Discipline: Operation of electrical network equipment
Lecture No. 9 "Maintenance of Systems of operational DC"
9.1 Operation of acid batteries. 1
9.2 Requirements for battery rooms. 3
9.3 Acid electrolyte preparation, safety measures. 3
9.4 Control of operating modes of domestic storage batteries by voltage 4
9.5 Mode of operation of ventilation systems. 4
9.6 Inspection of domestic batteries during operation 5
9.7 Imported rechargeable batteries, a brief description, their advantages in operation. 5
9.8 DC boards and their maintenance. 12
9.9 Technical documentation, instruments and inventory for AB operation, repairs. 20
Operation of acid batteries
During the operation of battery installations, their long-term reliable operation and the required voltage level on the DC buses in normal and emergency modes must be ensured. When accepting a newly mounted or overhauled battery, the following should be checked: the battery capacity with a 10-hour discharge current, the quality of the electrolyte being poured, the voltage of the cells at the end of the charge and discharge, and the insulation resistance of the battery relative to ground. Batteries must be put into service after they reach 100% of their nominal capacity. Rechargeable batteries (AB) must be operated in the constant recharge mode. For batteries of the SK type, the charging voltage should be 2.2 ± 0.05 V per cell, for batteries of the CH type 2.18 ± 0.04 V per cell. On domestic batteries, the recharging installation must ensure voltage stabilization on the battery busbars with deviations not exceeding 2% of the rated voltage. (for domestic AB). Additional battery cells that are not constantly used in operation should be operated in the constant recharge mode. Acid batteries should be operated without training discharges and periodic equalizing recharges. Once a year, an equalizing charge of an SK-type battery with a voltage of 2.3 - 2.35 V per cell should be made until a steady value of the electrolyte density in all cells is 1.2-1.21 g / cm 3 at a temperature of 20 ° C. Duration equalization charge depends on the state of the battery and should be at least 6 hours. Equalization charges of CH type batteries are carried out at a voltage of 2.25 - 2.4 V until the electrolyte density reaches 1.235 - 1.245 g / cm 3. At substations at least 1 time per year the operability of the battery should be checked by the voltage drop at inrush currents (by turning on the maximum load, the voltage drop should not exceed 0.65 U N, and control discharges are made as necessary. The value of the discharge current should be the same each time. Measurement results during control discharges should be compared with the results of measurements of previous discharges.It is allowed to charge and discharge the battery with a current whose value is not higher than the maximum for this battery Rei. The temperature of the electrolyte at the end of the charge should not exceed 40 ° C for batteries of the SK type. For CH type batteries, the temperature should not exceed 35°C at maximum charging current.
The electrolyte level should be: above the upper edge of the electrodes by 10-15 mm for stationary batteries with surface-box plates of the SK type; within 20-40 mm above the safety shield for stationary batteries with smeared plates of the CH type.
When using rectifier devices for recharging and charging batteries, the AC and DC circuits must be connected through an isolating transformer. Rectifier devices must be equipped with shutdown signaling devices.
The ripple coefficient on the DC buses should not exceed the allowable values according to the power conditions of the RPA devices. The voltage on the DC buses supplying control circuits, relay protection devices, alarms, automation and telemechanics, under normal operating conditions, can be maintained 5% higher than the rated voltage of power receivers .All assemblies and DC ring lines must be provided with backup power.
The insulation resistance of the battery, depending on the rated voltage, should be as follows:
The insulation monitoring device on the auxiliary DC busbars must act on the signal when the insulation resistance of the poles drops to the level of 20 kOhm in a 220 V network, 10 kOhm in a 110 V network, 6 kOhm in a 60 V network, 5 kOhm in a 48 V network, 3 kOhm in a 24 V network. Under operating conditions, the insulation resistance of the DC network must be at least twice the specified setting of the insulation monitoring device.
When the alarm device is triggered in the event of a decrease in the level of insulation relative to earth in the control current circuit, measures must be taken immediately to eliminate the malfunction. At the same time, work without removing the voltage in this network, with the exception of searching for a place of insulation damage, is not allowed.
For power facilities where microelectronic or microprocessor relay protection devices are used, it is not recommended to use the method of determining the places of insulation resistance decrease by successively disconnecting connections on the DC shield. An analysis of the acid battery electrolyte should be carried out annually on samples taken from control cells. The number of control elements must be set by the technical manager of the power facility, depending on the state of the battery, but not less than 10%. Control elements should be changed annually. During the control discharge, electrolyte samples should be taken at the end of the discharge. For refilling, distilled water, tested for the absence of chlorine and iron, should be used. It is allowed to use steam condensate that meets the requirements of the state standard for distilled water. To reduce evaporation, storage batteries of types C and CK should be covered with plates of glass or other insulating material that does not react with the electrolyte. The use of oil for this purpose is prohibited.
The article deals with the application and operation of lead-acid sealed batteries, the most widely used for backing up fire alarm equipment (OPS)
Sealed lead-acid batteries (hereinafter referred to as batteries) that appeared on the Russian market in the early 1990s and are designed to be used as direct current sources for power supply or backup of alarm, communication and video surveillance equipment, have gained popularity among users and developers in a short time. . The most widely used batteries are manufactured by Power Sonic, CSB, Fiamm, Sonnenschein, Cobe, Yuasa, Panasonic, Vision.
