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Valve-controlled lead-acid-free battery charge and discharge characteristics

Return Listsource:Gratene date: 2022-06-17

Valve-controlled lead-acid-free battery charge and discharge characteristicsLead acid is maintained during use, if the temperature rises, the charging voltage must be lowered; otherwise the chemical reaction in the battery will enhance, produce a large amount of gas, increase the pressure in the battery, and release the gas through the pressure reducing valve, Reduce the electrolyte in the battery, which will cause early aging of the battery to reduce the battery life. Many brands UPS are based on this principle, and the function of floating charging changes with temperature to optimize battery life.

1, battery discharge characteristics

The discharge characteristics of the battery are a curve. At a certain ambient temperature (25 ¡ã C), the relationship between the battery terminal voltage and the discharge time is referred to as the discharge curve. It can be seen from the discharge curve:

(1) The maximum discharge time is 10 hours, the current is constant, we call it 10-hour discharge rate curve, and the battery capacity of the measured battery capacity is represented by C10.
C10 = 6a ¡Á 10h = 60ah
If you use 1 hour constant current discharge to determine this same battery, then
C1 = 41.9a ¡Á 1H = 41.9ah
Thus, the battery capacity is a comparable determination value after calibrating the discharge system.

(2) Regardless of the discharge current size, the end voltage is lowered, and then slightly rose, because the battery is changed from the charging state to the discharge state, the charge near the battery pole is quickly released. Come out, and the electric charge farther away from the plate needs to be gradually transported to the polar plate, and then it can be released, which forms a large trough with a larger battery voltage.

(3) Regardless of the discharge current size, the battery-side voltage will eventually have a sharp drop, and the curve obtained by the turning point connection of these curves is called the termination voltage curve at the time of safety operation. The end point of the UPS battery voltage work is designed here. Near the turbine of the abject point. The curve after the turning point has a tendency to drop sharply, until the end of the discharge curve, the curve obtained by these endpoints is called the minimum termination voltage curve, which indicates that the discharge voltage will cause the battery to cause the permanent failure of the battery, that is, the battery cannot Recover the storage capacity. It can be seen that the protection function of the UPS is designed to prevent depth discharge from the battery is extremely necessary.

2, charging characteristics of the UPS battery

The charging characteristic curve of the battery is also measured and scales at 25 ¡ã C. Charging curves usually have three:

(1) Charging current curve: The charging current is a constant value in the stage of charging, and the charging current gradually decreases as the charging time is gradually declined, and eventually tends to be 0. This is due to the large amount of charge in the battery, and the charge is faster, and the chemical reaction will produce a large amount of gas and heat, and the chemical reaction will produce a large amount of gas and heat. Even if the battery can be The gas and heat are discharged, but the hydrogen ions and water will lose simultaneously, so that the battery is lowered, so the current value of the charging must be defined, and the charging current will be automatically lowered as the battery capacity is restored. When the charging current drops below 10 mA / aH, it is considered that the battery is basically full and transferred to a floating charge. The deeper the battery discharge, the longer the constant current charging, and it is short.

(2) Charging voltage curve: In the battery constant current charging phase, the voltage of the battery is always rising, so sometimes it is also referred to as boost charging. When the constant current charging ends, the voltage of the battery remains substantially unchanged, referred to as constant voltage charging. In the constant voltage charging phase, the current of the battery gradually decreases, and eventually tends to tend to end the constant voltage charging phase, transfer to the floating charge to keep the battery’s energy storage, prevent the battery from self-discharge.

(3) Charging capacity curve: In the constant current charging stage, the capacity of the battery is substantially linear; in the constant voltage charging phase, the speed growth rate is slow; after the constant voltage charging is completed, the capacity is basically returned to 100% to about 24 hours. Left and right; after transferring the floating charge, the capacity is basically no longer significantly increased. A set of dashed lines can also be seen from the charging curve. The charging characteristic after the battery discharge is 50%. Compared with the charge characteristics of 100% discharge, the constant current charging time is significantly shortened, and the constant voltage is charged for 9 hours, the capacity is basically restored to 100%. From the above you know:
1 constant current charging is to restore the voltage of the battery;
2 Constant voltage charging is to restore the battery’s energy storage;
3 floating charge is to suppress self-discharge or maintain energy storage.

The battery discharge capacity designed by the UPS is usually 50% ~ 70% rated capacity, and it is preferable to charge for 24 hours after the discharge is discharged. Regardless of 50% discharge or 100% discharge, constant current charging is 0.1c10 (6a), and constant pressure charging is 6.75V (2.25V / cell), which is carried out at a temperature of 25 ¡ã C. If the temperature rises, the charging voltage must be lowered; otherwise the chemical reaction in the battery will enhance, produce a large amount of gas, increase the pressure in the battery, and release the gas through the pressure reducing valve to reduce the electrolyte in the battery, will result Early aging of batteries, reduce battery life. Many brands UPS are based on this principle, and the function of floating charging changes with temperature to optimize battery  

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