less than the value of the selected center value, not always possible because the user equipment on the charge voltage adjustment.

    d) charging method used for both current-limiting value to automatically determine the standards are charging switch charging equipment, often in both state-of-charge after the end of the battery system is not adequate capacity. Therefore at this time must be adjusted float voltage value above the standard value in order to gradually sufficient capacity.

    e) Float voltage is too low to obtain, this will result in a sharp decrease float current, the relative charge time will be extended. If the load changes in time interval shorter than the battery required for a short period of time sufficient electricity, so the battery will charge enough battery discharge capacity will become increasingly smaller, while the battery float voltage is too low when the internal electrode lead sulfate synthesis can not fully PbO2 and Pb, the long run, lead sulfate will become coarse crystalline lead sulfate Second Pb (SO4) 2, the final can not be translated into PbO2 and Pb, which appears Sulfation electrode.

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  • 28Feb

    VRLA battery Substation Operation and Maintenance(a)

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    0 Introduction

    DC substation equipment, equipment selection and design concepts are changing, especially in recent years, new types of equipment are being born, DC charging device replacement, valve-regulated batteries made continuously improve the quality of DC equipment and related emergence of auto-monitoring equipment Substation DC System for the safe operation of the level of providing strong protection. VRLA Battery in the substation to be a relatively wide range of applications, a lot of call for the maintenance-free batteries, in fact it is compared with the open battery biggest advantages is to reduce battery maintenance of labor intensity, but the day-to-day charge maintenance work is still indispensable. However, because of “maintenance-free,” the term misleading, enabling users to relax on the valve-regulated lead-acid battery maintenance and management of day-to-day, resulting in reduced battery capacity and the damage early. Therefore, in order to strengthen the use of maintenance-free battery maintenance requirements and methods of propaganda, the correct understanding of “free” means to ensure that the DC system of safe and reliable.

    The impact of one VRLA battery life a major factor in

    VRLA battery in the normal life of 8 ~ 10a above, in theory, can be 15 ~ 20a, but in the actual use of the frequent occurrence of inadequate capacity or early failure phenomenon. Factors that affect battery life much, but compared with the valve-regulated lead-acid batteries for the following main factors are currently the most vulnerable to the run.

    1.1 Operating environment temperature

    Battery at 25 ℃ environment available to a longer life expectancy. Temperature, the battery plate corrosion will be increased at the same time will consume more water, thus shortening battery life, long-term operating temperature if the rise 10 ℃, the service life of about halved.

    1.2 Float Voltage higher impact on the battery

    Higher float voltage for the majority of normal cells is no doubt in the off state-of-charge. There is no doubt that this will have a large amount of O2, H2. Theoretically, valve-regulated batteries are losing water, but the truth is inevitable. First of all, the re-combination reaction efficiency is not possible to reach 100%, the gas should not compound formed in the battery internal pressure, pressure threshold over the safety control valve, the valve open, gas from the control valve in the discharge. Secondly, batteries are not totally sealed, battery water loss is a slow process. In previous battery maintenance, along with a balanced process of charging the battery are to adjust the proportion, that is the approach used to add distilled water to add water in order to maintain the equilibrium of the battery. However, maintenance-free batteries, the maintenance of the existing system are not under water, so that will inevitably result in cell loss, the battery dry.

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  • 27Feb

    Apply to single or two battery-powered portable applications a complete battery pack design(c)

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    Battery authentication

    Portable devices rechargeable battery in the device must be replaced before the end of life. This will give those who provide cheap alternatives to battery manufacturers to open up a huge market, and these batteries might not be original equipment manufacturers require the safety and protection circuit.

    Therefore, in addition to battery monitoring function of outside the battery pack may also include authentication features (see Figure 2). Host will verify the calculation includes cyclical redundancy check (CRC) IC (TI’s bq26150) of the battery pack. This CRC, as well as based on this authentication secret in the definition of IC in the CRC polynomial above. Host CRC also calculated, and a variety of values than the right, in order to determine whether a successful authentication. If not, then the host will decide yes or another authentication system does not allow the battery power supply.

    Once the battery through the authentication, then the bq26150 will receive a command to ensure that all lines through the data communications in the host and battery power to be transmitted between the monitoring of dollars.

