Several Characteristics of Lead-acid Batteries
(1) With the increase of battery capacity, the volume and mass of the battery also increase. The significance of understanding it is to fully understand the allowable area and weight of user's computer room when choosing battery capacity.
(2) The internal resistance decreases with the increase of battery capacity. Understanding its significance lies in dispelling some users'worries: Will small capacity batteries be damaged when parallel connection between small capacity batteries and large capacity batteries? Related information shows that the internal resistance of batteries with internal resistance of 100Ah/12V is about 6m in floating charge state a year later, while that of new batteries with internal resistance of 200Ah/12V is 0.6-0.7m, and that of new batteries with internal resistance of 3000Ah/2V is 50-70m.
(3) Batteries with the same capacity emit different capacities at the same time at different temperatures. The lower the temperature, the smaller the capacity emitted. The significance of understanding this feature lies in: in the case of strict backup time, in order to meet the requirements, it is necessary to master the local working temperature.
(4) There are some limitations on the charging current of batteries. If the charging current is too small, it will affect the timely recovery of the battery capacity, which is very important for the poor condition of the power grid. In this case, the life of the battery decreases rapidly; if the charging current is too large, the temperature rise inside the battery is too high, the lighter makes the battery shell expand, and the heavier causes the shell rupture. There are also some limitations on the voltage of battery charger, because the excessive charging voltage will lead to the reaction of electrolytic water and shorten the battery life; the low charging voltage will make the chemical reaction in the battery inadequate, and also shorten the battery life.
(5) The discharge current of the battery varies with the termination voltage required. With the increase of discharge current, the termination voltage can also be reduced appropriately. This is because the chemical reactions of batteries are required to proceed violently during high current discharge, which hinders the movement of charged ions, resulting in a rapid drop in terminal voltage, which is forced to stop discharge. Since then, those ions that have not time to move to the electrodes continue to react, causing the terminal voltage to rise again; but if small current discharges, because the movement and reaction of charged ions have sufficient time, if the discharge is stopped when the terminal voltage is still the same as that when large current discharges, the battery will be greatly damaged, or even can not recover capacity, so that the life of the battery will end earlier. So at present, many UPS shutdown voltages are based on discharge current.
(6) If the floating charge voltage of the battery is kept unchanged, the life of the battery will decrease with the increase of ambient temperature. Therefore, temperature compensation charging is set up in many UPS. The higher the temperature, the faster the capacity loss of the battery. This is because the leakage current of the battery increases with the increase of the temperature. Therefore, it is necessary to charge the batteries in time according to the requirements. There are recommended time in the general instructions, such as charging once in 4-6 months in winter and once in 2-3 months in summer. If the battery is not charged in time, the lighter one will reduce the capacity of the battery, and the heavier one will make the capacity of the battery no longer recoverable. IEEES t 1188-1996 recommended that when the capacity of fixed standby batteries is reduced to less than 80%, it is considered as the end of life, because the batteries will accelerate aging from then on.