Batteries of this type have the following advantages:
Figure 1 - Dependence of the battery discharge time on the discharge current
- tightness, no harmful emissions into the atmosphere;
- electrolyte replacement and water topping up are not required;
- the ability to operate in any position;
- does not cause corrosion of OPS equipment;
- resistance without damage to deep discharge;
- low self-discharge (less than 0.1%) of the nominal capacity per day at an ambient temperature of plus 20 °C;
- maintaining performance with more than 1000 cycles of 30% discharge and over 200 full discharge cycles;
- the possibility of storage in a charged state without recharging for two years at an ambient temperature of plus 20 °C;
- the ability to quickly restore capacity (up to 70% in two hours) when charging a completely discharged battery;
- ease of charge;
- when handling products, no precautions are required (since the electrolyte is in the form of a gel, there is no leakage of acid if the case is damaged).
Figure 2 - Dependence of battery capacity on ambient temperature
One of the main characteristics is the battery capacity C (the product of the discharge current A and the discharge time h). The nominal capacity (the value is indicated on the battery) is equal to the capacity that the battery gives out during a 20-hour discharge to a voltage of 1.75 V per cell. For a 12-volt battery containing six cells, this voltage is 10.5 V. For example, a battery with a nominal capacity of 7 Ah provides operation for 20 hours at a discharge current of 0.35 A. When calculating the battery life at a discharge current other than from 20 hours, its real capacity will differ from the nominal one. So, with a more than 20-hour discharge current, the actual battery capacity will be less than the nominal ( picture 1).
The capacity of the battery also depends on the ambient temperature ( figure 2).
All manufacturers produce batteries of two ratings: 6 and 12 V with a nominal capacity of 1.2 ... 65.0 Ah.
OPERATION OF BATTERIES
When operating batteries, it is necessary to comply with the requirements for their discharge, charge and storage.
1. Battery discharge
When the battery is discharged, the ambient temperature must be maintained within the range from minus 20 (for some types of batteries from minus 30 °C) to plus 50 °C. Such a wide temperature range allows batteries to be installed in unheated rooms without additional heating.
It is not recommended to subject the battery to a "deep" discharge, as this may damage it. IN table 1 the values of the allowable discharge voltage for various values of the discharge current are given.
Table 1
The battery should be recharged immediately after being discharged. This is especially true for a battery that has been subjected to a “deep” discharge. If the battery is in a discharged state for a long period of time, then it is possible that it will not be possible to restore its full capacity.
Some manufacturers of power supplies with a built-in battery set the cut-off voltage of the battery when it is discharged as low as 9.5 ... 10.0 V, in an attempt to increase the standby time. In fact, the increase in the duration of its work in this case is insignificant. For example, the residual capacity of a battery when it is discharged with a current of 0.05 C to 11 V is 10% of the nominal, and when discharged with a high current, this value decreases.
2. Connecting multiple batteries
To obtain voltage ratings above 12 V (for example, 24 V), used for backing up control panels and detectors for open areas, several batteries can be connected in series. In this case, the following rules must be observed:
- It is necessary to use the same type of batteries produced by the same manufacturer.
- It is not recommended to connect batteries with a date difference of more than 1 month.
- It is necessary to maintain the temperature difference between the batteries within 3 °C.
- It is recommended to maintain the required distance (10 mm) between the batteries.
3. Storage
Figure 3 - Dependence of the change in battery capacity on the storage time at different temperatures It is allowed to store accumulators at ambient temperature from minus 20 to plus 40 °C.
Batteries supplied by manufacturers in a fully charged state have a fairly low self-discharge current, however, with prolonged storage or using a cyclic charge mode, their capacity may decrease ( figure 3). While storing batteries, it is recommended to recharge them at least once every 6 months.
4. Battery charge
Figure 4 - Dependence of battery life on ambient temperature
The battery can be charged at an ambient temperature from 0 to plus 40 °C.
When charging the battery, do not place it in a hermetically sealed container, as it is possible to release gases (when charging with a high current).
CHARGER SELECTION
Figure 5 - Dependence of the change in the relative capacity of the battery on the service life in the buffer charge mode
The need to choose the right charger is dictated by the fact that an excessive charge will not only reduce the amount of electrolyte, but will lead to a rapid failure of the battery cells. At the same time, a decrease in the charge current leads to an increase in the duration of the charge. This is not always desirable, especially when backing up fire alarm equipment at facilities where power outages often occur,
Battery life is highly dependent on charging methods and ambient temperature ( drawings 4, 5, 6).
Buffer charge mode
Figure 6 - The dependence of the number of battery discharge cycles on the depth of discharge * % shows the depth of discharge for each cycle of the nominal capacity, taken as 100%
In buffer charge mode, the battery is always connected to a DC source. At the beginning of the charge, the source works as a current limiter, at the end (when the voltage on the battery reaches the required value) it starts working as a voltage limiter. From this moment, the charge current begins to fall and reaches a value that compensates for the self-discharge of the battery.
Cyclic charge mode
In the cyclic charge mode, the battery is charged, then it is disconnected from the charger. The next charge cycle is carried out only after the battery is discharged or after a certain time to compensate for self-discharge. Battery charging specifications are shown in table 2.
table 2
Note - The temperature coefficient should not be taken into account if the charge proceeds at an ambient temperature of 10 ... 30 ° C.
On figure 6 shows the number of discharge cycles that the battery can be subjected to depending on the depth of discharge.
Accelerated battery charge
Accelerated battery charging is allowed (only for cyclic charge mode). This mode is characterized by the presence of temperature compensation circuits and built-in temperature protective devices, since when a large charge current flows, the battery may heat up. For battery boost characteristics, refer to table 3.