    Figure 2 with the bq27000 and authentication IC circuit

    In this connection, the host can continue to use battery power monitoring of function. Disconnecting the battery and re-connected to the battery, they must repeat the entire validation process.

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  • 27Feb

    Apply to single or two battery-powered portable applications a complete battery pack design(a)

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    Battery monitoring Principle

    Monitoring of the battery is a battery of automatic monitoring IC, its power management system to make a decision to monitor the situation the report processor. A good monitoring of battery power required at least some measurement of battery voltage, battery temperature and current methods, a microprocessor and a battery have been validated to monitor the method of calculation.

    bq2650x and bq27×00 are complete battery fuel gauges, which have a voltage and temperature measurements for the ADC (ADC) and a current and charge sensing ADC. These monitoring of battery power to run TI also has a battery monitoring method for calculating the internal microprocessor. These algorithms will be lithium-ion (Li-ion) batteries self-discharge, aging, temperature and discharge rate to compensate. The microprocessor allows the host system processor without conducting an endless calculations.

    Monitoring of battery power to provide such as “residual state power” and other information, at the same time bq27×00 system also offers a “residual run-time” information. Host at any time that such information could be asked by the host to decide yes or through the adoption of LED screen display message to inform the end-user information related to the battery. The system processor is only required because of a 12C or a HDQ communication-driven, therefore monitoring of the use of battery power is very simple.

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  • 25Feb

    Manganese dioxide battery(a)

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    The twentieth century from the eighties onwards, electronic technology has been rapid development, the pace of the progress of human civilization on a variety of electronic devices rely on rapid growth, with the rapid development of the information age, growing stronger and stronger this dependence. And constraints of these new high-performance electronic devices is a major obstacle to the development of power. Especially civilian portable electronic devices to smaller, lighter direction, which requires the battery to provide energy with some advantages: small size, light weight, high specific energy, long life, than the maintenance, non-polluting and so on. Portable mobile communications currently positioning system, laptop, represented by the application of portable electronic equipment are made high on the battery requirements. The ever-changing era of electronic systems and information requirements of power supply must be adapted to the needs of scientific and technological development.

    Lithium, atomic number 3, located in the first main group of the periodic table the first known metal atoms in the lightest (6.94), the most negative electrode potential (-3.045V), the element name from the Greek, intent is “a rock.” 1817 Swiss scientists have through the analysis of lithium-tsung Chang quarry found. Because of its potential in the most negative, with the appropriate composition of cathode material to match the battery has excellent electrical properties. This has led the world wide attention from researchers, from the twenty-first century since the seventies study, lithium - manganese dioxide batteries, lithium - sulfur dioxide batteries, lithium - thionyl chloride lithium battery to become a cell of the three most widely used system, product serialization, as many as dozens.

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  • 25Feb

    Fuel cell hybrid power system characteristics(e)

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    Shown in Figure 9 for the experimental phase of rapid loading, fuel cells and nickel-hydrogen batteries power distribution practical. In the dynamic filter module under the protection of the fuel cell output power to 4.36kW / s slow the rate of increase in battery to provide accelerated phase of the sudden increase in power, played a role in the protection of fuel cells. Hydrogen flow meter data show that the hybrid test bench, economic Tatsu 5.618kg/100km, better than the current development of the actual vehicle’s economic level [2].

    3 Conclusion

    1) According to the study of the characteristics of nickel-hydrogen batteries, in fuel cell hybrid system, Ni-MH battery SOC should be maintained at 40% ~ 60%, and charge-discharge current should be in the range -160 ~ 240A, the temperature should be maintained at room temperature near to ensure the safety of the system and economy.

    2) The bench test showed that through the steady-state distribution + dynamic filtering algorithm model and appropriate parameters for matching, vehicle controller can make nickel-metal hydride batteries in the target area, so that hybrid systems to meet the dynamic conditions of urban public transport and economy demand, and fuel cell engine output power are restricted.

    3) The above method can be used for fuel cell hybrid vehicle system controller of the primary control algorithm development. Taking into account the experimental set weight for the 10t, while the actual fuel cell buses in vehicle weight of up to 13 ~ 15t, the actual economy of vehicles should be reduced, energy management algorithms also need to optimize the calibration of real vehicle.

