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BOOKS AND ARTICLES
2.2.1. Batteries, dryfit technology
Directory / Batteries and accumulators The most convenient and safe of acid batteries are absolutely maintenance-free sealed VRLA (Valve Regulated Lead Acid) batteries produced using the "dryfit" technology. The electrolyte in these batteries is in a jelly-like state. This ensures the reliability of the batteries and the safety of their operation. Technical characteristics of accumulators "DRYFIT". Depending on the expected mode of operation, two types of batteries are recommended: "dryfit" A400 for buffer mode and A500 for buffer + cycle mode. These batteries are produced by the German company Sonnenschein, which is part of the CEAC group of European manufacturers, and are characterized by the following advantages: absolutely maintenance-free during the entire service life; long service life (with retention of residual capacity of 80%); Eurobat classification - high performance (High Performance); "dryfit" technology: the electrolyte is fixed in a jelly-like state; spreading plates in block design; very low outgassing due to the internal recombination system; the ability to quickly restore capacity; "dryfit" batteries are not dangerous goods for air, road and rail transport (according to IATA); very low self-discharge: even after 2 years of storage (at 20°C) no recharging is required before commissioning; recharging is allowed; deep discharge resistant according to DIN 43539 part 5; capacity range: from 5,5 to 180 Ah for A 400 and from 2,0 to 115 Ah for A500; Batteries are accepted for recycling by Sonnenschein, because they contain many valuable materials; are certified by the German Federal Post, TL 6140-3003; comply with VDE 0108 part 1 for emergency power supply. The A500 batteries are more versatile and are a consistent design and are designed for mixed mode - "buffer + cycle". They have greatly improved self-discharge characteristics by changing the design of the cans and the composition of the electrolyte. They comply with the following standards: DIN, BS, IES and are also approved by VdS. The battery symbol "dryfit" contains: the first letter and three numbers following it - the type of battery; subsequent figures - nominal capacity, Ah; the last letters - the type of battery output (according to DIN 72311, the limiting discharge currents are achieved only when using a standard contact). Battery charging technique "DRYFIT" The battery is charged when a potential is applied to it that exceeds its operating voltage. The battery charge current is proportional to the difference between the applied voltage and the open circuit voltage. The battery voltage increases as it is charged until electrolysis begins. At the same time, the charge efficiency decreases, and the voltage at the battery terminals increases as the charge rate decreases. The charge rate of a battery can be defined in terms of capacity. If the battery capacity C is charged in time t, then the charge rate is determined by the ratio C/t. A battery with a capacity of 100 Ah, when discharged at a rate of C / 5, will be completely discharged in 5 hours, while the discharge current will be 100/5, or 20 A. If the battery is charged at a rate of C / 10, then its charge current will be 100/10, or 10 A. The charge rate can be estimated in cycle times. So, if the battery is charged in 5 hours, then it is said that it has a cycle of 5 hours. After the battery is fully charged, further continuation of the charge causes the release of gases (overcharging occurs). In classic batteries, during the process of recharging, water is removed and the electrolyte is sprayed with the release of gases. Part of the electrolyte is sprayed through the ventilation holes, i.e. is lost. When water is added to the electrolyte, its concentration decreases and the performance of the battery deteriorates. In batteries manufactured using the "dryfit" technology, the reactions of the electrodes occur with the participation of the electrolyte. The composition of the electrolyte does not change as it is charged or discharged. Therefore, the electrolyte is designed in such a way that the generation of oxygen during the charging process is compensated by other chemical reactions that maintain equilibrium conditions in which the battery can be charged for a long time without losing water. This is essential for sealed batteries. The charge voltage of A400 batteries for float charge mode must be between 2,3V and 2,23V/cell. When charging 12 V batteries, consisting of 6 cells (cans), this figure is multiplied by 6, i.e. the charge voltage for a 12 V battery should be in the range from 13,8 V to 13,38 V. For 6-volt batteries, the number of cells is 3, for 4-x - 2, and for 2-volt - 1. When the temperature changes, the charging voltage must be adjusted. In this case, the charge voltage can vary from 2,15 V/cell to 2,55 V/cell when the temperature changes from -30°C to +50°C. In buffer mode, the charge voltage at 20oC should be in the range of 2,3-2,35 V/cell. The voltage fluctuation should not exceed 30 mV/cell. When the charging voltage is greater than 2,4 V, the charge current should be limited to 0,5 A per Ah for two modes. The compensation charge is possible for cyclic and buffer modes of operation. For A400 batteries, the maximum charge voltage is 2,3 V/cell, and for A500 it is 2,4 V/cell. For A500 batteries, two modes are possible: buffer and cyclic. In cyclic charge mode, the charging voltage