Table 3
Note - A timer should be used to prevent the battery from being charged.
For batteries with a capacity of more than 10 Ah, the initial current should not exceed 1C.
The service life of lead-acid sealed batteries can be 4 ... 6 years (subject to the requirements for charging, storage and operation of batteries). At the same time, during the specified period of their operation, no additional maintenance is required.
* All drawings and technical specifications used in this article are taken from the documentation for Fiamm batteries, and also fully comply with the technical characteristics of the battery parameters manufactured by Cobe and Yuasa.
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What AB capacity do you need? When calculating an autonomous power supply system, it is very important to choose the right battery capacity. The specialists of the company "Your Solar House" will help you correctly calculate the required battery capacity for your power system. For a preliminary calculation, you can be guided by the following simple ...
Failure Cause Analysis of Sealed Lead Acid Batteries
About forty years ago, they managed to create a sealed lead-acid battery. All sealed lead acid batteries sold to date have a valve that must be opened to release excess gas, mainly hydrogen, during charging and storage. Complete recombination of oxygen and hydrogen cannot be achieved. Therefore, the battery is not called sealed, but sealed. An important condition for good sealing is a tight chemical and heat-resistant connection of structural elements. Plate technology, valve design and lead sealing are of particular importance. Sealed batteries use a "bound" electrolyte. The recombination of gases follows the oxygen cycle.
There are two ways to bind the electrolyte:
Use of a gel-like electrolyte (GEL technology);
Use of glass fiber impregnated with liquid electrolyte (AGM technology).
Each method has its own advantages and disadvantages.
Battery reliability is understood as its ability to maintain the characteristics specified by the manufacturer during operation for a specified time under specified conditions. The criterion for battery failure is the non-compliance of its parameters with the established standards. Requirements for sealed lead-acid batteries and their test methods are set out in GOST R IEC 60896-2-99 (IEC 896-2, DIN EN 60896 Teil 2). There are a number of factors that limit the achievement of a high degree of reliability for sealed lead acid batteries of any technology:
Strong influence of minor impurities on the properties of the active masses of the plates;
A large number of technological processes in the production of batteries;
The use of a wide range of materials and components for the manufacture of batteries, which can be produced at different factories (in different countries, where proper incoming control and unification of products is not always ensured).
The increase in reliability is associated, first of all, with careful incoming control of all incoming raw materials, materials and components used. Strict control of manufacturing technology is required at all stages of production. To achieve the accuracy of technological operations, production must have a high degree of automation and a single technological cycle (full production cycle).
The conventional (classic with liquid electrolyte) design of batteries ensures their high reliability due to the redundancy of the active mass of electrodes, electrolyte and current-carrying elements. In them, the excess of reagents and electrolyte is 75–85% of the theoretically necessary. Sealed batteries are less reliable than classic lead-acid batteries. Batteries of AGM technology have a small supply of electrolyte. GEL technology batteries use a complex multi-component electrolyte composition, and it is also difficult to achieve an even distribution of the gel inside the battery. New structural elements appear (hermetically sealed housing with a lid, a special gas valve with a filter, a special seal for current leads, special electrolyte additives, special separators, etc.). The polarization of the positive electrode in sealed batteries is greater than in classical ones, and can reach 50 mV. This leads to acceleration of corrosion processes, especially in the buffer mode of operation.
SEALED BATTERY DESIGN
Sealed lead acid batteries use paste electrodes. They can be trellised and armored. Shell electrodes are used in GEL batteries of the OPzV type as positive plates, and in other types, grid plates are used for positive electrodes. The use of different types of positive plates affects the electrical characteristics of the batteries. This is due to the internal resistance of the battery. Positive armor plates consist of pins that are placed inside perforated tubes filled with activated mass (see Fig. 1). The use of shell plates allows the production of sealed batteries (GEL technology) with a high capacity, the same as in classic batteries. Both small and large capacity sealed AGM batteries (see Fig. 2) use grid plates, which reduces their cost and simplifies their design.
In the production of batteries, both pure lead and its alloys are used. Antimony, which has an ambiguous effect on the performance of batteries, is not used for the production of sealed battery plates.
Sealed lead-acid batteries use alloys of lead with calcium or with tin and an alloy of lead, calcium, tin, there may be aluminum additives. Here the electrolysis of water starts at higher voltages. The crystals formed in the plates are small and uniform, and their growth is limited. The shedding of the active mass and the internal resistance of the battery when using calcium gratings are somewhat greater than in the case of lead-antimony ones. The destruction of the plates mainly occurs when the battery is charged. To reduce shedding, fibrous materials are introduced into the active mass, for example, fluoroplastic, and glass fiber pressed against the plates (AGM technology) or porous separators (bags, envelopes that hold the active mass) from miplast, PVC, fiberglass (GEL technology) are used; double separators can be used. Double separators increase the internal resistance, but increase the reliability of the batteries. Not all sealed battery manufacturers use double separators. In some battery models, multilayer separators are found, defects in one of the layers are protected by the other, and dendritic growth is difficult when moving from layer to layer.
The reliability of sealed batteries also depends on the case material, the quality and design of the current leads, and the design of the gas valve. Some manufacturers, in order to minimize costs, make a case with a wall thickness of 2.5–3 mm, which does not always provide high reliability. For higher reliability, the wall thickness should be 6 mm or more. Some increase the porosity of the electrodes, which does not always have a positive effect on the reliability of the batteries. In pursuit of increasing profits, many companies deliberately overestimate the parameters of batteries and distort the real service life, make hybrids, gel electrolyte is poured into AGM-technology batteries, etc.
