Degradation of battery performance is a natural consequence of use and aging on the one hand, and accelerates degradation due to lack of maintenance, harsh use environments, and poor charging operations. The following is a discussion of various insurmountable problems with rechargeable batteries, their causes, and ways to compensate for these problems.
High self-discharge rate
Various batteries have self-discharge, but improper use can promote the development of this state. The self-discharge rate is asymptotically linear, and the highest discharge rate occurs immediately after charging and then gradually decreases.
Nickel-based batteries exhibit a high self-discharge rate. At normal ambient temperature, after charging the new nickel-cadmium battery, its electrical height is reduced by about 10% during the first 24h. Thereafter, the self-discharge rate is stabilized to about 10% per month. Generally, the temperature is higher and the discharge rate is also increased. The general rule is that the self-discharge rate is doubled for every 10 °C increase in temperature. The self-discharge rate of nickel metal hydride batteries is about 30% larger than that of nickel-cadmium batteries.
Nickel-based batteries have increased their self-discharge rate after hundreds of cycles, and the plates of the battery begin to expand to more closely squeeze the separator between the electrodes to form metal dendrites, which are the result of crystal growth (memory effect). ), thereby damaging the battery separator and increasing the self-discharge rate. If the nickel-based battery has a self-discharge of 30% at 24h, it should be discarded.
The self-discharge rate of the nickel-ion battery in the first 24 h after charging was 5%. After that, it dropped to 1%-2% per month, and the battery safety protection circuit increased by about 3%. High cycle times and aging have no effect on the self-discharge rate of lithium-based batteries. The self-discharge rate of lead-acid batteries is about 5% per month or 50% per year, and repetitive deep cycle charging and discharging increases self-discharge.
The percentage of self-discharge of the battery can be measured using a battery analyzer, but this procedure takes several hours. The measured internal resistance of the battery often reflects whether the internal resistance of the battery is too high. This parameter can be measured with an impedance meter or with the ohmic test procedure of the battery analyzer.
Battery matching
Even with modern manufacturing techniques, battery capacity cannot be accurately predicted, especially for nickel-based batteries. During the manufacturing process, each battery is detected and classified by its capacity. High-capacity "A" batteries are usually sold at special grades for special-purpose batteries; medium-capacity "B" batteries are used in industrial and commercial products; low-end "C" batteries are sold at low prices. The charge and discharge through the cycle does not improve the capacity of the low-end category battery. Buying a low-cost rechargeable battery results in a low battery capacity.
In a battery pack composed of a plurality of batteries, the matching of the batteries should be controlled within ±2.5%. In battery packs that make up a large number of batteries, as well as battery packs that need to output large load currents and operate at low temperatures, more stringent battery tolerance control is required. If a small battery in a new battery pack has a slight mismatch, after several cycles of charging, it will be able to adjust to each other. Whether the batteries are well balanced or not depends on whether the battery pack has a long service life.
Why is battery matching so important? This is because a "weak" battery contains less capacity and it charges faster than a "strong" battery. This imbalance in the discharge process causes the "weak" battery to reverse polarity when discharged through a low voltage. When charging, the "weak" battery first enters the hot-charge overcharge state during the charging process, and at this time, the stronger battery can still receive the charging normally without heating. In both cases the "weak" battery is in an unfavorable state, making it more "weak" and causing a serious mismatch.
High-quality batteries are more consistent and more balanced than low-quality batteries. For high-end high-power tools, high-quality batteries should be used because of their high durability under heavy load and extreme temperature conditions. Despite the high cost, the reward is that the battery pack has a longer life.
Lithium-based batteries match their essential properties when they come off the production line. It is very important that individual batteries within the battery pack meet strict tolerances. All batteries in the battery pack must reach the full charge within a uniform time and reach the same threshold voltage at the end of the discharge. The built-in protection circuit of the battery pack should be used for safety protection when the battery is in an abnormal working condition.
