Nickel Hydride No. 5 battery.Battery quick charging method

　　Battery quick charging method

　　In order to maximize the speed of the chemical reaction of the battery, shorten the time for the battery to reach a full charge state, and at the same time ensure that the polarization phenomenon of the positive and negative plates of the battery is minimized or lightened, and improve the efficiency of the battery, fast charging technology has been rapidly developed in recent years. develop. Several popular fast charging methods are designed around the optimal charging curve, with the purpose of making the charging curve as close to the optimal charging curve as possible. The conventional charging method adopts a low-current slow charging method. It takes more than 70H to initially charge a new battery, and more than 10H for ordinary charging. If the charging time is too long, it will not only prolong the charging detection time and cause a waste of electric energy, but also limit the number of battery recycling times and increase the maintenance workload. The use of fast charging method can shorten the charging time of the battery, increase the charging rate, save energy, and increase the number of battery recycling times, which has great practical significance.

　　(1) Battery fast charging technology

　　In the mid-1960s, American scientist Maas did a lot of research on the gas evolution of the battery charging process, and proposed an acceptable charging current curve for the battery based on the lowest gas evolution rate. During the charging process, only the charging current is required, so the charging time is greatly extended. In the later stage of charging, the charging current is greater than the acceptable current of the battery, so a large number of bubbles are generated in the battery. However, if the actual charging current can always be equal to or close to the acceptable charging current of the battery during the entire charging process, the charging speed can be greatly accelerated, and the gas evolution rate can also be controlled in a very low range. This is the basic theoretical basis of fast charging. However, during the charging process, the polarization voltage generated in the battery will hinder its own charging and significantly increase the gas evolution rate and temperature rise. Therefore, the polarization voltage is an important factor affecting the charging speed. It can be seen that in order to achieve fast charging, we must try to eliminate the impact of polarization voltage on battery charging. It can be inferred from the formation mechanism of polarization voltage that the magnitude of polarization voltage changes closely with the change of charging current. When charging is stopped, the resistance polarization disappears, and the concentration polarization discharge channel and electrochemical scheme also gradually weaken. If a discharge channel is provided for the battery to discharge in the opposite direction, the concentration polarization and electrochemistry will disappear quickly, and the temperature inside the battery will decrease due to discharge. Therefore, suspending charging during the battery charging process and appropriately adding discharge pulses can quickly and effectively eliminate various polarization voltages, thereby increasing the charging speed. At present, the fast charging methods that everyone agrees with are pulse charging and pulse discharge depolarization methods.

　　(2) Technical approaches to achieve fast charging

　　1. Improve battery design and reduce ohmic internal resistance. If the battery uses a copper drawn mesh negative electrode grid, the grid resistance will be significantly reduced. This not only helps to improve the utilization rate of active materials and the specific power of the battery, but also improves the fast charging performance of the battery. 2. Increase the occurrence time of reactive ion diffusion current, that is, extend the time for the battery voltage to reach the gas evolution voltage, thereby allowing the charging current to be increased, the plate thickness to be reduced, the active material porosity to be increased, and the grid active material contact area to be increased. These measures are beneficial to the diffusion of reactants and products, reduce concentration polarization, increase the allowable charging current, and achieve fast charging. However, considering the life of the battery, the plates cannot be made too thin. 3. Reform the battery charging method. The theory of the pulse fast charging method is basically to superimpose negative pulses of a certain frequency and height or a short-term charging stop in the charging current, so that the lead ions participating in the reaction can be generated and increase their concentration, and the generated hydrogen ions and sulfate radicals can be generated. The ions have time to move away from the vicinity of the electrode, and the overall effect is an effective measure to reduce the concentration difference. The battery voltage rises slowly, allowing the battery to charge more electricity. The intelligent charging device currently developed is designed with these situations in mind. 4. The impact of fast charging on battery life. The impact of high-current fast charging on battery life is still under discussion. There are also different views in the industry. First of all, the service life of batteries is not consistent, and their cycle life can even vary by a factor of 1. Furthermore, during the long-term life test process, it is difficult to ensure that the test conditions of each batch of batteries are completely consistent. Although it is generally believed that high-current fast charging does not adversely affect the life of valve-regulated sealed lead-acid batteries.

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