Rice. Fig. 1. Construction of electrodes of lead-acid accumulator of GEL technology with shell plates (type OPzV)
Rice. 2. Construction of AGM Sealed Lead Acid Battery
FAILURE MODES OF SEALED BATTERIES
It is known that the deterioration of the electrical characteristics of sealed batteries and failure (failure) during operation are due to corrosion of the base (grid) and creep of the active mass of the positive electrode, which are sometimes called degradation of the positive electrode. The degradation of the positive electrode in classical wet batteries has a smooth dependence on the service life, and it can be traced over the period of operation. In sealed batteries, the degradation of positive plates is sharper and not fully understood, the battery cases are opaque, which makes it difficult to visually control the electrolyte level and the condition of the plates. The density of the electrolyte cannot be measured.
Corrosion of grids of positive plates- the most common defect in sealed batteries operated in buffer mode. Many factors affect the rate of corrosion of gratings: the composition of the alloy, the design of the grating itself, the quality of the grating casting technology at the factory, the temperature at which the battery operates. In well-cast Pb-Ca-Sn alloy gratings, the corrosion rate is low. And in poorly cast gratings, the corrosion rate is high, individual sections of the grating are subjected to deep corrosion, which causes local growth of the grating and its deformation. Local growths lead to a short circuit when in contact with the negative electrode. Corrosion of the positive grids can lead to loss of contact with the active mass deposited on it, as well as with adjacent positive electrodes, which are connected to each other using bridges or bars. In sealed batteries, there is either very little or no space under the plates for accumulation of sludge - the plates are tightly packed, therefore, the creep of the active mass caused by corrosion can lead to a short circuit of the plates. Short-circuiting of the plates is the most dangerous defect in sealed batteries. Closing the plates in one sealed battery, if this is not noticed by personnel, will disable all the others. The time during which the batteries fail is calculated from a few hours to half an hour.
When batteries are used in buffer mode, due to low charging currents, a defect may occur - negative electrode passivation. In sealed batteries of any technology, negative electrodes are made of lattice plates. The mechanisms of the processes occurring on the electrodes are complex and have not been finally established. It is believed that during battery operation, liquid-phase processes (dissolution-precipitation) predominantly occur at the negative electrode, and the limitation of its discharge is associated with the formation of a passivating layer. A sign of passivation of the negative electrode is usually a decrease in the open circuit voltage (OCV) on a charged battery below 2.10 V/cell. Carrying out additional equalizing charges (for example, in batteries of the OPzV type) can restore the voltage, but the batteries after that must be constantly monitored, as this may happen again. To reduce the passivation of the negative electrode, some manufacturers introduce special additives into it, which act as expanders of the active mass of the negative electrode and prevent its shrinkage.
If sealed batteries are cycled (with frequent power outages or cycling), then defects associated with degradation of the active mass of the positive electrode(its loosening and sulfation), which lead to a decrease in capacity during the control discharge. Using practice charges to destroy sulfate, as suggested by some manufacturers in their operating instructions, does nothing, and even leads to an even faster decrease in capacity. Loosening leads to loss of contact between the particles of lead dioxide, they become electrically insulated. Large discharge currents accelerate the loosening process. The presence and degree of sulfation of the active mass can be controlled, since it is accompanied by a change in the density of the electrolyte, which in AGM batteries can be roughly estimated by measuring the NRC of the battery after the end of the charge. The NRC of a charged sealed battery is 2.10–2.15 V/cell, depending on the density of the electrolyte; in AGM technology batteries, the electrolyte density is 1.29–1.34 kg/l; in gel batteries, the density is lower and has values of 1.24 -1.26 kg/l (due to the high density of the electrolyte, AGM technology batteries can operate at lower temperatures than gel batteries). During discharge, as the electrolyte is diluted, the NRC of the sealed battery decreases and after the discharge becomes equal to 2.01–2.02 V/cell. If the NRC of a discharged sealed battery is less than 2.01 V / cell, then the battery has a high degree of sulfation of the active mass, which may already be irreversible.
When sealed batteries are undercharged during operation (for example, due to an incorrectly set voltage of a constant recharge, malfunction of the electronic control unit, lack of thermal compensation), sulfation occurs on the negative electrode, a gradual transition of fine-grained lead sulfate into a dense solid layer of sulfate with large crystals. The resulting lead sulfate, which is poorly soluble in water, limits the capacity of the battery and promotes the release of hydrogen during charging.
If a thick brown oxide is observed on the positive electrode of the battery, then this is a sign of grid corrosion. Possible causes of corrosion:
Accumulators before operation lay for a long time in a warehouse without recharging;
During operation, alternating current was supplied (~ I), problems with the charger (rectifier, EPU).
In sealed batteries, specific corrosion processes can also occur on bridges (more often on negative ones) and on the boron. Since the corrosion products have a larger volume than lead, the compound sealing the terminal can be squeezed out, the rubber seal of the boron, the cover and even the battery case are damaged. Defects of this kind are often observed in batteries if there was no strict adherence to the technological process during their manufacture (for example, a large time gap between technological operations).
WORKING POSITION OF SEALED BATTERIES
Many manufacturers of sealed batteries indicate in their operating instructions that the batteries can be used in any position.
During the operation of sealed batteries, due to the inevitable loss of water when the gas valve is opened, some drying of the electrolyte occurs, while the internal resistance increases and the voltage decreases, as when the negative electrode is passivated.
