What Is Pulse Charging Of Lithium Batteries?

The charging time and service life of lithium batteries have always been the bottleneck in the use of electric vehicles. Traditional fast charging technology will shorten the service life of lithium-ion batteries when the polarization voltage is too high, and pulse charging can reduce the impact of polarization voltage accumulation. What is pulse charging of lithium batteries? According to incomplete statistics, pulse charging is divided into: negative pulse, positive pulse, positive and negative pulse. Pulse charging can select pulse current with adjustable amplitude and duty cycle for charging. The positive pulse charge is shown in the figure below, charge for one period, leave for one period, and so on. Adding and placing in the charging process can eliminate ohmic polarization and electrochemical polarization to a certain extent, but the effect of eliminating concentration polarization is limited.

In order to deal with this problem, a positive and negative pulse method can be used, a discharge pulse is added after the positive pulse is charged, and the discharge pulse and placement are used to enhance the depolarization effect.

Pulse charging mainly includes three stages: precharge, constant current charging and pulse charging. Compared with the conventional charging method, pulse charging can be charged with a larger current, and the concentration polarization and ohmic polarization of the battery will be eliminated during the stop period, so that the next round of charging will proceed more smoothly. The charging speed is fast and the temperature is high. The change is small and the impact on battery life is small, so it is now widely used. But its shortcomings are obvious: a power supply with a current limiting function is required, which increases the cost of the pulse charging method.

In the high-current pulse operation mode of the lithium battery, it is easier to decompose the lithium salt LiPF6 in the electrolyte into LiF. The existence of LiF makes the ion dispersion resistance and charge exchange resistance of the battery rapidly increase, so that the battery is charged at a high current. The polarization voltage of the battery rises rapidly, exceeding the limit voltage of the lithium battery, making the battery unable to finish charging.

As nickel-cadmium batteries are simply polarized during conventional charging, conventional constant voltage or constant current charging will continue to generate hydrogen and oxygen gas in the electrolyte. Under the effect of internal high pressure, the oxygen will penetrate to the negative electrode and the cadmium plate to generate CdO, forming a pole The effective capacity of the board decreases. Pulse charging generally uses the method of charging and discharging, that is, charge for 5 seconds, then discharge for 1 second.

In this way, most of the oxygen generated during the charging process will be reduced to electrolyte under the discharge pulse. It not only restricts the amount of internal electrolyte vaporization, but also for those old batteries that have been severely polarized, they will gradually recover or be close to their original capacity after using this charging method to charge and discharge 5-10 times. The selection of the charge and discharge pulse width should ensure that the plate recovers the original crystal structure and then eliminate the memory effect. After selecting the discharge depolarization method, the charging power can be increased and high current fast charging is allowed.

Smart chargers can provide different charging modes and corresponding algorithms for each battery's characteristics to achieve a good charging effect. Rechargeable batteries have high performance-price ratio, large discharge current, and long life. , Widely used in various communication equipment, instrumentation, electrical measuring equipment. But different types of batteries such as nickel-cadmium batteries, nickel-hydrogen batteries and lithium-ion batteries have different charging characteristics and processes.

Pulse is a type of current, which is different from pure direct current. The charging current is a pulsating current; an excellent smart charger first charges the battery with a constant current, and then uses a constant voltage to charge the battery when the charging is over. Charging ends automatically when the battery is fully charged. This charging method can charge more fully and is beneficial to battery life extension.

During pulse charging, the charging current uses a pulsating current. Pulse charging can also be made intelligent. Smart charging can not only control the charging current, but the excellent smart charger also has temperature monitoring, so you can't find a smart pulse charger, you can directly use the smart charger.

Pulse fast charging mainly deals with how to quickly reduce the polarization effect, so that the charging power can be improved, and then reach the intention of reaching full charge at a faster rate. The pulse charging method can improve the charging without devoting the life of the lithium battery speed. In order to better confirm the pulse amplitude and width, improve the speed and power, have a better grasp of the polarization characteristics of the lithium battery itself, so as to plan a suitable charging strategy.