Maintenance and management of valve regulated seal

2022-08-11
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Maintenance and management of valve regulated sealed battery for communication equipment

0 introduction

with the rapid development of telecom companies' business, the scale of communication network is gradually expanding, and the number of high-frequency switching power supply, uninterruptible power supply (UPS) and other power supply equipment is also increasing sharply, which makes the battery widely used. Valve regulated sealed battery has become the preferred battery for communication power supply system because of its small volume, explosion-proof safety, stable voltage, no pollution, light weight, high discharge performance, small maintenance and other characteristics. However, in practical use, there are many cases that the battery life is short and cannot reach the theoretical life expectancy due to various reasons, especially some factors of inadequate maintenance. Most of the batteries that should have worked for 8 ~ 10 years are damaged within 2 ~ 3 years, and some even cannot reach the service life of 1 year, which brings great potential safety hazards to the normal work of communication equipment and causes great economic losses at the same time. In addition to the quality factors of the battery itself, the cases of early scrapping of the battery due to unreasonable charge and discharge control and improper maintenance account for a large proportion. The unreasonable charge and discharge control of the battery has a huge impact, such as the early capacity loss of the battery, irreversible sulfation, thermal runaway, electrolyte drying up and so on, which are related to the unreasonable charge and discharge control. Reasonable and reliable management and maintenance of the battery can ensure a long service life of the battery, so as to ensure the uninterrupted power consumption of communication equipment and save maintenance funds. Therefore, in the maintenance of the power supply system for communication equipment, the maintenance and management of the battery accounts for a considerable proportion. How to give full play to the role of the battery as a backup power supply and try to reach or approach its design life in use has become a problem that maintenance personnel need to discuss in depth

1 Factors Affecting battery life

at present, 2V series and 12V series are widely used in valve regulated lead-acid batteries. The service life of these two batteries is quite different. Generally, the design life of 2V series is 8 ~ 10 years, and the design life of 12V series is 3 ~ 6 years. Considering the price factor, at present, the UPS is generally configured with 12V series batteries in the communication system, and the high-frequency switching power supply is generally configured with 2V series batteries

the design life of the battery provided by the general battery manufacturer is the theoretical value under the specific environment, and the actual service life is closely related to the ambient temperature of the battery room, the parameter setting of the rectifier, daily maintenance and operating conditions

1.1 influence of ambient temperature

ambient temperature has a great influence on the service life of battery. The increase of ambient temperature will accelerate the corrosion of the battery grid and increase the loss of water in the battery, thus greatly shortening the battery life. Generally, the service life of the battery will be reduced by 50% for every 10 ℃ increase in temperature. The higher the temperature, the greater the impact. The industry standard yd/t799-2002 for valve regulated lead-acid batteries for communication equipment stipulates that the high temperature accelerated floating charge life test is a charge discharge test of 42 days at an ambient temperature of 55 ℃ equivalent to a year of normal service life, which shows the impact of high temperature on battery life. The best ambient temperature for the battery is 20 ~ 25 ℃

1.2 insufficient charging

under normal conditions, the battery forms lead sulfate crystals when discharging, and can be easily reduced to lead when charging. If it is used improperly, for example, in the state of insufficient charging for a long time, a large number of statistical data will gradually form on the negative electrode, indicating that a kind of thick and hard lead sulfate, which is almost insoluble, is difficult to convert into active substances by conventional methods, thus reducing the battery capacity, and even becoming the cause of battery life termination. This phenomenon is called irreversible sulfation of the electrode plate

1.3 overcharge

under the long-term overcharge state of the battery, the positive pole is consumed due to the oxygen evolution reaction, and the hydrogen ion concentration increases, resulting in the increase of acidity near the positive pole, the acceleration of grid corrosion, and the reduction of battery capacity. At the same time, due to the aggravation of water loss, the battery is in danger of drying up, thus affecting the battery life

1.4 over discharge

the over discharge of the battery mainly occurs after the AC power supply is cut off, and the battery supplies power to the load for a long time. When the battery is over discharged to the termination voltage or lower (due to the inaccurate setting of the battery discharge termination voltage by the power supply itself, or some have no over discharge protection device at all), a large amount of lead sulfate inside the battery is adsorbed to the cathode surface of the battery. Lead sulfate is an insulator, which will have a great negative impact on the charging and discharging performance of the battery. Therefore, the more lead sulfate forms on the cathode, The greater the internal resistance of the battery, the worse the charging and discharging performance of the battery, and the shorter the service life. A deep overdischarge may reduce the service life of the battery by 1 ~ 2 years, and even cause the battery to be scrapped

1.5 long term floating charge state

in the long-term floating charge state, the battery is only charged without discharging, which has the same impact on the battery as overcharging