In sealed AGM technology batteries, in addition to electrolyte drying, electrolyte stratification can occur: sulfuric acid, which is in liquid form, flows down due to its higher specific gravity compared to water, resulting in a concentration gradient in the upper and lower parts of the battery, which degrades the discharge characteristics and increases the temperature of the battery. This effect is rare in small and medium capacity batteries, and the use of a finely porous glass fiber separator with a high compression ratio of the entire package of positive and negative plates reduces it. Tall, sealed high capacity AGM batteries are best operated lying on their side, but only use the side where the plates are perpendicular to the ground (must be checked with the manufacturer). Chinese and Japanese manufacturers produce high capacity sealed batteries with a low height and prismatic shape, which allows them to be operated vertically, just like OPzV batteries.
In sealed batteries of GEL technology, especially in OPzV, when used "lying" on their side, defects associated with leakage of the gel electrolyte may occur. During the operation of the gas valve due to silica gel and other components of the gel electrolyte, hydrophobic porous filters (round plates) are clogged, which should pass the gas, but not the electrolyte. After the valve stops passing gas, the internal pressure may increase to 50 kPa or more. The gas finds a weak structural point: it can be a sealing seal of a valve or a bore, a place in the body, especially near the stiffeners (for some manufacturers), a place where the cover is attached to the battery case, which leads to an emergency rupture, accompanied by the release of electrolyte to the outside; the electrolyte conducts electricity - a short circuit may occur. There were cases when electrolyte leakage, not detected in time by personnel, led to the ignition of insulating caps. The electrolyte can eat through the floor, etc. (see Photo 1).
Photo 1. Consequences of electrolyte leakage from a burst OPzV case
Gel batteries are best placed vertically so that aerosols of the substances that make up the gel electrolyte cannot enter the gas valve filter. Some manufacturers of 2V gel batteries are lengthening the battery case, developing various aerosol traps, making a complex labyrinth valve design in order to operate gel batteries “lying” on their side.
It is safer to use OPzV gel batteries in a vertical position!
BATTERY CONNECTION IN PARALLEL
Batteries can be connected in parallel to increase the capacity and reliability of the power supply system. European manufacturers do not recommend installing more than four groups in parallel. Asian manufacturers recommend using a parallel connection of no more than two groups. This is due to the uniformity of the battery cells, which is related to manufacturing technology and production quality. The homogeneity of elements from European manufacturers is better. It is recommended that the batteries in the battery groups be of the same type and the same year of manufacture. It is not allowed to replace one element in a group with an element of another type or install groups of batteries of different types in parallel.
SEALED BATTERY LIFE
According to the classification of the European Association of Battery Manufacturers (Eurobat), batteries are divided into four main groups (there may be subgroups):
10 years or more ( special appointment) - telecommunications and communications, nuclear and conventional power plants, petrochemical and gas industries, etc.;
10 years ( improved performance) - basically this group of batteries corresponds to the previous group (special purpose), but the requirements for technical characteristics and reliability are not so high;
5–8 years ( universal application) - the technical characteristics of this group are the same as for the "improved characteristics" group, but the requirements for reliability and testing are lower;
3–5 years ( wide application) - this group of batteries finds use in installations close to the domestic consumer, is popular in UPS, is extremely popular in non-stationary conditions.
The end of the service life is considered to be the moment of time when the output capacity is 80% of the nominal one.
The service life of sealed batteries depends on many factors, but the charge mode and operating temperature of the batteries have the greatest influence. For constant readiness for work in power supply installations (EPS), the batteries must be under constant recharging voltage (buffer mode). Constant recharge voltage - voltage continuously maintained at the terminals of the battery, at which the current flow compensates for the process of self-discharge of the battery. Please note that float charge current depends on float voltage and battery temperature. Both parameters change the constant charging current of the battery and thus affect the water consumption; water cannot be added to sealed batteries. Maintaining the optimum float voltage and optimum room temperature is essential to maximize the life of sealed batteries.
With an increase in battery temperature for every 10°C, all chemical processes, including grid corrosion, are accelerated. It should be remembered that when charging sealed batteries, their temperature may be 10-15°C higher than the ambient temperature. This is due to the heating of the batteries due to the oxygen recombination process and the sealed design. The temperature difference is especially noticeable at accelerated charge modes and when the battery is located inside the EPU rack. Operation of batteries at temperatures above +20°C leads to a reduction in service life. In the table below. the dependence of service life on temperature is shown. It is necessary to introduce an adjustment of the constant boost voltage from temperature. Compensation for the influence of elevated temperature by regulating the voltage of the constant float charge can mitigate this effect and improve the values given in Table. numbers, but not more than 20%.
It is necessary to place sealed batteries in such a way that ventilation of the room and cooling of the batteries are ensured. From this point of view, it is more preferable to place the accumulators so that the valves are placed frontally. Currently, manufacturers offer batteries with front terminals, the so-called front-terminal ones (terminals-outputs are located in front), but the valves of these batteries are located on top, like in conventional batteries. The experience of operating front terminal batteries in different countries shows their lower reliability in comparison with conventional batteries. Front-terminal AGM batteries are most prone to the phenomenon of thermal spontaneous heating - thermal runaway. The use of these batteries must be carried out after the calculation and study of thermal fields in the EPU compartments, racks and cabinets.
