maintenance of valve-regulated lead-acid batteries

DC substation equipment, equipment selection and design ideas are constantly changing, especially in recent years, new equipment are being born, DC charging device replacement, made continuously improve the quality of valve-regulated batteries, and related equipment, DC emergence of automatic monitoring equipment DC system for the safe operation of the substation level provides battery for camcordera strong protection. VRLA batteries have been compared in the substation is currently widely used, many people called it as maintenance-free batteries, in fact it is compared with open-type battery of the biggest advantages is to reduce the labor intensity of the battery maintenance, but routine Charge maintenance work is still indispensable. However, as "maintenance free" is a misleading term, allowing the user to relax on the daily valve-regulated lead-acid battery maintenance and management, resulting in reduced battery capacity and damage early. Therefore, we should strengthen the use of maintenance-free battery requirements and maintenance methods of publicity, the correct understanding of "maintenance-free" means to ensure the safety and reliability of DC system.

Affect the life of a VRLA battery the main factors

The normal service life of valve-regulated lead-acid batteries in 8 ~ 10a above, in theory, can be 15 ~ 20a, but in actual use in the often inadequate capacity, or early failure phenomenon. There are many factors affect battery life, but compared to VRLA batteries, the following key factors is the operation most vulnerable to the.

1.1 The impact of operating ambient temperature

Battery at 25 ℃ environment, availability of a longer life. Temperature, the battery will exacerbate corrosion of the plates at the same time will consume more water, thus shortening battery life, long-term operating temperature if the rise 10 ℃, life is about half-way.

1.2 the higher the impact on the battery float voltage

A higher float voltage for the majority of normal cells is undoubtedly in the overcharge condition. There is no doubt that this will generate a large number of O2, H2. In theory, valve-regulated battery is losing water, but the fact is inevitable. First, the re-combination reaction is impossible to achieve 100% efficiency and can not be combined to form the gas in the battery within a certain degree of pressure, the pressure rise above the threshold control valve, the valve opens, the gas discharged from the control valve. Second, the battery is not completely sealed, the battery water loss is a slow process. In the previous battery maintenance, along with a balanced charging process is carried out to adjust the proportion of the battery, that is used to add distilled water method to add water in order to maintain battery balance. However, maintenance-free batteries, in the maintenance of the existing system is not adding water, so a result, water loss will inevitably result in the battery, the battery dry.

1.3 Imbalance of charge and discharge of

The study results showed: grid alloy composition and structure in different parts of the distribution is different, which will lead to the unbalanced nature of grid electrochemical properties, this imbalance will, in turn in the float, and charge and discharge state The voltage generated difference, and will as the charge and discharge the cycle, so that this difference is increasing, and the formation of the so-called "backward batteries (battery failure)." The current domestic standards, in a group of the largest battery fIBM ThinkPad R50 battery，IBM ThinkPad R51 battery， IBM ThinkPad R52 batteryloat voltage difference should be ≤ 50mV, while the developed countries, standards are ≤ 20mV, so attention should be paid and to reduce the floating state battery operating voltage differences.

1.4 thermal runaway phenomenon

As the use of depleted fluid valve-regulated lead-acid battery design, battery electrolyte perfusion are adsorbed on the glass fiber, when the charge current increases, it is necessary to release the gas through the valve, resulting in the battery water loss, resistance by large volume attenuation in the charge and discharge a lot of heat generated in the process, which spread the heat as the temperature was too late surge, they will form a thermal runaway. Thermal runaway causes are not promptly reduced float voltage, lax safety valve or open valve pressure is too low, etc. In severe cases of thermal runaway if the discharge has the potential to transient voltage dip lasting battery and battery housing the temperature rose to 70 ~ 80 ℃, and therefore thermal runaway must be a high level of attention.

2 valve-regulated lead-acid battery operation and maintenance of

In response to these affect the service life of valve-regulated lead-acid batteries analysis of the factors, in order to improve the service life of valve-regulated lead-acid batteries, you must do the following work.

2.1 The strict quality control

In the battery selection and procurement process, we must fully understand the manufacturer's production processes, manufacturing process and quality control methods, as well as technical characteristics and so on, if necessary, require manufacturers to conduct the first in the capacity of experiments to screen a smaller difference in battery.

2.2 The rational choice Charging Equipment

Choose the VRLA battery charging equipment, the appropriate use of high-quality high-frequency switching power supply or a phased power supply, the ripple factor, regulation accuracy and precision of the main indicators of steady flow have higher demands, and should have real-time monitoring and intelligent management capabilities, enabling the work of sealing the battery always in the best condition. For the high-frequency switching power supply module when there is failure, should be able to immediately quit running, and does not affect the normal operation of other modules to ensure the battery is not due to module failures caused by excessive discharge.