2 equalizing floating charge control

the charging methods of communication batteries are mainly floating charge and equalizing charge. In order to prolong the service life of valve regulated battery, it is necessary to understand the characteristics and requirements of different charging methods and charge the battery in strict accordance with the requirements

generally, the date when sealed lead-acid batteries are put into use is a long time from the date of delivery. After long-term self discharge, the capacity of the batteries will inevitably suffer a large loss, and due to the difference in the size of self discharge of individual batteries, the proportion and terminal voltage of the batteries will be uneven. Before putting into use, the batteries should be charged evenly, otherwise, individual batteries will further develop into backward batteries and the whole set of batteries will be unusable. In addition, if the battery is not put into use for a long time and has been idle for more than 3 months, the battery should be charged evenly once

in the floating charge state, the charging current not only maintains the self discharge of the battery, but also maintains the oxygen circulation in the battery. However, in the floating charge state, the charging current is closely related to the floating charge voltage of the battery. Therefore, in order to make the valve regulated lead-acid battery have a long service life, the floating charge voltage should be set in full combination with the raw materials, structural characteristics and environmental temperature of the battery. According to the provisions of YD/t799-2002, the allowable variation range of floating charge voltage is 2.20 ~ 2.27v at the ambient temperature of 25 ℃. If the floating charge voltage is set too low and the battery is under charged for a long time, it will not only form irreversible sulfation inside the battery plate, but also form a high resistance barrier layer between the active material and the grid, which will increase the internal resistance and reduce the capacity of the battery. The floating charge voltage is set too high, and the battery is in an overcharged state for a long time, which makes it difficult for the H2 precipitated from the negative pole and the O2 precipitated from the positive pole of the battery to be fully reconstituted into H2O, resulting in water loss of the battery, accelerated grid corrosion, and early termination of service life. Therefore, the floating charge voltage should be set according to the data provided by the battery manufacturer during the use, maintenance and management of the battery. If the floating charge voltage of the single battery recommended by the battery manufacturer is 2.25V, then the floating charge voltage of the combined power supply should be set to 54V (2.25 24)

according to the regulations of telecommunication power supply maintenance, valve regulated lead-acid batteries should be charged evenly in one of the following situations:

1) the floating charge voltage of more than 2 single batteries is lower than 2.18v

2) the discharge depth exceeds 20%

3) idle for more than 3 months

4) the full floating charge time exceeds 3 months

3 temperature compensation

in some remote communication stations, because there are few air conditioners, and then manually rotate the handwheel of the tester to zero the torque value, the ambient temperature changes greatly, which has a great impact on the chemical reaction speed inside the battery. Generally, the ambient temperature is required to be 0 ~ 40 ℃ when the battery is standing still. Too high temperature will aggravate the self discharge of the battery. However, the battery has more stringent requirements for the ambient temperature, usually 20 ~ 25 ℃. Under this condition, the battery has the best performance and the longest service life. Low temperature will reduce the battery capacity, the charging receiving capacity and the charge discharge cycle life; High temperature will aggravate the Pb + 2H2O PbO2 + 4h + + 4E reaction, resulting in water loss and increased grid corrosion. Therefore, the communication power supply monitoring equipment should have the setting of battery over temperature alarm. Once the battery temperature is too high, the system will send an alarm. When the battery does not work at the best temperature recommended by the battery manufacturer, the charging voltage of the battery should be adjusted. The higher the temperature, the lower the charging voltage, which is called temperature compensation. The monitoring equipment of the combined power supply adjusts the charging voltage through the parameter of temperature compensation coefficient. The voltage adjustment value is

v=- temperature compensation coefficient (mv/℃) (battery temperature - reference temperature) n (1)

where: the reference temperature is usually 20 ℃ or 25 ℃

n is the number of battery cells in the battery pack, usually 24 or 12

due to the different processes and materials used by various batteries, the temperature compensation coefficient in practical application should be adjusted according to the data given by the battery manufacturer

the temperature compensation function of communication power supply is to minimize the impact of temperature on the battery, but it is by no means that with the temperature compensation of charging voltage, the battery can be used at any ambient temperature. You should know that when the temperature is low, the increase of floating charge voltage will also cause a series of problems, such as the increase of floating charge current and the acceleration of grid corrosion; When the temperature is high, the floating charge voltage decreases, which will also lead to a series of problems such as insufficient battery charging, and actively enter emerging markets represented by Brazil, Russia, India and China; Plan to launch diagnostic business market problems

4 some matters that should be paid attention to in the process of use and maintenance

4.1 use environment

the battery should be installed far away from the heat source and easy to produce sparks, and it is best to use it in a clean environment. The battery room should be well ventilated, free from sunlight, and the temperature should be maintained at 20 ~ 25 ℃

4.2 parameter setting of power supply

some parameters such as floating charge voltage, average charge current, average charge frequency and time, transfer average charge criterion, temperature compensation coefficient, DC overvoltage alarm, undervoltage alarm, charging current limit, etc. should be determined after communicating with each battery manufacturer

4.3 capacity configuration

the battery capacity configured for some power supplies is too small, resulting in high current discharge of the battery during AC power failure, affecting the service life of the battery. Generally, the configured capacity of the battery should be at the rate of 8 ~ 10 hours

4.4 routine maintenance

it may be due to the influence of some battery manufacturers on the maintenance name of valve regulated battery crown in the past. Some maintenance personnel mistakenly believe that valve regulated battery does not need maintenance, so they ignore it. In fact, the change of the battery is a gradual process. In order to ensure the good condition of the battery, it is very important to make a good operation record. The items to be checked every month are as follows: floating charge voltage of monomer and battery pack; Whether the shell of the battery has deformation, expansion and seepage; Whether there is liquid seepage and acid mist overflow around the pole and safety valve; Whether the connecting strip is tightened

4.5 discharge test

for the storage battery configured by the communication power supply in the exchange office with normal AC power supply, the checking discharge test should be carried out periodically. For the 2V battery configured for the switching power supply, it is recommended to do it once a year to release 30% - 40% of the rated capacity; For 12V power configured by UPS

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