Discussion on the Causes of Battery Aging
(1) Deep discharge: The deeper the discharge depth, the shorter the life of the battery, or even damage it and make it unusable.
From the perspective of battery safety, a capacity test has to be done.。
(2) High current discharge: Using a large discharge current will shorten the service life of the battery. This can be explained by the corrosion and cross-sectional area of the lead plate of the electrode. Generally speaking, the natural damage of the lead-acid battery is due to the corrosion of the lead plate of the positive electrode, which makes the cross-sectional area of the current flow smaller, so when a large current is discharged , a larger lead plate area is required to provide such a large current flow, but when the cross-sectional area of the lead plate is not enough for the discharge current to flow, it will affect the life of the battery.
In order to use the safety point of view, we have to do a large current discharge test.。
(3) High current charging: When charging with high current, when the gas generated exceeds a certain amount, it will exceed the rate that the battery itself can absorb, so that the internal pressure will rise, and the gas will be discharged from the safety valve, resulting in a large amount of electrolyte consumption, reducing the battery life. lifespan.
In the constant voltage charging mode, the charging current will decrease as the battery is fully charged. When the battery is fully charged, the charger will automatically enter the float charging mode to keep the battery in a fully charged state. In this method, at the initial stage of charging, the initial charging current is too large due to the low voltage at the battery terminal, which easily damages the plate of the battery and increases the temperature of the battery itself, thereby shortening the life of the battery. Overcharging: If the battery has been overcharged , its components (plates, separators, etc.) will be damaged due to the oxidation of the electrolyte.
(4) Effect of ambient temperature: The ambient temperature of the battery will affect its life. If the battery is charged at a constant voltage, when the surrounding temperature is too high, the deterioration of the internal materials of the battery will be accelerated, resulting in shortened battery life. Charging at too low temperature will generate hydrogen gas, which will increase the internal pressure or reduce the electrolyte, resulting in shortened life.
Generally speaking, the working temperature of the flooded battery is 20°C to 40°C as the best environment.
The working temperature of the lean liquid battery (including AGM or GEL) is 20°C to 25°C as the best environment.
battery deterioration
(1) Whether the lead-acid battery is charged or discharged or floated, it will cause the water on the positive plate to dry up, or the sulfation of the negative plate.
(2) The reasons for the deterioration of the positive plate can be divided into three types: softening of the active material, corrosion of the grid, and barrier between the grid and the active material interface. After charging and discharging, the positive electrode active material repeatedly dissolves lead dioxide and precipitates lead sulfate, and then condenses into larger cavities and develops into a delicate colloidal structure. This process current flows to the surface of the active material with low resistance. At the same time, it is an ideal structure from the perspective of ensuring the diffusion of sulfuric acid. However, if the active material particles that form this colloidal structure are combined, they will gradually weaken. , the active material becomes inactivated to reduce the discharge capacity.
(3) The electrochemical reaction formula of the lead-acid battery is shown in the figure below: Because in the chemical reaction formula during the charge and discharge process of the lead-acid battery, the water in the electrolyte in the lead-acid battery will be consumed. Insufficient, too much gas will be directly discharged out of the battery through the exhaust plug, so that the water in the electrolyte will gradually decrease. In addition, when the battery is discharged, or when the temperature of the battery is higher than the external temperature, water vapor may also penetrate the wall of the electrolytic cell and escape to the outside of the battery.
(4) The sulfation of the negative plate is most likely to occur when the lead-acid battery is not fully charged and is usually used in a partially discharged state. Especially in the lower layer due to the high specific gravity, the sulfation of the plate will occur through the stratification of the electrolyte, and the large lead sulfate crystals that are not easy to charge will be formed in the lower layer of the plate, resulting in a decrease in capacity.
Three common judgments for battery deterioration
(1) Outlier voltage: When the battery is used in series mode, due to the inconsistent characteristics of the battery itself, the battery will have greater inconsistency after cycle use of charge and discharge, causing some batteries to be overcharged and some batteries to be undercharged phenomenon, thus accelerating battery damage. Generally, the floating charge voltage of a 12V battery is set at 13.5±0.2V. If the voltage is too low, the battery performance will decline and the capacity will decrease. When the voltage is too high, the overvoltage of the plate will rise sharply, resulting in rapid gas generation. At this time, if the gas re-reaction rate is lower than the gas generation rate, the gas cycle efficiency will decrease, the internal pressure of the battery will increase, and the gas will escape through the exhaust valve. Therefore, the floating charge voltage must be controlled below the overvoltage vaporization point, that is, to control the gas generation rate, so as not to cause the battery structure to crack due to excessive internal pressure or cause water loss, thereby reducing the service life of the battery.
(2) Float charge internal resistance: The general failure mode of VRLA batteries is corrosion of the grid body of the plate, deterioration of the active material of the plate and dryness of the electrolyte. Unusual failure modes are deterioration of the conductive path and excessive drying up of the electrolyte. These conditions will affect the battery and increase the internal resistance of the battery. If the internal resistance of the battery increases by 30% compared with the new one, the battery should be tested again to determine the cause, and if necessary, the battery or system can be tested for capacity to ensure its reliability.
(3) Battery capacity: The battery system must undergo a battery capacity test under load every two years, ideally close to the result of the original installation acceptance. Once it is found that the battery has reached 85% of the rated capacity, the annual capacity test must be carried out.