Sealed batteries release a small amount of hydrogen during charging. We need a small (natural) blowing of the battery. During long-term operation of a battery with high-capacity batteries, one should remember the need for ventilation of the premises due to the possibility of hydrogen accumulation and compliance with the temperature regime. It used to be thought that high capacity sealed batteries did not require ventilation like small and medium capacity batteries. But taking into account the experience of installation and service of imported sealed batteries, we recommend installing equipment for ventilation and air conditioning of battery rooms.
Sealed batteries generate more heat during charging and heat up more than classic batteries (for example, type OPzS):
Qm = 0,77 ∙ N ∙ I ∙ h, (1)
Where Qm– Joule heating, W ∙ h;
0.77 - pseudo-polarization, V at 2.25 V/el;
N- the number of 2 V elements;
I– charge current, A;
h– charge duration time, h.
Batteries classic (OPzS): Qm= 0.04 W/100 Ah el/h. Joule heating occurs - gas evaporation (heat is released with gas).
Sealed batteries: Qm= 0.10 W/100 Ah el/h. Joule heating + gas recombination occurs.
Capacity, %
Rice. 3. Influence of the depth of discharge. Data for AGM batteries. GEL technology batteries – more resistant to deep discharge
For sealed AGM-technology batteries (see Fig. 3), frequent discharges-charges are harmful, batteries with gel electrolyte have the best cycling. But GEL batteries emit more hydrogen when charged than AGM batteries. In gel batteries at low temperatures, the electrolyte freezes earlier than in AGM batteries, and case ruptures may occur, since the electrolyte occupies the entire volume of the can.
Sealed batteries of both technologies are very sensitive to overcharging. On fig. Figure 4 shows how quickly float life decreases as float voltage increases. Undercharging batteries is also harmful.
Rice. 4. Dependence of the service life on the constant charge voltage
To ensure a long service life of a sealed battery in buffer mode, it is necessary that the steady-state deviation of the DC output voltage of the EPU does not exceed 
1%. The variable component of the float charge output voltage is harmful to sealed batteries. Maximum critical value ~ I(AC) \u003d 2 - 5 A (rms) per 100 Ah. Bursts (peaks) and other types of pulsating voltage (when the battery is disconnected, but with a connected load) are considered acceptable if the spread of the EDA voltage ripple, including regulation limits, does not exceed 2.5% of the recommended voltage for continuous battery charging. Large AC ripples can lead to thermal heating (thermal runaway) of batteries. AGM batteries are more prone to thermal runaway than gel batteries. When using sealed batteries in inverters, frequencies below 50 Hz (46-35 Hz) are considered critical. This is usually due to a faulty inverter. For example, a frequency of 20 Hz can lead to a large recharge of the battery and its failure within a few days. AGM batteries are especially sensitive to such malfunctions. At frequencies below 20 Hz, the electrochemical reaction in batteries may stop altogether.
For the long service life of sealed batteries, the thickness of the positive plate (4–5 mm), alloy composition and grid design are important. Some manufacturers claim a long battery life, while using standard (thin 2.5–3 mm) plates; the actual service life of such batteries remains unknown and can only be determined during operation. When choosing batteries, we recommend paying attention to the weight, which is related to the thickness of the plates.
In OPzV type GEL batteries with shell plates, the service life largely depends on the corrosion rate of the electrode rod. The thickness of the plates is large and equal to 8–10 mm, which leads to a long service life and a low rod corrosion rate.
It is very difficult to trace the statistics of the causes of failures of sealed batteries in Russia. Battery suppliers carefully hide this so as not to lose credibility and the sales market. Many failures occur due to violations of operating conditions, as well as obsolete equipment. Among them, the negative impact of VUK-type rectifiers on the service life of batteries should be noted. The technical resource of using these rectifiers has exceeded all conceivable limits. VUK type rectifiers have neither stable nor filtered output voltage. You can pay attention to rectifiers of the outdated VUT type: incorrect phase sequence of the supply industrial network leads to the failure of rectifiers. This failure is recoverable and manifests itself in an unacceptable increase in the output voltage, followed by an emergency shutdown of the rectifier. If the incorrect phase sequence coincides with a failure, the overvoltage of the supply causes damage to the battery (strong overcharging), which can no longer be restored. VUTs do not have a device for automatic switching from the current stabilization mode to the voltage stabilization mode. Sealed batteries with old type devices (VUT, VUK) do not last long, and their use with these rectifiers is unacceptable.
When choosing a battery for stationary operating conditions, one should be guided, first of all, by the operating conditions. If there is a battery room equipped with supply and exhaust ventilation for accommodating serviced classic batteries, then it should be used for its intended purpose and only for classic batteries with liquid electrolyte (for example, type OPzS (in Russia - type SSAP, TB-M), OGi (type SN, TB), Groe (type SK, BP). Sealed batteries are best used in the presence of a good modern rectifier (for example, UEPS-3 manufactured by OAO YuPZ Promsvyaz). Sealed batteries only at first glance cause less trouble to their owners. application does not mean that maintenance is completely excluded.In any case, it is necessary to monitor the condition of the batteries (voltage, capacity, condition of the case and terminals, temperature of the batteries and the room). , all the requirements that apply to the charge of the sealant were implemented oval lead-acid batteries.