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  • 23Feb

    PEM fuel cell cathode catalyst layer properties(b)

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    Paper presents a mathematical model to study the PEM fuel cell cathode catalyst layer of oxygen volume fraction distribution, current density distribution, impedance distribution and temperature distribution for the PEM fuel cell cathode Optimize provide useful help.

    1 Geometry and mathematical model

    Humidification of air along the direction of the arrow to enter the battery cathode, the cathode diffusion layer after arrival catalyst layer, oxygen in this and the anode to the proton and electron redox reaction to generate water happened. Generated by the anode water and the water will migrate to the cathode gas channel proliferation, or by counter-proliferation back to the anode. Figure 1 is a model of the region involved in the calculations.

       

    Model set up the necessary basic assumptions:

    (1) batteries throughout the fluid flow is laminar;

    (2) fuel cell system is in steady state;

    (3) gas diffusion layer, catalyst layer and proton exchange membranes are isotropic porous media;

    Continuity equation:

    One of, ε is the porosity. In the gas channel, if there is no liquid water, the porosity is 0.

    Momentum equation

    Mixed gas and liquid momentum equation

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  • 23Feb

    PEM fuel cell cathode catalyst layer properties(a)

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    Abstract: in order to improve the characteristics of the catalyst layer and PEM fuel cell performance, speed up its promotion and application. Give a PEM fuel cell cathode heat and mass transfer mathematical model, simulation of the cathode catalyst layer of oxygen volume fraction, current density, impedance and temperature distribution patterns. The study found: Analog conditions, in the cathode catalyst layer and mass transfer, the proton transfer process is the control of the process of cathode performance; direction along the gas channel and catalyst layer of oxygen concentration, current density, impedance and temperature were gradually reduced; along the Y-axis direction, oxygen volume fraction, impedance and temperature gradually decreased, while the current density increased. The results of the PEM fuel cell cathode structure optimization and improve the performance of an important reference role.

    Key words: proton exchange membrane; fuel cell; mathematical model; heat and mass transfer

    CLC number: TQ 031 Document code: A

    0 Introduction

    Proton exchange membrane (Proton Exchange Membrane, referred to as PEM) fuel cell is a clean, efficient power generation system with a very wide range of applications, many well-known international scholars have invested substantial effort to study it [1]. You and other people such as [2], Wang et al [3] and Sun et al [4] set up separately within the PEMFC two-phase heat and mass transfer model, simulation study of its internal law of the two phase mass transfer and its influencing factors. Sun et al [5], Liu et al [6] and Mench et al [7] adopted the measurement points, respectively, film, son of the battery and fluid partition on PEMFC internal current density distribution of the study, analysis of its internal current density distribution law and its influencing factors. Wang and others [8-9] experiments and a comparative study of simulated snake-like flow field and cross-finger PEMFC performance characteristics. Although the literature has made a lot of valuable results, but so far, few studies have PEMFC cathode catalyst layer performance literature.

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  • 22Feb

    Dynamic power path management to simplify the solar panels for battery charging(b)

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    Figure 5 the use of solar panels to recharge batteries

    The properties can be used in applications as shown in Figure 5. Among them, a solar panel being used as a monomer rechargeable lithium-ion battery. The solar panels by a number of battery strings, each battery string includes 11 silicon cells in series. Its role is similar to current limiting voltage source, current limit is by the size of solar panels, as well as exposure in the above to determine the amount of light.

    From the solar panel to obtain the maximum output voltage (VOC) are usually between the range of 5.5 ~ 6V. Since the voltage is lower than 6V predefined bq24030 output regulation voltage, Q1 is completely turned on (turned hard-on). RSET defines a maximum charge current of 1A.

    If its more than the solar cell output current (depending on the strength of light), solar panels output voltage will drop, thereby reducing the bq24030 OUT pin voltage. Bq24030 carried out on RDPPM programmed to automatically reduced to a ICHG allow VOUT maintained at 4.5V level. The reason why the use of VDPPM this value, because it is very much in line with solar panels the maximum power point (MPP). Q1 assumptions at both ends of the voltage reduced to 300mV, then the voltage on each battery will be turned into 436mV, this will maximize the power output of solar panels. If VOUT is higher than 4.5V, the dppm will not work, solar panels will depart from the work of the state of MPP. However, only the necessary power less than the solar panels can provide power only when there are, at this time to reduce the efficiency of there will not be much affected. As shown in Figure 3, with output power close to MPP, the output power curves become very smooth, and then suddenly dropped drastically. Therefore, setting a slightly higher VDPPM more than set up a more than slightly. This may be inappropriate for the job point output power to minimize the impact.