Shorted battery
Battery manufacturers often fail to explain why some batteries exhibit high leakage rates or electrical shorts when the battery is still in a new state. The suspicious cause is that the battery may be contaminated with foreign particles during the manufacturing process. The other is that the rough spots on the electrodes cause damage to the diaphragm. Therefore, the battery should improve its manufacturing process, which can greatly reduce the "infant mortality" of the battery.
The reverse polarity of the battery caused by deep discharge can also cause a short circuit in the battery. This state may also occur if the nickel-based battery is discharged at a high current to a complete discharge. A high reverse current can cause a permanent electrical short. Another cause is diaphragm damage caused by the formation of an uncontrollable lens, which is the so-called memory effect.
A battery that attempts to repair a short circuit with an instantaneous high current pulse has a very limited success rate. This short circuit may be temporarily evaporated, but damage to the diaphragm material still exists. This repaired battery often exhibits a high discharge rate and the short circuit will reappear. It is not advisable to replace a shorted battery in an aged battery pack. Unless this new battery is matched in battery voltage and capacity to other battery performance in the battery pack.
Electrolyte loss
Although the batteries are all sealed, some electrolytes are lost during their service life, especially if excessive gas pressure is generated due to improper charging of the carelessness to cause gas discharge. Once gas emissions occur, the spring-loaded vent seal on the nickel-based battery may be difficult to reclose completely, resulting in the deposition of white powder around the gasket, which ultimately reduces the battery capacity.
Permeation or loss of electrolyte in gas-regulated lead-acid batteries (VRCA) is a long-standing problem. The reason is caused by overcharging and working at high temperatures. The effect of replenishing the electrolyte with water is limited. Although the battery capacity can be partially restored, the performance of the battery will not be reliable.
If properly charged, the lithium ion battery should not generate gas so that there is a problem of exhaust. However, lithium-ion batteries also generate internal pressure under certain conditions. Some battery internal configurations - circuit switches that cut off current when the battery pressure reaches a certain threshold. Other batteries are designed in a controlled manner or open a safety diaphragm to release gas.
The product obtained by coating organic coating on hot-dip galvanized steel coil is hot-dip galvanized color steel coil. In addition to the protective effect of zinc, the organic coating on the surface of hot-dip galvanized steel sheet also plays the role of insulation protection and rust prevention, and its service life is longer than that of hot-dip galvanized sheet. The zinc content of hot-dip galvanized base plate is generally 180g / m2 (both sides), and the maximum zinc content of hot-dip galvanized base plate for building exterior is 275g / m2. Zinc coating weight code: Z100, z200, z275; zinc coating weight refers to the total amount of zinc on both sides of the steel plate, expressed in grams of zinc per square meter of steel plate (g / m2), for example, Z100 means that its zinc content is not less than 100g / m2.
According to the surface structure of galvanized coil, it can be divided into the following surfaces:
(1) Regular Spangle
In the normal solidification process of zinc layer, the zinc grains grow freely and form a coating with obvious zinc flower morphology.
(2) Minimized Spangle
During the solidification process of zinc coating, the zinc grains are artificially limited to form the smallest possible zinc flower coating.
(3) Spangle free zinc free coating
The coating obtained by adjusting the chemical composition of the bath has no visible zinc flower morphology and uniform surface.
(4) Zinc iron alloy coating
After heat treatment of the steel strip passing through the galvanizing bath, the whole coating forms an alloy layer of zinc and iron. The coating is dark gray in appearance and has no metallic luster. It is easy to be powdered in the violent forming process. It is suitable for coating that can be painted directly without further treatment except for general cleaning.
(5) Differential coating
For both sides of Galvanized Steel Sheet, the coating with different weight of zinc layer is required.
(6) Smooth skin pass
Finishing is a kind of small deformation cold rolling of galvanized steel sheet for one or more of the following purposes.
Galvanized Coil,Regular Spangle,Galvalume Steel Coil,Galvanized Steel Coil,Galvanized Steel Sheet
Jinan Hengming Steel Co., Ltd , https://www.jnhengmingsteel.com