In order to increase the reliability of EPUs with sealed batteries, it is necessary to obtain more frequent information about the state and operating modes of the power supply system. This is possible through the use of alarm systems and power monitoring. For these purposes, you can use a device for monitoring the discharge-charge (UKRZ) of batteries. UKRZ can automatically perform battery test tests, automatically control parameters. Based on the test results, you can predict the timing of replacement and plan maintenance. Modern EPUs of the UEPS-3 type can be equipped with UPKB element-by-element battery monitoring devices that allow you to remotely control the voltage and temperature of each 2V element or monoblock and transmit via Ethernet, GSM, PSTN, RS-485 (module type is determined when ordering). It is possible to use a battery buffer voltage monitor (BCV) with remote signaling to notify the personnel on duty. Mobile operators recommend building a monitoring system based on a radio network and modern universal microcontrollers equipped with radio modems that regularly send information to the center and to mobile phones of technical personnel. In addition, the monitoring systems will serve as the basis for integration with ASKUE and the climate control system, which are being actively implemented at communication, energy, transport and industrial enterprises.
Despite the fact that the lead battery has been known for over a hundred years, work continues to improve it. The improvement of lead-acid batteries goes along the path of finding new alloys for gratings, lightweight and durable case materials, and improving the quality of separators.
Sealed lead-acid batteries are characterized by a wide range of parameters associated with manufacturing technology, the quality of raw materials and the technical level of equipment used for the manufacture of batteries.
“... Despite the complexity of power supply systems (EPS), modern technologies for rectifying alternating current and inverting direct current, the battery is the most important and most critical part of these power supply systems ...”, - from an article by M.N. Petrov.
The main task that needs to be solved in the near future is to create the production of sealed lead-acid batteries in Russia!
When creating production, it is necessary to take into account the accumulated experience in other countries and in Russia itself.
6.5.1. The device and principle of operation of an acid battery cell.
Electrolytic dissociation is the disintegration of sulfuric acid molecules under the action of water molecules. H 2 SO 4 2Н + + SO 4 − −, as a result, ions are formed in water, regardless of whether there are plates in the solution. In general, the solution is electrically neutral. If this solution is an electrolyte, poured into a structure consisting of a set of positive and negative plates separated by sectors and placed in an ebonite container closed with a lid with positive and negative plate leads, we get a positive battery cell.
The formation of ions in the electrolyte
As a result of the interaction of the electrolyte with the lead atoms of the negative plate, a certain amount of lead atoms is ionized. In this case, doubly charged positive lead ions pass into the electrolyte, and on the surface of the negative plate, two electrons remain from each lead atom, so the negative plate is charged negatively relative to the electrolyte. As a result of the interaction of the active substance of the plate with the electrolyte, electric charges are formed on both plates.
Fig.6.5. Acid battery device
On the positive - four-charged lead ions, on the negative - electrons.
This state of the element can be theoretically arbitrarily long until the circuit is closed to the consumer of electricity. As soon as we close the circuit, the electrons from the negative plate move to the positive plate along the external circuit. Each lead atom on the negative plate donates two electrons. They go to the positive plate and combine with (Pb++++), forming a lead ion (Pb++) doubly charged, which combines with the positive residue SO 4 ¯ ¯ to form a lead sulfate molecule (PbSO 4). Since the solubility of sulfate is low, the solution becomes supersaturated and sulfate precipitates on the (+) plate in the form of crystals, while water molecules PbO 2 + 4H + SO 4 ¯ ¯ + 2e- → PbSO 4 + 2H 2 O are formed near the positive plate
On the negative plate Pb ++ + SO 4 ¯ ¯ −2е- → PbSO 4
Each element has a capacity in AH. This is the amount of electricity given by the element to the final discharge of 1.8V. The capacity depends on the amount of active substances. With the passage of an amount of electricity equal to one faraday, 103.6 grams of lead will be consumed to form lead sulfate at the negative plate. 1Faraday-26.8 A.Ch. the atomic and molecular weight of lead is 207.21 and two electrons participate in the reaction at the negative plates, then the gram equivalent of lead is
and with a return of 1 A.Ch. 26.8 times less lead, i.e. 3.6 g.
In the same way, it can be found that with a return of 1 A.Ch. 4.46 g of lead dioxide will be consumed from the positive plate to form lead sulfate, and 0.672 g of water will be formed in the electrolyte from 3.66 g.
The nominal voltage of 1 cell is 2.1 V; the operating voltage at the beginning of the discharge quickly reaches 2 V, then gradually decreases to the final = 1.8 V. If you continue the discharge, it will reach 0.
6.5.2.General rules for the use of acid batteries
1. Maintain electrolyte level 12÷15m
2. Do not discharge below 1.75V.
3. Charge to full capacity
4. Regularly recharge the battery.
5. Do not allow the battery to stay in a semi-discharged state.
6. Regularly clean the surface of the battery from dirt and oxides.
7. Avoid electrolyte contamination.
8. Do not allow overcharging and do not charge with a current higher than the rated one.
10. Do not allow the battery temperature to rise above +45ºС during charging. It is necessary to interrupt the charges and let the battery cool down to +30ºС.
11. The operational density of the electrolyte is determined as reduced to +15ºС and should differ by no more than ±50.
12. After pouring the electrolyte into the battery, let it stand for 4-6 hours.
13. The charging current is determined from the tables depending on the capacity of the battery.
14. When charging the battery in a marine environment, ventilation is preliminarily turned on.
3. Maintenance of lead-acid batteries
Modern lead-acid batteries are reliable devices and have a long service life. Batteries of good quality have a lifespan of at least five years, provided they are carefully and timely cared for. Therefore, we will consider the rules for operating batteries and methods for regular maintenance that will significantly increase their life with minimal time and money.
GENERAL RULES FOR OPERATION OF BATTERIES
During operation, the battery must be periodically inspected for cracks in the case, kept clean and in a charged state.