    If the solar panels to provide electricity supply is not sufficient for the system, even when the battery charge current has been reduced to zero when, Q2 will be turned on, VOUT will drop to just below the battery voltage VBAT, and the battery can provide any solar panels Can not provided by the current.

    bqTINY-III also allows the adoption of USB ports for charging batteries. In this case, Q3 will be used to adjust the input current to ensure that the USB specification of ISET2 under IC pin state meet the requirements of 100mA or 500mA. If the system and the charge current exceeds the sum of the selected USB current limit, then VOUT will drop dppm function and reduce the charge current, or as it was before the battery back into add mode.

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  • 22Feb

    Dynamic power path management to simplify the solar panels for battery charging(a)

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    Solar cell is generally composed of pn junction, the incident-ray energy (photons) through the pn junction led to electron and hole re-combination to generate a current. Because of similar characteristics of pn junction diode characteristics, so we usually as shown in Figure 1 of the circuit characteristics of solar cells as a simplified model.

     

    Figure 1 simplified circuit model of solar cells

    Current source and IPH will have a solar cell is directly proportional to the light of the current measure. In the absence of load connection, almost all generated currents are flowing through diode D1, the forward voltage determines the solar cell open circuit voltage (VOC). The voltage due to different types of solar cell characteristics vary. However, for most silicon cells, this voltage are between 0.5 ~ 0.6V (which is the standard pn junction diode forward voltage). In the actual solar cell applications, the parallel resistance of the leakage current small RP. With the increase in load current, IPH produce large current from the diode into the load-out and mid-stream. For the majority of the load current, the output voltage for this process only a small impact. IV characteristics of diodes because of a slight change, and because of the reasons for RS series resistance (loss of its connection), voltage will drop slightly, but the output voltage has remained roughly constant. Sometimes, however, the current flowing through D1 is too small, resulting in less bias diode, and diode voltage at both ends as the load current increases drastically. Finally, if all generated currents are flowing through the load only (without flow through diode), then the output voltage will become zero. This current is known as solar cell short circuit current (ISC). ISC and VOC are the definition of job performance of solar cells, one of the main parameters (see Figure 2).

    Figure 2 A typical IV characteristics of solar cells

    In most applications, people have expectations of solar cells can provide electricity as much as possible. Output power because the output voltage and current are multiplied, it was important to determine the battery life which part of the region arising from the largest power value, which is known as Maximum Power Point (MPP). When the output voltage to its maximum value (VOC), the output current is zero, this is an extreme case; and when the maximum output current (ISC), but the output voltage is zero, it is another extreme conditions. In both cases the product of VI are zero, there will definitely not MMP-point. We can easily prove (or through experimental observation), in any application, MPP will normally appear in the solar cell output characteristics (see Figure 3) the lower half of a location. But the problem is that solar cells MPP will be the exact location of the incident line and the ambient temperature varies. Therefore, designed to dynamically adjust the output current of solar cells in order to achieve solar power generation system to maximize its practical application in the MPP can point or near the point of their job.

    Figure 3 Output characteristics of solar cells

    The implementation of the program (maximum power point tracker) has a lot of ways, but all very complicated, especially in satellite and other mission-critical systems. However, in a lot of small applications, does not require extremely precise tracking of the MPP program, only a required utilization about 90% ~ 95% of available power low-cost solution can be easy. TI linear charge controller bqTINY-III series of dynamic power path management (DPPM) feature can be used for, such as simplifying the implementation of MPP tracker.

    Figure 4 bqTINY-III linear charger dppm working principle

    The main principle of dppm function shown in Figure 4. Temporarily ignore the USB input, the circuit working principle is as follows: Q1 on the OUT pin voltage regulator, Q2 according to a typical CC-CV charge curves of lithium-ion regulated charge current. If the pin is connected to AC power can not be less than current power supply for the system and to charge the battery, then VOUT begin to decline. If VOUT has reached a predefined threshold VDPPM, bqTINY-III will be automatically reduced to a charge current to maintain the level of VOUT when VDPPM.

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