should be higher than in buffer mode in order to increase the time between charge cycles. Battery discharge technique "DRYFIT" Batteries manufactured using the "dryfit" technology are not very sensitive to discharge conditions. In addition, the capacitance is also insensitive to discharges at rates below C/10. With more intensive discharges, the capacity decreases as the discharge rate increases, but not as "dramatically" as in the case of batteries made according to traditional technology. Therefore, it is sufficient for the manufacturer to provide a relatively limited number of typical discharge curves. With the specified battery capacity, the discharge rate is chosen low (for example, C / 10) in order to maximize the capacity of the cell. At a high rate, the discharge is actually limited, because due to the presence of internal resistance of the battery, the voltage decreases below the cut-off voltage (the cut-off voltage is the minimum voltage at which the battery is able to deliver useful energy under certain conditions). This occurs before the start of "depletion" of electrochemical energy. However, reducing the discharge current reduces the voltage drop IxR inside the cell, while the cell voltage rises compared to the cutoff voltage, and the discharge continues. With an open battery, the power output is zero because the current is zero. If the battery is short-circuited, then the power output is again zero, since the voltage is close to zero, although the current may be very large. The average voltage depends on the drawn current, but there is no linear relationship between these values. The maximum output power occurs when the load resistance is equal to the internal resistance of the battery. Lead batteries have a unique feature - the ability to release hydrogen during overvoltages and oxygen when the voltage of the lead battery approaches the value characteristic of a full charge, while there is a significant voltage rise necessary for the passage of the charging current through the electrolyte. If the voltage causing the charging current to flow is fixed and high enough to charge the electrodes, but not so high as to cause outgassing, the cell voltage will rise until it equals the voltage of the charging source. In "dryfit" technology batteries, each cell is closed with a valve, which prevents the penetration of oxygen from the outside. With internal overpressure, the valve opens to then close the can again. Batteries should not be placed in sealed rooms. Installation in any position is allowed. When permanently installing "dryfit" batteries in rooms, cabinets and containers, the regulations of VDE 0510 must be observed, make sure that the valves are at the top and are not blocked by anything. The maximum capacity of rechargeable batteries is realized at normal temperature (20 °C), low discharge rates and low cut-off voltages. The mobility of ions and their rate of interaction with the electrodes decrease as the temperature decreases, and most batteries with water-based electrolytes reduce the energy output compared to what they can deliver at normal temperature. If the electrolyte freezes, the ion mobility can drop to the point where the battery will stop working. With a decrease in temperature, equipment should not be designed to operate at low operating voltages. When the battery is discharged at low temperatures, its internal resistance increases, which leads to the release of additional heat, which to some extent compensates for the decrease in ambient temperature. As a result, battery performance is determined by its design and discharge conditions. Internal resistance is part of a complete electrical circuit. Since the load current also flows through the battery, the voltage at the battery terminals is really the voltage produced by the battery's electron system minus the voltage drop caused by the current passing through it. Most of the cell's internal resistance is created by the active materials of the electrodes and electrolyte, which change as the electrolyte ages and state of charge. The internal resistance of the battery can limit the required current delivered to the load. To determine the internal resistance of a cell or battery, you can use the method, which consists in measuring its characteristics on alternating current (frequency 1 kHz and higher). Since many reactions on the electrodes are reversible, it can be assumed that no chemical reactions occur when measuring with alternating current, and the impedance corresponds to the internal resistance. AC measurements can be combined with DC measurements. A rechargeable battery is considered to have reached its end of life when its capacity drops to 80% of its stated original capacity. In this case, 30% DOD corresponds to the battery's maximum cyclic life. So after two years of storage, the battery retains 50% of its capacity. After charging, the A400 and A500 series batteries restore 100% capacity. They have much improved parameters (in comparison with the previous types of A200 and A300 batteries) due to changes in the design of the cans and the composition of the electrolyte. Service life of dryfit batteries: A 400 8...10 years A 500 5...6 years A400 and A500 batteries are resistant to deep discharge according to DIN 43539. It is not recommended to use a deeper or soft discharge mode. , which reduce the length of the cyclic battery life. Back (Sealed batteries) Forward (Sealed nickel-cadmium batteries)
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