Contamination of the battery surface, the presence of oxides or dirt on the pins, as well as loose tightening of the wire clamps cause a rapid discharge of the battery and prevent its normal charge. To avoid this, you should:
- Keep the surface of the battery clean and monitor the degree of tightening of the contact terminals. Wipe the electrolyte that has fallen on the surface of the battery with a dry rag or a rag soaked in ammonia or a solution of soda ash (10% solution). Clean oxidized contact pins of the battery and wire terminals, grease non-contact surfaces with technical vaseline or grease.
- Keep the battery drain holes clean. During operation, the electrolyte releases vapors, and when the drain holes are clogged, these vapors are released in various other places. As a rule, this occurs near the contact pins of the battery, which leads to increased oxidation of them. Clean them if necessary.
- Periodically check the voltage at the battery terminals with the engine running. This procedure will allow you to estimate the level of charge that the alternator provides. If the voltage, depending on the speed of the crankshaft, is in the range of 12.5 -14.5 V for cars and 24.5 - 26.5 V for trucks, then this means that the unit is working. Deviations from the specified parameters indicate the formation of various oxides on the wiring contacts on the generator connection line, its wear and the need to diagnose and troubleshoot. After repair, repeat the control measures in different engine operating modes, including with the headlights on and other consumers of electrical power.
- When the car is idle for a long time, disconnect the battery from the ground, and when it is stored for a long time, periodically recharge it. If the battery is often and for a long time in a discharged or even half-charged state, the effect of sulfation of the plates occurs (coating the battery plates with coarse crystalline lead sulfate). This leads to a decrease in the capacity of the battery, to an increase in its internal resistance and a gradual complete inoperability. For recharging, special devices are used that lower the voltage to the required level and then switch to battery charging mode. Modern chargers are mostly automatic and do not require human supervision during their use.
- Avoid long engine starts especially, during the cold season. When starting a cold engine, the starter consumes a large starting current, which can cause the battery plates to warp and the active mass to fall out of them. Which will eventually lead to the complete inoperability of the battery.
The serviceability of the battery is checked by a special device - a load plug. The battery is considered to be working if its voltage does not drop for at least 5 seconds.
CARE OF A MAINTENANCE-FREE BATTERY
Batteries of this type are becoming more and more popular. Caring for a maintenance-free battery comes down to the standard actions required for all types of batteries, described above.
Maintenance-free batteries do not have technological holes with plugs to control the level and top up the electrolyte to the desired level and density. Hydrometers are built into some batteries of this type. In the event of a critical drop in the electrolyte level or a decrease in its density, the battery must be replaced.
CARE OF A SERVICED BATTERY
Batteries of this type have technological openings for pouring electrolyte with tight screw plugs. General maintenance of a car battery of this type is carried out in the same order as for everyone, but additional work must be done to check the density and electrolyte level.
The electrolyte level is checked visually or using a special measuring tube. On the exposed (due to the drop in the electrolyte level) parts of the plates, the process of sulfation occurs. To raise the electrolyte level, distilled water is added to the battery banks.
The density of the electrolyte is checked by an acid hydrometer and the charge level of the battery is estimated from it.
Before checking the density, if electrolyte was added to the battery, you need to start the engine and let it run so that the electrolyte is mixed when the battery is recharged, or use a charger.
In areas with a sharply continental climate, when switching from winter to summer operation, and vice versa, battery
remove the battery from the car, connect it to the charger, charge with a current of 7 A. At the end of the charging process, without turning off the charger, bring the density of the electrolyte to the values \u200b\u200bspecified in Table 1 and Table 2. The procedure must be carried out in several steps, using a rubber bulb, by suction or by adding electrolyte or distilled water. When switching to summer operation, add distilled water; when switching to winter operation, add electrolyte with a density of 1.400 g/cm 3 .
The difference in the density of the electrolyte in different banks of the battery can also be equalized by adding distilled water or electrolyte.
The interval between two additions of water or electrolyte must be at least 30 minutes.
CARE OF THE REMOVABLE BATTERY
Maintenance of collapsible batteries does not differ from the conditions of maintenance of non-separable serviced batteries, only it is additionally required to monitor the condition of the surface of the mastic. If cracks appear on the surface of the mastic, they must be eliminated by melting the mastic using an electric soldering iron or other heating device. Do not allow the wires to be pulled when connecting the battery to the car, as this leads to the formation of cracks in the mastic.
FEATURES OF STARTING DRY-CHARGED BATTERIES.
If you purchased an unfilled dry-charged battery, it must be filled with electrolyte with a density of 1.27 g / cm 3 to the specified level. 20 minutes after filling, but no later than two hours, measure the density of the electrolyte using an acid meter-hydrometer. If the density drop does not exceed 0.03 g/cm 3 , the battery can be installed on the vehicle for operation. If there was a drop in the density of the electrolyte above the norm, it is necessary to connect the charger and charge. The charge current should not exceed 10% of the nominal value, and the procedure is carried out until abundant gassing appears in the battery banks. After that, the density and level are re-controlled. If necessary, distilled water is added to the jars. Then the charger is connected again for half an hour to evenly distribute the electrolyte throughout the entire volume of the cans. Now the battery is ready for use and can be installed on the vehicle for operation.
Regular care of the battery will extend its life and avoid sulphation of the plates or their mechanical destruction. Proper operation of the battery significantly increases its resource, which makes it possible to reduce the cost of operating the car.