2.3 do maintenance work to improve the quality of maintenance

2.3.1 Use and maintenance of new battery

The new valve-regulated battery is put into use, first of all to conduct additional charge (ie, all charge). When the voltage at 25 ℃ for 2 35V / monomer ± 0 02V. Charging time about 16 ~ 20h. If you are not a standard temperature should revise its charge voltage. Only in the case of fully charged battery can be checked against the capacity tests, the battery charge and discharge criteria should be (ministerial standards), due to the battery electrode active material from the surface to be fully within the chemical reactions take some time, so Recommendation 2 times charge and discharge time interval should be larger than 10d (depth of discharge cases). The longer the charging time is relatively deep depth of discharge for some.

2.3.2 On-line battery charging maintenance

Battery in use, it should be in accordance with the manufacturer of rechargeable batteries require battery charging parameter settings. In particular, the current microcomputer-based charging 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, it is best to take in the 2 25V ~ 2 26V / monomer, that is, slightly higher than the central values.

b) battery systems are often only single cells in series by a multi-use, so the system floating-Chong Chongdian current value depends on the current value of which a floating lower monomer. Under normal circumstances, series system, even if individual monomer higher voltage, but because of float charging current is limited, its maximum value will not exceed the specified value. Therefore, within the provisions of the float current value (usually 2mA/Ah), to suitably increase the float voltage value for the individual is still not sufficient capacity in the midst of the backward voltage of single battery is useful.

c) Unattended station select the value of the float voltage can not be less than the center value, because the user is not always possible on the charge voltage adjustment devices.

d) are charging for the value with the limit switches to automatically determine both the standard rechargeable battery chargers, often in both state of charge after the battery system can not be sufficient capacity. Therefore, when the value of float voltage must be adjusted above the standard values in order to gradually sufficient capacity.

e) to obtain low float voltage will cause a sharp decrease float current, the relative charging time will be extended. If the load changes in time interval shorter than the battery fully charged within a short time, so the battery will be charged less than the battery discharge IBM ThinkPad T40 battery， IBM ThinkPad T41 battery， IBM ThinkPad T42 batterycapacity will become increasingly smaller, while the battery float voltage is too low, the internal plates of lead sulfate synthesis can not fully PbO2 and Pb, long term, the lead sulfate will become the two lead sulfate crystals thick Pb (SO4) 2, the last can not be converted into PbO2 and Pb, which appears sulfate electrode.

2.3.3 periodic maintenance measures valve-regulated batteries

2.3.3.1 on a regular basis are charged. Were charging voltage with 2 35V / monomer ± 0 02V. Every three months to 6 months should have been charging a times, should be considered normal float voltage difference between the degree to decide. Both charging time is generally 8 ~ 12h. On a regular basis are charging objectives are: elimination of temperature changes and failure to make timely amendment to float voltage change; battery float voltage is often discharged, but not within the specified time to its fully charged.

2.3.3.2 on a regular basis to amend the float voltage battery system

Since the battery float voltage of the system influenced by temperature, it should be based on the use of battery systems to changes in ambient temperature and timely amendments to the charging system voltage. Usually adjusted each year to set 2 to 4 times. Adjusted criteria: environmental temperature is increased by 1 ℃, the lower float voltage 0 003V / monomer; ambient temperature decrease 1 ℃ per, the increase in float voltage 0 003V / monomer. Battery in under high ambient temperature operation (greater than 30 ℃), due to battery internal resistance become smaller, the battery charging efficiency, battery capacity will increase. And a suitable reducing float charge voltage value, reducing the float current of the battery capacity is not affected. When the battery is reduced when operating ambient temperature (20 ℃ or less), batteries lead sulfate solubility and dissolution rate of reduction, electrolyte concentration polarization increases, while the electrolyte resistivity change induced by the battery internal resistance increases, thus requiring the at low temperatures have a higher charge voltage, in order to meet charging requirements. Otherwise it will create the phenomenon of charging enough.

2.3.3.3 checked on a regular basis discharge, test

Float a long period of testing battery system work, the negative electrode active material due to over-design and the presence of oxygen-evolving complex, resulting in a total some of the negative plate active material is charged less than the state, but also due to the long float current values are smaller and not enough to make a very board is fully active substances inside the electrochemical reaction caused by the internal electrode active material sulfate, thereby reducing the negative plate capacity, the battery life be affected. To avoid these phenomena, and a floating charge for a long time in the working state  battery for digital of the battery system should be different depending on the work of the state to take every 6 months or 12 months a second check of discharge test. When the 6-month discharge a time when the shallow depth of discharge can be more, should adopt the 30% ~ 40%, if the 12 months to deepen discharge tests may be appropriate to some, should 50% ~ 60%, the depth will be easier to observe post-deepening battery system failure occurs single battery.

3 Conclusion

In short, the maintenance of valve-regulated lead-acid batteries is very important, according to the different characteristics of valve-regulated lead-acid batteries, valve-regulated lead-acid batteries that affect a major factor in life and constantly improve the level of maintenance to achieve the purpose of improving life in order to DC operation of the system to improve the reliability of substations to ensure the safe operation of power grid.